I've got a bit of an issue. Quite frequently, under braking, the coolant level warning light will illuminate. Once the vehicle has been stationary for a few seconds, the light will turn off. I haven't noticed any regular symptoms beyond this light.

That's the only time I ever see it, only right when I come to a stop under braking, such as when slowing to a stop at a traffic light.

The level of coolant appears fine at the expansion tank.

Now, it has been the case in the recent past that the vehicle would overheat in situations that were difficult, such as a hot parking lot, or stop and go traffic if the air conditioning was turned on, but I'm not too sure these are related. They could be, but the warning light issue doesn't seem to have been happening that long.

I'd love to hear any advice someone might have as to where to look first.

 

What year you got, 6 cyl, or real car V12. many different coolant sensors used, and locations vary with years/engines etc.

 

RATS!

I forgot to mention that.

It's a 1996 4.0L straight six.

What do you mean real? I wouldn't **** on that V-12 to put out a fire. It's too much engine in such a little box. I prefer a nice lump of nasty Jaguar straight six thunder and mayhem. Sure, it's not as smooth, nor is it as powerful, but it's the feel of the thing that I love.

It's less, but it's less from one side of the tach all the way to the other, spread evenly across the entire dial like a layer of butter, nails, and the year 1943. Why that year? I just picked something out of thin air that seemed to fit the rest of the description.

I bought the six on purpose, passing up the 12s along the way. Aside from the things I like about it's character, I've got plenty of room to turn a wrench in there. Do you?



Just some friendly jabbing, no offense meant, naturally.

 

Hah, no spirit of adventure, but a Jag is a JAG, is a Jag.

I reckon yours MAY be the same as the X300 AJ16 where the sensor is pushed into the plastic header tank from the bottom, PITA to see, impossible almost, and even worse to change. The V12 is right there in the side of the header tank, reach down, pull it out, refit, drive on, mmmmm.

Room for spanners, hell yes, when I took the engine out I refilled my tool box with what I found, so YES plenty of room for spanners, hahaha.

I love my 3.2 big block AJ16, but NOTHING beats a V12 at full cry, and all 12 firing sweet, almost, and I say ALMOST better than "wild women". Cant use the other word, might get banned, bugga.

Had our V12 XJ-S since 1996, travelled all over OZ in it as our everyday car, nothing like it on the open road, and the maintenece requirements are not that bad once the car has returned to "spec", coz as we know ALL these cars are lacking that TLC factor by now, which is sad.

 

Oh bugger.

Does this make sense, then? The only thing I can think of is the weight and perhaps a bit of water transferring forward, or the sensor being altered in position by inertia depending upon it's type. Having not delved that deeply into this cooling system, I'll have to check to see what type it is. If you just happen to know, I'd appreciate the help.

Yeah the 12s are nice, this is true. I just about fell out of my chair on the spanners under the engine comment.

In my case, it's just the spanner trying to use the spanners that's the problem.

I've just got some sort of obsession with the straight six. I'm not sure it's curable, nowadays.

This car was kept very well, in wonderful conditions, but was neither driven long enough nor often enough. And the shakedown driving really showed it's true colors. There are a few things I need to handle, and a couple of them are aggravating me.

This coolant thing is one of them. Now I've lost my tech CD, and I'll have to buy another, as I think I left it in another state. I might get lucky, though, and find it.

I suppose it's for me to go and find this sensor. That might take a lift to make it easy, and I don't have one yet. I know someone who does, though.

 

You could be right on the coolant wash theory, coz my tech brain hahaha, seems to recall that the sensors use the coolant as an earth path, hence "no light", coolant washes away, no earth, light ON. Try a top off in the coolant tank, maybe 500ml or so, and see if there is a difference????.

We have a saying down here. "If when working on a V12 and you drop a spanner and it hits the ground, YOU AINT WORKING ON A V12". I used to laugh at that, but its true. I tie a string on the little spanners, and tie the other end to my wrist, saved heaps of money that way, sounds silly but it works for me, especially now arthritis is my friend.

I too love the 6 cyl, had toooooo many, its just that 15+ years living with the V12 is a different bug totally.

Enjoy

 

I too have an intermitant "coolant light" on my dash. Blew a rad(upper)on I95 bringing it home to Canada two weeks ago. That's when I noticed that the light would come on occasionally. The resevoir was not topped up....so I've done that. Was told that each day I should start it up and try to top up the coolant level. There are air pockets that will continue to cause the light to come on! Sound true?
91 XJS 12 cyl.

 

Opps...lots of spelling mistakes! Blew the upper rad hose.....reservoir!

 

The V12 is a fickle beast for air, and if NOT bled properly will reek havoc. The top up each day will eventually get it bled, but I would be doing it correctly from scratch, and dont risk hot spots in that engine, too many $$$$ will leave your pocket if it overheats.

If you dont know how to do it, search around here, OR ask, we will go thru it step by step for you, but I reckon it will be in the archives.

The 6 cyl is a lot easier, it is "self bleeding" as such, as long as you fill it slowly.

 

The temp stays pretty constant but occassionaly the coolant light will come on. Think I have just about got it worked out!

 

I feel like an idiot.

I believe the problem was too little coolant in the reservoir. There is a small sensor in it's rearmost wall. Under braking, the fluid should naturally pass away from that sensor. I could see the sensor through the water.

So, considering that there could be some air in the system, or that the mixture might be wrong as well, I had the entire system flushed. Now, the coolant level is higher, and I don't see the darn light. At least, I haven't so far.

Hopefully, this thing isn't eating coolant. Since I'm pretty sure the coolant was changed before I bought it, or, at least, a few thousand miles before I bought it, I'm hoping that it just took a bit for what was in there to fill the system.

The problems may have started when I inspected the system to begin with, when I opened the coolant cap. If that is the case, it may have allowed a void to be filled, and thus lower the level enough to screw with that sensor.

We shall see. For now, though, it's on to a few more problems. I'll have to post another thread, I'm afraid. I'll come back here if the problem persists or if it turns out it's eating coolant.