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Hi, I own a 1992 Toyota Hilux Surf 2.8 diesel, 340,000kms and have had it for twelve years. It is serviced every 5000kms which includes filters. Any problems and they are fixed. Aside from wear and tear there have been no major mechanical issues. I live in Wanaka and we have had an incredibly hot, dry summer. Following a recent service, the truck overheats following use. This only happens when it has been sitting for a while in direct sunlight. It did happen last summer but when the colder months arrived, it stopped. It doesn't happen all the time and I check constantly. There is minimal loss of fluid and I know it is water due to the colour. i.e. it has anti freeze. There are no other leaks of any kind. Sounds bizare and I struggle with my diagnosis but it has me completly baffled. Haven't been back to the garage where servicing is carried out as I would like your opinion as to whether or not I'm on the right track. I've removed the sump guard and looked all over the truck top and bottom and there seems to be no clue as to where the leak is coming from. That includes overflow etc.

Hope you may be able to offer an opinion.

Regards,

Cyril Ashby

Overheating is always alarming to us as we see more engines ruined from overheating than anything else.
My first thought when I began reading your question was perhaps that the radiator was partly blocked, due to your comment that it gets hot during summer months, but not in the winter. Obviously, there are numerous things in the cooling system that could cause overheating (water pump, thermostat, radiator, head gasket, cooling fan etc), so anything we mention is only speculation.
However, when I went on to read that the car is leaking coolant, I felt more comfortable that the fault should be easier to diagnose.
The very best advice is to take it to your mechanic and get him to perform a system pressure test. This should be able to track down the leak, and hopefully the source of your cooling system problem, with more certainty.