Cold-Related Coolant Leak

[More Power]

On the second day of the recent cold snap, I started the truck at about 1:00pm without having plugged in the block heater. Outside temperature was about zero at that time, but the previous overnight low was something like -10. The engine spun a little slower (synthetic oil) but started quickly, and I let the engine idle for about 10 minutes before driving away.

On the way into town I noticed that the "Low Coolant" warning light illuminated. I pulled over in less than a mile, looked under the truck, didn't see any leaks, but did see that the coolant level in the surge tank was low.

Continued with my errand, then drove home. Upon arrival at home I saw that there was a puddle of coolant on the ground and a drip trail about 3 feet long. I looked under the truck & under the hood again, but didn't see any coolant leaking anywhere, so I poured in enough Dex 50% mix to bring the surge tank level back to where it should be.

Based on where the truck had been parked, the puddle under the truck was centered under where the radiator/engine front would be.

Yesterday, I visited a local shop with a lift, so I could pull the splash shields and look for the source of the leak. The truck hadn't leaked any more for 2-3 days. A mechanic friend and I looked and looked and looked. We could not identify the source of the leak. The water pump neck's weep hole was dry and there was no evidence of ever having leaked. Hose clamps were tight, and no hose was leaking that we could see. No trail of orange anywhere.

So, what happened? What leaked? Thanks,

Jim

[CrashTestDummy]

Did the leak ever return? I was searching for 'coolant leak' on this forum after discovering a couple of drips under the front of the engine on our 02 2500HD. I figured it was a water pump letting go, but after a trip to the other side of town and back, have seen no additional leaks. It's been cold here lately, certainly not -10-degree F cold, but cold for us.

Can the water pump o-ring leak in cold weather and then stop? I'm kind of hoping that is what has happened.

[More Power]

No additional leaks since.

The weep hole on the water pump in my truck does not show any evidence of ever having leaked. I could not locate a drip path or see any coolant on any engine or cooling system component when we had it on the lift. We may have missed it, I don't know. We did tighten a couple hose clamps in the area we thought might have been a contributor, but saw no evidence of a loose clamp being a problem (none were really loose). Still a puzzle.

Aside from water pump weep holes, I've seen other engines leak at various hose clamped fittings when there was a cooling system overpressure condition (like when there's a bad head gasket or cup seal). With normal cooling system pressures, those hose fittings didn't leak.

So, check for cooling system overpressure - like upper radiator hose still pressurized after an overnight shut-down.

Jim

[CrashTestDummy]

I'll do that. This truck's been rock-solid as far as performance and reliability are concerned since we ordered it. It only has about 70K miles on it (It's a spare-spare vehicle that's normally used to tow our open race car trailer around), so it's barely broken in.

When it's not near freezing, it's been warm and humid this past month (typical southeast Texas weather), and we frequently get moisture condensing and dripping off the vehicle parts. There were a couple of small puddles under the truck that I discovered that were orange and tasted sweet like anti-freeze, so I got concerned. It's been parked in the shop overnight, so I'll go look at it some more after work.

Funny, sort of, but we have a 96 Impala SS that has a Meziere water pump on it, and I had a couple of drops of A/F off of it, too recently. The weep hole and mating surface to the pump housing seems dry. Weird.

[More Power]

The leak remains a problem that's just lying in wait. I just haven't found the source yet. Hoping it waits till spring when I can spend more time looking for it. :)

[Kennedy]

My suggestion would be to pressure test it while cold. That and/or tracer dye in the coolant.

[More Power]

My suggestion would be to pressure test it while cold. That and/or tracer dye in the coolant.

Good ideas.

Seems odd that it leaked when it had been sub zero overnight, but started fine without being plugged in. I doubt there was any pressure in the cooling system at that time.

Since that time, I plug in the block heater for a couple hours before starting. No leaks since.

[Kennedy]

Cold/shrinkage can be a real issue. When you start up you build temperature in the block which creates expansion/pressure and the remote areas are still cold.

My tractors like to leak in cold winter months from the radiator hose clamps.

[JetBoater]

i had the same mystery leak more than a week ago when it hit -8° C overnight. I noticed a small wet puddle under 1 corner of the rad.

I figured it was frost melt and ignored it... my low coolant light blinked a few times the next time I drove the truck.

Once home I popped the hood and found the overflow canister a bit low, not much, but I topped it up.

I noticed a larger 10 inch diameter puddle a couple of days ago so I inspected the rad closely. I had a tiny trickle leak from the tranny coolant hose on the radiator... and another tiny trickle leak from the upper rad hose on the opposite side. I replaced the clamps on both and have not seen the leak return yet.

I attribute these tiny leaks to years without tightening the clamps and the thermal contraction caused by the very cold weather.

I always look for leaks although I don't expect to find them.. especially coolant.

I am watching to ensure they don't come back.
:cool:

[More Power]

Cold/shrinkage can be a real issue.

Thought about cracking a joke here, but thought better of it.... :D

I'm hoping just putting a little more on the clamps does the trick... Still no leaks since that first day, but I have been using the block heater for 2-4 hours before each cold start. Sure makes starting easier...

On another subject, my P0302 related service engine soon lamp went out by itself today. I'm procrastinating on getting it in for an injector replacement. Will soon though. Wife says...

[JetBoater]

If you were more bold with your sense of humour, the thread would be called 'cold causing thermal contraction?'

You could lay the blame on thermal expansion just as easily if it sounds better.

Hoping the coolant stays were it belongs! :)

[Mark Rinker]

My 2001 LB7 (...that was subjected to copious amount of LPG and stacked with 50-80hp fuel rate increases) developed a head gasket leak that only reared its head on cold morning startup.

My theory was when both thermostats were closed, it pressurized the cooling system sufficiently to cause the overflow jug to overflow out the vent. It was rarely observed once the truck was warmed up, and never an issue in the six months of warm we have in Minnesota.

I added many gallons of DexCool on these days, washed the orange off the passenger side of the white truck, and put on another 50K before selling the truck to a couple of brothers from Wisconsin that intended to rebuild, stud, and truck pull the 200K war-horse.

Like a rock...with a little blood dripping from it.