[Ggang]

hello, this is my first post, I can’t seem to find a good reason for my issues with google so I thought I would try here.
I have a 2011 gmc sierra 2500 which the 6.6 (obviously 😂) and I noticed that my coolant tank always seems low when engine is hot, and returns back to normal when it cools off. It also tends to build a good amount of pressure in the top radiator hose, but not to a point where it’s alarming. Sometimes the low coolant light pops on while driving, It takes a few miles before the light turns on and half the time it doesn’t turn on at all. No visible leaks I can see and she drives just fine, no overheating, gets up to operating temperature just fine and everything works as it should.
I just replaced the radiator in hopes it would fix it but it’s the same deal. After that I took it to a shop to see if maybe it had a failing head gasket, but he couldn’t find any sign of head gasket issues.
I’m at a loss as of right now, I’m hoping someone knows what’s going on bc this is weird to me and quite frustrating. Thank y’all!!

 

[roachwe]

Since you stated new radiator. Did you have this issue only after replacing? If so this may be you problem. When I replaced my head gaskets this is what I had to do for everything to work out.

 

[Ggang]

Since you stated new radiator. Did you have this issue only after replacing? If so this may be you problem. When I replaced my head gaskets this is what I had to do for everything to work out.

No, the issue was present with the original radiator as well. I thought it was the problem, which led me to replace it. But it didn’t fix my issue

 

[roachwe]

Ok on mine when the head gasket began leaking it started almost like you state. Then after a few months I notice driving on the interstate as long as the under normal throttle issues started. Could drive for miles but when I would take my foot completely off the pedal longer than the normal slow down then it would leak coolant out the over flow. Almost like clock work at the end before replacement. Drive somewhat hard for a few miles let foot off pedal coast to side of road and leak at the front right tire.

 

[Ggang]

Ok on mine when the head gasket began leaking it started almost like you state. Then after a few months I notice driving on the interstate as long as the under normal throttle issues started. Could drive for miles but when I would take my foot completely off the pedal longer than the normal slow down then it would leak coolant out the over flow. Almost like clock work at the end before replacement. Drive somewhat hard for a few miles let foot off pedal coast to side of road and leak at the front right tire.

Alright I tried your idea and I didn’t see any signs of leaks, I have no idea what to think. I just feel like if it was a head gasket issue there would be more issues or at least this coolant deal would worsen.

 

[DaJokr]

Have you inspected underneath for any visible signs of leaks? How did they test your headgaskets? I had a shop test my 06 and say they were fine, but they were shot.

 

[Ggang]

Have you inspected underneath for any visible signs of leaks? How did they test your headgaskets? I had a shop test my 06 and say they were fine, but they were shot.

I took it to a local diesel mechanic and he checked the pressure in each cylinder and saw no issue, on top of not coolant in oil/oil in coolant, and didn’t detect any exhaust gases in coolant reservoir, and no loss of power or engine knocking.

 

[roachwe]

To test coolant for pressure just use a pressure tester for coolant and let truck run at operating temperature and watch gauge. The ford 6.0 I just work on with bad head gaskets only took 8.5 minutes to reach 25 psi. About the easiest test to do to check added coolant pressures. Parts stores will even let you rent one and return your money once you bring back.