Hi all, having problems keeping my car cool. seems to be getting very hot.
Anyone know if the cooling fan should run after the ignition is turned off.

 

Yes, the fan should run after shutdown if the engine is actually hot. Mine runs when the a/c compressor is running as well.

Have you checked the fan clutch on the belt driven fan? Also, the rads on these cars are famous for being internally and externally plugged up. Just blowing the dirt out of the rad from the fan side with some compressed air will help.

The actual temp gauge may be faulty as well. Are you sure it is running hot or could the gauge be giving false readings? This may explain why the fan does not run after shutting the car off.

 

You do not say if the car is overheating at highway speed or stopped in traffic.

If it's only getting hot in traffic I would suspect your fan clutch. You can test it by warming the car to operating temp and having someone switch it off while you watch the fan. it should only turn a couple of times (2-3 at most) before it stops. If it turns more than this the clutch is bad.

If it's overheating at 100km/h them your radiator needs to be removed and cleaned.

Later cars mine is an 89 the aux fan does not come on with the AC. It is only operated from a thermo switch in the water pump inlet (pre 6.0L).

It is likely that both these things will need attention if the car has not has them done in the recent past. A lot of people swap the fans out for twin electric. I did this as it was cheaper than a new fan clutch.

 

Its a '92 MY V12. one of the first facelifts.....has Jag key for the doors and fuel tank and Ford keys for boot and ignition.
Only done 43000 KM

Temp gauge has never worked properly from new, put it in for warranty work a couple of times. spends a lot of the time pegged on the red then suddenly works again. Twice now it has boiled over in traffic, last time was last week in heavy NY stop/start traffic. Had to pull over and wait 2 hrs till it had cooled down to put some water in and the traffic moving better.
Called up my mechanic who serviced and flushed out the cooling system and asked if he had done the flushing and was it blocked. He said of couse he did and no, it was clear and that l should try changing both thermostats.

As the fuel gauge has also started to play up and the low brake fluid light keeps coming on guess its time to clean up the dash contacts.

I think my fan is working properly, although some cars fans run after shut down. Now taken to opening the bonnet and putting the heat on hot in traffic (its only 91f / 32c outside temp here in Florida), and have learnt to close it again with my left foot. Not quite what l had in mind to do........!!

 

I would have the radiator removed for professional cleaning at a radiator shop.

As for the fan clutch, if there's any doubt then there is no doubt that it should be replaced.

New thermostats......*correct* thermostats.....are often advised after boil-over overheating episodes.

Finally, the cooling system must be *properly* bled after any work. This can sometimes be a PITA ....but it's an essential PITA. I'm not sure every shop knows the procedure or takes the time to ensure it has been properly done.


Cheers
DD

 

Ok thanks for all the help.
I have looked at the bottom (outside) of the radiators last month. I had a small rust problem at the front around the spoiler so l took it, lower grill and panel off, de-rusted and put back on (. Genuine Jaguar Parts and Jaguar Accessories for Classic Jaguars from Jaguar Classic Parts UK) still have some new parts. All looked clear and in order but l will blow it through this week. Where abouts and how easy, ha ha, is it to change out or check, the temp. sender ?

Anyone fitted one of these ??

http://www.v12s.com/jaguarxjscc.html#xjsrevm

 

Unfortunately an external inspection can't be used to determine the internal condition of a radiator





Not sure about a '92. On older models the temp sender for the temp gauge was just aft of the RH thermostat. Easy to replace, and easy to check if you have an ohm meter and the resistance specifications....which someone here might chime in with.





I believe some here have and gave good reviews.

Cheers
DD

 

So....fan only works when the engine is running...normal l guess for an engine driven fan !! The electric fan didn't seem to move, what turns that on. I put the A/c on and no movement. Guessing some sort of heat relay or should it run when a/c on ?

Checked movement of fan and does as said above, seems that the electric fan might be a problem so I will try putting a 12v feed directly to it to see if the motor works. (although l'm sure it was running the other day).
I cleaned up temp sensor pin and made sure that it was a tight fit but gauge still pegs to red after a few mins.
Next step is to remove dash panel and check connections behind there

 

Well a direct feed of 12v and the fan turns, so...what makes the little blue relay click the fan on......anyone ?

 

The fan should come on when the engine reaches a certain temp. Mine comes on just over the "N" on the gauge. You could try shorting the terminals at the temp sensor and see if the fan runs.

It sounds like your gauge may be faulty. Some suggest installing a redundant ground to the gauge cluster will help.

 

Yup, that's the nextish point of call. I've looked at the wiring diagram and it has confused the **** out of me......car was built in 1991 as a '92 MY and when l check the 92MY drawings they talk of a black and a white fuse box (with the fan fuse in) under the hood (bonnet) and mine only has a black one....which has all good fuses.

Wrong '91 diagram. found '92 MY one. Looks like l should check the run diode...

 

I have the same problem mine is an 89 and many things do not match the wiring diagram.

Have you checked the fuse for the fan. On my car it is in the fuse box on the LH side of the engine bay, there are 2 small fuse boxes it's in the white one.

Big_W is correct the fan comes on when the radiator outlet temp reaches a set temperature 90something degC the switch is in the waterpump inlet elbow.

If the car is boiling do not mess around just pull the radiator and have it rod cleaned or recored, replace the fan clutch or install twin electric fans (usually cheaper). My twin electric fans cost $90. Lastly new thermostats and the car will be good for the rest of its life. Otherwise you will be mucking around with this for weeks or months.

 

Right, checked the fuse..my car has only one black fuse box not the two on older models. couldn't short the two wires into the thermo switch as engine was tooooo dam hot. I think its the two wire contacts on the very front of the engine down low..as the fan doesn't come on with the a/c I think its most properly the diode pack relay. So better order one of them. For the moment l've jumped a wire across from the side light relay to the fan relay so as l drive with the lights on the fan is also on. And the temp gauge stay just above the middle so seems that's my heating problem sort of sorted....lol

Thanks all for your input. I got the wiring diagram from the link above. Captain something....good stuff.

Now you should see how I've got my rear windows to go up . . . . . .involves scotch connecters, wire and a 12v power source... and a hammer to tap the motor with.

Gotta love Jags

 

I had continuous problems with both of my 1989 XJS's. Not only did they consistently run hot from day 1 of purchase, the heat inside the car was uncomfortable, especially since the A/C was not working. Here in Southern California, that's generally not a problem, but it got old fast and I got tired of watching my temp gauge like a hawk to ensure it didn't creep much beyond the "N". So, I did the unthinkable, I ditched the crazy Jag dual input radiator and went with a late model Camaro aluminum substitute. I used the Camaro fan set up as well and what a difference. To be completely truthful, I also got rid of the troublesome V12 and went with an LS6. Since the swap, my temperature gauge has not crept off the "C" one time. The GTO A/C compressor and Modine condenser set up keeps the cabin nice and cool and I enjoy my XJS much more than I used to.

 

I don't get it... Why ditch the great V12 for a boring V8? The Best thing about the car is the V12...

 

Read all the posts...there is nothing great about having your mechanic service the cooling system and then still having to sit on the side of the road 2 hours while it cools down from an overheat. I assume that service wasn't free to boot. For some, including me, my dignity is worth more than the idea of having 4 extra cylinders.


Overheating contributes to the common problem of valve seat drop and now that the engine has been over heated multiple times it's like dead man walking, it could drop a valve seat any moment. For me having a V12 was like the sword of Damocles experience.


Converts have more power, are more fuel efficient and much more reliable. You also loose the weight of a small elephant over the front wheels which greatly improves handling, braking and acceleration. If done well, converts using LS engines are smooth, almost as smooth as a V12 at idle and once off idle, there is no discernible difference. LS engine use a different firing order that earlier SBC's which significantly improves smoothness. Imagine the XJS with a extra gear, 100+ more horse power, 40% more fuel efficiency and weighing 400Lbs less. If you don't understand a convert, it's because you've never driven one properly done.


There is nothing boring about a V8. Ferrari's have 'em, newer Jag's have them. Nascar, Indy and just about every racing series use V8's. What is boring... is the endless machinations is takes to live with the V12. High repair bills and time stuck on the side of the road waiting for a tow gets old fast. Distributor fires, fuel system fires, over heating, dropped valve seats, petro hoovering, lack of performance & the general service difficulty. All that's fine if you like the challenge. For some that's the allure and good for them. But other want reliablability, speed, serviceability and efficiency wrapped in a classic body and held up by a sophisticated suspension. SBC converts do loose a noticeable amount of smoothness, LS converts loose almost none.

 

Heh heh, if you wanted a non-overheating XJS there are much much easier ways to get there than a full engine swap.

Just sayin






Well, shoot, that's no good! You need to get that engine up to proper operating temperature. Too cold is not good!



I'm not knocking V8 conversions, though, as I'm well aware of the 'pro' arguments.

Cheers
DD

 

I have well serviced my XJS and so far it stays cool. My gauge does not get near the N and the car runs fantastic. If you maintain the car like it should be, then you will have a very reliable vehicle. Remember people, these cars need to be driven, not stored for months/years on end and any car that sits, will have issues. My friend with his Mercedes V12 had so many problems, it was absolutely crazy. LOL...

 

So...just curious...when you yanked the V12, did you take the logo off the back too?

John
1987 XJ-S V12
64,000 miles

 

Sorry, 6 years in and none of the problems you describe here including the lack of performance part. No unreliability, fires, over heating, valve seats etc, etc,...none...none...none and none. There's a lot of boring here, least of which is the Jaguar V-12.