Cordial Greetings,

Had a bit of fun getting home from work today. The bleed fitting on the upper radiator hose left to pursue other opportunities, as HR might say. Lost a lot of coolant, but fortunately I was pulling into a hardware store. I was able to plug the opening with a rubber stopper, secured by several tie wraps. I refilled the reservoir (lost about two quarts), leak checked my temporary repair, and was soon on my merry way.

Much to my surprise, the temp gauge soon started climbing. The coolant temp reading on my OBD II scanner agreed. About three or four times, the gauge rose over 3/4, but I was always able to pull over and let things cool down. No leaks from the plug, had what seemed to be normal pressure at the cap, and the coolant level stayed steady. After a few miles of this, everything settled down and the temp stayed steady for the last 15 miles home. Still, it was quite a nerve wracking trip, never knowing if the plug would fail or the overheating would return.

Two long paragraphs later: Is the erratic temperature normal after a coolant loss if you don't bleed the system? Kinda hard to do so when the bleeder fitting was somewhere by the side of the road.

Curiously, there was no cloud of steam or noticeable smell when the fitting blew. My first clue was cold air from the heater. Even with the coolant low and the system unpressurized like that, the temp gauge never climbed above the middle until after the repair ( I know the gauge "parks" there for part of the temp range.) Not sure how long I drove like that. I'm guessing about a mile, judging by when I noticed the cold air.

 

What model jag, year and engine do you have?

 

If you have a 3.0 litre engined car, the 'turret' bleeder on the upper radiator hose is prone to failure.

Given the age of these vehicles, it is probably a good idea to replace all the cooling system hoses and thermostat, then refill the system with coolant meeting the correct specification and strength for the climate and location the vehicle is being operated in.

 

Sorry, it's an '02 V6. Info was in my signature, but isn't included when sending from the mobile version.

This hose assembly was replaced about 6 months ago. Had a weeping crack in the big Y fitting. Didn't bleed it then, but also barely lost any coolant. No issues then with overheating.

The replacement was URO brand. Seemed fine at the time. Ordered a genuine OEM hose last night.

 

I went through two URO-brand upper radiator (turret) hose assembly replacements back in September on my 2005 S-Type 3.0. The first one leaked within a few days of initial installation and I quickly found the leaking spot. I sent it back to Imparts for a replacement with the leaking spot marked with tape. Now the replacement is occasionally weeping, though not nearly as much and I have not been able to pinpoint the exact spot(s). I won't be ordering any more URO hoses. An OEM hose assembly would have cost me about $20 more at Welsh Enterprises. I should have sprung for that the first time. With my monster hands, this is a two-hour job for me and I'm going to wind up having to do it three times due to the lousy URO hoses. Lesson learned....

 

While researching the hose needed for my '02 V6, I came across this version for the Lincoln LS:



I'm still planning to stick with the OEM Jaguar part, but I noticed this aftermarket Lincoln version mentioned a "Pressure Burst Disc Nipple".

Does the Jag hose assembly (including the URO brand part that just failed) also have this pressure burst feature? I was under the impression the Lincoln LS and Jag hoses were the same.

I'm now wondering if the hose failed due to an overpressure situation, and not necessarily due to a defect in the part. The part that blew out is the small disc (with a screwdriver slot on the face) where the small diameter hose joins the large Y fitting in the middle. I was thinking it was a bleeder port, but maybe I was less correct than usual...

I plan to hook up a pressure tester and see what happens when the engine is running, but I'm dead in the water until the new hose arrives.

 

The black plastic turret tops (discs) are a known failure point. With increased time and heat cycles, they eventually weaken, crack, leak, and sometimes blow completely off. I doubt if your cooling system has an excess pressure problem....

 

Unfortunately that particular hose is very common to leak. I haven't seen anyone make an aluminum part for this hose. The bleed pipe should be the one coming off the coolant reservoir. When you look at the coolant reservoir, do you see a small hose with a plug in it that comes out from under the wiper cowling trim. There's a plastic screw in the end and that's where you should be bleeding it from, since you have on 02. The later ones bleed on the top of reservoir.

 

Curiosity got the better of me today. I finally installed the new hose assembly after getting a break from the monsoon that is springtime in Oregon. Eventually I got to wondering about the need for bleeding.

Six months ago, when I changed the same hose, I didn't bother with bleeding. I figured skipping might only cause an erratic heater for a little while. Plus, I could always go back and bleed it later if needed. Turns out everything worked fine right off the bat and I never had to bleed the system.

Fast forward to last week. I had driven about 2 miles and was sitting in a parking lot with a blown radiator hose, about 25 miles from home. I was able to plug the leak and refill the system. I didnt bleed the system this time, either, but then had lots of trouble with the coolant temperature climbing.

Today, after changing that hose, again I didn't bleed the system for the third time. I wanted to see if i could duplicate the erratic behavior from last week. Much to my surpise, everything was fine.

What gives? The first and third times were fine without bleeding. The second time gave me nothing but trouble.

Any ideas? I wonder if it had to due with this scenario: The first and third times, when everything was fine, the engine was cold and full of coolant. For my test drive, i was on the freeway within 3 or 4 minutes. The second time, the problem event, the engine was very hot and had lost a lot of coolant. I also ran at idle for at least 15 minutes to make sure my parking lot repair was going to hold. After that, I was in stop and go traffic for at least another 15 minutes before getting on the freeway.

Does it seem likely these different scenarios would explain why i only had trouble the second time?

 

For anybody who might stumble across this thread in the future while researching bleeding of the cooling system: In addition to the different scenarios, it turns out there was another problem at play. The radiator fan had recently stopped working but I wasn't aware of it. That's the main reason why I had such trouble in stop and go traffic after my parking lot patch job. There was no problem after replacing the hose at home because I was up to freeway speed (good airflow through the radiator) within minutes on the test drive.

More rambling, non-pertinent, and rather obtuse details about the inop cooling fan in this thread:

https://www.jaguarforums.com/forum/s...-gauge-159542/