Luke Franklin

G’day Allan, I’ve been chasing an overheating issue in my TD42 Patrol for some time now and I don’t seem to be getting anywhere. It’s losing coolant over time, however there’s no temperature difference driving to and from work below 70km/h, but I notice the temp increases when I’m at highway speeds. There are no apparent leaks under the vehicle and when I dropped the oil there were no signs of coolant in the oil, and there are no bubbles in the coolant so I’m thinking that it’s probably not a head gasket, however the coolant loss is higher after driving at speed.

Do you have any idea what could be causing this?

Allan

Luke it would be interesting to know if the overheating only occurs once the coolant has leaked out. I don’t know if you have two problems or not. Keep in mind that if you’re driving all day, you can lose up to two liters per day through a leak in the radiator core when it’s under pressure. Thanks to evaporation there may be no visible signs of a leak.

To check the head gasket: put a dummy cap on the radiator, extend the overflow tube into the cabin into a clear, half full two liter bottle with the passenger keeping an eye on the bubble activity as you move from idle to full throttle up a steep hill.

Any compression leak will be shown as severe agitation in the bottle. Care needs to be taken to prevent either of you coming into contact with the hot water. If you’re still unsure after this procedure, you can take it to a mechanic who will be able to perform this test for you and let you know whether you’ve got a head gasket leak, which I suspect you have.