2002 Vanden Plas (base). I have read many threads (which are great) but cannot find the answer to my specific problem . After several weeks of only a slight discharge (few drops a day) the overflow tank is now discharging serious amounts of coolant. Cannot drive for more than a proximally 10 miles without overheating and refilling. (Obviously not driving it now) No work has recently been done on car. I have driven for 10 years. Here is what I have checked.

No visible coolant in engine compartment . Flowing from directly beneath overflow tank.

No leaks in any lines coming from expansion tank.

Expansion tank cap Seems in good order.

Removed skid plate and inspected overflow tank (behind fender) can not visually see any cracks.

After shutdown coolant does return to radiator when cooling - no line blockage.

Coolant appears to be coming from overflow tank. Is it possible that engine overheating and dispensing to overflow tank to maximum and forcing coolant out discharge port?

I am at a loss. Any help would be greatly appreciated.
Monty

 

Have a check done for head gasket failure and for thermostat sticking closed.

 

<p>I've moved your post from the General Tech section to the model specific X308 section where you will get a better response</p><p>regards,</p><p>Steve</p>

 

As said already, and,

The water pump impellor had issues on that engine, but I remember it being the earlier years, but maybe?. Insufficient circulation can cause all sorts if oddities.

The cap may be allowing return fluid as you state, but may NOT be holding pressure.

 

It sounds like you might very well have the bad luck of a failed head gasket.

 

Check and make sure the plastic hoses coming into the front of resavoir are correctly attached. When correct position it looks incorrect. Hose to overflow tank should be the one on top.

 

Fundamentally, what is happening is the presence of gas within the cooling system, which raises the pressure until the pressure cap releases.

Where does this gas come from?

There are two common causes :

1) Nucleate boiling (localised in the hottest spots, ie cylinder head), which is happening because the coolant is too hot, and maybe not pressurised.

2) A leak of exhaust gas into the cooling system.

It would be a good idea to eliminate (2), before going further. The best way is with a cooling system exhaust gas test kit, like this :

Combustion Leak Detector at National Tool Warehouse

(1) can be caused by lots of things, a partially blocked radiator, faulty water pump, faulty thermostat. The cooling system relies on being pressurised to not boil. So the slightest leak tends to form a vicious circle : air leaks in, makes it overheat more, and so on. The same goes for nucleate boiling, once you get the slightest bit, it's all downhill from there.

You can get pressure testers to check that the cooling system holds pressure. I tested my Land Rover V8 to just over the release point of the pressure cap, and found 3 different leaks, all from hoses.

So, in summary, while this might be a head gasket problem, it is just as, or more, likely to be a cooling system problem. Don't assume anything, verify.

My TR8 did this chronically. The final fix was a new pressure cap - it wasn't holding pressure.

 

Thanks - Great Advise from Post -

Quick update!!

Have replace expansion tank cap.
Installed new thermostat.

Eliminated any coolant loss while driving (YEA) however I am still getting discharged on cooldown after stopping. This is Random - it occurs sometimes but not consistent . In all cases engine is at normal operating temp prior to shutdown.

Additional advice would be greatLy appreciated.

Also - in the process I managed to crack one of the expansion tank flex hoses. ( One going from tank to top of thermostat housing ) I had to cut the flex line and run high temp hose from there to thermostat housing port. ( short term fix to say the least)

I cannot seem to find the Pre formed flex line online. Does anyone know where this can be purchased?

Thank you in advance for your good advice!

 

I think that line you are looking for, if I am understanding your description, is bleed hose part number MNC4582AC.

Here is a link to one possible place to buy it:

http://www.terrysjag.com/product/MNC4582AC.html

 

Unfortunately, the built in temperature gauge is a poor guide to running temp. It is fixed in software to stay mid range over a broad range of temps, and will hide chronic overheating. You really need something like the Ultraguage.

 

thank you very much for the link. Purchased the expansion tank hose and I am preparing to install. One additional question-is there a trick to disconnecting the expansion tank flexible hose. It appears the clip simply needs to be depressed while applying pressure to pull hose free? I am just trying to avoid damage to the expansion tank port. THANKS AGAIN!

 

The attached picture is of a simple plastic Jaguar tool that was supposedly included with our cars when new. I've never seen one in person.

Many use needle nose pliers to engage each side and then open the pliers to release the connector. I have done that, and it works.

My preferred method is to use snap ring pliers that open out (external, I think they are called).

 

Thanks Harvest14
perfect advice-was able to remove and re-install all hoses with no problems. Also your link for the hose purchase was perfect. Your valued advice has made my repair job very easy. MANY THANKS!

 

Thanks for the thanks, Montypeek,

I am very new on here myself and have had MANY questions answered by other members. It feels good to pay it forward a little.

This forum is the most valuable tool for working on your Jaguar.

 

Harvest14 I have 2 of those and surprisingly they were found located on the vehicle. When I did tensioners on my XJ-8 I found the tool in one of the fittings below the throttle body. Out of curiosity I went over the lines on my XK-8 and it to was found on a fitting under the throttle body. I think a lot of them were used and removed by mechanics and tossed in a tool box.
They are a handy little gadget and they do work. Interestingly with 2 of my friends XJ-8's I couldn't find theirs.