first time on the site so excuse me if I'm a bit slow. I have a 2004 Gmc 2500HD LB7 with 249K on it. I had an overheating issue on my last trip an found water leaking down onto the oil filter area, I let it cool and filled it with water, drove 600 miles with no problem. Pressure tested the system to 20lbs and no leak. Filled up the tank again and drove it around in 90 degree weather and it started leaking again. I cant tell exactly where it is leaking but it may be at the oil filter housing area. No oil in the coolant and no coolant in the filter. Just drove another 2500 miles with the pressure cap loose on the overflow tank and no leak and ran steady at 195 degrees. When I put the cap on tight and drive it, leaking again. Takes forever to warm up and will not warm up while idling. Put in two new thermostats after overheating and no change. Runs like a champ. Any suggestions. It's driving me nuts.
LB7: Overheating/coolant leak LB7
- Thread starter WVlogger
- Start date
First off, Welcome
As for the truck leak. It could be a few things... The oil cooler is in that area and has some seals that can leak. It would be easiest to remove the drivers inner fender skirt so you can see exactly where the leak is. If you run the truck hard and let it sit over night is the upper rad hose rock hard after the engine has cooled completely?
As for the truck leak. It could be a few things... The oil cooler is in that area and has some seals that can leak. It would be easiest to remove the drivers inner fender skirt so you can see exactly where the leak is. If you run the truck hard and let it sit over night is the upper rad hose rock hard after the engine has cooled completely?
Pulled the inner fender an nada. Drove it today and no leaking. Ordered a new coolant cap. Could it be the cap is not releasing pressure causing something else to leak.
Drove it today and leaked like crazy. Added over two gallons of water and couldnt get it to leak again so I could try to find the leak. Very frustrating. Is there a line on the top of the motor that could leak only under pressure.
Not likely. Might try pressuring up the cooling system and see if it will leak. May need to be hot also, be very careful removing the cap with hot coolant...
Fill it up with coolant and just let it idle, bet it dribbles after idling 15-20 minutes. The cap could be seized up and making a hose leak but I’ve never seen one do it.
only things that leak back there are freeze plugs, head gaskets (they can leak externally and give no other signs), the water pump tube o-ring that goes into the oil cooler, and the 90* elbow off the oil cooler into the mid plate.
at this point, its time you warm the engine up, pressurize the cooling system with a pressurizing tool and then start looking for where the leak is coming from on that side.
at this point, its time you warm the engine up, pressurize the cooling system with a pressurizing tool and then start looking for where the leak is coming from on that side.
I had one where the water pump would squirt and the owner swore it was leaking back by the cooler. Water pumps are also notorious for leaking at only a specific pressure/temp. You can pump them up to 20, and they'll hold for days, start it up, get 2-3 osi at 160 degrees and they'll piss like a race horse, then stop and not leak again until it cools back down. So make sure it isn't leaking furthur forward and getting blown back.
Found the culprit today. A rectangular rubber gasket on the oil cooler was never installed correctly from the factory. It last 250K miles. What a pain to fix. I'll post a picture when I figure out How to.