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Cooling System Pressures and No Heat Questions?

XJS ( X27 ) 1975 - 1996 3.6 4.0 5.3 6.0

Cooling System Pressures and No Heat Questions?

Old 02-14-2016, 11:52 PM
SouthernGypsy's Avatar
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Default Cooling System Pressures and No Heat Questions?

On my 1996 Celebration edition 4.0L Convertible I changed my radiator cap last fall with a new one, not because anything seemed to be wrong with the old one other than it was badly tarnished, about the only thing under my hood that didn't look as though it was still practically showroom new. So in October I bought a genuine Jaguar one online, even arrived in Jaguar packaging, correct part number, stamped with the correct 16 psi pressure, etc.

On Friday in preparation for a trip in her Saturday I took the cover off after 9 weeks of sitting (I have been out of the country since just before Thanksgiving) and started to check everything out before starting her up, but when I removed the coolant cap I noticed it spurted a little coolant back out just as soon as I loosened the cap (the new one I put on in October). The system was clearly under pressure even after sitting for 9 weeks of not being started at all. This seemed very odd to me, awesome that it shows the cooling system is well-sealed (wouldn't have any pressure left if it had leaks) but odd in that I would not have expected it to have enough pressure IN the system after 9 weeks of sitting to have spurted when I removed the cap. It never spurted in the past with the original cap.

Is this normal on the 4.0L cars and my old cap was just too weak to hold the pressure in?

A second question that may or may not be related; But I have little or no heat coming out of the vents inside this winter (this was the first time I have driven it this winter). In past winters this car has always had VERY WARM (read: melt you out even on the coldest days if you turn it all the way up) heat but I had virtually no heat on the trip I took Saturday...

I checked and the system shows to be full, the temp gauge is showing just above the N mark, the heater valve is moving when I move the control from hot to cold and back again so appears to be working, the hoses going to the firewall feel warm, and the car got a new 192F degree thermostat near the end of last summer. Anyone have any idea what I am overlooking?

Last edited by SouthernGypsy; 02-15-2016 at 12:02 AM.
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