: Front Valvetrain Clacking



Jkush
01-23-08, 12:58 AM
Hey everyone,

About 6 months ago I bought a 94 Seville STS for a bargain price of $2500. Car came with complete maintenance history from when the car rolled off the lot.
About a week ago I was running some errands and had turned it off for about 15 minutes while at the store. When starting it up again I noticed a fairly loud tapping/clacking noise had started coming from the engine compartment. Taking it home immediately the sound had progressed from a tap here and there to a tap almost full time. :banghead:
I don't drive the car as result and am getting it towed to my mechanic soon but was wondering if anyone has experienced this problem.
The sound is there at all RPM's and will disappear for about 5 seconds every now and then at idle. It is most definitely coming from inside the front valve cover.
The plugs are not fouled, the engine runs perfect with no misfiring, and no trouble codes present. Ran marvel mystery, seafoam, and brand new oil change resulting in no difference to the noise. 111,000 miles on clock.
Not much experience with DOHC motors but wondering if it is possible to be a broken valve spring or retainer.

Thank you in advance.

Crown Vic Owner
01-23-08, 01:58 AM
Sure its from the valvetrain?

Sure its not piston slap?

AJxtcman
01-23-08, 07:30 AM
Hey everyone,

About 6 months ago I bought a 94 Seville STS for a bargain price of $2500. Car came with complete maintenance history from when the car rolled off the lot.
About a week ago I was running some errands and had turned it off for about 15 minutes while at the store. When starting it up again I noticed a fairly loud tapping/clacking noise had started coming from the engine compartment. Taking it home immediately the sound had progressed from a tap here and there to a tap almost full time. :banghead:
I don't drive the car as result and am getting it towed to my mechanic soon but was wondering if anyone has experienced this problem.
The sound is there at all RPM's and will disappear for about 5 seconds every now and then at idle. It is most definitely coming from inside the front valve cover.
The plugs are not fouled, the engine runs perfect with no misfiring, and no trouble codes present. Ran marvel mystery, seafoam, and brand new oil change resulting in no difference to the noise. 111,000 miles on clock.
Not much experience with DOHC motors but wondering if it is possible to be a broken valve spring or retainer.

Thank you in advance.
I would guess the the exaust cam is bad. I have only seen 80% of the cams bad on the engine that I have had the valve covers off of. (Usually for head gasket)



Sure its from the valvetrain?

Sure its not piston slap?
That is funny. :cookoo: Wrong year

tateos
01-23-08, 01:18 PM
I would guess the the exaust cam is bad. I have only seen 80% of the cams bad on the engine that I have had the valve covers off of. (Usually for head gasket)


AJ - what do you mean by that? 80% of engines you have disassembled have bad cams?

I am getting ready to re-install my heads and the cams look OK to me...I think. The highest lift part of the lobes are very shiny and polished (the lifters are very shiny also) - the rest of the lobes are dull and seem to show the original machining marks. There are no score marks or pitting. Does that sound OK?

Ranger
01-23-08, 02:11 PM
Read and try this. See if it helps.
http://www.cadillacforums.com/cadillac-tech.html#full

AJxtcman
01-23-08, 03:18 PM
I would guess the the exaust cam is bad. I have only seen 80% of the cams bad on the engine that I have had the valve covers off of. (Usually for head gasket)


AJ - what do you mean by that? 80% of engines you have disassembled have bad cams?

I am getting ready to re-install my heads and the cams look OK to me...I think. The highest lift part of the lobes are very shiny and polished (the lifters are very shiny also) - the rest of the lobes are dull and seem to show the original machining marks. There are no score marks or pitting. Does that sound OK?

Don't look at the cam.
All these are bad

http://i224.photobucket.com/albums/dd25/AJxtcman/Northstar/Northstarlifter11.jpg
http://i224.photobucket.com/albums/dd25/AJxtcman/Northstar/Northstarlifter21.jpg
http://i224.photobucket.com/albums/dd25/AJxtcman/Northstar/Northstarlifter31.jpg
http://i224.photobucket.com/albums/dd25/AJxtcman/Northstar/Northstarlifer41.jpg

JC316
01-23-08, 03:20 PM
Are you sure that it's in the engine, and not something like the idler pulley, or belt tensioner? I wouldn't suspect the engine, I would look at the easy stuff first.

Jkush
01-23-08, 03:52 PM
Sorry, forgot to mention that I had pulled the serpentine belt to try and rule out anything on the pulley system but it was not the case.
In owning the car I have always taken her out for WOT now and then, changed the oil on time running Mobil-1 10W-30 and Delco filters, and Always ran 93 octane. It is time for new exhaust and was planning on that next month. I know how to take care of it but just have less experience with working on DOHC's. My first car when I turned 16 was an 86' SDV and it is still kicking on original factory HT4100 from when it was my fathers brand new. As a result of this little dilemma, I am driving it again with over 350k miles on it. Internal engine problems were never a problem to me until now which is why I'm seeking guidance from you who have more knowledge on this motor than myself. :D
The noise usually gets louder once the car gets up to temp, and is much louder once the oil fill cap is off.
As for it being piston slap I'm almost certain it isn't unless in the worst case scenario a rod bearing turned causing the piston to come back up with sufficient force, but even then wouldn't it be a full time sound?
It sounds like tapping on thin metal (possibly valve cover). When holding a screwdriver to my ear anywhere around the engine, the sound seems to be coming from the front valve cover and the cover also is the only place where you can feel the tapping with your hand.
I'll pull the valve cover and take a look at the buckets and the cam and check them to see if they are damaged or worn and update you further.

Ranger
01-23-08, 05:31 PM
Don't forget that you will have to remove the water pump drive pulley to get the cam cover off.

tateos
01-23-08, 07:59 PM
Thanks For The Pics Aj!

Jkush
01-26-08, 04:14 PM
Ok so I got the chance to take a peek last night, and I found that one of the exhaust valves on #6 has a weak spring. I could push it in easily with a screwdriver. But what I am wondering is can the one spring just simply be replaced? Or am I looking a pricey job to replace them all, or even a entire valve job?
The car sat dormant and covered for three years in the guys garage before I bought it, which can't be good for the springs can it?

AJxtcman
01-26-08, 04:29 PM
Ok, well pulled the cover last night, and I found that an exhaust valve spring is very weak. Can press it down with a screwdriver. Is it possible to just fix the one spring? Or do I have to have a whole valve job done?

Yes
how did the lifters look?

Jkush
03-12-08, 12:31 AM
Well I know its been some time since my last post but I thought I'd update you on the situation.
After pulling the engine and rooting through the mess we found a worn crank, connecting rod bearing gone, and piston damage.
I guess the piston was slapping the head after all Crown Vic.
Anyway, I figure its not worth rebuilding this heap, but seeing as the car itself is still mint, I'll start a search for a used motor from a wrecker and just sell the vehicle seeing as market value is around $6500 for one of these cars here.
But I have a couple questions...
Firstly, I've been finding that LD8's seem to be more abundant than L37's and I am wondering what would have to be done to the car if we dropped one in?
I'm going to guess the PCM will need to be changed out, but anything else?
Secondly, how much should I typically be paying for a used 93-95 Northstar? I know the 95 is slightly different but I have been reading that people have had no problems dropping them into 94's in most cases.

Any input at all would be great.

Jkush
03-12-08, 12:54 AM
I forgot to add that the front cam sprocket is badly worn on the front head, lifters were in fair condition, but found 3 weak valve springs out of 32.
My mechanic was stunned that the car was still able to run in the condition it was in and with all the iron filings that were accumulated in the sump.
I guess these cars have a hard time dying even when on their last legs.

chubbyranger
03-12-08, 07:41 AM
This search is usually pretty good for yards:

www.car-part.com

and I think there's come interchange discussion here:

http://www.cadillacforums.com/forums/northstar-performance-technical-discussion/122168-gm-now-offers-premium-remanufactured-4-a.html

Jkush
03-13-08, 03:30 PM
Thanks for the info, it was a tremendous help!
Found an engine with 78,000 miles for $700.
Apparently it has performance cams installed which is a bonus along with the 1 year warranty.
Anybody know if my car needs a modded PCM for these cams though? From my knowledge I don't think I do but the guy who sold me it seems to think so, and its kind of got me wondering now.

tateos
03-13-08, 05:59 PM
If it were me, I would do the head gaskets, rear main seal, and oil pan gasket now, on an engine that is 10+ years old with 78,000 miles. Will also give you a chance to clean out carbon in the combustion chambers and change the leak prone coolant crossover gaskets and the intake manifold gaskets.

I say this because I replaced my original N* engine due to blown HG around 2 years ago with a used engine. The used engine was perfect at first, but eventually leaked oil (1 year) and blew the HG (2 years - 23K miles). This time, I made the repairs rather than replace, and so far, so good

Jkush
03-14-08, 03:26 AM
You present a valid point, I didn't want to let this car slip away but for the amount of money I saved on this engine already, the extra few bills doesn't seem too bad now for the security of a sound engine. I guess I'll keep it.
Luckily, my mechanic is a good friend of the family and lets me participate in these adventures. Saves me a few hours in paying his labor, and I learn a little too. Looks like Ill be keeping this car around after all.

tateos
03-14-08, 02:44 PM
I keep fixing mine - I could afford to buy a new one, but I really like the car and they don't make them anymore. Maybe I will test drive a CTS coupe when they come out