So almost 2 years ago, I returned home in the xk8, engine off, parked the car in the driveway, went in to get some item, and returned to the car. Started the car and immediately hear clanging coming from engine, turned off immediately. Did some examination and listened carefully and determined something in driver rear cylinder was bad.
So I pulled the head and discovered that the inlet valve seats in that cylinder had dropped. So it has taken all that time to get the new valve seats installed, head machined and all valve gaps reset with new shims
So this week I got it all reassembled. Refilled with Jaguar coolant and started up, and noticed a slight leak from the outlet pipe where the top radiator hose attached. I decided to get a new outlet pipe.
Removed old outlet pipe and it was crumbling apart as I removed it.


I replaced with new pipe, the car warmed up well and I could check the tranny fluid level. Turned off engine and let car cooldown. Then I noticed that the lower radiator hose had collapsed. The radiator hoses were replaced 8 years ago. I decided to get a new pressure cap for the reservoir to see if it was malfunctioning. Mine was original.
Got a new URO cap and installed. I started the car and noticed that the lower radiator was under significant pressure when hot. I checked the overflow bottle in the wheel well and the level had not changed since cooldown. Within one minute the lower radiator hose was blown off its connection to the thermostat housing and I lost most of the engine coolant.



I will get an authentic Jaguar cap and new radiator hoses.
My lower radiator hose was from Jaguar in 2014 and it has only two bends in it unlike some others I have seen online for 2001 XK8.

 

My experience with URO replacement parts failures during the past decade or so thoroughly convinced me to stay away from URO, period....

 

The cap has two valves on at 15 psi to pressurize the system and another to allow fluid back from the "atmospheric tank" behind the RH wheel arch cover. Make sure you have that tank about half full for the system to recover expelled coolant or the system does not work.

 

Yes, I check that tank periodically and it does have 1/2 tank when system is cold

 

I had a hose blowing off and the problem turned out to be that the cooling fans weren't operating. Just a thought. It sounds like the heat soaked in and the hose blew off.

 

I think the coolant never got above halfway on gauge, just where thermostat kicked in. I'll watch for the fans next time. But pressure should never build up to what I felt in the hose.

 

So i checked the URO cap with my Mityvac cap tester and it does open at 100kpa. I will need to find root cause.

 

You need to check the return valve also ...you do that by sucking on the cap ..wash it first and put in in your mouth .

 

As we all know, their upper front suspension mounts are complete garbage.

 

so the vacuum works. I am just puzzled why the hose swelled and got rock hard and then blew off.
I took the corss-over tube off, disconnected the radiator hoses, and poured distilled water into the expansion tank and diluted coolant flows out from heads. I pulled the thermostat and the diluted coolant flows out of thermostat hole.
I blew on 1 inch hose connected to bypass hose and diluted coolant comes out of thermostat hole. I collected all the expelled liquid and there is no noticeable foreign object in it.
I had also replaced the water pump and thermostat with Jaguar version when I replaced the crossover tube.
I blew air through the hose from expansion tank to thermostat housing. All clear.
I checked the thermostats in hot water . The new one starts to open at 84 C and the old at 90 C.
I will reassemble with new radiator hoses and watch very carefully.

 

ran engine until temperature read 201 F, hose not as hard as before. fans will not tune on
starting a new thread
https://www.jaguarforums.com/forum/x...o-fans-260158/