Bad coolant leak: Pooling on top of engine

[IdahoMan]

Hello.

One of our vehicles (a burgundy 94 GMC truck) has a very bad leak of coolant. It pools on both sides of the top front area of the engine, and then drips down the front. Can't tell where it is coming from though.

Where do you think it is coming from?
Is there a step-by-step thread that can show how to fix this?

Thank you.


Sincerely,
IM

[Cape Codder]

If it is on both sides of the thermostat housing that is the first thing I would suspect. A pressure tester would help finding the leak also. My 98 4.3 had a coolant leak but only on the rt. side and it was the quick connect for the heater hose had corroded.

[special-K]

I would look at the thermostat housing and hose end at the housing.

[7echo]

When mine leaked like that it was the intake manifold gasket.

Here are a few write ups...

http://www.someotherplace.com/bb/proj/rh94intake.html

http://www.howstuffinmycarworks.com/...ake_manif.html

[ironroad9c1]

Yea it looks like its seeping up from that front coolant passage on the side of the intake to the head.

[Mr_Rich]

What you might be able to do is replace the bolts holding the intake manifold down to the heads at the coolant passage area. The bolts tend to deteriorate/ rust allowing the leaks. You don't really need the lifting bracket since that is a factory piece they use to install the engine. Use at least a Grade 8 bolt that is 3/8" coarse thread 1 1/4" long. The next option would be to replace the intake gasket. The tricky thing about replacing the intake gasket is to make sure all the coolant is sucked out of the reservoir at the bottom of the intake manifold so when you remove it you don't dump a pint of coolant inside your engine. BTDT.
These are the bolts I'm talking about:

I'm using stainless bolts myself to help avoid these types of problems. Over three years ago I installed this engine after storing it in my garage for over nineteen years. I replaced all the gaskets before I installed it and I've got over 50K miles since.

[68 TT]

I had one of the TBI intakes actually corrode all the way through from the inside of the coolant crossover passage block off part of the intake and leak coolant out near the distributor from a tiny pinhole. Maybe you have a corrosion induced pinhole up near the thermostat housing.

Pinholes are hard to find unless you remove the intake and scrub it clean. I couldn't see it from the outside but could see daylight from the inside after I cleaned it up. I ended up getting another intake that was in much better condition instead of trying to fix the one I had.