: Puzzling Clattering Noise During Warm Startups



Paul2020
04-29-14, 08:16 PM
This is on a 2002 Deville. It runs good and quiet except during a warm restart. When I have the engine warmed up, then shut it off, wait six minutes and start it up again it makes quite a loud racket for a few seconds and then runs quiet again.

The noise is like a clattering mixed with a knocking. The clattering sometimes will stop while the knock continues a little longer. Usually the whole thing is over in between five and 30 seconds. The clattering part is usually only about five seconds or less.

In addition to this, to complicate it somewhat, I've had a tappet (valve follower) noise - a clicking noise that lasted a lot longer. That tappet noise is now pretty well cured. I put some Rislone in it and it has quieted down substantially.

After adding the Rislone and with the clattering still continuing, I got to thinking that maybe it was caused by dry starts. I did another oil change and put Lucas in the crankcase instead of Rislone. When I did this, the tappet clicking noise got worse and the clattering still continued so I switched it back to the oil/Rislone combination.

Then I read about air cavitation noises in the water power steering pump. I worked with that some but found the noise was not coming from the pump. I put a long screwdriver up to my ear and touched the pump and touched near the valvetrain area and it was definitely not the power steering pump; quite pronounced on both banks as far as I could tell.

It really sounds kind of like a rattling detonation noise. With that in mind I ran the tank down to almost nothing and added 93 octane last night. It was the Shell premium that has the cleaners in it. It has made no difference in the clattering though. Maybe I need to give it a little longer.

I was reading another thread here on carbon rap and that made me wonder a little bit about the knocking noise I'm hearing (distinguished from the clattering). The knocking noise lasts longer than the clattering, but then goes away (I think it stops when the oil pressure builds up).

http://www.cadillacforums.com/forums/northstar-engines-system-technical-discussion/11297-does-northstar-have-lifters-how-replace-2.html

A while back I pulled the intake manifold and the valves did have a coating of carbon on them. It didn't seem to be excessive or very thick but it was there.

Today, since putting the higher octane in I noticed something else unusual. It sounded like sleet (or small bb's) hitting a window. Sort of a crackling sound. It seemed to be coming from the intake throttle-body area. I wonder if the cleaner could be breaking up particles of carbon or something. I don't know where that much carbon would be coming from if that's what it is.

Another idea might be a broken spring. What do you think?

I have not noticed any metal in the drained oil. I did not cut the filter in two yet.

I have not totally isolated the sound source yet. I suppose it could be coming from the oil pump, but it sure sounds like it is coming from the top.

So I've ruled out power steering pump and I'm thinking maybe one of these:

Broken or overly weak valve spring(s)
Something else in the valvetrain
Detonating.
Oil Pump
Carbon related noises

Any ideas?

Thanks!

basscatt
04-29-14, 09:22 PM
:bonkers::shocked::wacky:

Ranger
04-29-14, 10:32 PM
I'd rule out detonation, especially at idle.

A stethoscope might help a lot in locating it.

Listen to the AIR pump check valves.

Cold carbon rap sounds just like a collapsed lifter or two and goes away after a few seconds (sometimes as long as 60). A good WOT run will usually clear it, but it's not too common on the 2000+ engines.

Have you ruled out a bad tensioner?

Submariner409
04-30-14, 10:39 AM
Cadillac and many engine repair mechanics caution against the addition of snake oils and magic potions to the oil, gasoline, and air intakes of any car/engine.

Shell gasolines are all Top Tier fuels. ALL grades of Top Tier gasolines contain the "cleaner" - Chevron TECHRON.

http://www.toptiergas.com/retailers.html

http://en.wikipedia.org/wiki/Top_Tier_Detergent_Gasoline

Paul2020
04-30-14, 02:39 PM
Guess my next investment is for a stethoscope :-) . Maybe it is the chain tensioner.

Will probably pull off the valve covers too and see if there is anything obvious there.

Based on the expertise I've seen here I take it so far that this clattering restart when warm is not that common. Otherwise I think you guys would probably be all over it with recollections from your past experience.

Ranger
04-30-14, 03:22 PM
Chain tensioners are pretty reliable.

No, chattering on a warm start is not common and most likely not cold carbon rap.

Paul2020
05-01-14, 05:12 PM
That stethoscope helped a lot to narrow down the general area. I seem to have two noises going on during warm starts.

I pulled the valve cover. Looks like I definitely have a timing chain guide problem. (Glad it is on the front side). The nylon guide is broken and I assume flopping around in there randomly, especially on warm restarts for some reason. I can't see the other piece that broke off. I'm assuming it is laying in the bottom of the timing chain cover.

Just getting ready to change it now. Anything I should pay particular attention to?

Thanks!

Submariner409
05-01-14, 05:29 PM
The oil pump is driven by friction between the crank pulley hub, the oil pump drive sleeve, and a machined face on the crank snout. There is a very specific torque + degrees of turn that you must follow during install or you have no oil pressure. The flexplate needs to be locked to obtain the high "tightness" required.

While you're in there, you might as well replace all the tensioners (nylon slipper faces worn) and the nylon guide slippers. The tensioners are hydraulic, you collapse them and pin the shafts - pull the pins when it's all timed.

Ranger
05-01-14, 09:35 PM
That stethoscope helped a lot to narrow down the general area. I seem to have two noises going on during warm starts.
The things you can hear with one of those is amazing.


I pulled the valve cover. Looks like I definitely have a timing chain guide problem.
WOW! That's a rare one.

JoeTahoe
05-02-14, 10:35 AM
I not saying he is the only one to get it from. But Jake at Northstar Performance has a kit with tensioners, chan and sprockets and guides. He has a really good price on all of it. I would change it all. How many miles are on this. I always Torque the dampner bolt to 250 ftlbs and always use a new bolt. I have streched many of them.

04GrandAmGT
05-02-14, 03:00 PM
http://www.northstarperformance.com/partsstore.php

$225 for the entire kit, sprockets, chains, guides, tensioners

Caddy-EaRL
05-04-14, 01:23 AM
http://www.northstarperformance.com/partsstore.php $225 for the entire kit, sprockets, chains, guides, tensionersI got that kit from northstar performance when I studded and resealed mine last year. It was half the price from our wholesales where I work. High quality parts and awesome studs btw.

04GrandAmGT
05-05-14, 10:32 AM
I got that kit from northstar performance when I studded and resealed mine last year. It was half the price from our wholesales where I work. High quality parts and awesome studs btw.

Thank you :)