Coolant loss, no external leak or coolant in oil

[AnarchyX]

I've got an '04 Impala with 73k miles and my reservoir is showing coolant loss. I took it to Firestone and they did a pressure check and they found no leaks. There's no coolant in the oil either, and the car drives great. No check engine light either.

I had my headgasket blow in my GMC envoy and it chugged and surged when driving. This is nothing at all like that. It's frustrating, especially since it drives just fine and nothing was found.

I read that it might be an intake manifold leak, but if it is, why is there no coolant in the oil and why is it driving fine?

Any help or ideas would be appreciated.

 

[TmanP]

I know, this can be frustrating. I would give a second look at the intake manifold gasket. It could be a smaller leak-- how much coolant are you losing??

 

[SatinSilver]

A UOA would confirm if any coolant is in the oil. How fast is it disappearing? Some loss over the course of a year can be normal. If it's going from the full mark to the low mark on the overflow tank over 3 months then there's an issue. Which could be a leaking water pump if it's disappearing quickly.

 

[Ojustracing]

Common on these are intake manifold gaskets and if its a 3.8 I have replace a bunch of upper intake plenums for coolant loss around the EGR tube. Which motor 3.4 or 3.8?

 

[AnarchyX]

It depends. I drove 1300 miles - all highway - and didn't lose a drop. In this past week I've lost about 6 ounces, or almost 2 inches in the resrvoir.

 

[AnarchyX]

3.8

And actually it did throw an EGR code over a month ago but that was also when I was having a problem with my gas cap. When I replaced the gas cap there were no more codes.

 

[007]

Do you puff any white smoke at a cold start?

 

[Ojustracing]

If nothing external I would suspect the intake gasket. Pay very close attention to the upper manifold where to EGR tube goes in. The plastic erodes and there is coolant right behind it.

 

[AnarchyX]

Nope, and it just passed the vehicle inspection 4 weeks ago.

 

[AnarchyX]

So is it possible I'm losing coolant through the EGR valve? And is that why it's not getting into the oil?

 

[Ojustracing]

Its not going through EGR valve itself. It leaks on the outlet end of the tube into the manifold(air stream). They start small. When they get really bad will hydro-lock the motor and you will know something is wrong. GM thought it would be a good idea to put a metal pipe that fills with hot exhaust gas tight against a piece of plastic. If not external leak. I still say intake gasket. Very common!!!!!

 

[Kuato]

Might want to have a look inside the tailpipe. If it is wet, or smells like coolant when running it is a head gasket leak into the exhaust.

 

[AnarchyX]

So do you think the dealer would be able to find what firestone didn't? Would they be able to do more than a pressure test?

Sorry for all the questions, this is just new to me.

Also, about how much would it cost to have this fixed?

 

[Wheel]

I'm thinking it could be intake manifold (but that would probably show on a pressure test) or the start of a HG leaking into the combustion chamber. Did they do a leakdown test, or just pressure test the cooling system ? How do the plugs look ?

 

[AnarchyX]

They just said they did a pressure test.

 

[SatinSilver]

I'd take my car to Firestone for tires and that's about it. The dealer or a good indy shop would be my suggestion. Dealers do vary so make sure they check out and have good reviews. Even check them out on www.bbb.org, yelp etc. Try to deal with the service manager to avoid being upsold by the service advisor.

 

[sciphi]

Originally Posted By: Kuato
Might want to have a look inside the tailpipe. If it is wet, or smells like coolant when running it is a head gasket leak into the exhaust.


Not on that generation of 3800. Intake manifold gasket leak. Head gaskets on that iron block/iron head engine are basically a lifetime part.

The fix is actually pretty easy. Order a new upper intake manifold and a set of aluminum lower intake manifold gaskets. It's a Saturday in the garage to replace it all.

Did the shop test the radiator cap too? Those were known to fail regularly on the 3800's, and would produce the exact symptoms you're describing. Cheap to replace, too.

 

[AnarchyX]

Is it going to be under $1000? I'm hoping it'll be closer $500 actually.

 

[TmanP]

I would guess around $600 at an independent mechanic, for the intake manifold gasket.

 

[Nick1994]

A GM 3800 losing coolant? Intake manifold gasket, it's a no-brainier.

My mom has a 3.4L in her Buick and overheated it a year ago. Loses a lot of coolant, not in the oil or externally leaking. It blew the head gasket and the coolant is getting into the exhaust