Like most of the classic car pilots I have experienced my MG's running hot during the summer months. These are a few of the techniques I have used to combat the problem.

The main problem seems to be at idle. When sitting at a stop light or sitting in traffic my MG's will warm up to the point where I will pull over to let them cool off. With higher compression or a performance cam the situation compounds itself. I have had a cooling problem at driving speed only once. This turned out to be a rubber bumper distributor which advances too much at higher RPM's.

First I tried a cooler thermostat. The Thermostat sets the minimum temperature not how hot the engine will get, so this did nothing.

Then I added an electric cooling fan. This did help some. There was a longer time needed for the engine to heat up. So this was a helpful improvement. But not a cure.

Then I put some wetter water in the cooling system. I did not see any difference at all. Some people have told me that it worked great for them however I did not experience any improvement.

I decided too try cleaning out the whole system. By using a coolant flusher. The type used was a heavy duty cleaner. The system must be drained of antifreeze and water only put in, then open the heater valve full, and put the cleaner in. After running the car for 30 mins the system was drained, flushed with water to clean it out, and antifreeze put back in. This made a large difference. The car would get warm but I could idle for 25 mins in 90 degree weather before heating up to 205 degrees coolant temperature.

To improve the situation more I continued. Next a flex fan was installed. There was no noticeable change. I then installed a fan shroud and again no noticeable improvement, but it did look cool!

After putting a screw driver through the radiator (on accident) I had the radiator recored with a four core (stock for crome bumpers) but, more tubes. This had a mild change. I was very puzzled as to why this new radiator did not chill things down.

One day while working on the 75 I noticed that the crankshaft and water pump pulleys were bigger than on the crome bumper. The ratio is the same for water pump speed between the two cars they were just different sizes. So I then took a late model crankshaft pulley and installed that on the crome bumper car with it's original smaller water pump pulley. I thought this would speed up the water pump at idle so as to provide more coolant flow.

The car had been working fine I just was not satisfied and wanted to settle this problem once and for all. It would still get to 195 degrees with a 170 degree thermostat in traffic so the cooling system was barely adequate.

After installing the larger crankshaft pulley every thing works well. The car can idle for at least one hour in 90 degree days with the coolant getting no hotter than 180 degrees.