Temp going up when going over 60 mph in highway for long time

[CheddarGau]

Coolant stay good all the time, I did change the reservoir cap cause it was making bubbles like it was about to boil but the temp stayed at the middle and after the cap change it worked all good.

The only time the temp goes up is when driving at 60 mph or more for too much time (20-30 mins) and then goes down back to the middle if you slow down and stay at 50 mph

Thermostat (spring side) will be facing the engine. If it's facing the rad, then it's backwards. Did replacing the expansion tank cap making the bubbles go away?

 

[u2slow]

I believe the electric fan assembly also constitutes the fan shroud. I have had vehicles before that didn't cool properly when the shroud was missing, although that's usually been a slow-speed problem. Highway speed tends to move all the necessary air regardless.

 

[Danihound]

Thermostat (spring side) will be facing the engine. If it's facing the rad, then it's backwards. Did replacing the expansion tank cap making the bubbles go away?

Yup they went away

 

[Danihound]

I believe the electric fan assembly also constitutes the fan shroud. I have had vehicles before that didn't cool properly when the shroud was missing, although that's usually been a slow-speed problem. Highway speed tends to move all the necessary air regardless.

I do have the fan shroud

 

[Danihound]

just to add, this jeep do has a head gasket leak, so it burns a small percentage of oil, that could be part of the problem right ?

I never lose coolant tho

 

[CheddarGau]

just to add, this jeep do has a head gasket leak, so it burns a small percentage of oil, that could be part of the problem right ?

I never lose coolant tho

Well if your vehicle has a known head gasket leak, then you have your over heating issue..... High RPM, and in cylinder pressure can definitely over come coolant pressure and cause over heating, especially at highway speeds. It is possible to have combustion chamber gasses enter the cooling system and never lose any coolant. I think you should have a shop look over your concern and verify it. They will have the appropriate tooling to do so.

How do you know you have a head gasket leak? Your oil consumption can be from oil getting past the piston rings (worn or gummed) and burning that way.

 

[CheddarGau]

Yup they went away

Interesting. A weak cap typically releases coolant through the cap (it will also have a soft rad hose when at operating temp) vs having bubbles come up. Bubbles in the cooling system (assuming it's not coolant being pushed into the expansion tank through the bypass, splashing around and creating bubbles ) is an indication of a head gasket issue. You should have a shop check it out.