Last week while driving the "Low Coolant" message came on and then the temp gauge went to max. I pulled over and saw the nipple on the coolant tank had completely snapped off. So I filled up the tank and managed to clamp the hose and got the car home. I put a new coolant tank in and filled with dexcool. Ran it in the garage a few times to bleed the air out. Drove around the neighborhood a few times, everything seemed fine. Drove to work and at about the 8 mile mark, boom, upper radiator hose blows off. Went through the above again thinking I must have had air in the system. Took it for another test drive today and at about the 8 mile point, boom, off it goes again. The oil dipstick looks fine and I don't see any oil in the coolant. Help!!!

 

Its a 2005 XJ8

 

Can you expand on "and filled with dexcool". Dd you fill to the level indicator on the inside of the header tank, or just fill it to the brim ? If you filled to the brim, then I can understand the hose blowing off, as the coolant expansion on warm-up had nowhere to expand to.

 

Filled just to the max level indicator, not to the brim. The upper hose does seem to have pressure when the engine is hot, i.e. you can't squeeze the hose with your hand.

 

Rad cap should release pressure I know this is going to sound stupid but did you you check to see if there was a bung in hose connection this would stop water entering the cooling system it's just a thought as we had a mechanic at work do this with a truck header tank

 

No bung in the hose connection, I went through the running til hot, then refilling the coolant tank when it cooled a few times last night. Upper hose still gets pressurized and I'm not sure if this is normal. I know it doesn't happen on my pick up, there's no pressure at all.

 

You could try removing some coolant from the header tank and parking Jag on steep slope with nose upwards and run engine with heater on say 25 deg C and fan running.
Also consider replacing rad cap.

You may have air in your coolant circuit.

On second thoughts try replacing rad cap first.

https://www.jaguarforums.com/forum/x...pop-off-97979/

 

Is there any pressure in the system when the engine is stone-cold ?If there is, it suggests a head gasket has failed. Many shops have apparatus that detects combustion gases in the coolant, so maybe worth checking out. I hope you don't find any, BTW !!.

 

Thanks, that scenario has always been at the back of my mind. Yesterday, I noticed that the hose had started to slip again from the original position. Lo and behold the neck then lost a big chunk as I pressed down on it. Hopefully this was the problem all along, a new radiator is on the way. I'll report back when I install and run for a while. Thanks for the suggestions everyone, I appreciate it.

 

Good chance; best of luck.

 

I hope the radiator is your problem, but your symptoms sound like my 06 Super V8.

I had a coolant leak and replaced the thermostat and water pump and repaired two electric coolant pumps and it was OK for 3600 miles, but about 3000 miles ago on a trip, the top radiator hose backed off and it lost a couple of gallons of coolant and the Temp got up to 230F before I could stop and replace the hose and find an auto store to replace the Dex-Cool coolant. After that it developed a leak at a plastic quick connect fitting to a heater pipe which I replaced along with the top radiator hose assembly, but since then the new top radiator hose with a new spring clamp backed off twice (I put two jubilee hose clamps on it) and now it loses about a cup of coolant from the pressure cap per 100 miles due to high coolant system pressure, A block test indicated combustion gas in the coolant.


So...I don't know if the first time the radiator hose blew off was a cause or a symptom, but I have a definite problem and have to decide if I try some Blue Devil head gasket sealer or bite the bullit and replace the head gaskets

 

Well, I bought a block tester from NAPA and yes, I have a blown head gasket.

Not sure if I have the energy/desire to put a new motor in. It may be the end of the road for my beloved XJ8.

 

Another motor or rebuild this one.

 

Can anyone recommend a shop in Phoenix? I really like to do most work myself, but this one may be too much. If I can get a swap done for around 3k, I will go for it.

 

Upper end rebuilds are usually not all that difficult, do the timing chains, with adjusters at the same time.

 

I feel your pain because that's the status of my 06 SV8. I am considering trying Blue Devil head gasket sealer before I get into the considerable task of replacing head gaskets (still researching the tools needed for that job)

Blue Devil recommended locating the leaking cylinder(s) and removing those spark plugs to do the treatment and said I will need to flush the cooling system, remove the thermostat, and use the head gasket sealer with water starting from a cold engine and let it idle for 50 minutes.

I am thinking of using compressed air one cylinder at a time with the block tester in the expansion tank filler to watch for bubbles to try to find the cylinder or cylinders that are letting gasses into the cooling system. My leak seems to be one way only because the system holds pressure after cool down for as much as a week (that's the longest I've let it sit between starts).

One odd thing I saw was that the yellowish used test fluid, which I had in a shot glass to compare with fresh fluid, turned back to blue as it sat for a week. I wonder if the chemical reaction reverses itself over time.