The aux fan has one speed and is not that good. Well worth replacing with an aftermarket one. The 'big' fan is not electric as standard, but engine driven, so proportional to engine speed. If you have a 'big' electric fan it is an aftermarket one, and is the cause of your tickover overheating problem.

Either it is (a) not strong enough (could be poor fan, poor wiring - it should be fed from the firewall post via a relay), (b) it is revolving the wrong way, or (c) is not cutting in at the correct temperature - or all of the above! It should blow an absolute GALE when switched on, such that the heated air coming out the bottom of the engine compartment towards you is easily felt when you get out of the car.

If yours does not do this, buy a new fan 16 or 17 inches, the best you can find, and install it ASAP!

Greg

 

Agree with Greg

I've just been through a similar saga of trying to solve my overheating problem by fitting lots of "upgraded aftermarket parts". Unfortunately, in the case of electric fans, they all look black and are made of plastic, but their performance can differ by 2x or 3x in terms of the air they move.

My sequence of events was....

1) Standard rad (20 years old) + standard mechanical main fan + standard elec aux fan --> Overheating

2) Changed out mechanical fan and elec aux fan for 2 high flow electric fans --> still overheating

3) Changed out standard rad for upgraded aluminium rad (kept 2 high flow electric fans) --> still overheating

4) Changed stats twice. Bled the car 100 times --> still overheating

5) Took to drinking heavily. Left the car alone for 3 weeks.

6) Sobered up. Had a flash of inspiration. Bought an anemometer, borrowed a friends unmodifed XJS and measured windspeeds........ worked out the 2 "high flow electric fans" weren't high flow at all

7) Bought my own set of "high flow electric fans" (Zirgo ZFU14S @ 2785CFM each) and fitted these --> EUREKA ! Car has never ran cooler.

My conclusions from all of this were :

1) My real problem from the beginning was a blocked radiator due to old age. I confused the problem by messing around with the fans. I basically masked the improved performance of the new aluminum rad with sub standard fans

2) Aftermarket "upgrade" doesn't always turn out to be that way

3) The XJS cooling system can be upgraded to perform better than the original system BUT every link in the chain has to be solid.

At the risk of being picky, please confirm for us again exactly what you took off the car and exactly what you put on. If you say "I put on a modified high flow fan" I'm going to challenge you on whether it really is high flow (because I don't want you to take to drink as I did) :-) There is a lot of good reasons to changing everything at one time on the cooling system as you did...... the only risk is that if one part is not working properly, you can't easily work out which part it is

 

Scott you got new fans? how did you install them? with the same equipment that came with those other ones you got?

 

Hi Shawn

Yep. I found that fans are pretty standard size, so I was able to fit the new fans to the older shroud without any modifications.....

 

Hi i am in no way familer the the xjs. But am very familer with over heating engines. So a couple of thing to look in to would be have you flushed the rad out properly i mean taking it out the car are any of the fins bent. Is this said engine fan a viscouse fan could the viscous coupling have failed these can be tested by trying to stop the fan when the engine is hot. Could any of the hoses be perished and starting crack or even blocked hoses. what about the heater matrix could this be blocked. And lastly have you had the coolent sniff tested for exhaust gases. Good luck

 

If the engine is running correctly. Mixture and timing must be spot on otherwise you are fighting a futile battle. Have you cleaned the condenser fins? Also make sure the fan shroud is sealed properly and the rubber flaps work otherwise air for the fans will short circuit and not go through the radiator.

You replaced the thermostats. Did you buy ones from a Jaguar supplier or the local auto parts store? Some of the thermostats parts store try to sell you do not have the disc to block the bypass passages. This will cause overheating for sure. If the thermostat is not the right length it will not completely block the bypass passages.

Is the fan clutch completely locked up when it is this hot? I know it is new but never rule out a new part.

Measure the temp of the upper hoses and compare to the lower hose. If you have more than 20 deg or so your radiator is either blocked or you have no flow through the radiator.

 

A very important "BUT" and great point :-). No margin for any aspect of the system to be sub-par.


Cheers
DD

 

I have all orig parts. The only aftermarket piece is the fan clutch. New fan (black) aux fan is working when its supposed to. When engine is hot the fan will maybe turn a quarter revolution nothing more than that. I'm going to replace the stats again this weekend. I'll keep my fingers crossed. The radiator is new (recored). The thing that boggles me is that if I start out driving long distance the temp guage goes up to only the bottom of the N once I slow down or stop, the guage rises and will stay at that location even if I continue dring again. It will never come back below the N again. Basically the guage will stay wherever it is during idle and not return to normal during driving.

 

Then it is an airflow problem. If you take off the front bumper and go for a test drive, I am almost 100% sure you will find the temp comes down from hot. The front bumper goes right across the middle of the rad, and driving without it hugely increases the airflow to the rad; This is a very good test, as it will prove, one way or another, that it is or is not an airflow problem.

The mechanical fan, at tickover, does not flow much air. One of the advantages of replacing the mechanical fan with an electric one is that it will give you much better airflow at tickover.

 

Since we don't know how long ago you installed the new rad, have you cleaned out the gunk between the rad and condenser?

Are the two "mudflaps" in the bottom left corner of the fan shroud (as viewed from inside the car) in place?

Is your front air dam in place?

Have you checked for a head gasket leak?

Checked your trans temp?

 

Haven't check for a head gasket leak or transmission temp. How do I check the tranny. Also, on another note. Today I removed and clean the catch tank behind left front tire. The lines were completly clogged. The drain and the hose from the expansion tank to the catch tank completly clogged as well. Soaked in CLR for a few hours ( squeeky clean) goin to see if that helped at all tomorrow. Not sure what else there is to look at. I'm ready to drive this car into a lake :-(

 

Why not concentrate on the known problem, which appears to that the car will overheat at tickover but not at speed. This absolutely looks most likely to be an airflow problem. There are a number of things that have been suggested, have you tried any of them yet?

One other thing: If you go to a tool hire place you can hire a huge mains electric fan. Try putting this against the radiator and seeing if it drops the temperature. Even a torpedo-shaped space heater without the heat going will produce an absolute gale. If this drops the temps at tickover, you know the fans are not doing what they should. In this case, change them! I do not think you are going to solve this except by tackling this area.

 

Hi, I had the same problem, after months on checking thihs and checking that, it was the fan control module,bought a recondtioned one and the car is running well,no more over heating when staionary

 

I noticed on mine (which is still overheating after a rad flush and new thermostats) that the blade tips on the main fan are shiny; the mechanic reckons that some clown has jacked the car up on the front cross member which has pushed it up enough to move everything else up enough such that the fan tips contacted the shroud and worn them down. They are therefore too short!
Has anyone on here on the eastern side of the Atlantic successfully fitted an electric main fan and if so what make and model is it?
Steve

 

Steve, I have. First the small original electric fan. This fan comes on when the thermo switch in the pump inlet triggers OR always when the aircon is on my model (but on some models only comes on with the thermo switch). This original fan is best changed to a 10 or 11 inch aftermarket one. My make is Pacet. SPAL are very good indeed but pricey. 10 inch will fit in the original shroud. 11 may not.

Second, the main big mechanical fan: I have removed this, saved a drive belt, and various pieces of belt tighteners, jockey pulleys etc etc and fitted a 17 inch Pacet. Once again a 16 inch will fit in the original shround, a 17 inch will not. SPAL make a great 16 inch. The Pacet fans are very good flowers but my 17 inch one was not that well made. I had to rebuild it because the crappy circlip holding the fan blade on the spindle failed, thereby causing the drive flat to fail on the fan blade. Maybe just bad luck.

If you keep the shroud, then fitting the electric fans on the shroud is quite easy, and they should be mounted as close to the rad as you dare. You can use a couple of adhesive backed foam pieces to protect the fins here and there. BUT, you do not have to keep the shroud as all electric fans have their own outer ring which acts as a shroud. But then mounting it is slightly more difficult. I dumped my shroud because both my fans were too big for the shroud holes. What I did was to weld some studs on the rad cross member, pointing backwards, and use alloy struts to join from here to the fan bottoms. The fan tops can be mounted using short alloy struts to the same studs that the original shroud used on the rad top panel.

Cautions: The thickness of the fans, front to back is critical. There is only room for about 100mm (4 inches) total depth, so measure any fan before you buy. If I did it again I would go for a 10 inch and a 16 inch. I have 12 and 17, and room is VERY tight width-wise. The smaller fan can be just wired up using the same wires as went to the original. The large fan must use a new relay and take its main feed for the fan motor direct from the firewall (bulkhead) 12 volt post. You can use the coil 12v feed for the relay trigger feed wire.

How to switch the big fan: Manual switch, or thermo switch? or both. My small fan is wired into the compressor feed, and only comes on with the aircon. My big fan's relay is triggered by the standard themostatic switch on the water pump inlet. Grant Francis suggested this scheme and it works a treat. Diagrams available if needed. I have also fitted a separate cabin operated big fan switch, as a manual fail safe. You can use a dedicated aftermarket thermo switch that sticks into the hoses. If you do, the bottom hose is best, as the top hose temp changes very fast from fan on to fan off as the engine speed changes. This resulted in a couple of blown relays as they were switching on and off all the time. Hence the system I describe above. Maybe the 'bulb' type capillary thermo switches are better than the sort I used which was digital and had no way of adjusting the on/off temp differentials, which were far too close.

Does it work? Yes. I have NO shroud, just the fans, I have NO packing round the rad, and the fans recently held the temp just at the top of the N for 40 minutes in a solid jam on the autoroute in temps of 100°F, aircon on. Advantage of no packing is that you get much better general airflow into the engine bay.

While I am on the subject of cooling, it is my experience that the front bumper ruins the airflow to the radiators. I have done a couple of things to improve this: relocate the second coil to the side; relocate the horns one to each side; cut a slot in the bumper to enhance airflow. The sole advantage of this slot is that the temps drop much more quickly as speed builds up after a hot halt. It was not overheating before, or anything like it, but now the temps fall and the fan cuts out, much faster. I calculated that I have got about 40 square inches more than standard of uninterrupted airflow straight into the radiator stack

Side benefit of electric main fan, + 1.5 to 2 MPG.

Greg

 

Hi Greg, thanks for all of that, I would be interested in those diagrams that you mentioned.
My auxilliary fan has now stopped working for some reason which is annoying but the car doesn't seem to be overheating as much although I haven't been far due to lack of time.
When I bought the car the auxy fan wasn't working at all which I traced to a missing relay/module (the red one). I replaced that and the fan cut in just about the normal temperature and ran for about a minute after switching off and then the next day it just didn't run at all. The fan runs off a direct feed from a spare battery so the motor is ok.
I've seen lots of posts about it only working when the a/c is switched on but there is no gas in my system so it is never switched on yet the fan was running.
I'm away for a week so I'll check the fuse and whatnot when I get back and take the car for a longer run to see what the temperature gauge gets up to.
I'll also fit the new Xenon headlights that I have bought and see if they are any better than the sealed beams that are currently fitted (well, the 3 of the 4 that actually do work).
Steve

 

Steve, the aux fan was wired differently by the factory from time to time. As follows:

Some models: Always on with aircon, Also comes on, even if aircon off, when thermo switch closes. This was how line came from the factory.

Some other models:: Only comes on when thermo switch closes, regardless of whether aircon is on or not.

So whichever your is, the aux fan should always be activated when the thermo switch closes.

If you still have the mechancial fan, and no aircon, the mechanical fan willl probably do the cooling job anyway. Maybe test the aux fan by hot wiring it engine off, and see if it still runs?

Greg

 

Have you measured the temps of the upper hoses and the lower hoses when it is running hot? If not please do that and post the results.

 

When performing the work on the cooling system - was it flushed and purged of air? Trapped air in the cooling system can also cause overheating conditions at idle...

 

Wonderful info on the fan options Greg. I too would be interested in your diagrams and anyhing else which may help with a potential changeover.

I have a 35,000 mile 1994 V12 XJS and live in Phoenix, AZ. I have replaced the fan switch and stats, recored the rad (work was done by a Jaguar certified shop). Both fans are original and test out fine as to flow. The original waterpump remains in place. Everything is as it should be.

My temp gauge tends to creep up to about 3/4 towards hot but still well within the N range. With a heat gun it measures an average of 215 degrees F at the 3/4 point on the gauge. The highest measurement was 221. If I place the engine under a sustained load such as long hill, the gauge starts approaching the maximun line of the N range. It has never passed the maximum line. Also, at idle, the temp will eventually reach the 215 F range mentioned earlier with an ambiant temperature of 105-110 F. However, the same results are occurring now with much lower temps - 90-95 F. In 70 F temps there are no concerns in any driving situation.

This is obviously still much better than the 270 F mentioned earlier! However, I am not pleased with the temps and am considering improving the fans. However, these won't anything for me at highway speeds. If you or anyone have suggestions I would love to hear them - other than move to a cooler climate that is!

The shop I used does not seem concerned. Maybe I should not be?