Hello,
I have a 1998 XK8 convertible. My son noticed the heat gage higher than normal the other day as he was pulling up the drive way. After he parked, he also noticed steam coming from the engine. When I came home, I checked the water reservoir and noticed it was empty. I filled it with coolant, noticing there was water leak. I thought it was the hose, but surprisingly, I discovered it was a crack in the lower part of the reservoir tank.
After changing the reservoir tank, I filled it and ran the car for about 10 minutes, making sure the coolant level is good. The engine temp was good. As soon as I drove it around the block, the temp soured to the red mark and a (low coolant) message came out. I waited for the engine to cool, added more coolant and started it again. The same thing happened again. The temp was good at idle, but as soon as I drove around the block, it over heated again.
I did notice when the engine was hot, the radiator hoses were bulged up (swollen), and when the engine is cool, the hoses were collapsed (shrinks on itself).
I thought it could be the thermostat went bad. I called a friend who had a repair shop before; he also thought it could be the thermostat.
I replaced the thermostat (original part), but to my disappointment , the overheating still happening with the same condition.
What do you guys think it is? Please advise...
Thanks..

 

I've moved your post from General Tech Help section to XK8/XKR section.

There are many previous threads here on this topic but I'm sure you'll also get a lot of advice posted in reply.

Graham

 

Check the water pump next, the plastic impeller may be broken or worn. Also replace those coolant hoses that are bulging and collapsing before one of them bursts on you. Be really careful and do not drive the car into overheating repeadedly or you will destroy your aluminum alloy engine. It is better to monitor the temperature with an OBDII reader since the gauge only registers once you are overheating already.

 

Also, if the secondary tensioners have not been upgraded on this car, the time to do it is once the cooling system problem(s) are repaired.

The plastic bodies on the tensioners will likely have accelerated cracking from the overheating events and become even more likely to fail catastrophically.