: 2001 DTS valvetrain noise after HG job?!



97EldoCoupe
12-13-08, 01:19 PM
OK- car number 45 or 46 came back to me, first one ever because of a valvetrain noise (lifter noise) at cold, completely gone at operating temp. The HG's are now perfectly fine.

When it left my shop it had absolutely no noise at all. I test drove it and gave it a few shots of WOT to test my work, no issues at all. Delivered it back to the owner and drove it into his driveway, no problems. The owner had it emission tested in the next couple of days (here in Ontario they run the cars on a dyno) and it was after this that the noises started.

I want to keep my reputation for good work on the Northstars. I have the car back in my shop now and have verified the noise is there when cold, disappears at operating temp. I gave it fresh oil (5w30) and a filter before the car left my shop the first time. I did this again just in case there was a problem with the filter or the wrong viscosity oil was packaged in a 5w30 container. Still the valve rattle.

Removed the rear cam cover (since I could see through the oil cap in the front) to ensure the chains are tight and oil is circulating. Oil is circulating very well and the engine is clean.

I ALWAYS double check EVERYTHING- that all tensioners are tight, all bolts are tight, everything. This is the first time I've had this problem. I never removed the cams or valves, anything when I did the HGs. It's all back together as it was with new HGs now. I never removed the oil pump either, or the filter mount.

Any ideas from other members? I'm thinking lack of oil to the valvetrain when cold. That's all I can think of, like oil is bypassing somewhere but eventually the noise disappears totally.

Either way I'll do everything I can to get this straightened out for the owner. I have a second set of heads for a 2001 L37 engine if I need to use them but I'd like to know what's going on.

I never trust e-test guys- a local shop near me over-revved one owner's car and blew the engine. But it could just as well be something I missed.

I'm about to pull the engine out again but if someone can suggest something before I do, that would be terrific!

Ranger
12-13-08, 01:45 PM
Someone had a problem like this a while back (within a year I think). As rare as it is, I think it was a cam or lifter problem or something like that. Wish I could be of more help. You might find it with a little searching.

EDIT:
The more I think about this I seem to recall the problem was that someone tried to seal a halfcase leak with RTV and used too much. It oozed out and clogged the oil pickup. That however does not sound like your problem. His noise was constant as I recall.

STSj90
12-13-08, 02:02 PM
could it be excessive carbon build up?? Dont know what carbon knock or tap sounds like..(NEVER HAD A PROB WITH IT...I WOT alot:D) But could that be it??? Cause ive heard that it will do it only at cold..

I dont think its your fault.......

97EldoCoupe
12-13-08, 02:02 PM
Thanks Ranger. I believe I'll be pulling the engine out again but I need to get to the root cause before I re-install the engine for the second time. If the oil gallery was plugged somewhere it would make sense- I'm always super careful to make sure oil passages stay clean during the whole process. I removed one camshaft bearing cap (technically it is the bearing itself) and turned the engine over with the starter, oil shot right out. Theres no shortage of pressure at the cams, or at least that one. When the engine is warm there is no noise whatsoever other than the normal fuel injector noise.

97EldoCoupe
12-13-08, 02:04 PM
I cleaned the pistons and valves/combustion chambers and removed all visible carbon.

I don't think it is my fault either, but in case it is, I'll do what I can to correct the condition. I want to keep a good rep with N* owners- this is the only one to run differently (noisy) after it leaves my shop and that's one too many for my liking.

97EldoCoupe
12-13-08, 02:06 PM
Actually it had NO NOISE when it left my shop - this came of 90 miles later....

Ranger
12-13-08, 02:12 PM
Weird. Please let us know what you find. Curious minds want to know.

STSj90
12-13-08, 02:12 PM
I cleaned the pistons and valves/combustion chambers and removed all visible carbon.

I don't think it is my fault either, but in case it is, I'll do what I can to correct the condition. I want to keep a good rep with N* owners- this is the only one to run differently (noisy) after it leaves my shop and that's one too many for my liking.

I didnt think about that lol....I knew you cleaned stuff pretty darn good before reassembly..(Seen some pics of piston tops you cleaned....Damn good cleaning job!) I dont see why in hell there would be a noise unless someone did somthing to there car without them knowing... Well, i guess its obviously not carbon build up.


:cool:Good luck man

Submariner409
12-13-08, 02:20 PM
This is a 2001 DTS.......which means it has the new roller cam follower setup. The lash on those is loaded by the static hydraulic adjuster which is fed by the small D-shaped oil gallery running the length of the cam. Is there any chance that the runup/run down on the emissions dyno sent a chip or piece of sealant or gasket into the oil feed from the block to the head ? That could affect either one or both cams valve lash.

97EldoCoupe
12-13-08, 02:21 PM
Thanks. I guess this is a bad thing for my reputation, first car in almost 50 to come back. Until now it was 0! The head gaskets are still great- no issues there. I'm out of 4.6 HGs, waiting on another shipment but in the mean time I might as well pull the engine and see what the hell went wrong. I've got another 10 cars on the list for HG repairs- and a few owners who are patiently waiting to get their cars. Warranty work gets first priority so they'll just have to wait another day or two. The owner needs his car back.

97EldoCoupe
12-13-08, 02:24 PM
Sub I thought about that- and that's the only thing I can think of right now. I am so VERY careful with the aluminum machine work- everything gets taped up, all holes sealed, timing cover re-installed to do the machine work. No RTV is used around the oil passages unless doing the lower seals and the owner didn't want the lower seals done. But you may be on the right trail. Looks like she's coming out again for diagnosis. I will kick myself if I screwed up somewhere.

97EldoCoupe
12-13-08, 07:07 PM
I think I've got it figured out - before pulling the engine I decided to hot-wire the starter and remove the cam covers. All lifters are being well oiled. I noticed the left bank chain is slightly loose. The right bank is tightened as it should be. The hydraulic chain tensioner is not working on the left bank. Either the tensioner gave up or there's no oil pressure behind it.

When I re-installed the engine, I primed the oil system, and then it started up and had no valve knocks at all. The car worked fine (no noise) until a day or two later then developed this noise. Could the tensioner have collapsed in that short of a time?

This tempts me to replace each tensioner on every engine I work on.... but then something else would probably fail.

I'll change the tensioner and then go from there.

97EldoCoupe
12-13-08, 07:30 PM
I spoke with the owner of the car and he gave me the go-ahead to order and install 3 new chain tensioners. This should solve the problem. The chains seem to be in good condition still and the guides as well. I just figure that if I'm going through the work of replacing one, I'll do all three. I'd be damned if I replaced only one and then the right bank tensioner would give up a week later.

68Futura
01-04-09, 12:12 AM
Did that valve noise job work out? was it a bad tensioner? I have a similar problem with my 98 sls, although I figure its something different. I have it stored in my garage for the winter, but like to start it every couple of weeks. I dont know if its necessary, but It gives me peace of mind.
I start it and let it run for 10 or 15 min, then give it a little throttle now and then. But last week, AFTER it was warmed up, I started hearing a distinct knocking under the rear valve cover. At idol its a slow knock, about the frequency of a valve opening and closing. I turned off and restarted the engine, and it was quiet till I gave it a little throttle, I'm talking probably 30-40%. Any thoughts? At first I thought piston slap from carbon build-up, but they say thats only when its cold...

97EldoCoupe
01-04-09, 12:43 AM
It was a bit of a mistake on my part. The chain tensioner shoe (the curved one) was too tight for the tensioner to adjust chain tension. The one bolt that holds it is supposed to tighten up against the head and allow the shoe to move freely, and the shoe was too tight.

I always check them for free movement when I install them. Occasionally I have to file the shoe down to allow free movement.

But here's my mistake- I always double check torque on all of the bolts after the timing is set and before I install the timing cover. I probably gave it just a slight turn to the correct torque and installed the cover.

So I used a thin metal shim and shimmed the bolt to allow free movement. cranked the engine with the cam covers off, and the chain tightened as it should.

I will never make that mistake again. I corrected my mistake immediately when the owner informed me of the valvetrain noise and apologized for the inconvenience. That should never have happened.

But... That wasn't the cause of the knock, or at least not all. The valves still made noise, as if the lifters weren't pressurized. The noise disappeared when the engine warmed up, and after a few test runs almost completely disappeared even when cold. I asked the owner to drive it for a week and let me know if it works itself out. It did, within a few days. My guess is there was just an air pocket in the oil system around the lifters.

Lesson learned about the tensioner shoe. I'm so careful to make sure all the bolts are all correctly torqued. To my list of "last checks before installing the timing cover", I've added "make damn sure those tensioner shoes are moving freely, one last time...".

AJxtcman
01-04-09, 08:23 AM
I think I've got it figured out - before pulling the engine I decided to hot-wire the starter and remove the cam covers. All lifters are being well oiled. I noticed the left bank chain is slightly loose. The right bank is tightened as it should be. The hydraulic chain tensioner is not working on the left bank. Either the tensioner gave up or there's no oil pressure behind it.

When I re-installed the engine, I primed the oil system, and then it started up and had no valve knocks at all. The car worked fine (no noise) until a day or two later then developed this noise. Could the tensioner have collapsed in that short of a time?

This tempts me to replace each tensioner on every engine I work on.... but then something else would probably fail.

I'll change the tensioner and then go from there.


It was a bit of a mistake on my part. The chain tensioner shoe (the curved one) was too tight for the tensioner to adjust chain tension. The one bolt that holds it is supposed to tighten up against the head and allow the shoe to move freely, and the shoe was too tight.

I always check them for free movement when I install them. Occasionally I have to file the shoe down to allow free movement.

But here's my mistake- I always double check torque on all of the bolts after the timing is set and before I install the timing cover. I probably gave it just a slight turn to the correct torque and installed the cover.

So I used a thin metal shim and shimmed the bolt to allow free movement. cranked the engine with the cam covers off, and the chain tightened as it should.

I will never make that mistake again. I corrected my mistake immediately when the owner informed me of the valvetrain noise and apologized for the inconvenience. That should never have happened.

But... That wasn't the cause of the knock, or at least not all. The valves still made noise, as if the lifters weren't pressurized. The noise disappeared when the engine warmed up, and after a few test runs almost completely disappeared even when cold. I asked the owner to drive it for a week and let me know if it works itself out. It did, within a few days. My guess is there was just an air pocket in the oil system around the lifters.

Lesson learned about the tensioner shoe. I'm so careful to make sure all the bolts are all correctly torqued. To my list of "last checks before installing the timing cover", I've added "make damn sure those tensioner shoes are moving freely, one last time...".

Give ma a call if it comes back. I will clue you in. Does it sound like #7?

97EldoCoupe
01-04-09, 09:50 AM
Actually it sounded like it was on the left bank but the sound can fool ya. Clue me in AJ - I've done a few cars '00-'01 and only had that issue with one of them. All I can figure is the lifters had to bleed the air out. So far the owner says the car is doing great, and he's still very happy with the work. He has a '96 Fleetwood Brougham sitting in his garage as well...