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O.T. GM Minivan 3.4 coolant leak

R

RoyIA

Member
My son"s minivan has been leaking coolant the last 10 days or so. There are no apparent external leaks. I checked the oil and it had the proper level and did not show any water or antifreeze.From my experience with 3.1 engines I am pretty sure it is a intake manifold gasket. I changed 1 of them this year and one last year and one about 5 years ago on the same car.

Is there any sure fire way to check the exhaust to identify antifreeze fumes. It was fairly windy and I couldn"t verify that I was smelling any.

The job was tight enough on a Lumina and a Malibu. I don"t see how it could be done on this van. Has anyone done this job? Are there any tricks to getting it done?
 
A 1/4 inch air ratchet helps. You don't have to take the rear valve cover off. A 12mm tube wrench will grab the rockers so you can lift them to get the push rods out. It looks worse than it really is.
 
Intake could be a likely culprit.

My dad, uncle, and I just did one last weekend in a chevy venture. Undo the motor mounts on the front? (I think it was front.. I was absent from "class" at this point) and push the van as to "rotate" the engine for better access to the rear bank. Once it has rotated, lock it in park and block the wheels. I should stay "turned", as it did for us.

As said previously, an air ratchet makes it much easier.

Hope this helps a little

Brad
 
Thanks for replies!

Front cover of what? If it is the timing chain cover, that would be an oil leak, not antifreeze.
The coil pack mounting bracket has to be taken off to get the valve cover off I believe.
Are you saying that you can rotate the rocker with a tube wrench to get the push rod out? I would think you would have to rotate the crankshaft to take the pressure off the valve springs.
 
If it were leaking into the valley instead of going thru the combustion chamber and out the exhaust, I see what you mean.
There is no sign of coolant in the oil.
Warning! If you run too much antifreeze out the exhaust it will plug up the catalytic converter. At that time you will not get any medium to high rpm's. That is also a costly problem.
 
The front covers leak externally. It can be very hard to see it leaking.

Head gaskets are fairly common on these engines. They aren't that hard to repair. If you have put intakes in 3.1's you could easily do head gaskets or a front cover gasket. Not hard just a little time consuming getting everything out of the way.

To get to the right side (rear) of the engine remove the dog bone mounts from the left (front) side of the engine and use a ratchet strap to pull it forward.
 
OK,

I've done hundreds of lower intakes,fist-fulls of head gaskets and a few timing cover gaskets on 3.1/3.4 GM engines.

You won't confirm anything until you pressure check the cooling system while engine is COLD.This is when the engine will most likely leak.

I'm leaning toward timing cover or lower intake gaskets as head gaskets generally cause overheating problems.

If lower intake leakage is the cause,check into Fel-Pro Perma-Dry replacements which are made from steel instead of plastic OEM.
 
The 1995 -2003 3400 and 3100 GM motors are notorious for leaking intake and head gaskets.I used to frequent a website devoted solely to this problem.There were thousands of people on there and quite a few had ruined engines.How GM got away without a recall is beyond me.
 
Pour only the liquid of Barr's stop leak in the radiator, the exhaust will smoke when it gets in the cylinder.
 
It's a shot in the dark, but my first guess would be intake gaskets.

We once had a Pontiac minivan with that no-account 3.4 and I finally got so fed up with trying to keep ahead of coolant leaks I just got rid of it.
 
Flush all the Dexcool/Wrecks-cool and replace with demin water and propylene glycol anti-freeze. Not ethylene glycol which ruins bearings.
Remove the “O” ring from the coolant reservoir if that is the “pressure cap”. Or turn the rad cap on the rad to the sealed but no pressure position.
Dump in a jug of the rad sealer that contains “water glass” . Then tell your son to trade the vehicle.
Good used vehicles 2-3 years old are going very reasonable at the moment.
 
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