2001 Northstar - Head Gaskets blown or not?? I'm stumped!!
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Northstar Engines and System Technical Discussion Discussion, 2001 Northstar - Head Gaskets blown or not?? I'm stumped!! in Cadillac Engine Technical Discussion; Hi gents...I purchased 2001 Eldorado that was diagnosed by Caddy dealship to have blown HG's. I've done a bettery of ...
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    hms200 is offline Cadillac Owners Member
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    2001 Northstar - Head Gaskets blown or not?? I'm stumped!!

    Hi gents...I purchased 2001 Eldorado that was diagnosed by Caddy dealship to have blown HG's. I've done a bettery of tests before breaking into the engine attempting to validate the blown HG's...but no definitive evidence yet...HELP!!

    What I think I know:
    1. Definitely overheating
    2. Excessive back pressure boils coolant from tank
    3. Upper & Lower hoses hot and under pressure
    4. Water Pump does NOT leak
    5. Conducted block test (blue chemical test) multiple times correctly using reliable test ket - zero evidence of exhaust in coolant (tested 4 times)
    6. No exhaust smell in coolant tank that I can detect
    7. Zero white smoke from tailpipe
    8. No water from tailpipe once it reaches normal operating temp (after initial condensation is gone)
    9. No funky coolant smell in exhaust
    10. Conducted compression test - "wet test" results as follows (dry tests were a bit lower but equally consistant):

    Front Bank (Left to Right)
    183 - 192 -191 - 180

    Back Bank (Left to Right)
    184 - 196 - 189 - 205

    Ok...so unless somebody spots anything I'm missing, I'm not getting definitive evidence of blown HG's at this stage. Compression appears good (I think?), within reasonable spec and all cylinders within spec range of each other (within 10%)...yes? As I understand it, the Northstar CAN pass compression test but still have blown HG's due to nature of high compression engine under normal operating condition/load. Right? But other tests don't give me evidence either...so I'm reslly stumped!!

    What are the odds that I have radiator blockage or a failed thermostat rather than blown HG's? Odds seem slim to me from all I've read about widespead failure of head bolts, but evidence sure is pointing away from HG's with all I see so far.

    So all you really smart gents please chime in with your thoughts, questions, ideas.

    Many thanks - Howard

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    hms200 is offline Cadillac Owners Member
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    Re: 2001 Northstar - Head Gaskets blown or not?? I'm stumped!!

    I should also add to the "What I do know" section...

    I've also confirmed there is NO WATER in the oil and all spark plugs were clean; looked completely normal. There was no evidence on the plugs of burning or blowing any coolant. - Howard

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    Ranger's Avatar
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    Re: 2001 Northstar - Head Gaskets blown or not?? I'm stumped!!

    A compression test won't tell you anything regarding a head gasket. A leak down test is what you need. Northstars won't put coolant in the oil so forget that as an indicator. How about the purge line? Have you verified that it is open and flows coolant? A radiator blockage or a failed thermostat is not common, but worth checking out. The multiple negative block tests are confusing. I wonder how the dealer diagnosed it?

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    hms200 is offline Cadillac Owners Member
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    Re: 2001 Northstar - Head Gaskets blown or not?? I'm stumped!!

    Thx for your reply Ranger...

    Yes, I read much data indicating that compression test isn't proof if it passes, but can at times prove things if it fails. Also plug condition is suppose to be a good potential indicator, but as I said, they were all very clean.

    I'm confused as well on block test giving me no positive results. That's suppose to be one of the most sure tests of blown HG's, and especially given the degree of back pressure or boiling that happens in very short order. I have no clue how dealership diagnosed it. They performed that diagnosis for prior owner, whereby he then sold me the car after getting the grim news and quote for the HG repair.

    I have no further test gear at my disposal, so a leak down test (is that pressure testing the cooling system?) I'm not able to perform.

    I know nothing about the purge line sir...where it is, what to look for and where a blockage might be in the line. I'll try researching that and if you can provide more info I'd greatly appreciate it. It goes from where to where and how best to confirm blockage and clear if present?

    I agree that radiator/thermostat are both stretches...seldom the cause if neither are leaking or in obvious poor condition. That's why I'm hesitating before running out to get replacement parts for either. Both seem to be first things many shops change out on their way to determining HG's and I don't want to follow that same monkey trail blindly without more evidence. But, I also don't want to simply dive into the engine on just the unqualified word of a prior dealership diagnosis without securing some reasonable supporting evidence of my own.

    More info...

    I can make the engine overheat very quickly and easily with it simply sitting in my garage. With coolant level topped off I simply have to rev the engine up/down to ~2500 rpm's for maybe 5 minutes and then temp will start clocking past mid point. I've read where many folks can drive-drive-drive without overheating so long as they avoid grades and severe speeds. For how fast mine heats up I would have expected major/clear results from troubleshooting...but nope. The cooling fans DO work as they should by the way.

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    Re: 2001 Northstar - Head Gaskets blown or not?? I'm stumped!!

    also, w/ a blown HG you'll be losing coolant so if the system isn't losing any coolant there's reason to believe that something else is going on.... that said, if it continues to overheat then there's a good chance that the HG's will blow... the hotter the block gets the more likely those head bolts will pull out of the block
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    hms200 is offline Cadillac Owners Member
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    Re: 2001 Northstar - Head Gaskets blown or not?? I'm stumped!!

    Thanks Rippy...

    I'm not driving vehicle at all since purchase from gentleman that received the grim news from dealership. It's garaged with hood up and me sitting in engine compartment trying to figure out this mystery.

    As for losing coolant...that is happening, but only as a direct result of boil over from the tank. It overflows from tube and I can hear/feel the boiling when that happening. With cap off then it simply surges up and over like an angry volcano. No leaks anywhere else in the cooling system. - HMS

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    Re: 2001 Northstar - Head Gaskets blown or not?? I'm stumped!!

    Bad pressure cap, stuck or missing thermostat, and a plugged purge line are all possibilities. Usually bad HG's cause little pressure on the top hose.

    On initial HG failure the block test can be "iffy" as there is usually some pressure on the gaskets but yours sounds like it should be giving a positive indication.

    I would usually advise someone to do the block test before too much else (only the 3 things I listed) but in your case it might be worth flushing the radiator, possibly a lot of stop leak has been added.

    Since you said the WP is not leaking I assume the belt is good?.?.

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    Re: 2001 Northstar - Head Gaskets blown or not?? I'm stumped!!

    yeah, that ^^^^ W/P belt/tensioner/pulley is suspect. On the driver's end of the front intake cam.

    The constant bleed purge line runs from a hollow bolt/nipple at the rear of the thermostat housing and goes to a nipple on the top side of the coolant reservoir. That hollow bolt is one of the clog culprits - a proper sized drill and care is what it takes.......coolant should constantly flow into the top side of the reservoir - remove the line, hold it in the open filler neck, have an assistant start the engine, and it should show a steady stream.

    Fans go to slow at 224 and fast at 236, and they run all the time in slow if any A/C mode is called for.

    Open these and study them...............

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    hms200 is offline Cadillac Owners Member
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    Re: 2001 Northstar - Head Gaskets blown or not?? I'm stumped!!

    Thx Zonie...

    Just confirmed no blockage in purge tube.

    Yes, water pump belt is fine.

    The block test was very first troubleshooting I performed. Expected to get immediate positive results, but I was surprised...thus my reason for repeating four times...I simply couldn't believe it.

    Cap I never considered...but you raise a good point to confirm. Seems my next step, though I had hoped to get more definitive proof of yes/no before doing so, is to replace radiator core and thermostat so as to rule them out completely. I simply can't make myself avoid that step before tearing down engine without rock solid evidence of blown HG's...which I don't have yet. A professional radiator flush (so there can be zero doubt there) may cost same as a new aftermarket radiator core...plus same effort to pull it and reinstall for the boil out flush. I wouldn't trust the in-car flush results at this stage given the ramifications...simply not definitive if it still overheats after the flush. Did I really completely rule out radiator blockage...100% doubt removed...did the in-car flush really do the job?

    Here are other details I also must consider and ask you all to maybe also ponder as well...

    The dealership (SAME one that diagnosed the blown HG's to prior owner) rebuilt the lower engine ONLY 15.000 miles ago...I have the prior owners receipt and the dealer service record. The engine was rebuilt for piston slap, so most everything in lower engine was replaced...all new pistons, verious gaskets and any/all wear items associated with such a repair...a very long list. So...heads WERE pulled, but there was no indication in records of a head job having been performed and I saw nothing about head bolt thread repairs being performed. Did Mr Goodwrench fix the threads or simply bolt the heads back on? Who knows! Only way to prove that one way or the other is to pull um. So this service history can be a negative to support blown gaskets...or a positive to suggest strongly toward an alternate cause for overheating. Honestly it seems very suspect that there is this overheating so soon after a major engine overhaul given the very rich history of head bolt problem. I deep down believe the dude flubbed the job...failed to fix the threads...but hey, who knows. If so, then it lasted long enough to clear their warranty period...but isn't that always the case with shoddy dealership repairs?

    So...I'm still scratching my head gentlemen...what to do next.

    Howard

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    hms200 is offline Cadillac Owners Member
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    Re: 2001 Northstar - Head Gaskets blown or not?? I'm stumped!!

    Quote Originally Posted by submariner409 View Post
    yeah, that ^^^^ W/P belt/tensioner/pulley is suspect. On the driver's end of the front intake cam.

    The constant bleed purge line runs from a hollow bolt/nipple at the rear of the thermostat housing and goes to a nipple on the top side of the coolant reservoir. That hollow bolt is one of the clog culprits - a proper sized drill and care is what it takes.......coolant should constantly flow into the top side of the reservoir - remove the line, hold it in the open filler neck, have an assistant start the engine, and it should show a steady stream.

    Fans go to slow at 224 and fast at 236, and they run all the time in slow if any A/C mode is called for.

    Open these and study them...............
    ++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++++++

    Thx Submariner...

    So if WP belt is turning nicely, with no noise and no indication whatsoever of wear then the idler pully is fine? I would expect idler pully to scream, rattle or make some sort of noise if it's bad...and also wouldn't it be doing nasty things to the WP belt?

    Howard

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    hms200 is offline Cadillac Owners Member
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    Re: 2001 Northstar - Head Gaskets blown or not?? I'm stumped!!

    Quote Originally Posted by submariner409 View Post
    yeah, that ^^^^ W/P belt/tensioner/pulley is suspect. On the driver's end of the front intake cam.

    The constant bleed purge line runs from a hollow bolt/nipple at the rear of the thermostat housing and goes to a nipple on the top side of the coolant reservoir. That hollow bolt is one of the clog culprits - a proper sized drill and care is what it takes.......coolant should constantly flow into the top side of the reservoir - remove the line, hold it in the open filler neck, have an assistant start the engine, and it should show a steady stream.

    Fans go to slow at 224 and fast at 236, and they run all the time in slow if any A/C mode is called for.

    Open these and study them...............
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~

    So...I "think" I know what one would expect from a suspect/failed idler and/or tensioner pully...but maybe not? Might there be issues other than what I noted in my prior supply if the pully has gone or is going bad that could be to such extreme as to cause overheating? I would think that what you guys are describing would be a condition to have either busted the belt, seized it altogether or significantly slowed it down whereby WP wouldn't be functioning properly, yes? Wouldn't I notice that in some way...squealing, smoking, burning...something? The belt is there, appears in fine condition and appears to be turning cleanly as it should...no unusual noise whatsoever.

    So...on to 1) cap pressure validation, 2) thermostat replacement, 3) radiator core replacement...in that order? Any better ideas from anybody?

    Thx

    Howard

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    Re: 2001 Northstar - Head Gaskets blown or not?? I'm stumped!!

    I saw your post over at caddyinfo, but figured I'd respond here rather than duplicate it.

    A leak down test is when you pull all the plugs and get each cylinder up to TDC compression stroke and pressurize it with shop air one at a time and let it set. If it has a leaky HG in that cylinder, pressure will drop and bubbles will eventually work their way to the surge tank.

    The block test IS confusing. IF you did it shortly after adding coolant, it can give you a false negative. Is it possible that the fluid was old and unresponsive (not even sure if that is possible). I assume that you are only filling the surge tank half full and not to the top? That WILL cause it to overflow as the coolant heats and expands.

    If the dealer did insert all 20 bolt holes as they should any time the heads are removed it would show it on the bill. That is insurance even if the threads are OK. They are in fact only aluminum and have been known to fail later after a removal and retorquing. Sometimes while retorquing and sometimes later down the road.

    Before replacing any parts, the cap and thermostat can be checked and the radiator can be flushed, though I doubt the radiator is the problem unless as mentioned the previous owner dumped some stop leak in it.

    I can make the engine overheat very quickly and easily with it simply sitting in my garage. With coolant level topped off I simply have to rev the engine up/down to ~2500 rpm's for maybe 5 minutes and then temp will start clocking past mid point.
    5 minutes is probably long enough to reach normal operating temperature and with an uncapped system the coolant (50/50 mix) will boil at about 224 degrees so I'm not sure that is a good indication. If the system is capped and sealed, that's another story.

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    hms200 is offline Cadillac Owners Member
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    Re: 2001 Northstar - Head Gaskets blown or not?? I'm stumped!!

    Thx Ranger...

    I performed the block test properly and with good chemicals...it's a industry leading tester. Coolant wasn't just added, though it was new...added it and circulated thru the block before weather got cold since car is/was just sitting. Did the test with tank 1/2 full yes. though at one point it did boil up on me to where I sucked up coolant into the tester and contaminated that specific test.

    Thx for info on leak down test. If I take things that far then I'll have to have a shop do it since I don't have the gear necessary for such a test.

    I purchased the cap and stat tonight so I'll give them a shot. As much as I hate to, I'll most likely replace the radiator if cap/stat doesn't fix the issue before I take extreme step of diving into the engine. All things in perspective, replacing radiator is a low cost elimination since I can never be sure what prior owner may have done. At least then I will know for certain, and hey...I'll have a nice new radiator either way.

    I'm trying now to find the shop bill for the rebuild to see what all I can spot. I reviewed in when I first purchased the car a few months ago, but I've since gotten a cram education so I should have much more insight on what to look for within the documentation.

    So let me ask you...BBF didn't like my premature question.

    Any idea if I can make the head bolt thread repairs with engine in car? I simply don't have facilities to pull or drop the engine is why I ask. Do you know how to tilt the engine forward? Norm said that's what I'd have to do for rear bank access, along with a 1/2" right angle drill, which I have.

    Thx again...

    HMS

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    Re: 2001 Northstar - Head Gaskets blown or not?? I'm stumped!!

    My car passed the block test. It is, in my opinion not that definitive of a test..My 2000 deville was acting weird for over a year before the headgaskets finally went completely..It would randomly overheat on some days..and then some days in the summer with 90 degree + days it would be fine.. I did it all, new radiator, new thermostat, new water pump, new surge tank..took off the purge line and hollow bolt..cleaned them thoroughly.. even when the gaskets were at their worst..when the car would overheat just idling..the car past the block test...thanks to Jake my car is running cool again..

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    Re: 2001 Northstar - Head Gaskets blown or not?? I'm stumped!!

    Thank you postman 2000.

    These cars don't show definitive symptoms or clear cut symptoms showing "yes", it's the gaskets. As Postman stated his acted up over a year before it finally said enough.

    I know to a lot of new comers to the northstar scene, you don't want to "think" the worst of your engine. Yet, it has been well documented that these headgaskets have no particular point when they fail. Some sooner, some later.

    Of course, you check the simple things first, yet in the grande scheme of things, what's the worst thing that's going to happen? You have to do headgaskets? If you are aware of the worst case scenario and can live with that, then don't beat yourself up. Fix it and be happy.

    The car I lucked up on went through the same thing. New radiator, water pump, thermostat etc. Just fewer things I have to replace, but in the end who knows. I may change all of that out to have peace of mind. Once I fix it, I don't plan on touching it again.

    My studs are on the way......

    Good luck with your repair, whichever route you go.

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