Bad coolant leak: Pooling on top of engine - The 1947 - Present Chevrolet & GMC Truck Message Board Network

IdahoMan · 09-04-2016, 01:03 PM

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 · 09-04-2016, 01:42 PM

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** · 09-04-2016, 02:40 PM

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

7echo · 09-05-2016, 09:24 PM

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 · 09-27-2016, 02:36 PM

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

**Mr_Rich** · 09-29-2016, 01:13 PM

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 · 10-01-2016, 01:14 PM

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.

09-04-2016, 01:03 PM	#1
IdahoMan Registered User Join Date: Oct 2014 Location: IDaho Posts: 89	Bad coolant leak: Pooling on top of engine 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 Attached Images

09-04-2016, 01:42 PM	#2
Cape Codder Registered User Join Date: May 2013 Location: Centerville,Ma. Posts: 1,223	Re: Bad coolant leak: Pooling on top of engine 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.

09-04-2016, 02:40 PM	#3
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,851	Re: Bad coolant leak: Pooling on top of engine I would look at the thermostat housing and hose end at the housing. __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~

09-05-2016, 09:24 PM	#4
7echo Registered User Join Date: May 2015 Location: coastal georgia Posts: 38	Re: Bad coolant leak: Pooling on top of engine 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

09-27-2016, 02:36 PM	#5
ironroad9c1 Master Hater Join Date: Apr 2006 Location: Temple,Tx. Posts: 402	Re: Bad coolant leak: Pooling on top of engine Yea it looks like its seeping up from that front coolant passage on the side of the intake to the head. __________________ 1997 C1500 ECSB 4.3/NV3500 8.5 3.42 "This evening, all of you bleeding hearts... why don't just go ahead and hug yourself for the next 20 minutes or so, because there's a really good chance you're gonna be offended".- Captain Owen Honors

09-29-2016, 01:13 PM	#6
Mr_Rich Registered User Join Date: May 2006 Location: Yucaipa, Calif. Posts: 790	Re: Bad coolant leak: Pooling on top of engine 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. Attached Images __________________ 1989 K1500 Chev. EC Original owner; some of the aftermarket parts I've installed are Borla headers, Hypertech chip, Edelbrock water pump, and a Stillen rear disc brake conversion kit. 2009 Hummer H3T 3.7L 5M (sold) 1997 K2500 Chev. EC 7.4L/ 4L80E 2018 Dodge Ram 2500 HD R/C

10-01-2016, 01:14 PM	#7
68 TT Still plays with trucks Join Date: Jul 2009 Location: Spokane, WA Posts: 3,556	Re: Bad coolant leak: Pooling on top of engine 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. __________________ miSSed opportunity - ground up creation of an AWD 1994 454 SS that never was http://67-72chevytrucks.com/vboard/s...d.php?t=795577 69 C10 shortbed stepside 400 small block - built like what a super sport truck could have been 69 K20 lwb TBI 350 4L60E NP208 14-bolt Dana-44 w/disc 68 Camaro SS / RS 500hp 439 inch roller cam big block 4L80E 79 Malibu TPI 350 4L60 w/ Z28 steering & sway bars



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.