coolant leak at cold temperature

Redneck53 · Jan 4, 2005

Hi All
Happy New Year
I have this most puzzling problem. When the temperature is very cold (-20 degC or more), I get a small coolant leak from the block, just under and behind the throttle body. This only happens on the first start at cold temps. After the engine warms up the leak stops

This does not happen when the ambient temp is above 0 degC. I have no idea what's going on. The last UOA was neg for glycol. The engine is a GM 3800 with ~100,000 km on it. Anyone have any suggestions,clues, advice.

Thanks,
Bry

ZR2RANDO · Jan 4, 2005

I used to have a leaking hose that only leaked when cold...took me a while to find it because it wasn't leaking after warmup. Finally found it at startup, cleaned up the mating surface, tightened the new clamp and everything was solved. Sounds like you have a leaking gasket that stops leaking when block heats up,,any chance it is a heater hose connection- sometimes they are connected in those nether regions that are hard to see clearly???

Kestas · Jan 4, 2005

I remember last year during the cold snaps there was a rash of posts complaining of coolant leaks. Your problem could be at the coolant hose connections, especially where they slip over aluminum outlets. Aluminum has high thermal expansion (and contraction) rates. The aluminum shrinks in the cold weather causing coolant leaks. This is one reason why the simple spring clamps are better than the screw type - they accomodate thermal cycling and comply with the dimensional changes.

Drew99GT · Jan 4, 2005

I'd get it looked at for a possible external intake manifold gasket leak. I dunno how the 3800s are design wise, but the 3100s/3400s leak externally right under the throttle body as well, forming a puddle there on the lower intake manifold.

Matt_S · Jan 4, 2005

The 3800 V6's pass coolant through the throttle body. I believe the purpose is to warm it up quicker in winter and keep it the same temp as the rest of the engine. Anyway, you could have a gasket leak where the TB meets the intake manifold. I would look there first. It might just be necessary to re-torque the bolts.

Chris142 · Jan 5, 2005

There's a weird shaped rubber O-Ring between the throttle body and the intake manifold. I've replaced a few in the last 2 months or so.

The nuts and bolts that hold the TB to the intake manifold are a bear to remove! Well the nuts are not too bad but the heads of the bolts are very thin and it's nearly impossible to get a wrench on them to keep them from spinning.

pitzel · Jan 5, 2005

quote:

Originally posted by Matt_S:
The 3800 V6's pass coolant through the throttle body. I believe the purpose is to warm it up quicker in winter and keep it the same temp as the rest of the engine. Anyway, you could have a gasket leak where the TB meets the intake manifold. I would look there first. It might just be necessary to re-torque the bolts.

The reason for running coolant through the throttle body, according to GM documents I have read, is for anti-icing purposes. Given the right combination of humidity, operating conditions, and temperature, tbe engineers felt that they needed to heat the throttle body as a safeguard against ice accumulation.

Drew99GT · Jan 6, 2005

Now that I think about it, there is a TSB out for this very condition on the 3800 I believe, and it does have to do with coolent leaking around the throttle body coolent passages. I believe there are revised bolts and torque settings for the throttle body. Go to the NHTSA website, and it'll list all the TSB for your vehicle.

Redneck53 · Jan 6, 2005

Drew99GT,

Thanks a million. I found the TSB and it describes exactly what I am seeing. Now for the big question......will the stealership pay for the repair????????

Bry

Matt_S · Jan 6, 2005

If it's under warranty, this will certainly be covered. If not, though, I very much doubt it. It should be an easy repair, regardless.

Redneck53 · Jan 6, 2005

Easy for me (a DIY job) or easy for them. I don't mind doing this, but it's bitc**n' cold right now and I don't feel like freezing in the driveway. Maybe I'll just put up with the small leak for now 'till it warms up a little

Matt_S · Jan 6, 2005

Easy for them, I suppose. It's not bad, but the bolts can be a little tough to get to. Check out the GM Service Manual for the procedure, if you'd like for a better idea of what's involved.

Redneck53 · Jan 6, 2005

Thanks Matt

Bry

Matt_S · Jan 9, 2005

quote:

Originally posted by Redneck53:
Thanks Matt

Bry

No problem.

Let us know how it goes.

Redneck53 · Jan 10, 2005

Will do. This weekend seems like a good time to get at 'er. The temp is supposed to go up to a balmy +7 degC !!!!!!!!!

Matt_S · Jan 10, 2005

That's downright summer-like compared to what it's going to be like here. More like +7 F. Brrrrrrassssss!!!!!

Redneck53 · Feb 6, 2005

Finally got the job done. It has been too da** cold to work outside. I phoned the service guy at the dealership and explained exactly what was going on. He looked up the service record and saw that the mod had never been done, so he said that they would do it for the cost of the parts, even though the warranty expired 20,000 Km ago

However, upon further inspection, they discovered that the intake manifold (the #$^%ing plastic one) had a hole in it and for the sum of $450 Cdn + labour would be happy to replace it.

Cheaper than an antifreeze wrecked engine. Will post the UOA as soon as I get it back (Redline 5W30)

coolant leak at cold temperature

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