Tackling My '85 XJ6 Again

[tony barnhill]

Holds water so long as the engine's not running...engine running, the water goes somewhere...no hoses leaking, no white smoke out tailpipe, no smell of antifreeze....no leaks anywhere along head/block......tried prressurizing a sparkplug hole to see if water squirted out of any others - nothing.

Guess all that's left is to pull the head???? Engine has 165,000 on it.

 

[DrEntropy]

Have ya tried putting a pressure tester on the cooling system?

Oil level not rising? No "chocolate mousse" in the rad? If not, leave the head where it is. Leak-down and the above test first.

It's goin' ~someplace~ man. Water doesn't just *disappear*. Check the area around the reserve tank. They develop pinholes.

Have you pulled a Jag head before?

 

[Silverghost]

My Mini had a "mystery leak"..I'd put water in, it kept "going away". No puddles under the car, no drips, etc. In the end, there was a very small leak in the lower rad hose coupling that would only leak at speed and under pressure. When I finally found it, it looked like the area around the leak had been steam cleaned. But until I got under the car in just the right position I couldn't see it. Had me baffled.

 

[DrEntropy]

A Stant pressure tester is a cheap diagnostic tool...

Pulling the head on a Jag with that time/mileage is a can of worms with no bottom.

 

[tony barnhill]

No "chocolate-mousse"....oil lvel not rising.....called myself doing a leakdown last Fall.....but, I want to drive the car this year & keep the mileage on the '87 Jaguar under 45,000.

& I hate to even think about removing the head.....maybe I'll just become a parts changer....I've already pressure tested the radiator - no leaks....I'll move to the hoses next, I guess.

Have you pulled a Jag head before?

1 & I'll not do number 2!

 

[LarryK]

Tony:

Pull the knee bolsters on each side of the console where the vents are. The heater core is behind the radiator. When panels/bolsters are removed you can see the housing and pipes. Also check the A/C drain tube on bottom of car for antifreeze, comes out same as the A/C water.

 

[DrEntropy]

Good point, Larry.

 

[tony barnhill]

I'll check them, Larry...AC is good & cold though.

 

[Exotexs]

if you're absolutely sure that there are no leaks anywhere, and no evidence of coolant show up under the car, zero, nada, then your cooling system is not full, and the coolant level keeps going down after the engine is warmed up and goes through 2 or 3 thermostat cycles. Keep adding a mix of 60% coolant and 40% water. Drive the car and allow engine to cool completely. Check again, add again if neccesary. You also need to run the heater at full blast, (TEMP knob at 85, SELECTOR knob in FAST), after engine reaches normal running temperature, for coolant to settle into the heater core/matrix, and that will consume even more coolant.

Also check under the driver's side front fender/wing. There is a plastic "bladder" there that serves to hold excess coolant, sort of an expansion tank for the expansion tank, if you will.

There is a coolant drain plug on the block, on the driver's side of the engine, hidden behind the engine oil dipstick, make sure the bolt is sealing.

Ex

 

[DrEntropy]

I'll check them, Larry...AC is good & cold though.

Larry is suggesting there may be a coolant leak in either the matrix or connections and the coolant would then be mixed with the condensation from the A/C and escape thru the drain. Diluted, less noticeable than if it were undiluted and just coming from a leak to the ground.

 

[tony barnhill]

I'll check them, Larry...AC is good & cold though.

Larry is suggesting there may be a coolant leak in either the matrix or connections and the coolant would then be mixed with the condensation from the A/C and escape thru the drain. Diluted, less noticeable than if it were undiluted and just coming from a leak to the ground.

Don't think that's the case...it losses coolant too quickly.

 

[LarryK]

Tony:

Get a mechanics mirror and look at the core plugs. Hard to see under the manifold and behind the head. Also, there is one in back of the block in the bellhousing area. There is an inspection plate under the bellhousing. Warm engine and then remove spark plugs ( I know you're not supposed to remove warm plugs, do it carefully ) and pressurize the cooling system then take a slim light and check in the cylinders ( being a hemi, you can see if the pistons are extra clean from coolant or you will see coolant as the block is warm and system pressurized. Last resort is to use dye and a black light to see external leaks. dye will stay in cylinders and come out exhaust eventually if there is a leak.

 

[tony barnhill]

Thanks, Larry - I've already checked core plugs - even the one in the rear of the engine...but not under the manifold....I'll do the warm plug idea.

 

[Michael J.]

What you describe is like the head gasket problem I had.

Put a compression leakdown tester one by one on each cylinder. Have the expansion tank cap off. If you have a gasket problem, when the compressed air is applied to the cylinder that has the leak, the coolant wil bubble up out of the expansion tank due to air displacing coolant in the head.

My failure was at about 170,000 miles.

I kept loosing coolant and could not find where it was leaking either.

 

[LarryK]

How's the Jag Tony? Find anything yet?

 

[tony barnhill]

Nothing except antifreeze goes somewhere when I drive it - but, it runs like a bat out of you know where....after I get back from Disneyworld next week, I'm gonna take it to a friend's shop & let his mechanics have a go of it.

 

[RonMacPherson]

See if you can find a shop that has a gas sniffer for exhaust systems. Out west just about every shop that does smog checking has one. Dunno if they do back in your neck of the country.


A sure way to diagnose internal leakage. Warmed engine, remove radiator cap, with the coolant level a couple of inches low insert the co/h2o analyzer in the neck of the reservoir. If you get a reading you have a leak. The combustion gasses enter the cooling system and head for the reservoir..(or any other outlet they can find).

A nice plus about smog machines..

 

[tony barnhill]

I'll look around but we don't have emissions testing here.

 

[LarryK]

NAPA sells a block exhaust gas tester. A blue fluid put in a jar and sniffed from the rad reservoir, like a turkey baster, then turns color if exhaust gas present. In their tool catalog about $50 over the counter. I use it on aluminum block Rovers.