coolant leak

alz · February 2, 2006

I have a 99 Suburban, 5.7 4x4. It has a coolant leak coming from somewhere below the distributor. It only leak when running. There's so many emissions and hoses I can't pin point it. Can someone point me in the right direction? Is there something common there that causes leaks?

bowtie_pasta · February 3, 2006

A heater hose that runs through your firewall to the heater core? Can you trace those out? Just an idea as I'm not very familiar with your specific truck.

454ss · February 3, 2006

if i remember right a heater hose connects to the rear of the intake on the 350 vortecs and the coupling that it plugs into is probably leaking, common problem for them to go bad, your dealer should have them in stock.

alz · February 3, 2006

It looks like it is pooling up around the knock sensor and then flowing down the back of the block around the trans. After reading a few other posts, is this a tell tale intake manifold gasket leak?

454ss · February 4, 2006

could very well be the intake gaskets, i had to do mine twice in 140,000 miles. the coupler that i mentioned before started leaking first though.

alz · February 5, 2006

There is no leak at the coupler you speak of. This Suburban only has 65,*** miles on it. I got myself an inspection mirror and will take a look at it tomorrow. I have a feeling it's the intake gasket. When they talk about upper and lower intake, do they mean throttle body as upper and intake manifold as lower?

alz · February 5, 2006

I put a bottle of Bar's Leak in a few days ago and today I don't see it leaking. I know this is only temporary, but I hope it holds until spring or summer when it's a little warmer for intake manifold gasket.

bowtie_pasta · February 7, 2006

Fwiw, I had a coolant leak on my 4.3l that I could not find and it ended up being the intake manifold. That was a bummer.

96Z71asskicker · February 8, 2006

by upper and lower intake you'll see the lower intake gasket (most prone to failure) is the one that meets up with the heads. check the croners of the intake manifold towards the back you will usually see it leaking out there. The factory gaskets they sold are crap, but gm did redesign them so when you replace them get the gm ones not flo pro's.

PaulQ · February 9, 2006

If I remember correctly my intake gasket on my 94 Blazer went out with about the same amount of miles....I would definitely check into that coupler though before you tear it down. Also try to minimize that chemical crap in your motor it usually tends to do more harm than good in the long run.

Paul Q.

FivePointSevenLiters · February 22, 2006

In some cases, an intake gasket leak will create a distinct whistle under certain failure conditions, decreasing intensity under throttle. Do you notice any sounds? A head gasket failure (in the location between a water jacket and the outer engine surface) will not create any symptoms of a head gasket failure (water in oil, white smoke, decreased compression) however will create a coolant leak during operation (or when system has pressurized coolant). For a few bucks, I'd invest in a nice extension mirror (throwing out my girls compact on stick) and see if you can pin point the leaks location. Peace.

awdco56 · March 8, 2006

Just finished replacing the lower intake gaskets on my Savana van. It's a "98" but only has 49,000 miles on it. When I removed the gaskets I couldn't believe the condition they were in. Between cracks and distortion it's no wonder they were leaking. I replaced with the GM gaskets. They're reinforced at the bolt holes to protect against over torque.