Timing cover leak. To fix or not to fix?

[tractorman]

I have a '94 Corsica with 155,000 miles. I've fixed lots of stuff on it over the years (including the intake gaskets)- most of it properly. The car runs good, everything works, gets good mileage, and is probably good for at least another 50k- possibly more.

I noticed a small antifreeze puddle near the passenger side wheel today. Looked around, cleaned things off real good, drove it, let it cool down, checking occasionally. I've finally determined that the coolant leak is coming from the timing cover gasket- it's a fairly slow leak, but enough to leave a 6" diameter wet spot on the concrete after sitting overnight.

There's very little room on the passenger side of this engine- is there enough room to remove this timing cover?

Looks to me like all the accessories have to be removed, then support the engine, remove motor mounts, tensioner, and vibration dampener, then the cover will come out. Have I left anything out?

If I choose to remove the cover, I'll go ahead and replace the timing chain. Any tricks to this?

What about the joint between the oil pan gasket and this timing cover? Should I just leave the original oil pan gasket in place, put some silicon on it, and put the thing back together? I'm assuming that one need not remove the oil pan to do this job... I sure don't want to.

I've also considered stopleak. I generally avoid the stuff, but I've SEEN the GM tablets work wonders. I'm seriously considering dumping in some of those GM tablets, tightening the front cover bolts, and crossing my fingers. This could defer this job indefinitely... or at least for a few years.

What do ya'll think?

[PCGUY112887]

I would see if all of those bolts on the timing cover are still to-spec before anything else. They are supposed to have threadlock on them but who knows...

Quick interesting fact - the 3500 uses less timing cover bolts than other 3x00 engines, at least mine did. 2 bolt holes near the top were totally unused on my 3500, however they were used on my old 3100 so I grabbed 2 bolts off the old engine and put 2 extra ones in my 3500. I thought maybe they were just missing but if you looked at the threads they indeed never had a bolt in them.

[IsaacHayes]

I did this not too long ago on my 94. Yes it's a tight fit not as nice as say a W body would be but it's do-able. You basically have it right. I put silicone on both sides of the gasket, and on the bottom of the cover and in the corners where the block, pan, and cover meet as suggested by several others here. Timing chain and dampener is what I replaced. The new gears in the cloyes set were smaller so I went with the stockers and that combo was the tightest. I put a new crank seal in the cover while it was off. It helps to have another person to help hold the flywheel from turning when doing the dampener, and to help lower down the cover from the top while you position the bottom in place while keeping the pan gasket pushed down and aligned. There are 2 pins in the bottom of the cover that are in the block that help align/hold the cover, keep that in mind when removing it so you don't crack it.

Mine was a slow leak, your's is not. Mine was just seeping by the left (firewall) passage and running down to the crank pulley. No leak inside and not enough leak to put coolant on the ground. It was enough to put air into the system and cause hot spots/trapped air as the temp would be high on the highway then fall down. I also was worried about it leaking into the oil side eventually.

6" puddle over night is a serious leak. Fix it now so it doesn't eat away at the cover any more. The cover is likely pitted where it was leaking. I will be changing my coolant more religiously than I have in the past to make sure corrosion inhibitors are working.

[tractorman]

Well GodDamnIt.

Lazy ba$tard that I am... I initially decided not to fix this properly. I dumped in some of the GM stopleak pellets and waited a few days. This stopped the leak at the timing cover... and I'm happy enough about that. I check my oil for signs of coolant religiously, and haven't seen anything to be concerned about.

But I was poking around under the hood with the engine nice and cold, and noticed that my LIM gasket is once again leaking- externally this time. I replaced it about 4 years and 30k miles ago... back before Felpro came out with their new & improved gaskets. I've known for some time that a second failure was eminent, considering that the replacement gaskets were essentially the same as the originals- just wasn't expecting it quite so soon.

So now I have a massive weekend project ahead of me- not immediately (the leaks are very minor, and there's no visible sign of coolant in the oil), but in a few weeks when I have time. I'll go ahead and replace the LIM gaskets with the new Felpro "problem-saver" gaskets, replace the oil pump drive o-ring with the new & improved GM o-ring, and replace the timing chain & front cover gaskets. And I'll upgrade my leaky plastic '94 valve covers to the aluminum '95+ models. I expect this to kill the whole weekend.

I'm quite familiar with the LIM job, having done this to several different 3100 engines. I've done front covers, timing chains, and such on lots of engines over the years, but not on a 3100. Posts so far have answered several of my questions, but here's one more:

Do I need any sort of pullers for the timing chain sprockets?

Also, I've been told that cheap timing chain sets (from Autozone, etc.) don't wear very well. I'll likely buy this from a dealer... but just to satisfy my cheap nature: Is anybody familiar with an aftermarket timing set that's as durable (or more than) the stock chain & sprockets?

[IsaacHayes]

Yes that would kill the whole weekend. I'd suggest start to tear it apart friday night. Have all the little odds and ends you need too, coolant, oil, filter, gaskets, coolant adapter thing that goes to LIM to the heater core pipes, etc that you always run into to avoid extra trips to parts store.

Only puller you would need is for the crank sprocket. The cam one just unbolts with a big socket. Also order all your parts ahead of time as they had to ship in the timing set. I got the set with chain and gears and it was the same price as just the chain but ended up only using the chain... Others say to get a chain from GM as they've had their cloyes stretch out faster than OEM. Also you WILL need a dampener. There was a set from advance auto that was by S&A gear or something and was more expensive but I don't know how good it is. I would just get a chain from the dealer and get a dampener from whoever and call it good. My gears were not worn significantly after 200,000m.

The timing chain cover will take some time and you will have to figure out the bolts to remove them for the engine support bracket and how to get them out. Going back in was surprisingly easy for some reason. It was just lowering the cover with fresh silicone and getting it into place without the pan gasket coming out which was the rushed/worried part. I put silicone on the bolts to seal them back up. I used black silicone, the high temp red seems not to stick/seal as well.

The pan gasket was swollen/stretched maybe from my carb cleaner and I had to push and hold it down with my fingers while the cover was lowered into place. It was like it was too long. But it fit back down and sealed fine. Just was a pain a little bit to not push the cover on and have it pop up and get cut.

You need to drain all the coolant out, using one of the block drain plugs would be good idea. I didn't think of that and just siphoned it out from the coolant port after I had the cover off. Some coolant did get into the pan so I drained the oil plug a few secs to get the little coolant out before firing it up. I then changed the oil too of course.

Hope this helps.

[tractorman]

Thanks for the advice. One question:

What about the sprocket on the crankshaft? Does it just slip off? No puller required?

[CNCguy]

Be sure to properly torque the bolt for camshaft gear.

[ForcedFirebird]

Thanks for the advice. One question:

What about the sprocket on the crankshaft? Does it just slip off? No puller required?

I just pulled apart a 3.4, and the gear is pressed on. It only has to come off a little bit and will fall off after that. Problem is finding a puller with jaws small enough to get a good bite on the gear.