Hello guys,

A few weeks ago my car overheated while driving, turned out to be a cooling fan, it was replaced and back in business. As it turns out I have another problem somewhere. I was driving the other day and it overheated again, within 5 minutes from cold. NO COOLANT LOSS this time. I tow it to mechanic, and he couldn't figure it out... he had the car running for 3 days and couldn't get it to overheat again. He drove it on highways, city driving, etc. Ugh. The coolant was full when my mechanic got it. Less than 3 days later I get a low coolant warning that went away.

It was suggested by another forum member that the waterpump may be original and causing poor circulation... but my mechanic says that it wouldn't be an intermittent problem if that was the case. He says it takes time to take it apart to find out if I have the water pump with plastic impellers or not, so he says if he opens it up, he's gonna charge me labor, and told me $250 for that job including the pump. BUT he feels that's no the problem and doesn't suggest it.

 

it needs a thermostat, they tend to stick closed, and have him pop off the brass check ball on the new one as that cause the lower radiator hose to suck flat when the engine is off and it eventually works itself off the t stat housing blowing coolant everywhere......whue nice run on sentence eh, almost out of breath on the 1

 

I would guess an intermittently sticking thermostat...relatively cheap to replace and try.

If that does not work have the cooling system pressure tested...there may be a small leak that is preventing the system from holding the pressure needed to prevent overheating.

Another possiblility is the coolant overflow tank pressure cap is defective..also an inexpensive item to replace.

 

You can run the cap loose to not build pressure and force coolant out small leaks to by you time till you can repair and its not gonna overheat

 

Brutal, I stand corrected regarding my concerns over pressure leakage and overheating.. I have seen this on other vehicles, but I will defer to your experience on the XK8.