03 coolant leak

[BoB393]

Hi all, been a while.

Does anyone know the first place to look for a coolant leak into the oil.

Any known problems?

I seeing foam on the oil cap and the antifreeze level is going down, and it's getting worse quickly. Nothing is showing up on the ground so we all know what that means. Just looking for some input before I start o tear it down or cheep out and try some barsleak.

Oh yeah it's a 2003 limited with 145,000 mi on it and otherwise it runs and drives fine.

[aleekat]

Compression test, more than likely head gasket.

[BoB393]

Originally Posted by aleekat

Compression test, more than likely head gasket.

Crap!
I hope not. But I'll check it, like I said it runs and starts fine

[imidazol97]

Originally Posted by BoB393

Does anyone know the first place to look for a coolant leak into the oil.
Any known problems?
I seeing foam on the oil cap and the antifreeze level is going down, and it's getting worse quickly. Nothing is showing up on the ground so we all know what that means. Just looking for some input before I start o tear it down or cheep out and try some barsleak.

Check water pump. The bleed hole lets water follow back along the block.
Check the plastic elbow from the lower intake manifold to the tensioner pulley bracket for seeping.
Check the hoses and the radiator for leaks.

What is the oil like on the dipstick? Is it a brown milky color? Or are you just seeing condensing on the oil filler cap, which is fairly common in cooler climates?

The throttle body gasket can leak into the air intake. That gets burned but leaves some in the oil.

Lower Intake Gaskets tend to distort and start leaking which gets burned and eventually will stop where an open valve lets it leak into the cylinder and hydrolock your engine.

I'd recommend the APN upper intake with the metal sleeve in the EGR passage.
I'd recommend the GM aluminum-framed lower intake gaskets.
And you'll have to replace the coolant elbows to the tensioners and I'd recommend the new aluminum ones from Dorman instead of the plastic.

[BoB393]

Thanks!

The oil on the stick looks clean. The foam is on the inside of the oil cap.
I'll check the water pump and hoses but I don't see any water on the ground.

[Tech II]

Have you tried pressurizing the coolant system?

[BoB393]

No, I don't have the equipment for that. But I have looked at all the likely spots for a sign of a leak with the engine hot and the system under pressure. I see nothing.

[imidazol97]

Originally Posted by BoB393

No, I don't have the equipment for that. But I have looked at all the likely spots for a sign of a leak with the engine hot and the system under pressure. I see nothing.

If you're mechanically inclined, places like Oreilly's (Checkers), Autozone, Pepboys, loan pressure checkers for the coolant system. You pay for them then they credit your purchase on return.

Your easiest bet would be to assume it's leaking internally and do the gaskets and the Upper Intake Manifold as preventative maintenance, assuming there is leakage internally. Sooner is better. The coolant in the oil damages the bearings.

You could get an oil test kit (Blackstone Labs, Ft. Wayne) will send you free collection bottles to mail back with a sample of your oil. This works best when the oil has been run for a few thousand miles. You can siphon out oil with a small plastic tube through the dipstick tube or catch oil during an oil change. For $25 they will tell you in a phone call if they see sodium and potassium in the oil in amounts indicating coolant is ending up in the oil, whether directly into it or by burning in cylinder and having some residue on the walls end up in the oil.

I would choose one method because if you are getting coolant in oil, you're shortening the life of the engine.

[BoB393]

Next weekend is when I dig in. Thank you.

[BoB393]

Well I'm still haven't gotten to the bottom of it but it seem to have slowed down. We will get there.

[Majoroutlaw]

the first place to start if there are no visible leaks is to pressurize the system. if the system doesnt hold pressure but has no external leaks then id assume it to be one of the 3 common problems... head gasket, lower intake manifold, or the bypass in the plenum to throttle body. remove the throttle body and look inside manifold for dampness.if none visible i would lean towards lower manifold gasket. if the vehicle has no problem starting and runs effectively you can commonly cross out the head gasket, on most instances that is.
i would recommend getting a loaner tool to pressurize the system at your closest part store. you can manually pressurize it by running the vehicle but it is no where near as effective as a pressure tester. also you may want to eliminate the heater core being the problem as well. a leaking core into the heater box may not show immediate signs. so run the car to operating temp and turn on the defrost, smell sweet? if so core needs replaced. if not keep looking for the problem. MOST coolant leaks are where theyre visibly leaking. but internal leaks can only be caused by... leaking heater core, intake gasket, throttle body/plenum bypass, head gasket, or the slightly possible internal radiator leak. IF YOU HAVE a plastic intake thats where i would start first, for its a severely common issue!!!

[GAnOhio]

I have been doing a lot of reading on this subject. I suspect the Intake Manifold because it is known to be a common failure. I don't know how you prove it before having to take it all apart. I hear that the head gaskets are very reliable on these engines.

I would love to hear your results.

[imidazol97]

Originally Posted by GAnOhio

I would love to hear your results.

We've tried to tell you some ways to analyze what's going on.

Start with an oil sample and send it Blackstone Labs for analysis for sodium and potassium. Those show up in oil from coolant.

The foam on the oil cap is probably just normal moisture and gunk from cold starts.

The least likely is head gasket. You wouldn't be driving it this long because it would have gotten worse.

If you have coolant in oil after oil has couple thousand miles on it and you pull a sample out with a vinyl tube...

Do intake upper manifold, lower gaskets, and coolant return tube on the end of the lower intake metal manifold. You're past due.

There's a possibility you have a radiator crack that opens slightly under pressure and seeps, but you have to get a pressure tester to look for that on a cold motor. You don't seem to want to do that.

And if you are getting seeps through the lower gasket or the throttle body gasket or the coolant ports to the throttle body seals, it might be hard to distinguish.

If you are going to have this done, I'd suggest finding an independent mechanic and buying your own upper manifold, lower gaskets, and GM coolant elbow for the work and paying him well for his time since he won't be raking off a commission selling you poor quality parts from a parts house.

I'm sure folks here will recommend their favorite solution parts for each of those categories.

There are some information threads around the internet with pictures on doing the work yourself if you are a 4 out of 5 wrenches on the do-it-yourself scale.

[BoB393]

Originally Posted by imidazol97

We've tried to tell you some ways to analyze what's going on....

Yes you have and I appreciate it.

[imidazol97]

Originally Posted by BoB393

Yes you have and I appreciate it.

As you delay determining where the coolant is going, I'd do frequent oil and filter changes to keep the buildup in the oil to a minimum due to the potential for bearing damage.

The oil/water foam on the oil cap is meaningless. It builds up from normal condensation from cold starts that gets evaporated and hits the cap area which is cooler and condenses there under certain conditions.