Steam under hood and unexplained coolant loss, but no obvious leaks

ManglerYJ

ManglerYJ

Well-Known Member
Joined
Mar 20, 2005
Location
Lexington, NC
My wife's new-to-us 99 Oldsmobile Silhouette mini van is having some issues. It never runs hot, but we are getting some steam/smoke showing up under the hood after the motor warms up a bit and it seems to be losing coolant somewhere. I can't tell where the smoke/steam is coming from, however. It doesn't leak a drop of coolant anywhere. It also doesn't appear to be coming from the exhaust pipe as it looks normal.

I haven't checked the oil to see if I'm getting an oil/water mix, but the coolant looks good and fresh.

Any suggestions? It is the 3.4 liter V6. and I know the motor was replaced a couple years before we bought it with a factory crate motor at the dealership.
 
Possibly Easy fix: The cap may have cracked seal or lost it's spring poundage causing it to "steam" maybe???? Never done one before but I know you can do a pressure test somehow on a cooling system to pinpoint.

I had an issue with a Saturn once and ended out taking it to a known novice Saturn mechanic who knew exactly where to press on the radiator to show the common leak. It only leaked when the car was contorted on a hill. The only sign was a water stain where the 2 plastic halves of the radiator was mated. He knew his Saturn's well...

Good luck for I HATE cooling issues... Got one I'm working on myself. My best guess on mine now after replacing the thermostat is taking the radiator off to have it cleaned.

And what stinks is you can't just put pure water in it to figure out the leak in the winter time for it will freeze. You have to waste a $12 bill on antifreeze while figuring it out or you have to wait till Spring - in which I have decided to do on mine...
 
My uncle (mechanic) has had several Oldsmobile v6 cars that leaked coolant under the intake manifold. Check the oil ASAP.
 
This same problem occurs in my moms old Impala 3400. I figured out it may be a small pin hole leak somewhere in the head where coolant is sprayed into the exhaust side and immediately disapates so you can't notice any drips underneath.
 
Those 3.1 and 3.4 gm v6 are notorious for leaking water pumps and intake gaskets. If its the pump you can usually see a trail slung off the belt onto the radiator or hood. Intakes can leak internally or externally. Check the oil and look at the corners of the intake where it meets the head. Rarely will an intake leak make it to the ground so I'll appear a mystery like you're seeing. If u change the intake gasket felpro has an upgraded gasket design also change the oil pump drive oring to stop a common oil leak
 
Manifold gaskets. Pain in the ass. It's about a 10 hour job if you've never done one. Have to pull the pushrods and CLEAN EVERYTHING! Dexcool makes a mess of the cooling system. The one I did a couple years ago is still holding strong, though. Fel-Pro gaskets, did the O-ring oil leak fix, etc. while I was in there. Be meticulous. Follow torque specs. Get an inch-lb wrench. I used the 1/4" torque wrench from Harbor Freight and it worked like a champ. It's the only time I've seen a factory service procedure tell you to use a u-joint with a torque wrench, though.
 
The felpro gasket set will come with the oring for the oil pump drive, plenum gasket, valve cover gaskets, and the new intake gaskets which are metal and rubber not plastic and rubber. Alternator, coil pack and stuff will have to come off along with pushrods as said before. Its a good time to stick a thermostat in too. Not a terrible job. I've done enough that I can knock them out in a few hours.
 
Wouldn't a blown manifold gasket have other signs, such as SES light, running rough, etc? I have no other symptoms.
 
No. It will still seal at the intake runners so there won't be a vacuum leak. It'll just seep coolant either into the engine or outside but it'll be a small enough amount that you may not see a drip on the garage floor.
 
It's the intake gaskets. Buy the GOOD metal framed replacements and they'll last quite a while. The design on those seals so many things at one...it's ridiculous. Also, if you do them yourself, make sure not to mix up the pushrods. It's very possible and they'll go in the wrong lifters no problem. You won't really know you did it wrong until you try to crank it.

I never use DexCool in anything. The new green stuff they have says you can use it in anything and I do. No adverse affects in any of my GM vehicles and I don't have to buy that nasty, red crap anymore.

My uncle runs 4 or 5 of these vans back and forth to where he works and we've have to do intake gaskets on all of them. Gotta love working under that cowling...
 
I paid $26 for the pushrod removal tool when I did the one I did. Waste of money. Grab a 10mm wrench and loosen the rocker arm if you can't just pull them out. If you want to borrow my removal tool, you're welcome to. Also, the kit I bought was plastic framed, but was supposedly an updated material that shouldn't break down like the original. I went back with green universal coolant, and it's been on the road for a couple years. I recommended she get a coolant flush after a few months. I'm not sure if she did, but the water pump just went out, so hopefully the shop that replaced that flushed the coolant.
 
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