Coolant leak

[Doozy]

Hey guys so I have a 2007 Sierra 1500 sle and this coolant thing is stumping me. When I top off the coolant when it’s cold and take it for a 50 mile ride the reservoir is nearly empty and the whole passenger side of the truck is covered in coolant, I did a pressure test and it drops slowly in an hour from above 15 psi to barely below it. New upper and lower hoses was told the radiator was new from the guy I got it from and head gaskets have less then 20k miles on them. This is really annoying and causes my temp to fluctuate and go from 210 to 250-230 and back down periodically and sprays coolant over the side of my truck, the upper and lower hoses are new and the reservoir is brand new, any ideas?

[CamGTP]

Are you not able to top the coolant off and watch for the leak with the truck at idle or with someone holding the RPM at 2000-3000rpm to increase the coolant flow and pressure in the system??

 

Could still be a coolant hose leaking, even a heater core hose spraying coolant.

[richard wysong]

the proper way to fill the system is with the engine at operating temp and running so that trapped air is expelled. If it's not full it may overheat and blow the coolant out the overflow. could be a bad pressure cap as well

[carkhz316]

18 hours ago, richard wysong said:

the proper way to fill the system is with the engine at operating temp and running so that trapped air is expelled. If it's not full it may overheat and blow the coolant out the overflow. could be a bad pressure cap as well

Lol, no, unless you want to risk burning yourself. I don't care if you let it idle to operating temp. It should still be done when cold. Additionally, adding relatively cold/ ambient temp coolant to already hot coolant isn't good either. 

 

Doozy, if you're losing that much coolant and the passenger side is wet (of the engine bay, I'm assuming) then the only other item on that side is the heater hoses. The plastic quick connects are prone to leaking with age, so I would check or maybe even plan on replacing those.

[richard wysong]

I'm not saying run it down the road then try filling it, open the hood, remove the cap, fill the radiator or reservoir, start the truck and let it idle until the thermostat opens and closes at least twice while maintaining the coolant level. Some vehicles have bleeder screws to release trapped air. If there is a lot of trapped air you may get a surge before the t-stat opens and it's ok to install the cap loosely to avoid making a mess. I worked in a radiator shop for years and have over 50 years experience under my belt, if you don't believe me look it up in the service manual. Adding cold coolant to a hot engine without it running is a BIG no-no. I agree it could be the heater hoses, possibly just a pinhole spraying under hot pressure, try moving them around while pressure testing. If it still blows coolant with a proper fill, pressure test or replace the cap and then if it still does it put a pressure gauge on the system and see how fast it builds pressure cuz you may still have a compression leak into the system. Has any one done any work involving the belt or water pump? Check the belt routing make sure the water pump is turning the correct direction. Some early models had clockwise and counterclockwise pumps and trying to diagnose the wrong direction pump install was a real head scratcher and the symptoms were similar. If any one added "magic" sealer trying to fix the head gasket leak your new radiator may be clogged, use an infrared thermometer to see that there's no cold spots

Edited February 12, 2024 by richard wysong