1998 XJ8 coolant warning

[PaulB81]

Hi all

Firstly, apologies if this is a regular question. Search is not working at the moment.

I picked up a 1998 XJ8 today (3.2L), on the way home the coolant warning light came on. The water temperature didnt move a muscle all the way home so it didnt appear to be overheating.

When I got home and once the engine had cooled I opened the bonnet, at the back of the engine bay I found what I *think* is the coolant, opened it, orange fluid right to the top which I gather is correct.

Is there another place I should be looking for coolant or another cause for this?

Thanks all

-Paul

[NormanD]

They often get stuck showing low water

The float is in that water tank

[OneJag]

Hi,
I've occasionally seen this when the battery is low on charge. Charge it up and see if it goes away?

OneJag

[PaulB81]

NormanD said:

They often get stuck showing low water

The float is in that water tank

Thanks for the quick replies guys.

So just poke my fingers in and fish around for a float ?

[Tame Technician]

To stop the coolant false alarm u need to over fill it just a tad, what we used to do back in the day, when I worked at a jag dealer, 1998-2006. Have an assistant hold the engine at 3000 rpm, the coolant level will drop, at this point top it up to max and put the cap on quick.

[PaulB81]

Tame Technician said:

To stop the coolant false alarm u need to over fill it just a tad, what we used to do back in the day, when I worked at a jag dealer, 1998-2006. Have an assistant hold the engine at 3000 rpm, the coolant level will drop, at this point top it up to max and put the cap on quick.

I will give that a go. Any recommendations on where to get the orange coolant or shall I get some from a main dealer

[timolloyd]

PaulB81 said:

Hi all

Firstly, apologies if this is a regular question. Search is not working at the moment.

I picked up a 1998 XJ8 today (3.2L), on the way home the coolant warning light came on. The water temperature didnt move a muscle all the way home so it didnt appear to be overheating.

When I got home and once the engine had cooled I opened the bonnet, at the back of the engine bay I found what I *think* is the coolant, opened it, orange fluid right to the top which I gather is correct.

Is there another place I should be looking for coolant or another cause for this?

Thanks all

-Paul

If it's any consolation I've had exactly the same thing happen on my 2000 XJ8. Just topped up a bit more and never had a problem since. The garage were 99% sure there were no leaks anywhere.

[Tame Technician]

PaulB81 said:

I will give that a go. Any recommendations on where to get the orange coolant or shall I get some from a main dealer

For topping up just use water.

If you ever drain and refil, or if the strength is found to be weaker than -15 protection, then its best to get the correct coolant from the jaguar parts department at your local dealer.

[PaulB81]

Is it worth using distilled or is that a bit overkill?

[Jaguar steve]

The cooland level sensor is under the header tank at the front. Low level indications can also be caused by a poor electrical connection between the sensor and it's plug. Unplug, spray a shot of WD40 and reconnect.

You must not mix different coloured coolant. Buy the proper orange long life coolant from a Jaguar dealer and dilute it 50:50 with either tap or distilled water.

Cooling issues on pre 2000 cars - including actual, not indicated low levels - can be caused by waterpumps loosing efficency. With the engine stone cold open the header tank, start the engine and rev up to 2000-3000 rpm. You should see a reasonable flow of water into the tank. If not you may need a new waterpump now or perhaps headgaskets or even a new engine a little later.

BTW the temperature gauge is not an accurate indication all's well in the cooling system.

Edited by Jaguar steve on Monday 14th May 07:55

[PaulB81]

Jaguar steve said:

The cooland level sensor is under the header tank at the front. Low level indications can also be caused by a poor electrical connection between the sensor and it's plug. Unplug, spray a shot of WD40 and reconnect.

You must not mix different coloured coolant. Buy the proper orange long life coolant from a Jaguar dealer and dilute it 50:50 with either tap or distilled water.

Cooling issues on pre 2000 cars - including actual, not indicated low levels - can be caused by waterpumps loosing efficency. With the engine stone cold open the header tank, start the engine and rev up to 2000-3000 rpm. You should see a reasonable flow of water into the tank. If not you may need a new waterpump now or perhaps headgaskets or even a new engine a little later.

BTW the temperature gauge is not an accurate indication all's well in the cooling system.

Edited by Jaguar steve on Monday 14th May 07:55

Thanks for this. I feel a bit shameful asking this, but where is the header tank at the front. The only coolant related bit I could find in the engine bay is right at the back below the windscreen (or is that what you mean by front). Is the plug mentioned easily accessible or will I need to remove something in order to see it. Hopefully.... its just a sensor type issue!

The tank im looking at in this pic is in top top left of the pic, just above where the duct to the air filter starts. Is this where I should be looking? Incase you hadnt guessed, im a mechanical retard but willing to have a go

Edited by PaulB81 on Monday 14th May 13:09

Edited by PaulB81 on Monday 14th May 13:10

[Tame Technician]

I think steve meant the front of the header tank. (which is as you say at the rear of the engine bay.

[Jaguar steve]

Tame Technician said:

I think steve meant the front of the header tank. (which is as you say at the rear of the engine bay.

Yes I did. The OP's picture shows the view of the engine bay from the offside.
There are two small plastic pipe running from the front of the engine to the rear on the nearside. The pipe furthest away feeds into the coolant expansion tank under the front wing, the nearer one is the coolant return from the engine. Note these pipes crossover just by the front of the header tank which is concealed under the central trim with just the cap visible. The coolant level sensor is at the bottom of the header tank almost directly under the two pipes.

[mjr111]

So I'm also a bit of a mechanical beginner. I've been getting intermittent coolant low messages.

I don't quite understand where to check. When you describe the 'header tank' is this the one that needs to be full to the top?

i.e in the photo above, when I unscrew the pressure cap at the rear of the engine, should the tank that opens up be full? Or is as you say this just some header tank, and the actual container is below that? 'Cos it's rather empty at the moment!

However I don't want to over fill it.... Just getting a bit confused by expansion tanks, header tanks and actual levels!

[P700DEE]

Firstly if you live in hard water area do NOT use tap water to top up otherwise you will soon need a new thermostat. The header tank is very small and has two levels shown by a white step in the centre of the tank. It should fill to just over the top step, procedure above. Excess water is pushed to the overflow tank in the wing.

[Baryonyx]

To bump this old thread, is there a particular trick to getting the coolant cap off? I've located it, and the send and return pipes. But I can't get the fking thing off! Stuck tight, too tight to shift by hand and too soft to twist with pliers. I don't have a wrench big enough to lock it over the top and twist off that way either.

So, until I can get it off, I'm not going to drive my X308 XJ. I'm sure the coolant is fine and it's just a stuck sensor, but I need to get to it first to investigate...

[Jaguar steve]

Baryonyx said:

To bump this old thread, is there a particular trick to getting the coolant cap off? I've located it, and the send and return pipes. But I can't get the fking thing off! Stuck tight, too tight to shift by hand and too soft to twist with pliers. I don't have a wrench big enough to lock it over the top and twist off that way either.

So, until I can get it off, I'm not going to drive my X308 XJ. I'm sure the coolant is fine and it's just a stuck sensor, but I need to get to it first to investigate...

They can be a tight fit. With the engine stone cold pour a kettlefull of boiling water over the cap then try to twist it open with a rag. Another trick is to wrap a few turns of rope round the cap and a stick then twist. If that doesnt work you'll just have to go and get a big wrench.

[Baryonyx]

It's going to have to be a wrench. Nowt is shifting it. Off to B and Q tomorrow then! Haven't driven the fking car in days, sadly!

[spreadsheet monkey]

Tame Technician said:

To stop the coolant false alarm u need to over fill it just a tad, what we used to do back in the day, when I worked at a jag dealer, 1998-2006. Have an assistant hold the engine at 3000 rpm, the coolant level will drop, at this point top it up to max and put the cap on quick.

Just used this trick on my 2000 XK8. Coolant false alarm was annoying. Thanks for sharing!

[Jaguar steve]

spreadsheet monkey said:

Tame Technician said:

To stop the coolant false alarm u need to over fill it just a tad, what we used to do back in the day, when I worked at a jag dealer, 1998-2006. Have an assistant hold the engine at 3000 rpm, the coolant level will drop, at this point top it up to max and put the cap on quick.

Just used this trick on my 2000 XK8. Coolant false alarm was annoying. Thanks for sharing!

You cannot change the volume of a liquid but you can of a gas.

If you're actually seeing a drop in coolant level with an increase in engine RPM and a rise when the revs fall that indicates there must be some trapped air within the system being compressed as you speed the engine up. The volume of the air is being reduced by the increased flow rate from the water pump when running at higher speeds and that reduction in air volume is what allows the coolant level to drop.

The V8 won't tolerate overheating and replacement head gaskets are expensive. I'd investigate further to find and solve the underlying problem and start by making absolutely sure the system is completely free of trapped air rather than just try to work your way round it.