Hi everyone! 1989 Jaguar XJ6 (XJ40).


My coolant light came on today on my way to work. I've looked at the reservoir before and I have no idea how it works. Everything online seems to be referencing a different system. It seems as though there is two caps on the reservoir, or the "header" I think it's called. The top cap seems like it's a pressure valve of some sort, because it doesnt come off, only loosens and I can hear the pressure release when it does. The other cap is on the back of the reservoir facing the drivers seat. It's plastic and has wires and what I assume is a coolant sensor running through the middle. I could probably get that one off if I tried, but it doesn't seem like I should, considering its sideways. How the heck do I fill this thing!? It's nothing like previous cars that i've owned.

I've looked through the stock manual, and a third party "repair book". Nothing even comes close to describing this.

 

Ok, so the red circle is the metal cap that wont come off. It twists open to release pressure, but the threads slopes back down to stop it from twisting all the way.

The blue circle is the plastic cap I was referring to, with the sensor (?) going through the middle. Unscrewing the cap only allows me to pull out the plastic tube that contains the sensor. I havent tried that yet as I dont see the point, I obviously cant fill it at that angle.

Update: After unscrewing the top cap, releasing the pressure, and unscrewing the plastic cap, pushing in the sensor as much as I could, then re tightening the cap, I turned the car on and let it idle for a while. The coolant alert hasnt popped up yet. It may pop up if I start driving it around.

 

Fairly sure my ‘88 had a plastic cap but the steel one is the one that has to come off to top up the coolant, you will have to keep trying until its off.

 

I have a strong doubt that this cap is even supposed to come off. The way the threads are, its starts low, rises, stays level, then goes back down. The cap crimps around the threads too.

 

I'll give it another shot, but I just dont see how it's physically possible, short of breaking it.

 

Agree with Robman, the steel one is the one that has to come off to top up the coolant.

I suggest turning the cap till it rises then try working it off. The rubber seal inside has probably stuck itself to the tank so it won't just lift off.
Turning it further than the rise simply locks it on again.

Larry

 

You classic Jag owners must either be extremely wealthy or incredibly patient. This is just one of the billion little/big issues I have experienced with this car.

 

Try pushing down on the cap as you twist it counterclockwise.

 

We are just suckers for problem solving and won't give up til we get it done!!

Larry

 

I second this suggestion. Had a similar problem removing a cap until I did this.

 

Retired, not as wealthy as I would like to be, just an ornery old cuss that likes to win