Fan Clutch

[Mike L]

I tried searching and saw there is no real way to check the fan clutch. My car tends to run warm at idle but will go back down in temp. This makes me think the fan clutch is bad. It doesn't spin freely when it is hot and I check it but seems to not be as tight as a new one. Although I am not real sure since it has been about 2-3 years since I replaced it.

On occasion my rig runs hot going up steep inclines as well. The radiator is a GDI 3 core that I put in less than a year ago. I also replaced all the hoses at the time I installed it.

Any ideas? Has anyone welded the fan clutch so it is locked all the time? If so, are there any complications? I would think it would pull more air all the time since it will spin all the time with the belt. Thanks.

-Mike

 

[5-90]

The fan clutch is supposed to slip when it gets hot, but will tend to slip at any temperature when it fails. Here's the "quick and dirty" check:

1) Run your engine up to operating temperature.
2) Turn OFF your engine. Put the keys IN YOUR POCKET (Sorry, but when you've worked on vehicles with your kids, you tend to get a little paranoid...)
3) Grab a blade on the belt-driven fan and turn it. There should be significant resistance - if there isn't, your fan clutch is probably shot.
4) Replace as required.

I've heard of drilling it out to take a bolt - but I'd want to do at least two (dynamic balance) if I was doing it for any length of time. I'm also working on plans for a "fan clutch eliminator" which will be solid steel and use OEM parts on both ends - that one's a matter of time.

I've not heard of anyone welding a fan clutch, and I'm inclined to think it won't work (from what I remember, the casing is aluminum and the hub is steel - won't weld together well.) I've been tempted to try brazing it (which will work nicely with dissimilar metals,) but the opportunity has not presented itself.

5-90

 

[Mike L]

The fan clutch is supposed to slip when it gets hot, but will tend to slip at any temperature when it fails. Here's the "quick and dirty" check:

1) Run your engine up to operating temperature.
2) Turn OFF your engine. Put the keys IN YOUR POCKET (Sorry, but when you've worked on vehicles with your kids, you tend to get a little paranoid...)
3) Grab a blade on the belt-driven fan and turn it. There should be significant resistance - if there isn't, your fan clutch is probably shot.
4) Replace as required.

I've heard of drilling it out to take a bolt - but I'd want to do at least two (dynamic balance) if I was doing it for any length of time. I'm also working on plans for a "fan clutch eliminator" which will be solid steel and use OEM parts on both ends - that one's a matter of time.

I've not heard of anyone welding a fan clutch, and I'm inclined to think it won't work (from what I remember, the casing is aluminum and the hub is steel - won't weld together well.) I've been tempted to try brazing it (which will work nicely with dissimilar metals,) but the opportunity has not presented itself.

5-90

Tried the "quick & dirty" method and there was no real significant drag. I will try it again later when the engine cools down to see if there is less drag. I was thinking about doing something to eliminate the fan clutch altogether as well. Sorta like the blocks they make for the muscle cars. I have a couple left over but I have not tried them for fit yet.

I was wondering about the welding thing as well, but haven't really looked into it so i don't know if that would even work. i may pull it off in the next day or 2 and see what the materials are. I have heard of people using bolts to hold that thing tight, but I haven't seen any pics showing how they did it and where the bolts are. I have also seen mention of using pliers and tightening the spring, haven't tried that either. Thanks.

-Mike

 

[3XJFamily]

Seems like I saw a pic of the bolt trick somewhere where they refered to it as a "trail repair" - might help if you are browsing. . .

BTW, had same kind of problem with mine. Temp reading hotter than I wanted, replaced one part after another of the cooling system (including the fan clutch) and it only seemed to get worse. The last piece was the temp sending unit at the back of the head. . . that 'fixed' it. . .

 

[5-90]

If there was no drag while it was hot, it's shot and you should do something about that. Also, if it's over five years old (or worse, you don't know HOW old it is) do something about it.

From what you're telling us, I'd be replacing the clutch.

I'd not try to lock it up with a SINGLE bolt - you'll put it off-balance and accelerate wear of the idler bearing it rides on. You can do two or three bolts (at 180* or 120*) and help to balance things, but I'd think that brazing it would be better if you don't feel like replacing it outright (like I said, I'm pretty sure you'd be welding dissimilar metals, and the melting point of steel is up around the boiling point of aluminum, I believe. Booger welds.)

To recap - there should be little to no resistance when cold, and significant resistance when hot. If you don't have any resistance at operating temperature, that's why your overheating at idle and you'll want to replace the fan clutch.

5-90

 

[Genster]

have you replaced the thermostat at all??? all the fans in the world wont matter if the fluid wont flow through your engine.

 

[Mike L]

have you replaced the thermostat at all??? all the fans in the world wont matter if the fluid wont flow through your engine.

When I replaced the radiator, belts, hoses, I did replace the thermostat with a factory one. I was wondering if the fan clutch was bad would it possibly cause it to run warm/hot on steep inclines? Or am I dealing with something bigger for that entirely? Thanks.

-Mike

 

[Planetcat]

I installed a fixed fan spacer I got from either summit racing or quadratec. It's a $10 part and the fan always spins. I think it was Quadratec, since I didn't have to measure for the correct XJ application. Works great for me, but I know others will comment on the negatives (loss of hp and delayed warm up, etc.). To be honest, the loss of hp is not significant and the delayed warmup pales in comparison to always having to wonder if your fan clutch is going bad or not, or is it your t-stat, or clogged rad, or head gasket, or . . .

 

[Mike L]

I installed a fixed fan spacer I got from either summit racing or quadratec. It's a $10 part and the fan always spins. I think it was Quadratec, since I didn't have to measure for the correct XJ application. Works great for me, but I know others will comment on the negatives (loss of hp and delayed warm up, etc.). To be honest, the loss of hp is not significant and the delayed warmup pales in comparison to always having to wonder if your fan clutch is going bad or not, or is it your t-stat, or clogged rad, or head gasket, or . . .

I assume you reused the factory fan? Anyone thought about replacing the factory fan with the correct flex-a-lite fan? Even with the factory fan clutch, would it pull more air? Thanks.

-Mike

 

[XJ_MAC]

Also chk your header for cracks and leaks. Exhaust into the engine compartment will accelerate overheating.

 

[jeepsrock]

Go pick up a Fan clutch they arent really that expensive and can save you a lot of time trying to see if it works or not ? They range from 40-65$ depending on what radiator you have because of space.

Goodluck
pete

 

[Mike L]

Also chk your header for cracks and leaks. Exhaust into the engine compartment will accelerate overheating.

I was wondering that as well since I have a crack that goes almost all the way around one of the tubes by the collector.

I did check the fan clutch again and there is no difference in the resistance when it is cold and then after it runs up to 210 degress.

-Mike

 

[mynameisphunk]

Sorry to dig this thread up from the dead, but I'd rather that than post a new one.

I'm trying to diagnose running cold in the winter. My 1996 4.0L never even hits the 160 degree mark in the winter- heat suffers, gas mileage suffers, it sucks. I didn't even think to check the fan clutch - I figured the thermostat was stuck open, so I replaced that with an OEM thermostat tonight. It was after restarting it that I realized the mechanical fan is always spinning - should it be spinning at a cold start idle? Sorry for the noob question, this is literally the first vehicle I've owned with a fan clutch...everything else I've had has had electric fans only.

BTW, the OEM thermostat that I took out was closed, so it may still have been opening too early, but it wasn't completely stuck open (and it was OEM).

I still haven't driven it with the new thermostat in, so who knows - it may have fixed the problem. I'm just wondering how the standard fan clutch should operate at idle when cold started. BTW, in the summer, I have no overheating problems...it runs right where it should.

 

[winterbeater]

Not getting hot enough is ALWAYS the thermostat. It's not your fan.

 

[mynameisphunk]

Dammit, I can't get the freakin thing not to leak after putting the new thermostat in. There was a lot of crappy gasket material that I had a tough time getting off... I had it close to flat, figured it would be good enough, but apparently not. Should I typically use gasket sealer on the gasket, or should the gasket alone be good enough?

 

[joe_peters]

I'm old school, I put a little Permatex non-hardening on the thermostat housing, not the head, and leave the gasket dry on the head side. Makes cleaning next time much easier.

You really need to have a flat, clean surface.

 

[mynameisphunk]

I'm going to get a gasket scraper and go at it again tomorrow (busy today). Thanks for all the help!

 

[winterbeater]

I'm old school, I put a little Permatex non-hardening on the thermostat housing, not the head, and leave the gasket dry on the head side. Makes cleaning next time much easier.

You really need to have a flat, clean surface.

That's a good tip in general: Glue (gasket adhesive) the gasket to the removable part, but not to the engine or tranny or differential side. That way the gasket is held firmly in place, and next time you can put the surface you have to clean off up on a bench to better remove old gasket/glue.

:roll:

 

[dan89XJ]

How about replacing the fan clutch with a non thermal fan clutch ? I saw it listed at a parts website as a replacement part.. about 10-15 bucks cheaper than a thermal fan clutch.