Intake Manifold leak detection...

[McLin]

Hi,

how can I find out which intake manifold is leaking?

I lost coolant, so I can fill up every 2 wekks from hot to cold mark if the engine warmed up.

the oil looks fine, but the coolant must leaking somewhere.

So how can I find out which manifold is leaking?

Oh it smells like burned plastic in the engine area if the engine warmed up.

thx.

[Airjer_]

What year, what motor?

[McLin]

Sorry 3.8L Series 2 1998 LTZ

[maxwedge]

More than likely it is the upper intake, the egr passage is close to the coolant passage behind the throttle body, this melts thru and coolant gets into the engine.

[McLin]

Cool thx.

From Rockauto.com:

DORMAN Part # 615180 {OE Solutions; Includes All Gaskets and Seals as Required #89017272}
Includes All Gaskets and Seals as Required; w/5-5/8" (145mm) Diameter Alternator; Designed specifically to work with Dorman OE Solutions Intake Manifold Gaskets only.
Includes All Gaskets and Seals as Required; w/5-1/8" (130mm) Diameter Alternator; Designed specifically to work with Dorman OE Solutions Intake Manifold Gaskets only.

Is this a good replacement part?

[maxwedge]

Yes, had one on my 98 LTZ.

[McLin]

Today I had filled in some water in the coolant reservoir. I saw some oil on the top of the cooling water.

My question is: Is the same symptoms for upper intake manifold? Is there any oil line where can get oil in the cooling water?

I did replace the lower intake manifold on another Lumina, but the symptoms was that coolant goes in the oil...

[maxwedge]

Trans fluid could get into the cooling system thru the trans cooler in the radiator, but that would be reddish, not brown.

[McLin]

nop, it was brown...

If there is a leak in the upper intake manifold then its possible that the oil in the intake manifold can get into the coolant passage? Maybe if the engine is cold and the pressure is not high.

I dont know how possible that is.

[maxwedge]

It is all guesswork, take off the throttle body and look at the egr and coolant passages for a better idea of what may be happening.

[McLin]

I ordered the Intake Manifold Set and the Fel-Pro Intake Manifold gasket kit ,with all gaskets.

I dont open the engine without new parts. I report then what it is.

[mastertech1964]

its a common problem with the 3.1 and 3.4 engines to have the lower intake leak coolant gm has a redesigned gasket set available the quick check is to look for staining where the lower intake and heads meet the engine block at the lifter valley check both the pulley end and trans end of the engine

[McLin]

I I replace the parts, can I take away the lower cooler hose and run the engine a couple of second that the most coolant go out?

[maxwedge]

Yes.

[dazarooney]

Did you fix the problem McLin?