3800 Engine Problem

[Jolly_John]

Hi, Gang. My son-in-law (and his mechanic) thought he had experienced the typical upper intake manifold coolant leak on his non-supercharged 3800 engine. He had the plastic upper intake manifold and gasket replaced....but the coolant leak still exists. The engine is consuming about a half a cup of coolant every couple of days, plus there is a little external pooling of coolant between the upper intake manifold and the engine head (the head closest to the front of the car).

The lower intake manifold gaskets were NOT replaced when the upper job was done, and the mechanic now indicates that might be the source of the ongoing problem. The mechanic also stated the lower intake manifold could be warped. That was just a comment though, not based on any troubleshooting or disassembly.

My questions: In searching the internet, I found lots of info about this GM 3800 engine collant loss problem. However, the possibility of a warped lower intake manifold was never mentioned. Does anyone have a comment about the liklihood of this (the car has never been overheated)?

Second, if the lower intake manifold gaskets are bad, how in the heck would that cause the coolant pooling we're seeing up on top between the upper intake manifold and the one head. I guess I don't understand the theory on that.

Any comments would be appreciated. Thanks, John

[D-a-n-i-e-l]

You must be talking about a 3800 from 1991 or newer. I would look at what kind of gasket was used, and if the gasket had the improvements incorperated into it. I would buy a Fel-pro gasket and re-install. There were a couple improvements over factory that make for a much better gasket, ie.. metal rings to ensure the gasket is not prone to failure from overtightening, from those who choose not to use a torq wrench.

[Barney Eaton]

Jolly John did not mention the year but I believe it was around 1996 when GM put the plastic intake on the 3800.

Reattas do not have this problem.

My question......what kind of mechanic would only replace the upper gasket when he had the intake off the car?

[charlie1]

ZZZ

Edited August 2, 2009 by CHAS1 (see edit history)

[Guest squiretom]

my 91 had the intake gasket replaced at some point in time. they also used some blue formagasket stuff and i will have it done again.

in the attached pic , is it possible that coolant is leaking from manifold gasket or head. area shown is wet and green but no discernible loss of coolant or vapor from the exhaust is noticed.

car runs great.

[padgett]

There is a small coolant tube under the throttle body that I have seen corrode - did you chaeck that ?

[jonlabree]

It goes into and thru the throttle body.

[Guest squiretom]

thanks for the tip , i will look into that soon. i hope that is the problem. i think i will redo the manifold gasket also.

[D-a-n-i-e-l]

Some of the 3800 started to get the plastic intake as early as 91'. Unless the couple regals I have seen in that year had a motor transplant. The funny thing is these cars were still running the older trany, not the electronic vesion.

[Rawja]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Some of the 3800 started to get the plastic intake as early as 91'. </div></div>

Yeah, I'm pretty sure my '93 Trans Sport's 3800 has the plastic intake manifold.

[Guest Reatta1]

While you are pursuing this problem, I'd strongly recomend that you keep an eye on the oil. Look for any signs of coolant getting into the crankcase. My daughter had a coolant leak problem on her Skylark and it ruined the bearings. She had to replace the engine.

[Guest squiretom]

oil is clean and no foam or other film in the coolant tank, that is why i am looking at other areas for leaks. also had a leaking pan gasket replaced and so far nothing in the oil pan indicating a problem.

just for grins and giggles , what are we looking at in replacing the head gaskets ? does the motor have to be pulled ?

[Ronnie]

Buy or borrow a kit that has a pump and a special radiator cap for pressurizing the cooling system.

Clean everything up on the manifold. Then attach the kit and pressurize the system. Watch for external leaks.

[Guest spamseptictank]

You may want to invest in a UV dye leak detector kit. I borrowed one from a friend and found the leak in my wife's 97 Firebird's (3800 Series II) heater transfer tube. It's a plastic 90 degree elbow that connects the intake manifold to the alternator/ heater hose/ belt tensioner pulley.

FWIW

Grace and Peace,

Dave

[charlie1]

ZZZ

Edited August 2, 2009 by CHAS1 (see edit history)