Nigel

You don't give much background information about your car, but here's my story.

My TF, acquired 3 years ago, also overheated. It has a 1970 MGB 1800 engine reconditioned during the 1998 build with a DCOE Weber, fast road cam, unleaded conversion/skimmed head, straight through exhaust, electric fan, Lumenition ignition with a Lucas sports coil, 30 thou plug gaps and a steel radiator (no oil cooler). Coolant temperature would vary between 70 and 100 degrees, increasing rapidly at traffic lights. I was getting a lot of cream on the oil filler cap as well and warm tickover was very rough. It never actually boiled though.

In my view, the build was never finished and fettled. It only had 1000 miles on the clock. I corrected the ignition timing by trial and error, cleaned out the Weber float chamber and jets, fitted a ventilated oil filler cap (there is no engine breather connection on Webbers). I fitted a top shroud above the electric fan to make sure air is concentrated on the radiator matrix, and also fitted a cooling fan over-ride switch (This is also useful for tuning and MOT's). I then had the Weber set up properly by Tom Airey Tuning. He reduced the main jets, increased the 'idling' (actually mid-range) jets and fitted NGK BCPR7ES plugs, all set up on his rolling road and exhaust gas analyser. By then the car was running much better and making 130 bhp.

Finally, I fitted the (missing) radiator expansion tank as per the excellent article in the last NG journal 'Slobbering and Piddling'. I am now free of cream on the oil filler cap and operating temperature only varies by +/-1 or 2 degrees or so. I do however manually switch the fan on in congested traffic. Finally, Tom Airey advised me to always use 97 octane fuel, preferably Shell (it runs cleaner than supermarket brands).

Hope some of this ramble may be useful.

Paul Bracey

Check the voltage suppl

Check the supply volt

Check the supply voltage to the temperature meter. The old ones run off 10v and you need to drop the supply. I had the same problems bought a thyristor controlled regulator and it works fine
Im assuming that your beloved is not boiling up but just recording high temperature at the guage?