tow vehicle - coolant system question

Brian Linn

Brian Linn

Well-known member
We have a '98 Chevy cargo van with 5.7Lm with 50k mi. Prior to going to Calif Speedway last month, I thought I smelled anti-freeze. Had it pressure tested and showed no signs of leakage.

When I went to load up on Thurs, I noticed a spot of wetness on the ground where it had been sitting for a few days. Further investigation found the cross-member under the engine wet with droplets, and finally a drop just below the crank pulley. I figured the water pump, but when I took it to a mechanic to have it changed on Fri, he said (and showed me) it was a leak on the intake manifold gasket. There is a large expense ($700-$800) to strip the engine down to gain access.

Has anyone had success with Aluma-seal or other stop leak concoctions? concerns about other areas that it might plug. It is not a big leak at this point. I missing the snow day at Willow Springs today, but would like to get out there tomorrow.

Thanks in advance for any input.
 
I've used the aluma-seal stuff and had great success. That intake manifold leak is a common problem though and you'll probably end up having to replace it. It's not as hard a job in a pu truck but in a van it's much harder to get to.

That all being said, my brother had a leak like that in a chevy pu and it used a tick of water but he ran it like that for years and sold it that way, not a big problem.
 
Brian,

I've got a '98 C1500 pickup with the same engine. It's been weeping slightly from the intake manifold for probably the last 100K miles. I just keep an eye on the coolant level and top it up every month or two. It's never leaked enough to drip on the ground and hasn't gotten any worse.
 
Be careful about ignoring that leak. The coolant leaks in GM products from the 90s is well documented on the internet. The long life orange coolant has a bad habit of attacking the gaskets and engine. If it happens to leak INTO the engine it will destroy it. Ask me how I know!!
 
For weeping type leaks I use ground black pepper. Just add alittle every few months and it's not big enough to gum up the heater core.
 
Is it just a extrenal leak, or could it also leak into the intake port or into the oil?

If it's just a external leak, add some coolant sealer and if you can access the leak area, clean it and add some epoxy. Worlds best epoxy, T-88 from aircraft spruce, they have a web site.

If it could leak into the oil, keep a eye on the oil, first sign of water, would have to actually get it fixed. Fist sign of water in the oil, drain and add fresh oil, coolant not good in the oil. If you notice it leak in the summer get the coolant out and fill the radiater with water, OK for a little while, better than getting more coolant into the oil, water not good, coolant worse.

Halfway to MID OHIO I had a plastic coolant tank spring a leak, stopped at a hardware store, bought a wire brush and some plastic epoxy, that worked better than I thought it would. Of course I did replace the tank after I got back, but I bet it would still work.
 
As a mechanic, who makes a living off of this type of thing, DO NOT ignore this leak. It might seem small now, but how large will it be 350 miles from home at 11:00pm? Fix it now.

Russ
 
I have a '96 Chevy Express, the intake gasket has failed twice, all the antifreeze went into the valley and filled up the sump with a nice muddy looking goo. The first time at about 100k, I replaced the gasket then warmed it up with 5qts of tranny fluid in the engine and a new filter, drained and repeated this two more times. Put in regular 5W30 & ran a few arrands around town- maybe an hour driving, drained and filled with new oil and filter. This lasted till 266k when it happened the second time. So this time I put in a crate motor, but the new gaskets they make now have steel inside with a rubber type coating, the two that failed had plastic inside. If you replace the gasket make sure it has steel inside!!
 
Common problem on late 90's GM, they have a composite intake manifold. My 97 GM Suburban was doing the same thing. Replaced the gasket and manifold....when I put in the rebuilt engine, seems they also had rear main bearing problems with the block machining by factory. Mine bit the dust in a big way all of the sudden, sounded like the crank was machining its way out the oil pan. Good luck. If the van is a keeper I'd fix it the right way, Murphy's Law says its going to break down at the worst time and cause more aggrevation and cost even more.
 
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