Just double check my work here. I read a few older posts to arrive here. I had to take my XJS to work today due. to a car shortage at home. It was about 90 deg F out and in stop and go traffic (mostly stop) my temperature crossed the "N" and headed just to left of "H." Once I was moving again the temps came down but never to the middle of "N" again.


A few weeks ago I was running hot and found an electrical problem with the single electrical auxiliary fan, that's been corrected and it's coming on as it should so tonight I tested the main engine fan.


I drove the car around got it up to operating temperature and brought it back to my garage. The fan has nearly ZERO resistance when I spin it when the engine is hot. It also seems to have nearly zero resistance when cold as well.


Sounds like the clutch is bad?


1994 XJS 4.0L 2+2

 

If I recall I should spin by no more then 3-4 fan blades when hot, like barely a quarter turn. When stone cold it should move more freely but then come to a stop and not fly around like a lose wheel.

I've checked my clutch while engine reads slightly above normal it barely turns when hot. There is a Hayden heavy duty clutch you can buy that fits most jags to aside from the standard type replacement you'd find at <generic parts supplier>

 

Yes, there are fan clutches available at nearly every parts supplier near me fortunately. The rest of the balance of my cooling system looks near new. I can see what looks to be a new water pump and a nice green gasket between it, very shiny part. Nice fresh green coolant and I did a hydrocarbon test and that came out fine. Hoses all look spectacular too.

 

Yes


Cheers
DD

 

A clutch is cheap, if that doesn't solve it we'll be here to help. I've got tons of products/experience which can help rage-flush a shitty cooling system.

 

"Rage flush". I may need to borrow that some day.

 

Get one of the cheap digital tachometers on EBay. Takes the guesswork out of diagnosis.

Then run this procedure :

http://fanclutch.com/PicsDocs/BorgWa...ives_Only).pdf

 

Btw Hayden 2765 fits the 5.3, but won't come up as fitting on most websites. Notice it is only one number off from the part number typically given, which I believe is 2665. This clutch can be used, at basically the same cost, as a heavy duty replacement which features more lock-up. I have not noticed any increase noise as a result.

Also, in case it isn't described well enough, the fan test refers to the fan spinning if you give it a whirl. A long time ago I didn't understand this based on the typical description, which led me to think you shouldn't be able to spin the fan around more than 3-4 revolutions by hand before it locks solid. Instead it is referring to how much resistance the fan has when given a single good push.

 

Can you elaborate a bit? When hot mine spins infinitely, it doesn't seem to lock at all. My new Hayden 2665 should be here this afternoon.

 

Please put some cardboard down in behind the radiator to! Not alot of space there as it is, I managed to bolt my new fan and clutch together and slide the whole assembly in without removing anything except loosening the fan shroud...I do NOT recommend it as one wrong nudge and you'll break something. Also while there its good to inspect the fan itself as they develop structural cracks and can fly apart under high rpm causing a lot of damage. A new fan is cheap to, they come in plastic or metal.

 

Hi Vancouver

Where can I get a Metal Fan, I didn't know you could buy one, would you happen to have a Part Number for a 1990 Pre-facelift V12

 

I know I've seen it, trying to find it online. They switched to plastic after a few years but they were metal and obviously more durable.

 

Hi Yes!
That is why I want one, thanks for your help

 

Solid Fan Clutch

Proof! I'm getting closer! he had a metal fan on his car.

 

Hi Vancouver

What you have just Stumbled on could be a lot Bigger than you think! as in the UK you cannot buy the Original White Plastic Fan for these Pre-Facelift Cars anymore

And although they do a black plastic Fan, I'd rather fit a Metal one if it were possible and also do away with the Fan Clutch and from that very helpful link, it certainly looks like it's possible

Last Year my Fan Clutch seized up and so the Blades were Spinning at the Same Speed as the Engine and if anything keeping the Engine a lot Cooler, where the only downside as far as I could see

Was that it was Spinning my White Plastic Fan so Fast that I was concerned that it might Break up!

Which probably couldn't happen with a Metal Fan

Since I didn't throw that Seized Fan Clutch away, then maybe I could use that instead of having an adapter made but even keeping my New Fan Clutch, I'd certainly feel a lot happier to be Spinning a Fan with Metal Blades

I'm hoping that 'Greg' might slide by on this, as he has done a lot of R&D on this sort of Stuff

 

Hi Time-Pilot

From 'Stone Cold' with the Engine off, if you give one of the Fan Blades a good 'flick' with your Finger, it should Spin no more than about one revolution (two at most)

But if it Spins round like a Bicycle Wheel, then the Fan Clutch needs changing

Though assuming that it passes that Test, when the Engine is Running and the Fan Clutch starts to warm up, then the Fan should kick up a Storm of Air enough to flatten grass under the Car

After which the Speed of the Fan should modulate according to Engine Temperature and Ambient Conditions

This is not a definitive Test but more of a Rough Guide, if you think the Fan is 'playing up'

Changing the Fan and Fan Clutch is a reasonably easy job 'in the scheme of things' but is a whole lot easier if you remove the Bonnet/Hood Struts and then tie it up in an almost vertical position being VERY CAREFUL NOT to damage the Front Grill

Or you could take the Bonnet/Hood off, if you've got enough people to help you, although its almost as easy to do it with the Bonnet/Hood Still in place, if you can tie it up Safely so that it cannot fall

Also its a lot easier if you take off the Top Closing Panel but don't go losing the Copper Washers that go on the Banjo Bolt of the Pipe that runs across the Top of the Closing Panel

Whether you take that Top Closing Panel off or leave it in place is up to you but if you decide to remove it DO NOT OVER TIGHTEN it when you put it back, or you could strip the thread in the Top of the Radiator (So Be Very Careful!)

You can see how I did mine on Page: 48 of my 'Cherry Blossom' restoration thread and here is a link to that Page that also has Photos and the reason why I decided to remove my Electric efans and then go back to Mechanical
'Cherry Blossom' restoration thread page 48

 

Well this was in interesting project, all told the fan took about 30 mins to remove, probably because this is the 4.0 and there is a lot of room to work. I didn't have to remove the bonnet or tilt it forward there was plenty of room to work. But I think the cause of my overheating in traffic is now confirmed as the massive amount of junk I found between the radiator and the condenser. The pictures tell all.



It must be about 1" thick. I'll need to find a way to clean it tomorrow as I do not own a pressure washer.

The rest was a normal party.

 

To clean out all that you really should remove the radiator. Then you can make sure the fins really are clean. That's a fairly typical amount of debris between the condenser and radiator.

 

Damn, I totally don't want to drain the cooling system it makes such a mess.

 

The fan isn't designed to move at engine speed, so getting rid of the clutch isn't a great idea. The design speed is about 2/3 of engine RPM under lockup. Spinning the fan faster uses more fuel, and at higher road speeds actually impedes cooling. The fan at low road speeds pulls air, but at higher road speeds it acts like a barrier and doesn't let more air through.

Counter intuitive as it may seem, there are situations where spinning the fan faster results in worse cooling, not better.