It was a hot day and I was stuck in traffic jam for about half an hour, I switch on the air conditioner. As the traffic improves I accelerate and reach 35 or 40 miles an hour at 4th gear, suddenly the temp rises to 194 Fahrenheit or 90 Celsius and the car start to jerks badly especially at high rpm (the engine still on). I switched off the ac, put the gear to neutral and let the car cruise along, step on the accelerator and put to gear again this time at 3rd gear and it is back to normal, the temperature goes down to 82 Celsius or 176 Fahrenheit without ac on. This happen quite often during hot day.

  • My car is Land rover series III year 1975, original 2.25 petrol 3 bearing engine.
  • Using Weber 34ich carburetor
  • Sanden 805 Ac compressor, ac condenser installed in front of radiator
  • I use Mercedes electric fan for the AC condenser (only switched on when AC compressor engage) and use standard cooling fan configuration at the back of the radiator only replaced the original metal fan with plastic.
  • Replaced radiator and hose a year ago
  • I use standard mechanical fuel pump made by Bearmach
  • Temperature is normal most of the time at 82c

Is it head gasket, carburetor, timing, fuel delivery (vapor lock) or cooling fan problems?