On my 90 vdp, I'm losing 1/2 gal of coolant mix every 100 to 150 miles? Pressure test by nechanic, he says there is a leak in the resevoir tank. But when the dash warning comes on and i fill it, why would there be a discernable vacuum at the cap if the tank had a hole?

Somewhst rough idle at stop, but runs great

No apparent leaks, no hissing?

Thanks,

Poorest man to own a jag,
and I own two of them

1990 vdp 4.0 blk/ds w/ wires
1990 xjs 5.3 cc conv jrg/ds

 

Are you sure that you have no leaks? Brownish stains are an indicator, and this is really what you want to find at this point.

What did he pressure test?

I suppose that you could quickly replace the tank and cap with one from a scrap yard for testing purposes.

Because if you don't have a leak, then your coolant is going somewhere, in this case most likely through the engine and out of the exhausts.

Not a good place to be. Have you checked the oil for mayonaise like deposits and the coolant for oil blobs.

The loss of coolant and your rough idle would be pointing me towards a head gasket issue. Does or has the car ever over heated.

What happens when you (stationary) run the car with the cap off, do you see bubbling gases coming up? Again pointing to a head problem.

Are you sure you have a vacuum, ie air rushing in when you remove the cap and not the other way round? I suppose it could happen if the coolant was being consumed by the engine, but combustion chamber pressures and gases would usually increase the pressure in the coolant system. In my experience.

And unless you are prepared to strip and repair the car yourself IMHO that's about as far as you can go.

All the best,

 

THANKS FOR YOUR HELP. ALL THE "SURES" WAS YES, BUT NO MIX IN THE OIL. WE HAD AN OVERHEAT LAST SUMMER, WITH A BROKEN HOSE, BUT NO COOLANT ISSUES UNTIL JUST RECENTLY. EVEN DROVE IT OVER THE GRAPEVINE INTO LOS ANGELES IN DECEMBER. I'M GOING TO PACK A TRUNK FULL OF COOLANT, AND DRIVE IT TIL IT DROPS


Poorest man to own a jag,
and I own two of them

1990 vdp 4.0 blk/ds w/ wires
1990 xjs 5.3 cc conv jrg/ds

 

Oh heck, don't kill it. Why not buy your mechanic a beer and have him do a compression test/leakdown to confirm. It won't cure anything but just might turn up a water leak problem, rather than head.

And if you are going to drive it into the ground 'Sad vey Sad' there is a member called TOMALONIC over in the X300 section just below who is really wanting a set of Wires for his car.

Why not get in touch, you never know?

 

Thanks Chancezz,

That is the culprit for the "original" overheat. Took the dealer a week to come up with it, looks like a "s", twisted. But the coolant burn off maybe the key!

Sneeky!!!

Wires going on the conv, if this car dies!

Thanks,

Poorest man to own a jag,
and I own two of them

1990 vdp 4.0 blk/ds w/ wires
1990 xjs 5.3 cc conv jrg/ds

 

Might be the dreaded Water pump to Water rail hose, right up under the intake valves, hated that