: Headgaskets?

05-18-05, 08:54 AM
I know this is an overdone thread but my experience seems similar to some nonheadgasket failures as well as HG failures. The following is the procedure I have completed and would like advice on how to proceed...

98 ETC
Purchase: 68k miles
Problem: 75k miles
Now: 85k miles (had to make a few long eastern seaboard trips)

1) Rough idle on cold startup developed around 75k, especially bad at low outside temp
2) Replaced plugs - no dice
3) Did not replace wires as they were still very pliable and seemed fine
4) Used Seafoam to clean the engine out, sucked it in the vaccum line on the engine, blew out a massive amount of carb buildup doing some WOTs
5) Rough idle still at cold start
6) Had a headgasket test done at a Caddy dealership (Capital Cadillac on Cobb Pkwy in ATL), apparantly they didn't do a pressure test after I asked for it, instead they did a dye test on the engine coolant. On cold start the engine threw misfire codes all over the place until it warmed up. I was told that the dye started turning (indicating hydrocarbons and therefore a HG leak) but did not fully turn. The tech said it was prolly a HG and said it would be around $4500 for the fix.

I am at a crossroad, I do not have the necessary experience to diagnose the EGR, TB, FPR but I do have the factory service manuals/tools/time and can replace any of the parts myself but I'm trying to see if it's cost effective to look at these other things myself but I'm not 100% sure what I'm looking for.
If the replacement cost of these parts is <$500-$1000 I'll check them out, otherwise I'll just pony up the cash and replace the engine but I wanted to get an idea first.

05-18-05, 09:51 AM
There could be two seperate issues.

The test strip in the coolant seems to be inconclusive. Have you replaced the original coolant? If so, did you install the coolant supplement tabs?

Your misfires could be plug wires or a coil pack. Try a cold start in a dark location and spray-mist the wires and coils looking (and listening) for arcing.

Fuel pressure guages are not expensive and there is a simple leak test for your fuel pressure regulator. Pull the vacuum hose off the FPR and there should be no visible fuel or fuel aroma.

I would not throw money at the headgaskets until you have conclusive evidence of failure.

Louie the Drifter
05-18-05, 09:55 AM
Hey--Razeorc I just went through this with my 99 sts with 67k on the clock we bought this car on ebay it came from boston had it shiped to minnesota. Cost for shipping and car $12.000 got it home drove it for 3 weeks and it started missing on one cylinder when first started up, also noticed it was losing coolant.It smelled of antifreeze when my wife pulled in after picking up the car from the transport. When it started missing I thought oh no headgasket! We took it to a local independant garage looking for a deal he said he wanted $3,000 to do the heads. the GM dealer wanted $1,700 , the Cadd. dealer wanted $1,900. We took it to the GM dealer ended up costing $1,850 , not that bad considering the entire power unit must be dropped out! any how the car is back it works good kicks ass!!! its a beautiful black on black leather and cost us overall about what the cars est. value is. we love this car we went from a nice 92 camaro Z28 which rode like a hay rack compared to this luxury car. I wish you luck ! Farwell to you. Louie the Drifter

05-18-05, 09:57 AM
Maybe it's a stupid question but did you try adding the recommended sealant to the cooling system to find out if it helps?http://cadillacforums.com/forums/images/smilies/hmmm.gif

Anything is possible, but I don't think these tips will fix your problem, but here goes anyway:

You can check the FPR by 1) removing the vac line a smelling for fuel leakage, 2) by an inexpensive fuel gauge and measure the pressure at the fuel rail.

Wires can be "very pliable and seem fine" yet still be bad. Mist them with water in a darkened environment and look for arcing. Maybe they are absorbing moisture and "dry out" as the engine warms up.

Dang! JimD posted while I was replying and said most of what I suggested too!

Louie the Drifter
05-18-05, 10:11 AM
To check for leaky headgasket find cylinder that is missfiring and hook up 120 PSI thru sparkplug hole with this cylinder on comp. stroke then look for bubbles in cooling system or pressure build up in resivor tank.

Louie the Drifter
05-18-05, 10:12 AM
:tisk: To check for leaky headgasket find cylinder that is missfiring and hook up 120 PSI thru sparkplug hole with this cylinder on comp. stroke then look for bubbles in cooling system or pressure build up in resivor tank.

05-18-05, 10:29 AM
You need to pay attention to the vital signs: Does the car misfire only at idle, and ONLY upon first morning startup? Or does it misfire always, and throughtout the whole rpm band? Is it consuming coolant in any way or form? Does the engine's performance, and driveability suffer. Has the operation temperature changed from the norm recently? Do you hear any kinda of noise be it slight or loud, which are not common operating noises. Is the car hard to start in the mornings? Does the exhaust have a strange smell, or smoke any. These are things you can check without even getting your hands dirty, and will help you eliminate many "could be" issues and find the source of the problem. Visual diagnosis is the first step. Once you determine that the fault is comming from the fuel system, or the ignition, system or infact a mechanical problem, You can go ahead and invest the money on tools and equipment to diagnos the respective sub-systems. Good Luck

05-18-05, 11:27 AM
Ok, a bit more for you guys/gals to chew on:

The waterpump was replaced last summer and flushed, coolant pellets were not put in and I didn't get around to putting them in until 4 months later in the hose as directed.

Engine ONLY misfires on cold morning start, once it's warm, or restarting at any other point it's fine.

No tell tale white smoke blowing out the back (though depending on humidity & temp it'll blow the standard whisps of steam until warm).

No noticable loss of coolant, the GM tech said that even if it was a very small leak that's all it would take in the cylinder to foul the spark. He said it was probably the early stage of HG failure. It doesn't smell like coolant either like when the pump went...

I don't know what the temp tics represent is but I have never seen the thermo go above the little white tick immediatley after the big one in the middle, it'll go up to but never past, and only when it's 90+ outside and i'm idling in gridlock and even then once the fans kick on it settles back toward the big tic.

The engine has a slight knocking sound that developed over the winter, but after seafoaming the crap out of the engine/oil/gas and blowing loads of carb buildup out the back it hasn't been nearly as loud.

I have noticed over the past month a whining/growling that seems to be coming from somewhere in the dash, at first i thought it was the blower motor, but i have noticed that under acceleration, or whenever i put both windows up at the same time the noise stops but it definatley hums along with the engine. (Yeah more problems!)

At one point maybe 3 months ago I put some injector cleaner in and it drove fine for about a week, i'm curious, could a leaking injector foul a plug on startup?

And also, is there any other way that hydrocarbons could be getting into the coolant system, BESIDES a leaking/failed HG?


05-18-05, 12:14 PM
The knocking sound is most probably piston slap. And could be the reason for your misfire. Piston slap is basically too much clearence between the piston and cylinder wall. This causes noise, and poor compression in that cylinder. This will cause a misfire especially at cold start. However as the engine warms metals expand, reducing the clearence, and the noise. And depending on the severity of the problem, could cause the miss to go away. I would due a compression test with the car cold sitting over night, on every cylinder and compare the readings to the acceptable specs. Any cylinders low are at fault.

A leaking injector can foul a plug, no doubt about that.
HG's in the coolant can be from a blown gasket, cracked head/block. Block deck clearence issues. Oil cooler issues, transmission cooler issues. As internally are mixing the oil and coolant. Lastly cylinder sleeves leaking.

05-18-05, 03:21 PM
Replace the wires -- they are more likely to go than the plugs.
Come back and let us know if it still misses.

Get the engine pressure tested for headgasket failure -- it's the only definite way to know if it's gone or not.

05-22-05, 07:48 PM
OK so here's an update,

This weekend I replaced all of the wires (I found alot of corrostion on the plug ends of the back bank of wires), and the fuel filter (the sludge that came out was like watery mud). Unfortunatley the cold start rough idle has still not been fixed.

I have another question, could a broken/worn/sticking spring or valve be causing the problem? Also, If the valves were worn for some reason a compression test may not tell me 100% for sure if the HG has failed, I mean I can pull the valve covers off with the engine still in there (front bank at least easily) is it worth it?

I keep going over this in my head because some of what is happening doesn't make sense for a Headgasket. First off I've run the car with this idle problem since January, over 10k miles now, in all temps, all conditions, from idling in gridlock downtown in ATL 90 outside to running up the east coast (1000 miles in one day), and the temp is fine, there is no coolant smell, the exhaust smells normal, no white smoke, Oh, and I've done WOTs and had the car up pretty fast a number of times over the past 10k miles and nothing has gotten worse. I have noticed that it kinda feels like i'm skipping under idle though, even after warm, i didn't notice it earlier but i think it still might be, just no code being set off...

05-22-05, 10:30 PM
Well...if you really want to figure out if it is a head gasket or not there are two alternatives....

Make an adapter out of an old spark plug shell and put 120 PSI into each cylinder one at a time and check the cooling system for bubbling each time a cylinder is pressurized. Sure fire way to tell if the head gasket is leaking or not.

Since your only complaint seems to be the cold start misfire and the only way a head gasket would cause this is for coolant to seep into the cylinder overnight and foul the plug you could test the system to replicate this failure mode. With the engine cold one weekend....find a cooling system pressure checker and pump up the system to 15 PSI and let it sit for awhile. Keep pumping it up to 15 if the pressure drops off for some reason. While it is sitting there pressurized pull the spark plugs. Wait 2 hours or so. Put a rag over the spark plug wells and spin the engine over with the starter with the plugs out. Inspect the spark plug wells for any sign of coolant from the combustion chamber. If the pressure is pushing coolant into a chamber then it should show up this way. If it doesn't then I wouldn't think the problem is a head gasket.

Personally, I would suspect an ignition coil. Possibly one of the coils is intermittant cold and starts to work as it warms up. On the next few cold starts....pull the plug wires off one of the coils before you start the engine. Since each coil fires two cylinders, pull off both wires and start it. If it runs much worse then that coil was working fine. If there is no difference with the plug wires removed then that coil wasn't working when cold anyway...replace it. You could probably do this check in one cold start and see which coil is dead cold.

05-23-05, 08:51 AM
You've gotten a ton of knowledge in this thread, and with a factory service manual you can go wrong:D . Yet The only thing that makes me think you have an internal problem, is the fact that you say the engine is "knocking" ofcourse I haven't heard the noise personally, so when u say knock, I think of piston noise, or possibly rod noise, but it's hard to diagnos noise, when your told off hand, not experience it personally. Anyways good luck hopefully you can find the problem and avoid yourself a costly repair.

05-23-05, 02:41 PM
The knocking sound is most probably piston slap. And could be the reason for your misfire. Piston slap is basically too much clearence between the piston and cylinder wall. This causes noise, and poor compression in that cylinder. This will cause a misfire especially at cold start. However as the engine warms metals expand, reducing the clearence, and the noise. And depending on the severity of the problem, could cause the miss to go away. I would due a compression test with the car cold sitting over night, on every cylinder and compare the readings to the acceptable specs. Any cylinders low are at fault.

A leaking injector can foul a plug, no doubt about that.
HG's in the coolant can be from a blown gasket, cracked head/block. Block deck clearence issues. Oil cooler issues, transmission cooler issues. As internally are mixing the oil and coolant. Lastly cylinder sleeves leaking.

Piston slap will not cause loss of compression......and certainly not a misfire. For a loss of compression to occur there would have to be absolutely giant clearances between the piston and cylinder wall. I have never seen a case where there was wear enough to cause the rings to not seal due to "piston slap".

The piston can "slap" and make quite a bit of noise without any detrimental effect to the engine at all. If you ever get the chance to listen to any sort of race engine running forged aluminum pistons idle with mufflers on it you can hear attrocious piston slap...and they seal up fine. Piston slap basically has nothing to do with ring sealing and loss of compression.

As has been oft reported on this forum the Northstar can catch the "cold carbon rap" malady when it is not run hard enough for long enough and the carbon builds up in the combustion chamber to the point that the carbon actually will touch the piston at TDC in the squish areas where the piston comes very close to the head deck surface. The contact doesn't hurt anything but it will upset the deliberately designed piston motion as the piston traverses over TDC and changes direction...and thrust load. The change in direction and thrust at TDC is what causes "piston slap". Production OEM pistons have the piston pins offset slightly (relative to the centerline of the bore) so as to deliberately create some latent thrust load to control the piston motion at TDC to prevent slap. This and piston skirt shape and clearance are the main factors in piston slap. Opening up the piston/cylinder wall clearance is directionally incorrect for slap but has little to no effect on piston ring sealing or the tendency to miss fire. Misfire just does not happen due to piston slap. And the cold carbon rap can easily be avoided by frequently exercising the Northstar to keep the combustion chambers clean.

The check for combustion gases in the coolant is a crap shoot at best. DexCool, in specific, is known to not work with some of the test strips so be very leary of that type of analysis. The pressure checks are the only sure way to detect a head gasket failure.

05-23-05, 04:12 PM
But how would you explain the noise at cold, and then as it warms up the noise goes away and the engine even runs better. Not to flame, Im asking because I see you know, and I don't understand. I've only been working for cadillac for 8 months, and only taken apart 3 northstars. I'm a 21 year old "kid" so bear with me LOL. I know as well as you must very well know, that northstars suffer from piston problems. I've had 2 scenarios and both were similar cause, with the same fault. One customer complained of rough idle at cold start and later leveled out. A compression test was done after the car sat over night and was recorded low. The pistons were blamed and replaced, away went the noise and the cold start problem. Another was a complain of excessive oil consumption, and an intermitten misfire with about 125k miles, a test revealed worn rings. We mic'ed everything. All we ended up doing was replacing all 8 pistons rehone the walls, and go with new rings. The car ran beautifully, and aside from that had a strange startup noise, a rattle if you will which was eliminated. The first case was a 00 dts with about 48k miles. So my question why did both examples show poor compression and have a piston problem? I can relate to race motors, they are noisey as hell, and consume quite a bit of oil. But don't race engines make piston noise not because of clearance issues, but because of the floating design of the piston on the rod? I also own a 98 ls1. And it's not common to hear piston pin noise at cold start, or under excessive load. I thought all out race engines suffered from the same issue

05-23-05, 06:45 PM
I think you mean full floating wrist pins when you mention the "the floating design of the piston on the rod"....?? If so, understand that Northstar engines have full floating wrist pins also. If you changed pistons you must have taken the circlips out that hold the wrist pin in place in the piston. Those are full floating wrist pins....just like a "race engine". Full floating pins can contribute to noise at startup but it is a tapping much like a collapsed lifter would make. It taps several times about 20 seconds after startup and then stops. That is usually a full floating wrist pin that makes a little noise until more oil reaches it. Otherwise, full floating pins don't make any more noise than pressed pins.

Not sure what you "fixed" with the two cars you mentioned. If the pistons were replaced with the service parts with the higher tension rings then that change would have remedied oil consumption and would possibly have helped prevent carbon build up in the future. Possibly the rings were sticking in the ring grooves due to carbon build up from gentle driving. That is a common observation in Northstar engines. That could account for excess oil consumtion and variable compression in some cylinders. That is why frequent WOT accels to "exercise" the rings are recommended with Northstar engines. Also, many of the 2000 and later engines are torn down like you describe and the top rings are not even broken in to the sides of the piston ring lands due to the hard anodized ring land and lack of load on the rings due to a light duty driving cycle. Dissassembling the engine and cleaning the carbon off the combustion chamber will eliminate the carbon and carbon rap, too. Possibly, also, other things done to the engines at teardown helped with the driveablity cold...or the perception of the engine operation cold. I have had people tell me that the engine was "missing" when it had cold carbon rap. A few good WOT blasts cured the cold carbon rap...and the "miss".... I suspect it was never missing but the perception was that it was upon hearing the noise.

In any case, the service pistons would not have affected piston slap as the skirt design is similar and so are the clearances.

I have seen lots of Northstars apart with very high miles/hours on them and none of the ever wear the cylinder walls or piston skirts appreciably...certainly not enough to cause excessive clearance or piston slap.

My main point was that piston slap is not indicative of the piston moving or rocking enough to cause the rings to not seal. Especially in this case, when a cylinder is very low on compression, there is very very little likelyhood it is rings or the piston...unless there is a hole in the piston. As described the piston slap will be worse when cold...that is why the "cold carbon rap" is called "COLD carbon rap". The carbon touches the piston causing it to rock in the bore slightly making the piston slap noise. As the piston warms up and swells somewhat the clearance is reduced and the noise goes away. The piston motion at TDC is definitely more sensitive when the engine is cold and the clearances are greater.

Northstar rings will typically go way way over 100K miles and it is not uncommon to see them with 200K miles on them and still have some service life left. I have never seen a Northstar wear out rings in low mileage operation. That is the positive side to the aggressive hone pattern on the OEM cylinder walls. It does an excellent job of retaining oil and the pistons/rings/cylinder walls will run virtually forever. Worn out rings are just non-existant. How did you determine that the rings were "worn out" in that specific case..?? Besides, with 125K on it as you indicate that is hardly an unexpected situation to have some ring wear. Engines used to get re-ringed at 50 or 75K not too many years ago.

I simply cannot agree with your statement that Northstar engines have piston problems. The pistons in all years will run and wear virtually forever and there are few to none problems with piston scuffing, piston slap in general, other noises, broken pistons, etc. That is a very bulletproof area of the engine. Oil consumption with the piston/ring pack/cylinder wall finish is on the high side in many engines. While this is the down side to a reciprocating package that will live forever it is a complaint item to many customers due to ill conceived perceptions that an engine should consume no oil. Whatever...it can be improved at the expense of long term piston/ring/cylinder bore wear and it really isn't a "piston problem" at all.

Race engines are very noisy for a variety or reasons. Lots of clearance to reduce friction is one of the main reasons. The point is that a 'race" piston moves around and slaps much more than any production passenger car piston yet is seals up fine...so the "slap" cannot be causing the rings to loose seal. If the rings are worn out or the cylinder wall is scored or something that is another issue but just piston slap is harmless. Race pistons are forged, generally, so they must be run with much more clearance as the forged piston blanks are far less forgiving in terms of scuffing due to the increased stiffness of the skirts. Also, forged pistons do NOT have the pins offset to create a residual thrust load to control the piston motion at TDC. Stiff, forged pistons, floating pins with lots of clearance, lots of piston wall clearance, and lack of piston pin offset all combine to make race engines very very noisy....but you can't hear it over the open headers....LOL.

Concourson20s, what area are you from...??

05-23-05, 09:21 PM
Wow, intersting conversation. My car's knocking/ticking is constant with engine rpm but only noticable at idle. It never 'goes away' and as for exercising the engine/WOT, all I can say is I drive this car hard (i'm 22) and it does beautifully. I also took a can of seafoam to the engine a couple weeks ago, sucking it in the ECV (I think that's the line). The cloud of carbon I blew out was in one word - amazing, I just might do it again to see if I got it all and since it's a petroleum product it shouldn't hurt the engine.

I'm just wondering because I do know this about the car, it was a lease vehicle for the first 2 years of life in FL and only got 25k miles on it, then it sat/got traded around dealer inventories until 2002 when it was picked up and driven till last summer when it was traded in w/68k miles on it. In the 2 years from 2000-2002 the car acumulated just a couple hundred miles. I'm wondering if any seals or parts could have gone in that unexercied period. For the record the valve cover gaskets are shot to hell as there's an insane amount of oil around the bolts/seal line, and the car eats about 1 quart every 1k miles but It's mostly from leaking seals as there is never blue/black smoke coming out the tail pipes, maybe i should have mentioned this before?

05-24-05, 11:46 AM
I'm from Miami, FL. Hey bbob do you visit dealers, or are present at GM school?
Or do you work for like a seperate divison of GM? I'm aware northstars have full floating pins, but the noise of wrist pins and the noise this car was making was different. It sounded clearly like piston noise. I mean there was carbon build up, but not enough to say that it was disrupting the travel of the piston in it's bore, the car is a good customer, showing correct service intervals and even an induction and fuel system service at 80ish miles. One thing i've heard but I'm sceptical. A guy that works with me told me that he had a car that was slow speed driven, it was then stored and developed A carbon build up issue. He said it developed a knock, and he cured it by spraying water moderately into the throttle body, and keeping the engine speed between 2500-3000. He says this cleared up the carbon and cured the noise. Is this possible? I know water can break down early stages of carbon, and seeing that it would be under pressure... will this work? The northstar is a bad a$$ engine, and it's design is race inspired, but I will always beleive it was put into the wrong vehicles, unless you have an XLR or an ALLANTE. If they put these engines in camaros or grand prix gtps, where the engine would be exercised more often we would see less complaints. I mean lets face it no 55 year old mature adult want's to hear ohh you have carbon build up? When was the last time you did some WOT runs? When was the last time you saw a deville on the hwy doing more than 80?

05-24-05, 12:45 PM
I work in product engineering... I don't visit dealers much these days although I did quite a bit in the past. We do see a lot of the field return parts, though, as GM has been requiring more and more warranty parts back from the field to determine what the actual failures were so we review those parts very regularily and review all the engine pulls where the whole engine is R&R'ed.

If the car sat around and wasn't driven a lot the oil could have gotten very acidic due to the frequent starts and stops from marshalling it around dealers lots and such. If the oil picked up a lot of contaminants (fuel and water and combustion byproducts) from all the repeated cold starts and was never driven the natural tendency is for the oil to start to become very acidic. If it wasn't changed during that time and sat in the engine for over a year it could have started to attack all the silicone beaded seals in the engine .... such as the cam cover seals, front cover seals, etc. Look inside the spark plug wells and see if some of the wells have oil in them down around the spark plug boot. That is often a sign that the seals have been exposed to acidic oil at some point that is starting to attack the seals. An occasional spark plug well might have a little oil in it but if more than one or two has it then it can be a clue that this might have happened.

It is not uncommon to see that level of carbon come out from an engine that has been babied around. It takes quite a bit of WOT operation to eliminate all of it and free the rings up. I am not sure about the SeaFoam restorative or solvent powers but the GM Top Enging Cleaner is relatively good at softening carbon like you describe....so is plain water introduced slowly thru a vacuum line at the throttle body while holding the engine at a fast idle.....

Your car is the perfect candidate for the dedicated breakin procedure that I often recommend. Warm it up good and get on the expressway or other empty road and put the trans in manual 2 gear at 45-55 MPH. WOT accel in 2 until 70 or so...then lift off and let the engine brake the car back down to 50 or so. WOT to 70/80 near redline and then lift off to decel back to 50. Do this WOT accel/heavy engine braking maneuver 12 times or so, shift to drive and drive normally to cool things off. Repeat. This is excellent for cleaning out carbon and freeing up the rings if they are stuck. It is also good for seating the rings to the ring lands. The WOT accel done frequently is good but the engine/rings also need the hard overrun condition to move the rings around and to load them against the ring lands in the opposite direction. The combination of WOT accell and the heavy decel over and over is the best way to exercise the rings, load them both ways, seat the rings to the ring lands and remove carbon all at the same time. If you really want to stack the deck, do the "deep carbon clean" procedure to soften carbon around the rings and then do this procedure several times back to back after removing the solvent and changing the oil. The hard anodizing in the upper ring lands requires some dedicated load to break in and burnish the surface for maximum sealing and all the engines that I have ever done this to have improved noticeably in oil consumption. Try it.

05-24-05, 01:11 PM
Bbob, a head gasket question. For the North*, was any consideration given to using embossed metal headgaskets like a '53 Buick V8 or a '58 Chevy 283 and let the headbolt stretch do the breathing for expansion and contraction? Would this have resulted in fastener failures or what?

05-24-05, 01:24 PM
<snip> I mean lets face it no 55 year old mature adult want's to hear ohh you have carbon build up? When was the last time you did some WOT runs? When was the last time you saw a deville on the hwy doing more than 80?

If you'd been on the AC Expressway any weekday morning for the last three years or so, you'd have seen either a Moonstone '99 Deville or a Sable '01 ETC holding 85 to 90 between exits 12 and the AC toll booth.. LOL

Might wanna watch the cracks about us "old geezers".. not everybody with a Caddy is either a would-be pimp in da hood or a sno-cone in Ft Lauderdale.. :) No offense, either.. :D

05-24-05, 01:37 PM
Bbob, yeah I noticed alot of oil down 5 and 7 on the back bank when I changed the plugs 2 weeks ago, it was down the well and around the top half of the plug threads and up on the plug itself in both instances. Should all of the seals you just mentioned need to be replaced? I'm going have my mechanic check the coil packs / compression test when it goes in tomorrow, let u know how it goes...

05-24-05, 02:31 PM
I added to the top post was busy when i first posted and cut it short by accident:bonkers:

05-25-05, 03:16 PM
Well here it goes,

So my mechanic got my caddy in and found the following:

I was down 3 quarts of coolant, misfiring cold, compression was good on all cylinders 155-170ish while cold. There was exhaust detected in the coolant.

He thinks it's possible there might be a leak somewhere on the intake which is injesting coolant (is this even possible?) but honestly doesn't know, and the only way he can explain the exhaust in coolant is a slightly leaking headgasket but can't figure out the good compression. He was going to speak with a friend who's a cadillac mechanic about it. Without major surgery I'm not going to find out and by then I may as well swap the whole thing.

So I know the intake is hard to get off of this engine but not impossible, and I could do it myself, my question is, is it worth doing? I plan on just driving it and living with it until I swap out the engine, but I would be pissed if I swapped out an engine that had a bad intake and nothing more.

05-25-05, 05:30 PM
A blown head gasket will not always affect your compression, the only true way to determine if it's the gasket, pressurize the cooling system and check for any leakage. If the system does not hold pressure, and there are not any exterior leaks visible, you can suspect a head gasket. You can also pressurize the cylinder (on TDC) and see if any of the pressure back feeds into the cooling system, thats more work however. But I don't see why you have to go ahead with a complete engine swap. Unless you have some extra money to burn, and are looking at a quicker repair, if you truley have a hg concern, taking into consideration that nothing is wrong with your heads, simply replacing the gaskets, and cleaning up your heads, refilling the system to specs with the applicable number or tablets should put you back on the road for another 150k+ trouble free miles.

05-25-05, 10:56 PM
There are no coolant passages in the intake manifold to leak coolant so the idea of the engine injesting coolant from the intake causing the problem is not possible...

Same answer as before.....leak check the chambers by applying 120 PSI shop air to each chamber and/or pressurize the cooling system and pull the plugs an spin the engine over to see if coolant gets into the chambers while the system is pressurized. Did you mention either of these tests to your mechanic..?? He needs to run those two tests.....not talk with someone else or play a guessing game.

Pressure testing a full cooling system and simply watching for pressure drop is somewhat pointless. If the system is full and coolant is leaking while the pressure is on the system so little coolant will leak thru a small leak path that it is hard to identify whether the system is loosing pressure or not. Point is that if you pump up the system and it appears to hold pressure for several hours it could still be seeping coolant into a chamber and the pressure would hold fine as only an ounce or two of coolant might leak which is not going to affect the pressure drop much at all. Pump up the system, hold it for 2 hours, pull the plugs and spin the engine to see if coolant is in a chamber. Only way to make that test work correctly.

The two tests mentioned are NOT major surgery and WILL tell you if the head gasket is failed. Why ask for help if you are not going to follow the directions given....???

It is entirely possible that a heavy dose of the coolant supplement might stem the seepage of coolant into the chamber (IF that is the problem...test per above to be sure). The supplement is useless in preventing a compression leak into the cooling system but if the only problem is coolant seeping the other way at shutdown (due to latent system pressure) then the supplement/sealer will help that condition.

05-25-05, 11:04 PM
Bbob, a head gasket question. For the North*, was any consideration given to using embossed metal headgaskets like a '53 Buick V8 or a '58 Chevy 283 and let the headbolt stretch do the breathing for expansion and contraction? Would this have resulted in fastener failures or what?

Those style of head gaskets would live about 10 minutes on a deep thermal cycling test with an all aluminum engine...LOL. They would barely seal up a cast iron engine and were awful at sealing liquids in the cooling passages.

Seriously, the next generation of head gaskets after the compacted graphite gaskets used on the Northstar is the multilayer steel head gaskets. Those are analygous to the "steel shim gaskets" of yesteryear but they have some compliance and are coated to micro seal liquids. The MLS (multi-layer steel) gaskets are used on the supercharged Northstar.

The head bolts do "breath" already with the compacted graphite gaskets. The deflection is partially in the bolts and partially in the gasket.

The MLS gaskets are definitely the way to go but they require a very smooth deck and head surface to microseal for liquids and ANY surface imperfection at all in the decks can lead to a leak. The decks have to be ground to get a smooth enough finish for MLS gaskets.

05-26-05, 07:40 AM
Bbob, those cam cover gaskets you're talking about leaking oil into the spark plug wells...I seem to have that condition.

Are those relatively easy to change out? Is that a diy job, or do I have to take it in for service?

At 132k, I'm not about to, but if it's not that big a deal, I'll do it myself for the cosmetic aspect.

05-27-05, 09:30 AM
Well excessive oil in your plug wells will ruin your wires, and cause a missfire. They are relatively easy to change, you need a puller for the water pump pulley, and remove the shaft seal. access to the rear cover, is made simpler by loosening the two front cradle bolts some, and allowing the front to drop about 3 inches. That will give you all the room in the world to work back there.

05-27-05, 12:41 PM
Hey Bbob,

sorry about not following directions, I misred the 'pressure test' as a 'compression test.' I'll get the coolant system pressure test done as soon as i can get to it, thanks again!

06-03-05, 06:46 PM
hey razeorc, i am in marietta and i have just been diagnosed with the headgasket problem in my olds aurora which has the caddy engine.

they found hydrocarbons.

do you know of a reputable caddy mechanic near here?

06-20-05, 09:40 AM

Unfortunatley not yet, I have good mechanics up here in CT, but when I'm in ATL I usually just work on my car myself with some friends of mine that are real gearheads. If I find anyone I'll keep you posted.

06-23-05, 03:28 PM
Skipping problem located:

After replacing most of the coolant system due to a split radiator, did radiator, upper & lower hoses, clamps, thermostat, (waterpump last summer) my mechanic found the source of the startup skip, turns out i've got a bad gasket leak between the intake and the block.

looks like I'm going to replace it along with the valve cover gaskets while i'm at it sometime next week.

Oh, and the leakdown test on the engine came back negative :) wahoo!

06-26-05, 01:11 PM
Raze: Thanks for getting back to us with that info...it is good to know how these things are turning out.