high temp = cracked head?

[Yumsylux]

I was driving back to brisbane from gladstone yesterday and I encountered a problem in whenever I turned on the A/C the temp would start getting hotter. (higher than usual and climbing slowly) I had a Canoe on the roof which in the past has never caused any trouble, except for a little higher fuel usage. However the moment I turned off the A/C the temp would eventually come down after a couple of minutes.

Two months ago I had a split in the top tank of my radiator. I'm told it's a common occurance in a 2.8D hilux. My mate told of his surf blowing a top tank, and two weeks later his head cracked. (cylinder head) He states there's a theory about too much pressure from a crack in the head will lead to firstly failure in the cooling system and then bigger head damage. I'm pretty sure surfs have a common head problem though?

Can someone please tell me wether this theory is correct? Does this happen to a 250km old 2.8D motor? I've owned the car for the last 12months and it appears it's been looked after. What other problems could be causing these issues? Thanks in advance.

regards

[bad_religion_au]

sounds like a head issue

take it to a mech and get them to do a sniffer test and go from there

[Yumsylux]

Took the lux to a radiator shop to check out. They did some sort of pressure test and luckyily I don't have a cracked head. In fact there's no problem with the head at all. Says it's most likely the thermostat getting stuck. Has anyone had trouble like this? The thermostat was replaced when I had the radiator rebuilt. I was thinking cutting the guts out to the thermostat. I hear it'd take a bit longer to warm up but in a Qld summer do the experts here think it's alright?

[phippsy]

If anything I would have thought it would be way better to replace the thermostat than to not run with one at all. Even take it out and try it in some hot then cold water to see if it's working properly.

edit. the top tank of my radiator leaked for a couple of years on and off, I soldered it up then finally took it to a radiator place who resoldered the top tank, it still leaked so they soldered a patch onto it and it hasn't leaked since.

[shanegtr]

taking out the thermostat can also cause overheating. Because the water in the system is constantly flowing it will:
1: take longer to heat up - a cold engine will wear faster than a operating temp engine
2:May not have enough time in the radiator to cooling enough before its back into the engine = overheating