Hello all! Just bought my first XJS. Straight 6 1996 with 76k miles.

Couple of questions. Where should the temp gauge be? when she's warm and the AC is running and its about 87 degrees outside, just cruising through town, needle goes about 1/3 of the way past the "N" in the middle toward the red. So, she's about 2/3 of way from the red but definitely past the N. Is this normal? Should I try a cooler thermostat?

Also, both mirrors don't work. The switch or is there an ECU for the mirrors?

Thanks for the help!

 

You might wanna try a new thermostat on the (presumed) basis that the existing one is faulty and isn't opeing all the way. However, going to a cooler thermo won't help....you're beyond thermostat control range.

Not sure if your model has a mechanical fan with a clutch. I think it does. The clutch might be weak and not pulling enough air.

Does your electric fan come on?

A few XJS guys elsewhere in the 'net have had similar problems with the 4.0 six cylinder. In one case I know of the radiator was clogged. In another the gauge was flakey. Another isn't resolved...but I think a new radiator (or professional radiator cleaning) is in the future

Cheers
DD

 

Thanks Doug. Will trying flushing. Then looking into the fans. Are the fans a problem on these cars?

 

Worth a try but, to be honest, I'd go fro a professional boil-out job at a radiator shop. For one thing, a common problem is that the radiators get clogged 8externally* with leaves and debris. As long as yu have the radiator out to clean *that* you might as well have take it to a radiator shop for the full monty.






No more than any other car. If you have a mechanical fan (I'm pretty sure you do but my memory cells are a bit frazzled right now) it really isn't too unusal to have the clutch get weak and/or develop a problem with the e-fan on any brand of car.

Cheers
DD

 

Hi - just chiming in. Our cars have both a mechanical fan and an electric one. My car runs exactly as you described. If you don't pull the radiator, at least take your garden house out and get down in from of the car and throughly clean debris and crude from the radiator cooling fins. These cars are so low that lots of junk can make it's way in there and prevent airflow. My electric fan is not coming on (it works when I hook 12V to it), so that's next on my list. A few things to think about are the cooling fan relay (first light blue relay in the left side near the front of the car) and the thermostatic switch built in the radiator. They can fail preventing the electric fan from kicking on when the car gets warm. Also, I'd check the ground and all connections. The elecric fan connection is behind the grill. Remove the five screws that hold the grill in place and you can test/clean the connector. Good luck!

 

Thanks RayJack!
I will check those elements as well!

 

Hello, I drove my 96 XJS to Las Vegas from San Diego in the summer and experienced what you've described. It was getting too hot so I decided to take it to a shop and have them flush the cooling system and replace the thermostat. I would have done it myself but didn't want to chance it overheating on the way home since it was 107 degrees. The operation worked well and the car has been running cooler than it ever had. So, I'd try this before going to the other fixes. Good luck!

 

I fall into the "unresolved" category.

The coolant is good, the thermostat works, the electric fan works and the fan clutch was replaced.

On hot days, my temp gauge creeps up to about 3/4 the way to the H, from the N position. I hooked it up to a temp gauge and it seems that the coolant is at about 210 degrees.

When on N, the coolant is on 190, which is optimal.

210 isn't that bad but I don't know what to do about it. Another member member replaced the radiator as well, but still has issues.

I concluded that on hot days, the car is incapable of running any cooler than 210 degrees...

Someone did post that the O2 sensors could be to blame... I don't believe any of us went through the expense of changing the four O2 sensors these cars have.

By the way, you do have a mechanical clutch. I was thinking that perhaps an electric fan would solve the problem.

 

I put a cooler temp thermostat in that I purchased from Pep Boys. No more warm running! Best $20 bucks spent!

 

Could you please post the thermostat you replaced it with and much more importantly how the car is driving?

Much like Vee, I have replaced the thermostat (on multiple ocassions), the fan clutch (on multiple ocassions) rodded the radiator twice, made sure the foam around the radiator is good..changed the temp sender with a OEM one..and much more and still have the same problem (if you post on Jaglovers my name is Mark J),,and finally hooked up an OBD2 reader to tell me what the ECU temp sensor is sensing and I too am getting 199-210, just like Vee

The thing is that EVERY time I have placed a post anywhere about going to a lower thermostat I have been strongly urged against it, as it will throw the ECU out of whack, mess up fuel consumption, and driavability in general will suffer.

Please post the brand of thermostat, part number , temp, and how the car is behaving

 

I tend to disagree with that theory. Although it may change the walm up, once up to operating temp as most all thermostats are around the 190°C fully open so unless something else is wrong driveability should not change.

The difference between the 82°C and 88°C thermostats in the V12 is the temperature that they commence opening. Their fully open temperature is the same. ALL the higher thermostat in the later V12 cars does is bring the engine up to temperature quicker.

cheers
Warren

 

If the engine is running too lean it will run hotter, also as the the ignition is retarded this can also cause the engine to run hot.

The O2 sensors can have a bearing on A/F ratio so before running out and replacing the sensors have the car tested for A/F. If the A/F is lean it may not be the O2 it could also be dirty injectors.

cheers
Warren

 

Sorry, I don't have the part number. It was the cooler of the two that Pep boys offered.

Before, the car would run warm and creep well past the half way mark particularly with the AC on. That was stressful! Now she runs right at half way line or just below it. Heat is not a friend to your engine. All motors today run hotter than they should for emissions purposes. The Jag runs wonderfully now. No adverse affects and lots of piece of mind!

 

Thanks for the reply.

Going to the PEP BOYS website, it lists a STANT 180F/82c part number 13648 as the lower temperature option. The original part is 190F/88C.

This means that its opening 10F degrees early.

Personally I always thought that it would be a good idea to get a thermostat around 10 degrees cooler, but based on the input of guys with more experience, I have opted against it.

Perhaps its not a bad idea after all.

 

And of course this only applied to the 95/96 4.0 straight 6 AJ16 engines as the one original posters'

 

My 1995 XJS 4.0L has been running warm too, even at highway speeds (lots of airflow). I sprayed the radiator with a garden hose, but there wasn't much debris in there. The car was sitting for awhile (2-3 years), so I'm going to replace the thermostat and see if that helps. My electric fan is not coming on either, which I think is the thermostatic switch. Apparently, the switch is on national backorder so I'm trying to track one down. If all this doesn't work, I'll pull the radiator out and have it tested/cleaned by a competant radiator shop. I'll report back my results.

Thanks,
Ray

 

Update: I too tried the lower temperature Stant thermostat with no change. The car still is running 2/3 of the way to H whether it's idling or driving 60 MPH down the highway. I flushed the radiator with my garden hose while I had the thermostat out. The car has plenty of heat inside, which leads me to believe it's not the water pump or mechanical fan. Since it's the same temperature no matter what speed, I'm thinking something is wrong with either the gauge or the radiator. Also, I tried getting the electric fan to work. I replaced the electric fan temperature sensor with a Jaguar one (although it says made in China on it!), but it made no difference. The only way I get the fan to come on is to short the sensor or jump the relay. This reaffirms my thinking that the gauge may be wrong and it's not really as hot as it says it is or the radiator is blocked in that area and the sensor doesn't get hot enough to turn on the electric fan.

What do you all think of my logic? Vee, how did you test the gauge and confirm the working temperature of the system?

Thanks all,
Ray

 

95/96 guys:

Our gauges are unreliable POS for the most part. What we probably want to do here is plug an OBD2 reader that reads the sensors real time, and see what the water tempertaure sensor that feeds the ECU is reading.

In my case every single cooling item that you can think of has been replaced, except the radiator itself, which has been flushed boiled and rodded twice. I have no indication or feedback that a new one will achive anything different, so I have refrained from dropping the 700.00 for one.

These where my results with the OBD2 live-scan tool at the height of summer:

My car's temperature at 105 degree Houston city driving, no traffic jams, but stop lights of 4-5 minutes reached 205
While driving on the freeway, about 80mph under the same 105 weather the car registered 199-201 (although the gauge goes higher as I accelerate-bad grounding I imagine)
When I put the car on "D" put my foot on the brake, with the A/C on, sitting stopped for 15 minutes the car reached 215-219

Since we have so many 95-96 owners here, ideally we could compare the actual (ECU) temperature readings with each other , to see where we are really at, of course that means we would all need the OB2 live scan readers. I have tried and tried in vain to find any resource that can tell me what the factory temperature ranges are for the AJ16 engine to see if I am doing fine, but have been unable to.

 

In response to the earlier question, I started out believing what the mechanic told me when he used an IR gun.

Then I purchased something called Yhasi Movi Pro, for my Apple Laptop. That reads the temps using the OBD2 port. The readings were consistent with what the mechanic told me.

I don't know if that helps.

As for cooling, the only thing Spikepaga has seemingly not done is convert the mechanical fan to electrical. I am now kicking around that option.

 

Most engine builders will tell you the ideal operating temp for an engine will vary widly between installations. Although 90°C ±10°C (200°F) seems to be a consensus for many.

New car manufacturers tend to run engines on the walmer side as this has an effect on emissions.

Also if the engine is running too cool it will cause inefficient combustion and hurt power potential.

Engine oil temperature is probably far more important as the oil can break down if its operating temperature is exceeded.