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MG MGB GT V8 Factory Originals Technical - Adjustable Fan Thermostat

I purchased a new electric cooling fan and adjustable thermostat for the MG. Looking for some advice as to where to insert the temperature sensing bulb into the cooling system.
Jim Miller


I didn't insert my temp bulb anywhere but used "two-part" epoxy to attach it on the back side of the upper tank, just under the lip of the tank.

With the thermostat, I can still play with the setting at which the fans come on.

I didn't install it in the rad hose 'cause I didn't like the look of the small bit of rubber with the groove in it which is supposed to provide a seal.

I can send you a photo if you like but it'll be a few days as the car is getting a wet-sand and polish at the moment.

Simon Austin

I have a Ford Falcon Rad and it has provisions in the bottom of the rad to insert the probe.

The instructions stated, I was to leave the fan off and let the car come up to 'N' (or anywhere else I choose) and then turn the temp control until the fan came on.

So it probably doesn't really matter where the probe is placed as this will become your datum point

This will be the temperature at which the probe sends a signal to the fan thermostat control (that the car temp gauge is reading 'N') and turns the fan on.

Bruce Mills

Hi Bruce,
I have falcon/early mustang rad, where di you fit your probe? I have the two connections for the trans cooler, the drain plug and the bottom hose, that's all.
Tony Bates

I have a perma cool switch and I soldered a 3/8" pipe fitting next to the top radiator hose. I thought it better to have the sensor bulb a the top where the coolant is the hottest. My radiator is a recored factory V8.

Al Wulf


I installed it in the drain plug and then had another one added to drain the rad.
I have to drain the antifreeze out a couple of times a year for racing purpose's.
Now I have added D&D's swivel oil filter adapter to the picture and will have to work out a way to get the lower hose hooked up.

Bruce Mills

If just a bulb on a thin capilliary they are usually intended to be inserted in the top hose where it slides over the radiator inlet pipe, but on one I've seen it weeped during warm-up, being OK cold and hot. Normally you would set it so that it only comes on when the temperature is somewhat *above* normal, or you could get the situation where the stat has closed and the fan is still running. The factory electric sensors are designed to switch on about mid-way between N and H, although personally that is higher than I would like. The SU Burlen replacements switch on about 1/3rd the way from N towards H which is better, but unfortunately they have a wide hysteresis which means the temp has to get right down to N before they switch off, which means they are running for a long time.
Paul Hunt

Does anyone have a favorite body guy that could put louvres on a 1980 MBG Bonnet? I saw the GT up at Ted Lathrop's and they looked good and will be very functional. I am still looking for Omni's and Horizon's.

Curly Dave
D Kirkman

This thread was discussed between 12/03/2005 and 22/03/2005

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