My 89 XJS convertible developed an occasional but significant coolant leak behind the engine block. It appears to be losing ~1.5L of coolant at a time (but appears to release all of the coolant overnight). I cannot seem to replicate this very often but every now and then will find a large pool and streak of coolant on the garage floor. I looked at the pipes from the radiator and the expansion tank and both look fine. Any ideas? I don’t see anything there…
Tomasz,
Have you checked the condition of the heater valve?
Cheers
Hi Gary - I have not checked the heater valve. Would turning on the heater / ac be a an appropriate test? The AC does not work and it is quite warm outside so have not tried this yet. I will check the ROM for how to get to it!
Tomasz,
Start up the engine, get it up to operating temperature, and turn on the climate control system. It doesn’t matter if the A/C works or not. Then cycle the temperature control knob on your climate control system from full hot to full cool and watch the heater control valve. I have had to replace three of them in my drivable Jaguars because they leaked coolant. Some of them it was a few drops at a time, another was a steady drip. The fluid will leak down on the transmission housing and create a small pool beneath the car when it is parked. I suppose it could also be a coolant hose leaks, but that would create a spray that would be more easily seen like the one I recently had on my 1990 V12 Vanden Plas which created quite a mess.
The heater valve is on the firewall aft of the engine about in the center. It’s a PITA to get to because of all the stuff you have to remove in order to access it.
Regards,
Paul M. Novak
1990 Series III V12 Vanden Plas
1990 XJ-S Classic Collection convertible
1987 XJ6 Vanden Plas
1984 XJ6 Vanden Plas
1969 E-Type FHC
1957 MK VIII Saloon
Ramona, CA USA
Hi Paul and Gary - I tried the approach you suggested to diagnose the issue. I got the car to operating temperature and alternated between heating and cooling. I did not see coolant dripping (at all). I did notice was the air temperature not changing between the “cold” and “hot” settings. It looks like the valve, while not leaking, needs to be replaced regardless after all. One more item added to the list of projects.
One more observation: I am not sure if this was the only leak but I was topping off the expansion tank with coolant (which rightfully leaked through the expansion tank cap once it got to temperature). This was my biggest leak (or user error). I tried tracing through the hoses from the expansion tank but the 2nd and minor mystery leak is still a mystery.
My next projects: front shocks, steering bushings, and ball joints. Will search for the leak next!
One more question relevant to this topic: Is the expansion tank same as the atmospheric recovery tank discussed on a number of threads? I can’t seem to find the second connected anywhere in the system (or in the ROM diagrams).
Thanks,
Tomasz
The expansion tank is low down on the LHS inner fender, with a radiator cap . (Which should not leak when hot) It should be connected to the atmospheric container, which is hidden behind a panel aft of the LHS front wheel. (Some disassembly required!)
I want to provide an update on progress: I replaced the heater valve and coolant caps. The coolant leak appears resolved; however, weather has not cooperated in the last few days so the car has only been driven a few times since. I will let you know and ask for advice if a coolant leak is spotted again. This project looked intimidating with the air hoses in place for a novice home mechanic like myself and was a minor repair (it is the first time i worked on anything close to the engine).
Next up a real challenge: an attempt to tackle oil leaks (starting with the oil warning light and sender units)!
Working on the XJS is addictive and should carry a warning for prospective owners. I’ve owned the car for six months and ended up re-doing the front and rear brakes (rebuilt calipers, replaced rotors and pads), replaced all 6 shocks, repacked and tightened front bearings, and replaced both thermostats (it overheated out of a sudden a few weeks ago).