I took the car out for a run and a nice lunch out enjoying the sea views, car as always behaved itself. On the way home popped into local supermarket to let the wife pick up a few things. When she returned I stuck car in reverse and as I pulled out noticed the low coolant warning message as I stopped the car I glanced out of drivers window and saw coolant on the ground, a few words to myself as I got out and opened the bonnet. I expected to see signs of the leak splattered around, nothing but the fluid on the ground. I called the breakdown service, when he arrived and tried to find the cause nothing was obvious. He brimmed the expansion tank nothing, level stayed the same, dropped the level to max and started the car and brought her up to temperature and left her idling for 10 minutes, no leaks, so he followed me as I drove to my local garage no problems no fluid loss and no overheating temperatures at the time 32 degrees. The garage left her to cool down then pressure tested her overnight, result no loss of pressure. Everybody is now scratching their heads I lost about a litre of coolant at the time. When they examined the car with me , they said that the bottom left of the rad looked damp and a bit worn I agreed it was past it sell by date so I had that replaced and also the cap. So far no problems at all she drives as she is supposed to.
Anyone got any idea what caused this because I am going to be slightly paranoid about this when driving her. Cheers Keith

 

Hi Keith,

That's a real mystery! You posted your account in the forum for the X350, but the Jaguar in your signature line is an X100 (1999 XK8). Please let us know if that's the car with the mysterious fluid leak or if it really is an X350 so we can ponder the various components in their proper locations.

One thought is that if the pressure relief valve in the expansion tank/coolant reservoir cap has failed and will not release pressure above its set threshold (typically 1 bar / 14.5 psi), perhaps an overpressure condition caused coolant to escape somewhere such as around the plastic radiator drain plug. On an X100 the drain plug is at the lower left corner of the radiator, aimed toward the rear of the car. On an X350 the drain plug is also at the lower left corner of the radiator but aimed downward. This could account for the dampness at the lower left corner of your radiator.

Please keep us informed!

Cheers,

Don

 

Hi Don
My fault the car is an X350 NA 4.2. That sort of confirms some of the thoughts by various old school mechanics but none of whom are Jaguar trained so were just using good old deduction, but were unsure were the coolant would exscape from when an over pressure situation occurd. Hopefully the new radiator and cap will cure it, I will have to keep my eye on it. Thanks for that Keith

 

Couple of thoughts

When you say bottom left can you clarify which side

The expansion tank overflow in on the left (same side as the fusebox)
The coolant drain plug is on the bottom right of the radiator (same side as airbox)

One hose that develops a pin hole leak is the Aux coolant hose. It goes on the 90deg bend on the right side under the air box hose.

On the left check the aux coolant pump. The o-ring between the motor and body goes

Check the back of the engine just in case its the valley hose.

Best thing to do is check the car for residue from the coolant. A dark place and a black light will show it up really well.

When my aux pump was leaking I had a tough time finding the leak. I could smell coolant loss but not see any evidence. I ended up adding some fluro die to the coolant, same stuff I put in the AC. This showed up the leak really clearly but I need to use the endoscope to see it, tracing all the hoses till I found the die traces

Cheers
34by151

 

I had this issue and it was my thermostat housing dying in its famous way. They decompose after time. Have you had yours done?

Other culprit is the hose under the intake.

 

Just for clarity, here's the diagram of the X350 radiator - the drain plug is on the left if viewed from the driver's seat, right if viewed from the front of the car:



Cheers,

Don

 

Well thanks all for your replies gives me something to keep me busy for the next few days. I do think I will be traveling with a large can of water. Thanks Don for the diagram it was the drain plug area that was damp so hopefully the new radiator and cap will cure it. I think I will be replacing most of the parts mentioned as she has done 110,000 miles. Thanks Keith

 

I think you can say that this radiator is proper poorly. All I can say is the car with new radiator and cap is running fine at the moment, but I have my fingers and legs crossed. Keith

 

That radiator is toast

 

I can confirm that the best time to look for leaks is in the dark with a good torch. Little beads of coolant will glint back at you but you'll neve see this in daytime as the daylight overwhelms your eyes. I found a leak on a connection to the water rail at the back of the radiator on my previous X350. I had got a low coolant warning too,although coolant loss was minimal, fortunately.

 

Did you have to disconnect the AC tubing to get the radiators in and out?

 

I am lucky I didn't do anything, but my local garage full of grizzled old veteran mechanics managed to wriggle it pass the hoses without disconnecting them. In fact, it was a young mechanic being directed by the old that did the job, he was being taught patience and thinking before acting, something a lot of people should do in this modern instant world. Keith