temp gauge in the RED!

[f100stepside]

Hi just get the car running after fitting a new alternator. Five mins or so sat running temp gauge is rising then goes to the red line!. The electric fan has not come on don't know why. Fan is set at 70 deg turn the thermostat up nothing turn it down fan comes on at 30 deg. The fan temp sensor is inside the top hose fitting. Check to hose, it's cold! check rad it's cold and even temp all over. Squeeze top hose i can here the water gushing through. Carefully unscrew top rad nut (mk 2) while engine is running water starts to gush out but is fairly cool. Any ideas?, i'm thinking temp sensor on the block must be faulty.
Sorry for the long explanation!. john

[marshman]

Could be the new alternator has a higher output - i.e. more volts - than your old one and this is enough to have killed off the old 10V voltage regulator that feeds the temp and fuel gauges. Is the fuel gauge behaving itself?

Roger

[f100stepside]

Hi the fuel gauge seems ok but i have no idea how much fuel is in the tank. The gauge is reading between half and a quarter full. The alternator is the more powerful one 65 amps

[Scar]

Have you got one of those £12 ebay infrared thermometers? Worth getting, aim the red dot at the head and get an instant temperature reading.

[StagJonno]

1 - Knackered Temp Sensor
2 - Lead to Temp Sensor come adrift and touching an earthed surface
3 - Knackered V Regulator
4 - Stuck thermostat

That's all I can think of.

2nd item easiest to check, so do it 1st. Sensor located at the rear of the LHS bank (ie as if sitting in the driver's seat Otherwise as Scar suggests, do a sanity check on temperatures with an infrared thermometer to see if you do, in fact, have an overheating problem.

Jonno

[f100stepside]

Hi problem sorted. Ian P reminded me of the procedure for expelling an air lock. The top hose was cold and the bottom hose was hot. I should have realized! what it might be!.
Thanks Ian

[bonnietiler750]

If you're struggling to get the system purged dont forget it might help if you raise the front of the car (trolley jack will do) get ing the vent point really high does help.
Regards
Brian