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Well, my 2008 xk base (non SC) sprung a leak last week. I ‘knew’ it was the valley hose, @ 2 quarts of coolant puked onto my garage floor after returning from a trip to town. I couldn’t see any leak from up top and underneath the rear under tray was damp and dripping.
Several days later I pulled the intake manifold and low and behold the valley hose was not leaking (but is soft and squishy).
I added some fluid to the reservoir…no leaks…I pressurized the tank to 14 psi and held it at that pressure for @ 30 sec…no leak. I pulled the under engine pan…there was no signs of coolant. The oil pan does have several drops around its circumference but nothing major. I cannot find any tell-tale trails flowing down the engine block, nothing appears wet…running my hands around all hoses does not lead me anywhere.
you may need to run the pressure test with a hot engine to show the leaks.
Is that possible? Firstly. you can't remove the expansion tank cap with the engine hot and, secondly, as the temperature drops the pressure will drop and you will have to re-pressurise it until the system is at ambient temperature which is back where we started.
I guess I might need to purchase that tester, thanks for the linkage.
I have crawled around the underside after holding my handheld tested on the tank for 4 minutes (constant pressure from compressor) earlier today, there were no changes, no leaking fluid. Using another approach I added a schrader valve to an old reservoir cap and tried to pump it up, I couldn't build any pressure!
I can see one (1) drop of coolant located above the oil cooler on the base of the engine block. There is a very slight area behind the crank pulley that appears as if it was damp but ever so slightly. I recall that my last oil change 4k miles ago I did have several drops of coolant on the oil cooler. The oil cooler hoses are dry and the cooler only had a couple of drops on it when I dropped the underpans the other day. I guess the question is, could the water pump seal be going out and when the engine was warm it finally burped a bit?
Placing my fingers against the block in that area does not reveal any fluid or moisture, none of the hoses have any signs of fluid ever leaking. I'm asking a friend to stop by and eye ball it.
Since the car has almost 120 k on it I'm inclined to rip it apart a but further tomorrow, anticipating a water pump or thermostat housing issue. If nothing shows itself I'll get the 'real' tester ordered and go from there.
If I hadn't made my valley hose assumption I probably would have already determined the issue since I could bring it up to operating temps.
A few years back I did this with an old reservoir cap to find a leak in a Ford Escape:
Turn the regulator on the air compressor down to zero, plug the air hose on the cap, and then sloooooowly turn up the regulator until you have 5 or 10 PSI. Hard for a leak to hide under those conditions. Most coolant pressure caps blow at about 16 PSI, so I wouldn’t go any higher than that with the air.
Find the coolant Leak (not a game)
