[mikesz]

first thing I would do is check to make sure your coolant fans are working properly. PedrosBoard as a good diy. basically you remove the 4 fan relays above the fuse block and make a jumper using wire and a couple of spade connectors. Put 1 connector in the bottom middle slot and one in the top middle slot (before doing check pedros board I am writing this from memory). When I did this I found my right fan was not working at all the the left side only on high speed. the right fan was binding and causing my fuses and fuse block to fry. I replaced both fans and while I was at it cleaned the radiators. they weren't that dirty but while I was in there I cleaned them. Car ran much cooler but still had issues. replaced the thermostat, water pump, and front engine mount. I used a low temp thermostat. I found the thermostat was not working properly so that was another issue. the water pump was fine but while I was in there I replaced it. Lasted 2 years and just replaced it again, fortunately it just started to go so impeller hadn't self destructed. I also added an S center radiator from Woody. I have an 99 base. the center radiator was probably overkill but I can be stuck in traffic on the highway in 95 degrees and the car stays cool. I recommend checking fans first quick and easy. Contact me if I can be of any help. Just saw your initial post, oops fans are ok. I saw on Wheeler dealer big Edd used some kind of special coolant when they were restoring a TR6.