Aux fan question(i tried a search)

I have a 1990 xj 2door 4.0 with no a/c,i noticed my aux fan never comes on,i put 12v to the relay and it works .just wondering where the temp switch is located for this.The reason i ask is my stock cooling system boils over when i turn the engine off,when its running it stays around 210.

90exjay said:

I have a 1990 xj 2door 4.0 with no a/c,i noticed my aux fan never comes on,i put 12v to the relay and it works .just wondering where the temp switch is located for this.The reason i ask is my stock cooling system boils over when i turn the engine off,when its running it stays around 210.

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The fan don't come on untill 217. Are you sure it's hot or is your cap just bad?

langer1 said:

The fan don't come on untill 217. Are you sure it's hot or is your cap just bad?

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I guess my cap could be bad haven't looked at that,i have reach hotter temps than that,but still no fan.any idea where the temp switch is to replace it.

RENIX has a total of three temperature sensors...

The first is in the driver's side rear of the cylinder head, and drives the panel gage.

The second is in the lower driver's side of the engine block, and reports coolant temperature to the ECM.

The third is in the driver's side tank of the radiator, and turns the fan on and off.

Since you say you don't have AC, does that mean it's been removed, or was never there? I just want to be sure.

Other things to bear in mind:

The volume tank and cap require replacing at intervals - I change mine every five years (probably too often, but why wait? The ones in good shape get kept as "shop spares" in case I need one in a hurry.) I sign and date the bottom of the tank. Replacements can be had from Morris 4x4 Center (www.morris4x4center.com) for about $20 - both parts. That's where I get them.

Make sure you don't have a pinhole leak in anything - especially in the heater hoses. I've traced cooling problems like this down to things like that. The fact that it stays cool while you're running tells me you're getting good coolant circulation and cooling action, so there are other places you should look.

Check to see if you're losing coolant over time - that would be indicative of a leak. Isolating the leak is a matter of time and effort.

5-90

Sorry i didn't say specifaclly,it has never had a/c,and thanks for the heads up about the cap never thought to swap that out.

If you think the cap is going, might as well change the volume tank at the same time.

Look Here - about halfway down the page. For some reason, it's about a buck cheaper if you get them separately than if you get them together (no, I don't know why, either.)

Considering I've got about three restomods in the pipe right now, and the way Morris has been taking care of me, I think they're about to make a lot of money off of me over the next three years or so...

5-90

Just ordered them thanks for the help again.


Sean

A couple of other things to look at, is your coolant mix. The motor actually seems to heat up some when first shut off, and if it gets hot enough to boil a weak coolant mix, it will surge.
Air in the system has also caused mine to heat up and bubble or boil in the surge tank. I think it messes with the convection some. Either caused by a cooling system service, when I didn't get all the air out, or a small leak someplace. Leaks don´t always just push coolant out, they often suck air in during the cool down cycle, when it´s parked.
Simple thing, but I've seen many people fill the surge tank all the way up. it needs a little room for expansion. I usually fill mine half way up, cold.
I've pulled and tested a few thermo switches, all have switched lower than advertised (208 or so), but they were all old. Remember 210 at the temp sender for the gage in the top back of the block, probably isn't the same temp. for the thermo switch lower left of the radiator, which is probably one of the cooler spots in the system.