Boiling coolant

[Sephiroth]

So yeah... my coolant is boiling in the overflow reservoir. the temp gauge is where it should be coolant will start boiling after about 10 15 minutes of driving 45-50 mph i noticed this when i got home and stopped on the driveway. there are no leaks and oil is clean, fan comes on when i am on heavy traffic. the overflow tank cap has a little crack on the rubber seal could this be the cause? I am about to go on a 500 mile trip and i need to have the jeep in the best shape possible.

 

[LibertyTC]

My first question is ..when was the last time you had the dealer do a flush on their machine? A new thermostat while there would be a good idea!
HOAT coolant is good only for 5 years...and I always let the dealer do it right.
You could right now use a coolant tester and see what the rating is mine is set at -47c.
The coolant reservoir cap can be replaced as well.
I would want to know the water pump is up to speed as well & working correctly.
How many miles are on your KJ now?

 

[Sephiroth]

I had to replace the radiator about 3 months ago so it has fresh coolant i got it when it had 121000 miles and now has 185000 never been to the dealer since. i had to replace the radiator 3 times due to it cracking so I am sure the coolant is fresh. i will get a tester on my way back from work tonight anyway.

i just ordered the cap Part # 04596198 hope it is the right one.

 

[John3seventeen]

Cap is a good place to start as the pressure it provides increases the temp at which it will boil.

 

[TwoBobsKJ]

I had to replace the radiator about 3 months ago so it has fresh coolant i got it when it had 121000 miles and now has 185000 never been to the dealer since. i had to replace the radiator 3 times due to it cracking so I am sure the coolant is fresh. i will get a tester on my way back from work tonight anyway.

i just ordered the cap Part # 04596198 hope it is the right one.

Did you use HOAT coolant? Zerex G05 is HOAT and can be had at NAPA and O'Reilly's.

FWIW the boiling issue is likely a bad reservoir cap - but double check you have the right coolant in there :waytogo:

Bob

 

[tlrtucker]

the overflow tank cap has a little crack on the rubber seal could this be the cause?

I would replace the cap. Cheap enough and easy enough to do. I had an old motorcycle that would have the same issue, but it would leak coolant when it got hot, and when I put on a new $5 cap the problem went away and never returned in the next 10k miles....the old cap appeared to be just fine, but I replaced it anyway. Had the same problem on an old Cherokee that would over heat - replaced the cap and no more problems.

If the pressure isn't maintained the cooling system doesn't perform properly. If your gauge isn't reading hot, it is likely that the hot coolant isn't reaching the sensor. Replace the cap and I bet your problem goes away...

 

[Sephiroth]

tester shows 268 F for boil over and -45 F for freeze up so it is good :shrug:
I guess i just have to wait till the cap gets here.

 

[TwoBobsKJ]

tester shows 268 F for boil over and -45 F for freeze up so it is good :shrug:
I guess i just have to wait till the cap gets here.

What type of coolant is in there?