1999 Tahoe, 4WD, 5.7, 235,000 (yep) miles

Intake manifold gasket has been leaking for a while.....have to add water every few days...., but lately I started getting what at times is a loud clacking sound on cold starts. It sounds to me like valves, but I am no expert. It quiets down after a few minutes of running. Weird part is that some mornings it does not do it at all, but most of the time it does. Oil pressure is about 40 after warming up.

Put Lucas treatment in at last oil change which definitely helped for a week or so, but now its back the same. I am not seeing any visible sign of coolant in the oil.

Questions:

Could there be any connection between the intake coolant leak and the valve sounds?

Is there any chance that what I'm hearing could be a blown head or exhaust manifold gasket?

If I continue to run it with the intake leak, am I risking that causing other problems?

If the answer to the first 2 questions is no, what suggestions would one make on a solution for such a high-mileage engine?

Thanks in advance for any and all help. Money is mighty tight and I am trying to keep her together.

 

I hope this helps out a little.

 

Welcome to the forum.

Do you know where the coolant is going?

The lifter could just be one or more that have started leaking down at nite and are noisy at first until they pump up. If this is original, unrebuilt engine, then that is very possible.

 

Thanks to both of you for taking the time to reply. Much appreciated.

Do not know where the coolant is going, except that it is not leaking on the ground. Oil change tech said he could see that the intake manifold gasket was leaking, but I can't discern that.

This is the original engine....has never had a bolt turned on it.

Since oil pressure is still around 40, am I relatively safe in thinking that my bottom end is OK? I'm trying to weigh all factors before making a keep or dump decision. Transmission also needs rebuild.

What is involved in replacing lifters?

Thanks again.

 

235,000 miles on these engines is not a lot of miles. Taken care of they will last much longer. If it is a lifter tapping, it is not an immediate fix right now kind of problem. It's just a little noise the first few seconds until it gets full of oil. Once full of oil it works like before. That engine should have roller lifters, so just price of lifters will be quite a bit ($200-$300). In order to install lifters, the intake will have to come off (you will take care of gasket then), valve covers, rocker arms, push rods and all associated wires, hoses, pipes and injectors. If it were mine I would address the intake gasket quickly and try some different cleaners in oil to see if it helps lifter tap at start-up. If the intake gasket leak suddenly gets worse, it could at a minimum leave you stranded and worst ruin a good engine. The intake can be taken off and put back by most competent mechanics with no problem. The transmission should be tackled by someone with the skills. If you have friends who work or run mechanic shops, tire shops, muffler shops, tuneup shops, etc. start asking them if they know someone who does a good job rebuilding transmissions at their home or garage. I know someone like this and this is all he does for a living and has a better reputation than any trans shop within 250 miles.

 

Again, your help and time are greatly appreciated.

I have a highly recommended transmission guy here. He is saying about $1500.00 to R&R my transmission with a rebuild, $2500.00 if mine is not rebuildable (he is saying that is not likely) and he has to procure a new one. That will include torque converter, new rear main seal in engine, and new input shaft seal on transfer case. Have any idea how that compares price-wise?

If I have the intake pulled to replace the gasket, am I not then a good ways towards getting to the lifters? Looks like I can get a set of OEM roller lifters for about $125.00.

What cleaning fluids or additives should I try?

Thanks

 

I think the first thing on the agenda is to find where the coolant is going. Two places I can think of are out the tailpipe and into the crankcase. Neither are good.

 

I agree 100% with 73shark. Your first issue needing immediate attention is that coolant leak. If you are adding every few days, that is quite a bit of loss. If your oil is looking milky, it's going in the crankcase. If you see steam or white smoke out the tailpipe, it's being burned. Both of these will cause damage in areas you don't want damage. If it is the intake, then when you remove this you are halfway to lifters. If you do change lifters, check pushrods, rockers and valves for excessive wear. When tightening down rockers after installing new lifters, they need to be adjusted or you will burn valves or have a constant valve tap. Just remember, the coolant leak needs attention now, the lifters can wait.

The price for the transmission rebuild sounds reasonable. The parts to rebuild are not expensive, but the time to pull, tear down, clean, reassemble and reinstall is a lot.

The decision to repair, sell or trade relies completely on your like or dislike of the vehicle. Repairing is cheaper than buying a new one.

If it were mine and money was tight, then I would take care of coolant leak now and take care of trans when it dies. If lifter noise quits within a few seconds of cranking, I would not address that now either. When auto transmissions quit, they normally do not do damage to case or most "hard" parts (unless you race it and then parts can go through the floor pan when it comes apart).

 

OK, guess I have a game plan thanks to you guys.

I can only figure the coolant is going through the engine. I have not noticed any exhaust abnormalities (I'm never in a position to notice it, though) or moisture on the pipe. Oil is not milky. I have heard, though, on occasion a light hissing or gurgling from under the hood when I shut it down.

I will get the gasket replaced immediately, and if the added price is reasonable, go ahead and do the lifters while we are that far.

Problem with the transmission is a hard 1-2 shift after being at highway speed for a few miles. It does not slip, and shifts perfectly otherwise. Trans guy could fix that with a new pump body, but we both agree that at this mileage a patch is probably not wise.

I LOVE this truck. I have no complaints, having run up this many miles without any major repair. I really want to keep her around, and darn sure can't afford another one.

Thanks one more time.

 

I agree with most of what's been posted here, but, if you get into the motor at all, your first priority is to see what it really needs. First thing is the leak and a compression/leakdown test. Not just static compression. This will tell you how the rings/valves are doing. Not sure what your budget is, but if I was going to the trouble of replacing lifters, you might want to do the timing chain at the same time if all else is well. Leave the trans alone. Unless you were changing the fluid on a regular basis and it looks clean, don't do anything to it that will require a fluid change, that's a sure way to kill a tired automatic.