Re.: 1987 XJ6 Normal Operating Temperature

you may need a head gun to detect the difference, I have used it for sure, there is an AMway product that is less expensive however and does the same thing....Art

UPDATE

It's 108' today...driving with AC on...temp's range from 95-100' Celsius. I have added a product from Red Line called "Wetter Water" which seems to have some lowering effect.
In speaking to a tech at Red Line, he says in my type climate, above 32' F, they recommend 15% coolant with 85% distilled water AND the addition of their product. Anyone done this?

Scott

Doug,

yes it makes sense, so I have decided to go work in my Hammond organ which has no thermostats, requires no coolant or any other fluid, all it needs is a new 300 volt AC Cable.

Otherwise I conclude that there really is no cooling problem here, and that if the auxiliary fan was working as intended or modified to run with the a/c compressor, the exharcerbation would be minimized. All caveats still "ON".

"Of course the engine will reach the normal operating temp. sooner or later, eventually and decidedly."

If by "normal temperature" you mean the coolest temperature the cooling system is capable of providing, yes. The problem, though, is that a lower rated thermostat does nothing to prevent the temperature from *climbing*....which is the problem Scott has under certain conditions. See what I mean ?
.

"So why not later as with a thermostat that opens sooner? That's exactly what everyone wants in hot weather."

I understand what your saying. Hell, I've even done it myself. :-). The only problem is that it solves nothing and gains you only a few minutes (depending on variables, obviously) before the upward climb takes over. And, once the temp is higher than you want, a cooler thermostat will do nothing to drive it down again.

So, Scott doesn't need a cooler thermostat, he needs to find out what can be done to improve the performance of the cooling system.

Sorta like attacking a steep 5 mile long upgrade with a 25 horsepower VW Beetle. If you hit full throttle at the bottom of the hill you'll up in second gear, chugging along at 15 mph within a half mile. Get a head start a 1/2 mile out, so you've build up more speed before you hit the hill, maybe you'll go a couple hundred yards further....but either way you end up chugging along at 15 mph :-)

So.....The answer isn't a longer run. The answer is more horsepower :-)

Similarly, the solution to Scott's problem isn't a cooler thermostat. The answer is more cooling capacity.

Make sense?

Cheers
DD

"Hello Doug, perhaps I can answer your question with a question! Why did we always have winter and summer thermostats? "

Heh heh. That's just another tangent, William ! I can answer your question, of course, but it has no bearing at all on why Scott's car is running at 95-100??C.....which is BEYOND the control range of a winter OR summer thermostat.

Cheers
DD

Edited on 2008-06-06 16:39:50

Doug! don't give up on us lost souls!

The reasoning is what I was told in the past:

If the thermostat opens sooner, say 75 degrees, the coolant will flow sooner, instead of waiting for a higher temp in which to allow coolant flow.

Of course the engine will reach the normal operating temp. sooner or later, eventually and decidedly. So why not later as with a thermostat that opens sooner? That's exactly what everyone wants in hot weather.

Now, I am not inventing this. I use the lower temp thermostat myself because the two Jaguar mechanics I consult with, in Nashville and Orlando, told me to make sure I was using the lower temp thermostat in my engine. It was them who told me there are two thermostat ranges available for the XJ-6.

That's why I agree with Brady on the question of what thermostat to use.

With the hot June thru September "summers" we are having, one could almost replace thermostats depending on the season, same as connecting the auxiliary cooling fan in June and disconnecting it in October thru May.

"I'm going to agree on this one with Brady; The fact that a thermostat opens sooner means that the engine will run cooler, the coolant never reaching the boiling point as with a higher-temperature-opening thermostat. '

Ok. I'll ask you the SAME question that I asked William (to which I've rec'd no answer) .....

WHY would a thermostat opening at 74??C have any influence on reducing temps from 100??C ?? Opening *sooner* will not prevent the eventual rise to100??C if the rest of the cooling system isn't capable of keeping the engine any cooler than 100??C !

And, in case you didn't realize, none of these discussions involve temperatures anywhere near boiling...because the systems are pressurized to 16 psi...so the boiling point is about 129??C.

Ah well..........looks like I'm swingin' but no chips are flyin' !!

You guys have worn me out !

Cheers
DD

the problem with modifying the fan to run continuously everytime the compressor kicks in, (as when using the air conditioner), is in Winter, when you want the opposite, i.e, no auxiliary fan running at all.

Normalyy the auxiliary fan only runs automatically at a certain temp range, as it came from the factory. If you do the modification, the fan will run in Summer and Winter because the Delanair II system runs the compressor even with the Heater on., to dehumidify the air in Winter.

I've learned to disconnect the mod in winter because I want all the heat I can get , not to mention that this fan is very noisy when it is running. It's one thing to need it in Summer, another thing to have it running when it is not needed, as in Fall, Winter, and Spring.

William, point taken. But most XJ-6 owners I know, don't have overheating problems. I spent last Saturday with a friend who has four XJ-6 Series 3, going over all the mods he's done to all of them, and none have any overheating problems.
All of them have the "Southern climate" (74 degree) thermostat.

If the car is NOT overheating when moving, then I say there is no problem, the 4.2 engine runs hot ! Of course if you let it idling, a/c ON, and the temp outside is hot, you can expect the gauge to reflect the heat rise from lack of air movement.

Another item to check: the fan clutch.

Gentlemen:

I didn't want to start a fire storm! Remember, the raise in teperature is ONLY with AC running at idle waiting in line for gas for 10-15 minutes in 80 degree or higher temps. Not during normal operation. This is a fully rebuilt engine by a great restoration shop in my area which included the radiator being sent out for complete work. All new fluid, belts, hoses, etc.

Scott

Let me try to answer William Jenkins's Q. The subject car is not overheating, it is just running hot . As has been stated in the many posts there can be a number of reasons for this. This particular branch of the topic is dealing only with the thermostat, its purpose and operation. I have five series three cars, I have worked on perhaps thousands of them over the years and I do not see any pattern of running hot that can't be explained. Due to the fact that the manufacturers made the cars run hotter, the coolant gauges registered higher -past the centre posiion- this concerned many owners. The factory answer was to issue a "modification" in the form of a 10 ohm resistor which was fitted into the coolant temperature wire at the manifold. Rolls Royce did exactly the same thing, then decided just to eliminate the coolant gauge completely. They then used the Cadillac(GM) heat sensors in each cylinder head!

JAM and William Brady, youÔÇÖre completely missing the point here. If an engine has an overheating problem, installing a lower temperature thermostat probably wonÔÇÖt solve the problem as Doug Dwyer has explained over and over to you guys. IÔÇÖve had Series III XJ6s that run fine even in hot weather and my ÔÇÖ86 would run fine if the ambient temperature was under 80F but on those hot, humid summer days, the car always ran too hot (>100C) and would blow off antifreeze when I stopped and shut the engine off. I tried everything from changing thermostats to running the car with no thermostat, flushing the radiator, installing a new water pump, flushing the block, ensuring the electric aux fan came on at the right temperature and the engine would always run hot on hot, summer days. The problem got worse over time until the engine finally blew up on a day when the ambient temperature here was over 100F.

Once again JAM, youÔÇÖre lucky in that the only XJ6 you have first hand experience with is running fine. However, youÔÇÖre wrong when you say ÔÇ£these cars never overheatÔÇØ since youÔÇÖre basing your conclusions on your experience with only your one car.

If someone has a Series III XJ6 that is running at in the 95-100C range, like Doug said, itÔÇÖs wise to determine the answer to that question first or you may wind up overheating the engine and melting the pistons.

Hello Doug, perhaps I can answer your question with a question! Why did we always have winter and summer thermostats?

JAM and William Brady, youÔÇÖre completely missing the point here. If an engine has an overheating problem, installing a lower temperature thermostat probably wonÔÇÖt solve the problem as Doug Dwyer has explained over and over to you guys. IÔÇÖve had Series III XJ6s that run fine even in hot weather and my ÔÇÖ86 would run fine if the ambient temperature was under 80F but on those hot, humid summer days, the car always ran too hot (>100C) and would blow off antifreeze when I stopped and shut the engine off. I tried everything from changing thermostats to running the car with no thermostat, flushing the radiator, installing a new water pump, flushing the block, ensuring the electric aux fan came on at the right temperature and the engine would always run hot on hot, summer days. The problem got worse over time until the engine finally blew up on a day when the ambient temperature here was over 100F.

Once again JAM, youÔÇÖre lucky in that the only XJ6 you have first hand experience with is running fine. However, youÔÇÖre wrong when you say ÔÇ£these cars never overheatÔÇØ since youÔÇÖre basing your conclusions on your experience with only your one car.

If someone has a Series III XJ6 that is running at in the 95-100C range, like Doug said, itÔÇÖs wise to determine the answer to that question first or you may wind up overheating the engine and melting the pistons.

Doug,

I'm going to agree on this one with Brady; The fact that a thermostat opens sooner means that the engine will run cooler, the coolant never reaching the boiling point as with a higher-temperature-opening thermostat.

In a hot environment you would want a sooner-opening thermostat. I understand there are two thermostats available for the 4.2 engine: One for Northern climates, one for Southern climates. I have a sooner-opening (Southern) thermostat myself in my '84. It does not boil, achieves its normal operating temperature "normally", does not overheat even with the a/c on.

Has the space between the Radiator and Condenser been checked for debris like leaves and other trash? Perhaps someone left a rag between the two? These cars simply do not overheat, I remember Jaguar started testing them in Death Valley back in the 1970's.

In 17 years of owning my XJ, I've only experienced overheating ONCE, and it happened because the Water Pump BELT broke. Even then, I managed to bring the car home by removing the expansion tank's Cap, to eliminate pressure buildup. Once the Belt was replaced, the engine ran normally again.

If the auxiliary cooling Fan is not coming on when the gauge temp reads over 90, then the Red Relay is Bad, or the Fuse is blown, and the last check would be the actual Thermo Switch, which rarely go bad, if my car is any example.

I have thought about it :-)

I agree, obviously, that it won't run cooler than 90?? if it has a 90?? thermostat., as one function of the thermostat is to control *minium* temperature. But that's not the issue at hand at all, as minimum temperature is not Scott's problem. His problem is temperatures running waaaay past thermostat range !

Again, once fully opened, there's *nothing* a thermostat can do to control maxium temperature....so if an engine is running 100??, it has nothing to do with the thermostat opening at 74?? or 90??. It has to do with the the rest of the cooling system which, in this case, is not capable of keeping things any cooler.

Since Scott's engine is running at 95-100??, please explain how installing a 74?? thermostat would solve the problem ! In other words, how would a 74?? thermostat drive the temperature down from 95??-100?? ??

Cheers
DD

Of course it runs at this high temp, the stat is not opening until close to 90, how can the engine possibly run cooler? Think about it.

Respectfully, William, you're going off on a bit of a tangent here.

If Scott's engine is running 95-100??C, what difference does it make if the thermostat opens at 74?? ? Once the thermostat is fully open, as it would be in Scott's case, it can do nothing more to regulate coolant temp. Wouldn't you agree?

So, the *real* question here would be "Why does Scott's engine run at 95-100??C ?"

I propose solving *that* problem first and then, if strength remains, moving on to a good debate over the merits of an earlier-opening thermostat. :-)

Cheers
DD

Scott I STRONGLY suggest that you and anyone else driving in a hot environment switch to an original 74deg stat. The only reason manufacturers moved to hotter ubits was to help them achieve the limits set by the EPA. The hotter and more retarded a car runs the better the fuel consumption and emission readings were. At that time 75/76 I was involved in a number of tests with various thermostat options to see if there were any negative effects of lowering the opening point. THERE WERE NONE. In fact we advised our customers on the 1000 mile inspection to change them, The fact is if the opening range is set high it is harder for the system to keep it there, furthermore, as the engine is constantly running on the threshhold of boiling, it, little by little, cooks its-self. Witness the engine wiring on most jags ot the era, they break like plastic as they are so brittle. This is not just on Jags, all cars today are running close to boiling-continually. Modern cars are deliberately kept hot
-although the gauge has been callibrated to read lower- and they are fitted with so many plastic parts that too will become like the wiring and just crumble up. Any engine needs to be able rto quickly reach working temperature quickly although it is not as important as it used to be before electronic controls took over!

I'd say 89-92??C is fine. The Jaguar cooling system is not exactly over-specified so 96-100??C might be considered "fine" if we're talking about very hot ambient conditions. If it gets that hot in mild weather....let's say 80??F or less....then something is wrong with the system, with the fan clutch a likely suspect.

As for a 74??C thermostat.....

If you're running 95-100??C then a 74, 82, or 88?? thermostat won't really matter---any of the three will be fully open by then and no longer part of the picture. A 74 may well lengthen the amount of time it takes to reach 95-100?? but it won't prevent you from getting that hot eventually. After the thermostat is fully open its up to the rest of the cooling system to do the job.

In a perfect world all cars would have large enough cooling systems so that the coolant temp always hovered right at the thermostat's rated temperature....with the thermostat continually opening a closing just a bit to maintain that balance. My experinced is that Jags don't have such abundantly large systems so a rise in coolant temperature isn't a surprise in anything above mild ambient conditions....or with systems in sub-par operating condition.

In the early-mid 90s Jaguar "solved' this worry in the same way many other manufacturers do: using temperature gauges that are calibrated to read "normal" over a wide range of temperatures. On the X300 cars, for example, anything from about 190-220??F results in the needle remaining steadily fixed at the "N" designation of the gauge. Owners of older Jags, with "real" gauges, don't have that carefree luxury :-)

As for running too cool, yes, its is possible. As I mentioned earlier you want to get to 80??C as quickly as you can so you're out the the fuel injection's enrichment phase.

Cheers
DD

Edited on 2008-06-05 20:45:24

William,

I have been told by the restoration shop to run a 180' thermostat because the engine needs to achieve a certain amount of temperature to work properly. Only time it gets to 96-100 celsius is at idle waiting several minutes for Costco gas. Also told that this area of temperature is not a problem as long as it comes back down right away when driving resumes. What temperatures will I see under normal driving conditions if a74' thermostat is installed? Right now, with normal driving and AC on, temp's range 89'-92'.

Thanks,

Scott

Scott, I don't want to make this any more confusing than it is already BUT; If everything is functioning correctly the car should not overheat. The fan switch on the bottom of the radiator will come on between 91 & 96 Deg. The fuse for this fan is "hidden" in with the light fuses on the left inner front fender (wing). You can operate it manually by installing a switch which connects the relay terminal 86 to ground (earth). BUT i go back to my original suggestion, INSTALL A 74 deg THERMOSTAT. The only electrical mod we did on these systems was to install a cut off switch in the compressor feed. This was because the compressor worked continually, on heat or cooling and it was such a waste of energy, it also allowed the compressor to be switched off if stuck in prolonged traffic etc. and as the rest of the system was functioning cooling air was still provided for a few minutes.

Try this.....

http://forums.jag-lovers.org/avs.php?121688k21

With the aux fan running at all times you should get slightly cooler running. ...providing there's no other fault that overwhelms the effect. I think most using it live in areas where it gets very hot (like Las Vegas in August) where they need every advantage they can get.

It would be easy to disconenct the mod for winter driving so the fan doesn't operate when not needed.

Cheers

Doug,

Yes...1987 Jagauar XJ6 VDP with a 4.2 engine. Can you please tell me where to find the "mod instructions"...I can't open the link for some reason. What difference do you expect in temperatures with this completed?

Thanks,

Scott

Temperature switch only, which closes a relay, which operates the fan.

The wiring modification mentioned a couple postings back it what turns on the fan when the a/c compressor is engaged (which, by the way, is virtually at all times with the Jaguar climate control).

(Just for the record we ARE talking about a Ser III XJ6 with a 4.2 engine, right? And not the later "XJ40" type XJ6? )

The 12 cylinder models of similar vintage were wired differently using a switch and a diode pack to operate the fan whenever the a/c compressor engage OR by coolant temperature....perhaps that's what the parts guy was thinking of.

Cheers

I was told today by a major Jaguar parts outlet that my ' 87 Jaguar XJ6 has two switches that control the auxillary fan. One for 94' celsius and the other that starts the fan when the AC is turned on. Can anyone verify?

Scott W. Moseley

Edited on 2008-06-04 17:30:06

Doug, you mean you are not old like the rest of us? :-))

I just suggested it because Radio Shack is always out of stock with little parts like that..I always seem to get the old "we don't have that one but we have this one..."

With the price of gasoline..., well you know the rest.

BTW: it's on special for $7.51

Any Radio Shack will have the diode but, hey, I know what yer sayin'.

As I get older I find myself appreciating "convenience" a lot more than I used to :-)

Cheers
DD

you can also buy the kit here for around $10. Saves having to drive all over town looking for a dumb Diode.

http://tinyurl.com/6rpr87

Click "fan mod instructions" for info

Cheers
DD

Doug,

Please tell me the procedure to have the auxillary fan come on with the AC. I will speak to my mechanic about this. Perhaps my '87 XJ6 I sold 10 years ago had this modification done before I owned the vehicle. In any event, I recall the temp being more "stable" around 90' celsius.

Thanks,

Scott

I agree with Doug; The XJ-6 has a Thermo Switch for the auxiliary cooling fan, the one located in front of the condenser, under the front bumper.

It does not come on with the a/c unless it is modified to do so. Only in the XJ-12 does it come on with the a/c. Many of us modify it to come on like Brady says.

If the auxiliary fan is not coming on, the culprit is usually the Red Relay located on top of the Radiator Support, on the left side of the engine bay. Also check the Number 5 fuse in the engine bay Fuse Box located next to the coolant tank. Number 5 fuse is the closest to the front of the car, the other 4 fuses are one each for the headlamps.

Rarely do the Radiator Thermo Switches go bad. Those are located on the bottom right corner of the radiator, engine side of radiator. You can see it with a flashlight. It has two black wires coming out of it. It can be removed from the bottom of the car, though it is extremely difficult but with patience, it is doable.

Actually, on the Ser III XJ6, the aux fan is strictly temperature controlled with no relationship to a/c compressor operation....although a few have been modified to allow such operation. And that little fan does make a difference, so, Scott, if yours isn't coming on you should tend to it.

I agree about the fan clutch as it is a key player. A weak clutch just won't pull enough air. If in any doubt I'd just replace it.

As for thermostats just be careful. The fuel injection system is designed to richen the fuel mixture until the coolant gets to about 80??C....so you want to get up to at least that temperature as quickly as possible.

I don't see Scott's coolant temp of 94??C as a problem per se, but am slightly concerned that it wants to go that high in ambient temps of 75-80??F....which really isn't all that hot.

Cheers
DD

The problem may be a faulty fan switch-coming on late- but with the AC on the fan should work instantly. Also check the fab clutch is blowing stong. In any event my suggestion would be to replace the 88 deg thermostat with a 74Deg.

Edited on 2008-06-01 9:16:23

Normal temp is 88??-90??C. The aux fan comes on at 94??C. On a hot day in traffic you might see 100??C. I'd start getting nervous beyond that, especially if it just keeps going up-up-up.

The owners manual says that anywhere in the green band ----which is what? 90??-130??C or something like that---is perfectly OK. I don't know of anyone who is comfortable running at the upper end with an alloy head engine.

Cheers
DD