Hello fellow Jaguar owners.
I just got my 90 XJS road worthy, and have been putting miles on it. When I am driving, the car runs as cool as a cucumber. But at idle the temp raises at a slow rate. I haven't seen it go much beyond the middle of the gauge. I have not heard the electric fan kick on at all. I was wondering at what temp should it kick on and what else should I be looking into to prevent overheat?

 

The E-fan should come on at about 94ºC as I recall...something like that.

A weak fan clutch on your belt driven fan could also be a culprit.

Also look for debris blocking air flow through the radiator. I've seen some where the lower third of the fins are totally clogged.

All that being said I'm not so sure you have a problem. If a car runs at idle for a long time and/or in hot ambient temps it wouldn't be unusual to see the temp increase a bit. OTOH, if the temp starts increasing almost immediately, that's a different story

Cheers
DD

 

I had a similar issue with my '90. I put voltage directly to the electric fan motor and found that it was not working. I replaced the fan motor and now it comes on as it should and keeps the car cool in stop and go traffic.

Also, there is a temperature switch on the front of the engine that measures water temperature. That is the switch that controls the fan. If your fan motor is good then try replacing the temperature switch.

Mark

 

You might replace the electric fan switch with one that goes on 10 degrees cooler. Also: Thermostats. Replace them if you haven't yet. After recoring the radiator, replacing the fan clutch, mechanical fan blade (cracks), coolant reservoir, caps and electric fan switch, my car still got hot at idle. New OEM thermostats did the trick.

 

Thanks all your advise is helpful. I hit the panic button when I walked out this morning to a puddle of antifreeze. It wasn't much but I took the car on a😘ride and it was fine as far as temp, never went north of N. Paying attention to the coolant level I noticed it was acting like it needed blead. So I did, took it on another ride and after it cooled down it felt like there was air in the top radiator hose. I blead again. Went for a nice ride and the gauge never went above the beginning of the N. I hope to get through the summer before I recore the radiator and go through all that. That would be a good winter project. But if it ends up I have to do it sooner, so be it.

 

I think the cooler fan switch is a great idea as well as new thermostats. Does anybody make cooler thermostats for the V12. I can only find 190 degree and in past experience I have put 160 degree in my american v8's and been very happy, or is that just a bad idea?

So for now my plan is the fan switch, thermostats, rad flush, banjo bolt and bleeder line maintaince. I don't think the coolant has ever been changed. So yes I'm sure the rad is plugged up. Over the winter I will do a hose kit and record the rad. That should ease my concerns.

 

You really want to run @ 175-180ºF or higher. Less than that and you could engine up running a little bit rich as you're at the tail-end of the fuel injection system 'cold enrichment' phase

Cheers
DD

 

That's good, but remember that, on these V12s, it isn't just temperature that you have to worry about. Correct flow to *all* areas is equally important....probably more important, really.... than the temperature.

The engine doesn't really care so much if the coolant is a 180ºF or 195ºF or 210ºF. What the engine really needs to full flow....no air locks, no clogs.....to all areas.

Low or low-ish coolant temp does not guarantee that your flow is good to all areas.



What bleed process are you using?

Cheers
DD

 

I installed a Beck Arnley Thermo switch #201-1545 which has a temp of 82/77. The original I removed was a Elmwood EAC-2510 temp of 85 c... My electric fan will now come on if my temp gauge gets towards the middle of the N on the temp gauge. My car barely touches the lower part of the N on the gauge while idling at a stop light. I have to idle my car at 2000 rpm's for 5 minutes to get it in the middle of the N to have the fan turn on... It helps to start with a clean healthy coolant system...

 

good idea doug, my temps run around 178F to a normal high of 185F, rarely over that, sometimes AFTER shut down they creep up to 190F-195F,takes about 10-15 minutes,(considered normal)!


studies by TWR racing V12s the coolant can boil after shut down because the OIL temps are much hotter then the coolant, and heat rises up into the water jackets, NO coolant circulation when engine is not running!

 

I have a pair of thermostats that run 10 degrees cooler than OEM but it wouldn't pass smog, at least in part due to the running rich that Doug refers to. I had them removed and had OEM 'stats installed and the car's run happily (at least in regard to cooling) ever since,

 

Everyone should listen to Doug. Clean cooling system with the correct thermostats and I would also use a lower temp thermo switch.

 

Hi
I have been reading this with interest
Jaguar's have all ways Had problems with getting (Hot) if you look at the size of the tubes in the rads you will see why They silt up
i personally recommend New Rad Thermostats Full flush and a Kenlow Fan End of problem and No stress and a Happy Jag
i have put 3 Rads in my car over the years and no Problems evan in the South of France

 

true the fixed OEM fuel map cannot (easily) be modified, a standalone computor can easily be adjusted for rich or lean(while driving) for a bump higher or lower in any of the map tables!

also in the cold/enrichment phase, and any place in the entire fuel map, its surprising how much power is hidden in the OEM system, for safety reasons!

 

That's another very strangely-worded post from "Chris Jack" this week, resurrecting a thread from 7 years ago.

Administrator, maybe worth a closer look?