I found this on XJ Talk and it made me very curious...

All of us know XJs run hot and the Aux fan does not come on until the engine is well above the temperature the thermostat opens. If you have a Renix era Radiator, the fan switch is located in the driver side radiator tank. The factory switch comes on at 198° and off at about 185° The problem with that is that the coolant is supposed to be 10° cooler or more than what the thermostat is rated at in order to maintain an even temperature. This means that your auxiliary fan will not come on until the engine is in danger of overheating. Typically, if you put 198° coolant in the bottom of the engine it will come out at 220° I discovered a fix today for that. The threads on the radiator fan switch are common. There is a Peugeot, go figure> switch that fits the XJ radiator that turns on at 187° instead and shuts off at 174°. Thus with this switch will allow the auxiliary fan to come on sooner and keep the coolant ten degree cooler going into the engine. The model is apparently any Peugeot manufactured between 75 and 82

Has anyone on here heard of this before?

 

Interesting, I would like to know alittle more about this. This may be a weird question, but what the heck is a "Peugeot"??

 

A french carmaker

 

The dinky XJ rad works fine this time of year. 6 mos from now we'll again go from 'my heater doesn't work' threads to 'overheating' threads, regardless of the temp switch.

Why is coolant temp supposed to be 10 degrees cooler than t-stat temp?

 

The point is so the elecrtic fan automatically turns on at a cooler temperature.
Flipping a toggle every few minutes would get to me. Also, if I remember right, cooler running temps will get a leaner mixture, and possibly better mpgs.
Just thinking out loud.

 

Cooler temps get a richer mixture..........

 

can you post a link to this info????

 

My dad told me about a friend of his who raced in high school. Every time he got a new car he put a big carb on it an leaned it to the max. Every car he did this to blew up because they ran so hot.
This makes me think that lower temps would call for a leaner mixture so the engine warms up faster.

I really don't know enough to want to put money on it though so forgive me if I'm wrong.

 

Or you could get a $2 switch from the auto parts store and wire it up, then you say when the fan comes off and goes off.

 

Carbs vs fuel injection. A rich mixture is needed when colder.

 

http://www.xjtalk.com/showthread.php?t=7511

 

they never posted the part number for it...

 

.....but the XJ is designed to operate at 210. Sorry, couldn't resist.

 

I will probably end up doing that in the end lol. Would've been great for last summer! I think it would get annoying for me though.

 

I know! Pisses me off!