hi, my 2000 xj8 3.2 is losing coolant at about half a pint every 50 miles or so. there are no obvious leakage signs, no water in the oil, no puddles under the car, the temp guage always reads normal and no warning lights illuminate. could it be as simple as air in the system (the heater/air con. all work fine) and if so what is the easiest way to tell and rectify? thanks in advance, rod.

 

There are several places where you could be losing coolant and the coolant never makes it to the ground. Expansion tanks are known to crack especially around the level sensor.
The distribution pipe in front of the thermostat, the thermostat cap or housing, any of the connections for the small plastic tubes carrying coolant, etc. There also a maze of heater hoses under the intake manifold which can start leaking. Unfortunately these plastic parts deterioate with age and heat and have a tendency to develop small cracks over time. The coolant seeps out and evaporates before it ever hits the ground. You can always have the system pressure tested.

 

I wud it pressure tested or a leak down test

 

I've got a similar problem. Try checking near the recovery tank (plastic, drivers side behind bumper). I get leakage/dripping there right after I shut the car off (no leak when it's runnning). I doesn't make a sense to me, and I haven't got around to figuring it out .... but I'm adding a ****load of coolant, at least once a week.

 

Your recovery tank may be cracked or the fitting maybe cracked or loose. The coolant recovery tank is designed to contain the overflow which will only be fed when the temp and pressure is high right after shutting down a hot motor.

 

yeah, that sounds about right. I've been meaning to have a closer look, but it's in an awkward spot to work on. I'm wondering if electraglide has the same problem .... the leak is hard to find unless you look in the right place right after you shut the car off.

 

hi, thanks for all the info. i only get to use/see my car at the weekends as i work away all week but i'll have a good look over it this weekend and let you all know if i find anything. one thing i forgot to mention is that when the car is warm and the expansion tank cap is removed (with the engine running) the coolant level rises and falls in an irregular pattern. should it do this? if it shouldn't then any ideas why it does? cheers again fella's.