The top cooling hose keeps popping of before the fans kick on,if this was an overheating problem wouldn't the fans start before the hose popped of?

 

It's either overheating or has a compression leak into the cooling system (which is usually caused by previous overheating.)

 

Couled it be the hose leading from fill tank back to radiator? I discovered it broke in half.

 

Vettinrnd,

Did you ever determine the cause and find a solution ? I just recently had this happen twice . 1st time was Sunday afternoon. After a 5' cool-down, I refilled with water, reattached the pipe and drove ~10 more miles with a 6 hour stop then a much longer ~45 mile trip that (Sunday) night - both trouble free. The 2nd time was yesterday (next day) on a short (just a few miles) trip to the store at noon. Both times outside temp ~70*. Temp gauge never went above its normal halfway mark, even on the 1st time in which the fans did kick in shortly before I pulled into a gas station.

Haven't had the jag that long - only 2 months but have taken 2 long trips (~900 miles & ~700 miles) plus a few shorter ones (~60 miles or less) before all this happened with no problems or coolant loss.

As a temporary fix, I'm going to roughen up both the inside of the hose and the outside of the connecting pipe with sandpaper to hopefully obtain a better grip plus use a "worm screw" clamp for hopefully better holding power.

Though Beav in his reply to Vettinrnd considers the possibility, I would think normal internal pressure couldn't get above 15lbs, even if there's a complete or almost complete system blockage, overheating (not the case here) or a compression leak (no misfire or contaminant in coolant fluid) as the coolant tank cap should vent excess pressure. Is that a correct assumption ? If so, is 15 lbs enough to pop a (weak?) hose off ? Could the pressure cap be faulty thus letting the pressure increase above the normal maximum 15lbs ?

Since I've lost pretty much all the coolant, I figure this is the perfect time and am planning on replacing the top & bottom radiator hoses and the short T-stat hose with the thicker, better and less expensive APA/URO ones, T-stat, the plastic T-stat housing with an aluminum one and possibly the H20 pump if it looks original and/or has plastic blades.

Any additional info, suggestions, ideas from anyone would be most appreciated as I don't want to get stranded or worse, toast an otherwise healthy engine.

Thanks in advance,
JB

 

Hi people I am getting the same problem on my 3.2 V8 XJ. I've only had the car a few weeks and this has happened twice, normally when I put my foot down! Was wondering if anyone has found a solution? I have ordered a new header tank cap today in the hope that it could be that but I'm not convinced.

 

This problem has been reported in the past associated with a bad Thermostat.

 

...and I recommend having the cap pressure tested for proper release pressure. Lucky having the hose blow off rather than having the radiator swell and bow, then blow - it happens!

 

If it's just happening when you floor it, it might just be that the hose clamp is too loose. As the engine spins faster the water pump spins faster, too. That develops more pressure in the cooling system. The pressure then causes the hose to slip off. The same thing happened to me in my Expedition one time. I replaced the springy clamp with a regular screw down clamp and it hasn't happened since.

 

Ditto on the screw clamp and thermostat. Mine popped off last spring and I replaced the clamp (with a screw clamp) and a thermostat and had no more problems last summer.

Mike
2002 XK8