Diagnosing a timing chain problem


#1

1996 Chevy S-10, 2.2L I-4, 60K miles



The engine runs quite normally and smoothly, except that it makes an unidentifiable tick noise that seems to be coming from the front of the engine somewhere. It’s definitely not a valve/lifter tick (I’ve heard that before), and it recently occurred to me that it could be a problem with the timing chain and/or chain tensioner. The noise is most noticeable at idle and seriously sounds like something that’s rattling, but not a “loose” rattle…if that even makes sense.



I plan to do a full-out cooling system job in a few weeks (new water pump, thermostat, remove/backflush radiator, the whole works), is it worth my time to go ahead and replace the chain tensioner (or perhaps even the entire chain) while I’m at it? 60K seems like awfully low mileage to be having any chain-related problems. Having never worked on chains before, can anything be told simply by looking at it?



One incident made me think that a chain issue might be at work here: a few weeks ago I was starting from a red light, and the truck began to sputter and backfire very badly, but returned to normal within seconds. I wonder if the chain jumped a tooth for a moment and then righted itself; is that even possible?


#2

You can check for timing chain slack even if there’s no distributor. But it means removing one of the valve covers to observe valve operation.

Once the cover is off, hand turn the engine in one direction until the valves start moving. Now turn the engine in the opposite direction and observe how far the crankshaft can be rotated before the valves start moving. If the crank can be rotated 5 degrees or more before the valves start moving, you might want to check the timing chain components.

But ya know? A bad water pump bearing can make this kind of noise.

Tester


#3

Just out of curiosity I did an internet search and there are more than a few folks that have had timing chain issues on the 2.2 of that vintage, so it could very well be a problem.


#4

Could be little harmless piston slap. Does the noise go away after the engine warms?


#5

No, the noise is present whether the engine is hot or cold, though it’s only really noticeable at idle.

I only think this noise is out of place because I used to own a '95 with the same engine, and it at no time ever made the noise.

I’ve heard shot pump bearings make noises before (usually squeaking/screeching), but this doesn’t make me think of that. The pump is being replaced soon anyways, so I suppose that’s neither here nor there. I hadn’t thought of watching the valves, I might try that.

One other thing: if the chain gets replaced, should the sprockets go with it? The crank sprocket needs a puller to be removed, and I’d rather not do that unless I really have to.


#6

I’ve had a bad chain and it sounded just like a clank or clang against the front cover. Intermittant, hot or cold didn’t matter, but really gets your attention when it clangs. If something is banging against the back of the front cover, it would sure be worth a look. I’d do the whole thing though once its opened up and not just the tensioner.


#7

Here’s a couple of things to try to isolate noises or find sources of noise. Seriously, put a finger in one ear to block hearing. This will give a better sense of direction sometimes and works well with higher frequency noises. Another tool is a length of flexible tubing or rubber hose, holding one end near an ear and moving the other end near to or touching suspected sources will easily home in on particular noise. Just be careful to not contact moving parts! Stethoscopes with a solid rod really lights up internal engine noises…it’s kind of fascinating to listen closely to engines. Of course, the easier thing to do is just attach a microphone to the car, and let the feed give you a visual on the computer! OK, so I don’t have a clue about this part but, if amphibian populations were being counted by computer in the early 80’, in the field, why the heck can’t sound engine diagnosis be available to us in the 08’s? No pun intended.
BTW, my '88 S-10 sputters some when warming up. Hey, you don’t have a belt idler pulley going bad, do you?


#8

To update:

I used an old radiator hose to pinpoint the location of the noise, and it is most certainly coming from the timing cover area. I also found a few videos on youtube of noisy timing chains (one even from this same engine), and it’s pretty much exactly the same noise that I have.

I had all the parts ready: chain, sprockets, tensioner, crank seal and cover gasket. I got all the way to removing the timing cover, but there I got stuck. It seems like it will take an awful lot of force to pop that thing off of the engine, and that’s with prying like hell with screwdrivers. I also found that the timing cover has a dowel pin in one spot (probably for alignment), and that made removal of the cover virtually impossible since I don’t have female-Torx sockets to remove the studs on the bottom of the cover, running through the oil pan.

So I’ll have to wait until I can get hold of a set of those. I also noticed that, where the bottom edge of the cover meets the oil pan, they used a TON of RTV sealant. There must be a 1/2-inch thick bulge of the stuff coming out. I can’t imagine the force that will be needed to separate the cover from that.

Two minor questions: Will it be necessary to really pile RTV back in there like that, and does oil come gushing out of the pan once you finally do get the cover off?

On a side note I was thoroughly impressed that, not only did I successfully use a puller to get the crankshaft hub off, but I also hammered it back on all the way. That part worried me the most, and it actually wasn’t all that troublesome.


#9

Here’s what the OEM used when the timing cover/oil pan were sealed togetherhttp://www.permatex.com/products/Automotive/automotive_gasketing/gasket_makers/auto_Permatex_the_Right_Stuff_Gasket_Maker.htm. It’s spendy! But works! Once the timing cover is off, no oil will come gushing out of the pan. But it’s a good idea to change the oil once the job is completed.

The sockets you’re talking about are called E-TORX sockets.

Tester


#10

So I purchased a set of E-Torx sockets (Sears wanted $40, ha!! Salvo Auto Parts, $7), and also got a can of that Permatex “The Right Stuff” sealer that Tester recommended.

One timing cover stud came off quite easily, and the other had just enough sheared off of it that I couldn’t grab it with the socket. Still some worming and twisting to work the cover off, but I got it off. Installed all new sprockets, chain, and tensioner, new cover seal and front crank seal, and closed it up with a liberal dose of Permatex along the bottom. Per gasket instructions, added another dose of Permatex along the cover/oil pan joint. Started her up, and no more ticking noises!!

Turns out the tensioner part that is NOT spring-loaded (guides the chain around opposite the spring) was completely loose, and fell off by itself as soon as I took the original chain off. I bet that was it…

In any case, thanks to everyone for all the help. Good call on the Permatex, Tester!