Purchased car for my wife just over a year ago, one day the low coolant light comes on dash. Add coolant to expansion tank and all is well, next day light is on again. Check for leaks and pressure test all OK. Replace the following:
water pump, large hoses, expansion tank and cap,overflow tank in fender,
stat housing, plastic pipe.
When at operating temp cap will open as it should and expel coolant but will not suck back all that is spit out. Overflow tank will overflow and spill out on to ground. When engine cools top rad hose will collapse , my thinking was that maybe the hose collapsing was not allowing vacuum being created to pull coolant back into system? I inserted a coil into hose to stop collapse but no improvement. My current fix is to bypass low coolant light and keep coolant level in expansion tank very low, bypassing use of recovery system.
I am able to monitor head temp by use of a BBQ probe and temps are fine.
What am I missing? system will spit out more than it will suck back.
Thought cap was the problem and replaced 5 times from different suppliers.
Fantastic car except for sucking problem.

Glenn

 

Can be a sign of weak hoses, but sounds like you covered that. What about your thermostat? Was it changed (and installed correctly)?

Search the forum. Many threads on this topic. (here's one:https://www.jaguarforums.com/forum/x...or-hose-62028/)

One poster even mentions hose direction was a problem. I know when I changed mine, it was confusing on which way it went back on as it will connect either way of course. But only one way in terms of clearing all the other engine bits properly.

 

+1

Thermostat gets my vote unless you've accidentally connected the Bleed Hose to the wrong outlet on the Expansion Tank.

Graham

 

Mike
Yes the thermostat is new as is the hoses installed correctly . The original hose also collapsed and it was not until a coupe of months after purchase did the low coolant
level in expansion tank become a problem.

Glenn

 

Graham
The earlier XK models have a different expansion tank set up and hoses are of different size and can't be switched.
System does operate but does not return as much coolant as is released .

Glenn

 

Hi.

Make sure thin hose to reservoir is connected correct according to your model year. See attatched TSB.

 

Several members have managed to switch the two Expansion Tank Bleed Hoses on the early XK8 models. Others have connected the single Bleed Hose on the later XK8's to the blanked Expansion Tank outlet.

Graham

 

oyster,
Thanks for link to TSB, good info. All is connected correctly. A couple of days ago when I checked coolant level in expansion tank there was about 1/8" of coolant . Today it is half full,system works sometimes?? Wife took car out for a 70 mile trip today at 90 deg. will see where the coolant level is tomorrow morning when cool.

Glenn

 

If I remember correctly, the cover for the tank is not too expensive. Might be worth buying another one.

 

Hi again.

My next suspicion would be a partially blocked or pinched expansion hose (8) or overflow pipe (17). If you disconnect the expansion hose from the header tank, you could try to carefully blow some air through it.
I presume you are using an original Jaguar cap on the header tank.

 

Oyster
I have pressure and vacuum tested all lines and yes cap is correct. I even did an experiment, hooked up an another recovery tank hanging from opened bonnet .
Looked like car was on life support. With the aid of gravity all seemed to work OK but not able to drive with bonnet up. Suggested to wife I could velcro the tank to windshield but she would not go for that.

Glenn

 

The hoses on the XK8 have always been a problem however; the coolant tank has two functions. The first function is to release the pressure in the coolant system when necessary and the other is to return the fluid to the system when it cools down. My guess is that the coolant tank cap is not allowing the coolant to return back into the system and you can see that with the collapsed hoses. I would be replacing the tank cap.