Fan clutch

[oshen]

I think my fan clutch may have shat itself. Whats a sure fire way to check if this is my problem. I did use the search function, but didn't find a straight forward test. What is the best way to check this?

thanks in advance

[layback40]

Originally Posted by oshen

I think my fan clutch may have shat itself. Whats a sure fire way to check if this is my problem. I did use the search function, but didn't find a straight forward test. What is the best way to check this?

thanks in advance

I will probably get flamed for this !!

with the fan still installed.
Roll up a few sheets of newspaper into a stick.
With the engine running & cold the paper roll should be able to stop it when you carefully put it into the spinning fan.
If the motor is warm, the paper roll should not stop it.

[Tuffeb]

100 percent correct lb

I did this test my self wasn't dangerous if your careful

My mates mechanic said to use a rag wrapped around your hand!!!
Bit extreme

[Big Dave]

The guy doing my A/C re-gas a few years ago said the fan should stop almost instantly on a warm engine when you turn it off. If it runs on at all It's stuffed.
Also have a read of the answers to question 4 in this link http://www.daviescraig.com.au/Fan_Cl...b-content.aspx

[Roler]

OK, here we go (since I already have dived DEEP into this in the past ).
First of all, never EVER stick something inside the fan/belt area with engine running, I don't care what mates have said in the past, you are an idiot if you do that, and from work experience I can see a lot of dumb idiots coming into my ED. There is a big sticker for those who have problems reading that shows a hand, a moving fan and a no-not-do-that interpretation. So far the "this needs to be said", now move on
There are several different opinions on how to test the viscous when. Especially when it should be moving with less or more resistance and how it should behave when cold or warm.
The fan clutch operates on a principle that it will lock when warming up, but spins more freely when cold. There are some that say, it should spin more freely when cold and not when hot....and there are others that say the opposite. I went through a lot of info online as well as the FSM to sort this out.

From the FSM: "If the fan-assembly free-wheels without drag (the fan blades will revolve more than 5 turns when spun by hand) replace the fan drive. This spin test should be performed when the engine is cool"

However, that, in my opinion is extreme malfunction, spinning that freely. But there is no clear way of telling suboptimal fan clutch performance, because it usually does not fail in a black-or-white manner, it just looses its 'power' over time and what you might notice is that temps creep up when the cooling is dependant on the airflow created by the fan, at idle and in slow moving traffic that is.
I, for long, kept telling myself my fan clutch was fine, and it was because it never overheated in slow moving traffic or at idle (it likely would if the clutch was bad)....till I finally replaced it during a coolant overhaul. The new clutch brought temps eventually back to where they always had been when I got it 5 years ago.
They are relatively cheap, so when in doubt or when its been many years, replace it. Simply because testing and effectiveness are not correlated in its case. I've done the research on it, hoping to find a 'bottom line answer'. But the above, well, that just my input.

[BLAKLISTED]

100% agree with what Roler has said.

I had overheating issues and was about ready to change out my water pump. Lucky I replaced the fan clutch first. The clutch seemed fine after trying a few diagnostic techniques, so was leaning heavily towards a dud waterpump.

But after I changed the clutch my overheating problem was solved.

[carvesdodo]

There is also a process described in the FSM - involving sheets of plastic, thermometers, timing lights and things ... but its really only, as Roler mentioned ... indicative - rather than diagnostic.

X 2 with this ...

Originally Posted by Roler

From the FSM: "If the fan-assembly free-wheels without drag (the fan blades will revolve more than 5 turns when spun by hand) replace the fan drive. This spin test should be performed when the engine is cool"

However, that, in my opinion is extreme malfunction, spinning that freely. But there is no clear way of telling suboptimal fan clutch performance, because it usually does not fail in a black-or-white manner, it just looses its 'power' over time and what you might notice is that temps creep up when the cooling is dependant on the airflow created by the fan, at idle and in slow moving traffic that is.

If you're unsure of the age or condition of the fanclutch ... replacing it is probably the best option.

Then if you have a decent, after market, temp gauge ... you can monitor temps over the long term and note any variations, relevant to varying driving conditions - as the new fanclutch ages.

.... thats presuming of course - that all the other cooling system components are in, "known", good condition.

Ther is no simple fix for the XJs cooling system ... Its barely adequate in warmer climates, from new ... and all of it - needs to be in very good condition, for peace of mind, long term driving.

There are some mods may help the factory system a little ... but many are just bandaid fixes for underlying issues.


Sticking things in the fan blades for a test ... is like poking your nose up the exhaust pipe for an emissions test ..