Newbi to the jaguar world. My 16 year old son just recently purchased a 1990 jaguar XJ6 sovereign in great condition. Only has 80000 miles. He drove home from school one day, parked in the driveway and noticed he was leaking coolant. He added more coolant to it and drove to work and parked it. It set for 4 hours And when he went to crank it backup It would not run. Noticed a bunch of coolant underneath the car more than when he 1st noticed the issue. Had to get car towed home. When I looked under the hood I noticed that the O-ring gasket on the thermostat looked like it had been Squished from possibly overtightening of the thermostat housing. Some water had came from the housing as, I proceeded to look under the motor I noticed more water was coming from underneath. I checked the oil in the motor and it was not milky. My 1st thought would be to change the thermostat and the O-ring And then the water pump. My question after all of this, is in my experience I have never known a car to not start and run with a bad water pump is that something common for jaguars.

 

Coolant leaks, yes. Not starting because of it, no. The engines will gladly burn themselves up if run without enough coolant. That's not unique to Jaguar either!

How far was it driven with those leaks happening? Driving in that condition is dangerous for the engine. But it is likely still ok.

Is the car cranking and not running or not even cranking? A process of discovery must be undertaken and the no-start is probably unrelated to the coolant leaks. So while hose replacements are happening you can test the starter circuit, ignition system, etc.

Download the service manuals from this site and dive in. A car of this vintage doesn't happen without efforts. At least not for very long. But for sure his friends will not have a car just like it and he will become known for it too. Hopefully in a positive way!

 

Thank you sleek for replying. Yes further looking into vehicle is in process. The car never ran hot, but I have discovered and low coolant level sensor that is in the reservoir that was corroded. You can see in the pictures. My new question is if this sensor went bad, does it send a signal to the computer that water is too low and it would keep something from allowing the car to run. The car will crank just not run, and there is no water in the oil. It just seems weird to me that it was running fine when he parked the car, in the 3 hours that it sat, all the coolant poured out from wherever, whether it was the thermostat housing or the water pump gasket or gasket or hose, these are still to be determined, That it would all of a sudden not run. I know this particular model has a buttload of sensors and fuses etc. That's kind of why I was wondering if this sensor had something to do with possible fuel sensors or firing system that when this sensor is activated it has the computer activate other sensors to keep the car from doing more damage down the road and running until water level is normal. Also if this scenario is a possibility, will the computer need to be reset or cleared when said sensor has been replaced.



This sensor goes in the reservoir in the background on the left side in that black hole. That resistor or diode is broke. I had it soldered with aluminum solder back together. I have yet to put it back in the car to see if it is functioning properly.

 

Coolant on the front of the engine running down and contaminating the CKPS? (CKPS known to fail for NO REASON anyway)

 

The car is not THAT sophisticated, the sensor's function is to simply flip on the low coolant warning signal on the dash if the coolant is too low.
As far as the thermostat is concerned, very easy to install with gasket (o-ring) on the wrong side of the stat causing the housing to leak.

Also common to find a crack the housing caused by after incorrect installation and overtightening.
The functions of all the sensors etc are found in the engine management.pdf linked below.


xj40_engine_management.pdf

Larry

 

Thank you for the reply. With this car being so far ahead of its time and all the relays, fuses, etc. I just wasn't sure of its capabilities. Iean when a car has a inline fuse somewhere in the system that if not found you cannot install a aftermarket radio. I'm a dodge guy, first car was a Ford. Never had any interest in anything foreign and still prefer domestic over import. But with that being said kids make you do the damnest things. From what I'm learning about this model is that in 1990 there were only 3 cars that factory installed USB ports. They were not standard until early 2000's. To me that shows just how far ahead jaguar was at that time and has always been a step ahead. So typically I have to ask these questions because in today's times it's not a possibility, it's an actuality. Then it could of been a possibility.

 

Not sure where you're getting your info from but AFAIK USB ports were not even necessary of or even invented back in 1990! There was a OBD1 port (which I suppose was of the serial port family) as the car had the ability to be connected to an analyzer, but it wasn't til the 1995 (X300) model that the OBD2 RS232 serial ports were added.

cheers

Larry

 

Hi REDROOSTER,

Welcome to the Jaguar Forums! It's great to have you with us.

If the coolant leak and no-start conditions are related, I like Bob's theory about the Crankshaft Position Sensor (CPS) connector or the sensor itself being contaminated with coolant. The CPS is mounted on the front of the engine and is fairly easy to acces leaning over the right fender. Follow the harness from the sensor up to the electrical connector. Disconnect and inspect for coolant.

Another obvious question that has to be asked: are you sure the car didn't run out of fuel? Or had your son purchased fuel just recently, and if so, could the fuel be contaminated with water?

Cheers,

Don

 

Thank you all for the advice. After further investigation we found that the thermostat housing had a huge hole in the side, iwould assume from someone either over tightening or whatever. So we are replacing housing, gasket and thermostat. Also discovered fuel pump had went out so we have also replaced with new fuel pump, and filter. Hopefully we will be back up and running within a couple days. Thank you all

 

Great! Please let us know how it turns out.

 

She is back on the road. New fuel pump, sender, filter, and clean gas tank, water pump, belts, thermostat, housing, gasket, one or 2 swear words and several hours

of intense labor she is running like a charm.

 

Great job, REDROOSTER!

Thanks for letting us know it all worked.

Cheers,

Don

 

And a final top-off of coolant. What a neat car to have at a young age, I never had anything that cool. "Dad's car" was definitely not a Jaguar. Advise the young man that all the young ladies are going to want to ride in it! That's the reason to keep it in good running condition...

 

I so agree!!!! That is the car I WANTED when I was 16 because they were just being released to the public (FINALLY!) at least in the UK, and I was still following the car magazines as it was released here in the USA for 1988. And signal red! I don't normally care for red cars, but this car looks fantastic in this not-so-subtle color! It can get away with it because of its subtlely gorgeous looks. I finally did get mine a few years ago, and certainly worth the wait! Like the high school sweetheart you get reunited with later in life....there seems like no time lapse and ev everything just continues despite everything around you changing.....

Hah, even the middle-aged and older ladies will want to ride in it! But as a middle aged guy myself, I fit in the middle on that, so I'll accept that burden gracefully like any Jaguar owner would.....

 

Don't get your hopes up!
FYI: the primary reason older folks sell the XJ40 is because it's too difficult to get in and out of and too low LOL

Larry

 

HAHA, typical Larry.....always the cynic!!! Only able to see the glass is half empty (or the coolant reservoir in this case.) My observation is based on my own experiences of ownership, and I am actually surprised by the variety of women who have commented on the car to me. In a conmversation I had with a woman in her 70s who did not know what I owned waxed poetic in our conversation about a car identical to mine. I never told her what I owned because she wanted a replacement. She had no problem getting in and out of her S-Type with agility.

I don't seek attention, and I actually don't want it. The XJ40 is just a car that appeals to me for what it is and represents. That is all that matters, and even if I don't drive one of mine for a while, I just get great satisfaction looking at it. That being said, it is nice to feel a sense of sharing good taste and the connection with others who understand your aesthetic perspective. Besides, if earth tones and the 1970s can make a comeback, this can too, possibly. It's interesting how trends happen.