Hello

I scoured this great forum and used some advice already before putting this post together. I am hoping the someone else has been through this scenario.

On the second short drive after picking up this 2001 XJ8, the radiator hose popped off/slid off the thermostat outlet. The "Restricted Performance" message was triggered and the low coolant message also came up (obviously). The temp gauge was at just over half when this happened. I replaced the factory spring clamp with a worm screw clamp and refilled coolant at reservoir.

Afterwards, I cleared the code to clear the Restricted Performance message then let the car warm up. It got to about the same temp (half) and the message appeared again. Turned it off to let it cool down. While off about two minutes, the same hose just popped off again. Inspection showed the plastic outlet tube from the thermostat housing unit was in bad shape (which seems common). So I ordered the full aluminum verson from Welsh (thanks to this forum). It is perfect, and came with a new t-stat as well.

The old housing unit turned out to be worse than appeared, so it was a good call. Installation went fine (no 8mm crow foot, but an 8mm flat bicycle wrench worked perfect with along set of needle nose pliers for the back housing bolts). The hose holds now, but the temp still rises quickly the about half on the gauge within 10 minutes at idle or about half that time while driving , then the Restricted Performance message appears. And I bring it back to the house.

The hose leaving the top of the t-stat housing (running to the passenger side of the rad) gets very hot. The hose coming into the t-stat (from the driver's side of the radiator) stays cool. I have heat inside the car and plenty of coolant. At this point I am thinking it is a failed water pump (which I just ordered from Welsh today). This car has 120k on it and OEM water pumps seem a very common problem. I am also now getting (what I think) is a bearing whine from the pump. No coolant in oil, white smoke etc. Radiator seems cool and the cooling fans don't kick on (unless AC is on, and then they work fine).

I am hoping the pump is the main problem, and it is allowing enough heat in the upper hose (on the failing t-stat housing) to let the it slip off. Is this sounding like the likely candidate to you guys for this situation--that the water pump fins could be worn down enough to almost no coolant?

Of course, another possibility is a blocked radiator, but from searching, it does not seem that many people have this type of problem with these cars.

Thanks for any advice you might have.

- Paul (in Phoenix)

 

Paul:
Welcome to the wonderful, strange world of Jag ownership. Let's sort through this-
First, while you MAY very well have a cooling problem, your statement" <<The hose leaving the top of the t-stat housing (running to the passenger side of the rad) gets very hot. The hose coming into the t-stat (from the driver's side of the radiator) stays cool. I have heat inside the car and plenty of coolant.">> indicates nothing abnormal. Hot water is pumped from the engine "top of tower" through the radiator, where it is cooled, then it returns to the pump intake.
As to >>" but the temp still rises quickly the about half on the gauge within 10 minutes >>, that is also exactly right behavior. The thermostat causes the circulating water to bypass the radiator until the engine comes up to temperature, That is so the engine will run efficiently. It then opens and closes to maintain the temp. About half on the guage is right, and usually the heat comes up in 10 minutes or less. So you are A-OK there too.

Now, why the hose is blowing off. That indicates a pressure problem , assuming you have it on right. As you correctly assumed, higher temperatures can raise the pressure in the cooling circuit. However, that pressure is supposed to be limited by the cap on the coolant resevoir. So, you can try replacing the cap. It is pretty difficult to measure the pressure with the cap on, so chnging the cap is a reraconable diagnostic procedure. And, make sure the little hose that exits the resevoir up high near the cap and goes to the overflow tank in the wheel well is not blocked.

Changing the water pump might be an OK idea for the reason of historical problems, but it will change none of the symptoms you described.

You mentioned "restricted performance". And clearing a code. What was the code? I think you have a separate problemswith that one.

Good luck!

 

I think in 2001 they were on the second version of the water pump -- that one still had problems. I know at 2002 MY they had the final pump. Strange things can occur with a failing pump as the vanes disintegrate and can snap off --getting stuck in various parts of the system. If you take off the pump and the vanes are missing you should do some more research as to what is the best way to proceed. I remember it was best to (reverse?) flush different parts so as to not push any possible pieces into the heater matrix.

When the pump really fails you get no circulation and overheating to the point of steam -- and that can certainly pop a weak joint in the system. A failed thermostat can also create havoc - and staying closed could do the same thing.

I am not sure what the system does as to high water/ engine temperature and the introduction of "restricted performance" it is logical that Jaguar would have the engine do this if the engine overheated - I just do not know the parameters.

It actually sounds like the cooling system is currently working correctly since you are not getting a high temperature indication. You may have two different problems.

If the pump is making noised it will need to be replaced. Make sure to properly fill the system -- and use the correct coolant.

Hopefully the car gods are with you ---Good luck

 

Hello Sparkenzap,

Thanks so much for the reply.

I think I did not explain fully the hot/cool hoses. The top hose gets very hot and the bottom is cool BUT get warm to hot near the end close to the t-stat housing. It seems like it is just heat transfer from the housing into the closest portion of the hose (and the coolant within) that make it warm at all. It just seems as though all the liquid is stationary, no circulation.

The code is P0327 (Knock sensor 1 circuit low input bank 1). Clearing it immediately clears the Restricted performance message and the yellow caution light). The other code is just the P1000.

Am I correct in saying that pulling the t-stat out completely and testing whether the temp in the up/lower hoses somewhat equalizes should definitively determine whether it is a bad water pump?

Also, could this all be the result of a bad airlock?

You guys rock, by the way

 

Hello Yeldogt,

Thanks as well for the input.

I have only let it get to just near the 3/4 mark before shutting it down, though it seems like it would be happy to go farther.

Great information about the flush direction. Yes, the water pump is being replaced regardless, whether or not it ultimately resolves this problem. After that the vehicle will be transferred to one of the mechanics I use. I was actually going to limp it out there today (I am central Phoenix, he is in Mesa about 20 miles away), but the test drive last night did not install confidence.

Thanks again,

- Paul

 

Paul,

a warm Welcome from cold Germany as well!

The knock sensor is pretty easy (and cheap) to replace.
(See the FAQ section on top of this site for a DIY I wrote a few month ago.)

Anyway it would probably be a good idea to check the electrical connector of the knock sensor prior to an exchange.
The connector happens to be located right at the side of the T-Stat housing!
Maybe you are lucky and it's just leaking coolant that caused a conection problem.

Anyway, I second (or third?) that an exchange of the water pump to the newer style is a good idea.
Whether it solves your heat issue or not.

Cheers,

David

 

If you have the ability to install the water pump yourself -- you should be able to do the sensor. I have never had to replaced one but they do not look too complicated and as mentioned you may just have a contaminated connection.

I would inspect the pump vanes -- that will tell you how involved you need to get. I would also drain and inspect the condition of the coolant. If it is dirty or the wrong color I would do a simple flush and then fill with the proper coolant and distilled water.

 

Thanks Yeldogt,

I may take on the water pump project if I can carve out the time. It seems pretty straight forward. Or, I might have it taken to my guy who can pressure test and everything else on down the line. This situation almost prompted a car carrier purchase today by my business partner and I--we have been looking for any excuse obviously.

Either way, I very much appreciate the input from you and the others, and I will follow up when the diagnosis and fix is in (whether minor or catastrophe). Or at least let you all know where I parked it unlocked with the keys in the ignition.

- Paul

 

Hello Gentlemen,

Well, the word from the mechanic is headgaskets. So, full replacement of all the related pieces and parts that "should" be done, labor and everything he says $2400.

This car is part of a side business with a friend that we do for fun (we have dealer license auction access), so we knew what we might be getting into and luckily picked up this Jag for little enough that we can (so far) laugh it off. I will get another quote from another one of our mechanics, but if anyone has input on whether this first quote is way off the mark, please let me know.

I have to say that, even though this XJ8 needs work done, I really do like the vehicle. From the stance, to the absolutely beautiful design from every angle you walk up to it from, this era XJ8 is completely unlike anything else you can drive, and I have driven almost everything. I may pick up another one for myself in the near future. Heck, I might get this one fixed up and drive it for awhile. If it only had the LATCH system for the little kids!

Take care

 

a second opinion is always good with that kind of money quoted. One of the classic symptoms of over heating is headgaskets.....

What are you refering to with the latch system? it does have child locks on the back doors, look for the little black tab on the rear of the door.