Hello all,

I rescued my 89 V12 from a few years of neglect about a year ago, and I'm still busy sorting through the issues. With the help of the forum I recently replaced my yellow primary cooling fan with the newer black one (EBC4553), thanks for the help there!

I was driving home from work today, and while I tried to leave early to skip the traffic, I ran into a little bit of it. It seems the cooling system hit a turning point and couldn't recover from it; after getting very hot (while stuck in traffic) I finally managed to find a spot to park and let it cool off. I let it sit for about a half hour and then drove the short distance home without issue.

My question is if you guys found yourselves in a similar situation where the car ran, was parked, and then sat for a few years (put away wet no less, no preparation for letting it sit at all) what would you do to renew the cooling system? I know a hose kit is one of the things I need to do, and I already have the part number from SNG. I just would like the whole picture before I dive in. Do I need to flush the radiator or the system out or something?

Thanks for your advice!

 

I certainly would take the radiator out, see if it has the common problem of being full of leaves and debris between the radiator and the evaporator. Even if it doesn't it certainly couldn't hurt to have it flushed, or even taken apart and rodded out. When new, just like ANY new car, these cars would sit and idle for hours without overheating. They just have to be maintained to a higher standard than some Japanese cars.

 

+1 on removing and renewing the radiator core.

The Jaguar V12 gets very vexed by running hot or overheating, so replacing any hoses or other components that can cause that condition is a good idea.

 

If you had a problem of overheating because of traffic you are looking at a few likely culprits.

1. A blocked radiator (external) - the aerodynamics of the XJS causes debris to get picked up and lodged between the condenser and radiator. The first time I pulled mine it looked like all the fur off a gray cat had been sucked up and imbedded into the fins.

2. A blocked radiator (internal) - the stock radiator is actually a very efficient unit contrary to conventional wisdom, but it can get blocked up over time and a lack use and therefore circulation will tend to exacerbate the issue.

3. A failed fan clutch - (did you replace it when you replaced the fan?)

4. A failed thermostat switch or relay for the auxiliary fan.

At this age, you might want to pull the radiator and take it to a radiator shop to be tested and possibly recored. While it's out do all the belts and hoses, and replace the fan clutch. Test that the auxiliary fan is working.

In proper working order, the stock system does not overheat.

 

Also check to see the condition of the rubber flap on engine side of fan shroud. It stopd the air from bypassing the rad and drawing air from the engine bay. It should be soft and pliable. It allows the air to pass thru at higher speed but closes at slow speeds to force air thru the rad while the fans are running

 

Assuming you want to keep the car, in your position, I would redo the lot, thermostats, new/recore radiator, hoses, fan clutch, and replace aircon triggered OEM electric with a more modern design 11" with the highest flow rate you can get. Also, if that does not do it to perfection, replace the water pump.
Greg

 

Thanks everyone for the replies!

1) I will pull it and clean the outside, I'm sure that's never been done.

2) I will have it flushed as well and tested, possibly have it recored. Again, I'm sure it's never been done. The place that cleaned and coated my gas tank with RedKote is actually a radiator shop, and the guys there know what they're doing.

3) I saw on a thread on here that if you spin the fan and it doesn't freewheel (stops very quickly) then your clutch is good; mine appears to be working fine. I replaced the fan only and not the clutch due to funds not being in abundance. But a working motor is a happy motor, and I don't want to risk popping a headgasket or anything of the sort. I'll replace it if it needs to be replaced, in everyone's opinion.

4) When I first got the car the aux fan didn't work properly but upon investigation I found a faulty relay and replaced it. It works just as it should now, coming on at the proper temp (or what I assume is the proper temp) and turning back off once the temp drops down below the threshold.

Is the fan clutch a complicated entity? I don't have a problem replacing it when the radiator is out, it would be easy to do that way. I just thought that if it was working then there isn't a need to replace it.

Greg, My A/C doesn't work currently. I thought that wouldn't have any bearing on the motor running well and just on my personal comfort. I solve that problem by rolling the windows down. The cabin fans turn on but it only blows out the feet no matter what temperature I put it on, and only blows hot. I can hear the doors moving when I turn the car off (as the vacuum releases, I assume.) but they don't move at all with the A/C on.

I have read a little bit here and there and I'm scared to dive into the system. It appears to be a mess of vacuum tubes and the like, plus I'm sure it needs to be recharged and I've heard that freon of the proper type is more expensive than its weight in gold. Any advice in this arena would be helpful!

In addition, is there anything that should be happening that depends on the thermostat? The aux fan works properly as mentioned above and that runs on the thermostat, correct? Or is that a separate system? I tested the thermostat when I first got the wiring sorted out for the car by testing continuity on both ends and heating it up with a heat gun until the leads showed a continuous circuit. Again, I will replace this if you guys think it necessary.

 

It's not complicated, easy to do when you have the rad out, and because it's a design used on lots of cars they can be found inexpensively.

 

A couple of bits. The Asian cars and their stewards are not "cooling system failure" free!!!


1. In anther forum, a two Jag guy wanted to take a fairly long trip.
His SOI persuaded him that her daily driver, an Asian car, was more economical and dependable than his "quirky" Jags. Alas, half way down 101, the needle went full hot!!! Plastic tank to alloy core parted company. Only fix, a new one. The local "Asian car" dealer got one.
One day and night lay over. Good part, it wasn't all that expensive, the part that is!!!


2. Hot car tip: As these cars have forward hinged bonnetts, extra air flow can mean continuing on safely. Just pop the hood to the safety latch. Air flow is everything, or at least a large part of engine cooling...


3. Just pulling over doesn't help. with no water pump or fan, temps go up even faster..... Pop the hood and let the engine idle at least for a bit...


4. Don't press on ands hope. it don't come out well. been there, more than once....


5. Daughter's gal pal had an ancient well thrashed "Asian" wagon.
Ugh, got hot, it's little V6 blew a head gasket. Done for. Junk yard bound...






Carl

 

XJSMan
Your list of fixes looks a very good idea to me.


I meant change the water jacket thermostats, one each side in the ally casting the top hoses connect to. 82 degree ones from a proper jaguar supplier, fit them with the little hole and jiggle pin in it at the 12 o clock position.
As to the aircon, if your aux fan is working fine, leave well alone. The OEM fan is not that effective, but with a redone rad and a tip top main fan you will be fine. To prevent hot air to some extent (but in my experience an XJS gets hot in the footwells if the aircon is off, even when all is working properly) look at the water valve in the middle of the firewall, engine side. This is turned off by vacuum in a thin tube to the top of the water valve, and if your aicon system is off, this signal will not be happening. You can manually shut off the valve and tie it shut somehow. Bit of a bodge, but it will stop hot water going into the heater box. Worth doing in the summer when you do not need heat. The part looks like this
JAGUAR XJS HEATER CONTROL VALVE C41051 | eBay


I think you are wise to leave the aircon system to later. It is a certainty that all the pipes are shot and most of the engine bay components, and renewing them is expensive. Get the cooling bang on first, say I!
As far as the fan clutch is concerned, it is actually a viscous unit. When the car is cold the fan should spin very easily (essentially freewheel on the hub), and when hot it should go nearly solid on the hub because cooling fan drive is needed. If it is OK, then OK, but as you are in there, if you can find a new one at a decent price, worth doing. Others in the USA have found ones that are FAR cheaper than the OEM ones and apparently just as good.
Greg

 

Great information, everyone. I'll start with the short list, then. Remove and clean radiator inside and out, recore if needed, new hoses, and new fan clutch.

With the car cold the fan doesn't do anything close to freewheeling. It spins but not more than a quarter turn or more with a considerable amount of force applied. So it appears it isn't working correctly after all! I'll get a new one and put it on when the radiator is out.

A/C can remain as it is, message received!

Thanks, everyone!

Collins

 

That does sound s bit stiff. Rockauto.com is a good place for parts that are inexpensive, other places like Coventry West in Atlanta are good for Jaguar specific parts ( and everything else Jaguar!).

 

;

at least 75% of Jag V12s were lost because of overheating, they are at best difficult to cool, the original factory cooling system is barely capable of cooling with any measure of redundency(any cooling left to help cool engine).

i have witnessed the Jag v12 race cars many times DNF, 1/2-3/4 thru the race drop out from over heating, and thats with the best of radiators and pumps and anything else to help air flow cooling!

by far most,because of head sealing issues, and overheated oil cooling!

basicly the engine has some areas that are not the best for cooling!

and there are many posts on this forum that can help alieveate some probs.

 

Let me ask a follow-up question: I've never removed a radiator from a car before. I've heard of people not bleeding the air out correctly when they put it back in which causes a hiccup and a blown headgasket. And, apparently, every car is different.

From what I've read I can pull the radiator and leave the trans cooler/AC condenser/oil cooler apparatus (not quite sure what's in front yet) in place, but how do I ensure that all the air is out after I fill the thing back up with coolant? I've read about an air bleeder in the system, but that seems too good to be true. I don't just want to flush it out with a garden hose; I'm of the opinion that there's only one way to do things right, and I want to do it that way. So removal and professional flush and re-core it is! But I'd like to know how to put it back in properly before I go tearing things apart. Thanks!

 

Here are Doug Dwyer's instructions for bleeding the XJS:


He's not kidding, you spill a lot of coolant unfortunately.

 

I just wrote a very long post on exactly this topic a week or so ago. You may find it helpful. I followed the bleeding instructions in the ROM, the only changes I made were to elevate the front of the car, and to ignore any reference to Barr's Leaks. Filling was the easiest part.

In the front is the AC Condenser (above) and oil cooler (below). Clean both sides of these as well (air has to get through in order to hit the radiator).

You might as well replace the clutch while you're at it. "Freewheeling" to check it is never accurate. As you spin it, the oil heats up a little and then there is drag. For the price, it's not worth the aspirin to put it off.

Hope this is helpful.

 

i changed the factory system,1978 XJS V12, to what i think is much better.

one problem was air gets trapped in the system at different places, so air bubbles rise and i added this high mounted coolant expansion tank,OLD Ford idea 1955, tank collects any air that is moving around in the system, and it stays above any liquid ,that way only liquid gets back to engine!

so far 21yrs no heating problems, in Texas 100F temps! DIGITAL temp gage reads 180/185 F all the time , but after shutdown goes above 195/200F ,heat soak up from the oil in sump, oil runs around 215/220F gage .

and i use two electric fans, also removed the radiator transmission lines and run a front remote oil cooler.
works for me , i dont know about anyone else!

 

Thanks for all the posts, gents! This will all be very helpful when it comes to bleeding, of that I am sure.

I flushed out the LH side of the motor yesterday, and that went quite well. When it comes to putting the thermostat in I noticed that this one has a "top" and a weep hole, where the one coming out did not.



Do I put the weep hole at the top, or the "top" marking on the thermostat? Just want to make sure I do it right!

 

weep hole at top...

 

My v12 has consistently overheated the worst from the T-stats, but I have also had a problem with the fan clutch, water pump, and electric fan. Never had issues with too much air in the system or hoses getting clogged.

I replaced my aux electric fan with one online for $30 with some minor cutting to the shroud. With a bad temp switch, this fan has been wired to come on with ignition and stay on (also florida) for the last 4 years and it has been fine.

Don't dick about wondering which tstat to get, just order the proper Jaguar part.