First let me say thanks to those that have helped me in the past. This is a great forum and everybody seems to be very helpful.

My wife has a 2002 XJR. A few weeks ago it developed a very slow coolant leak. About every 7-10 days I have to add maybe 16 oz of coolant.

I don't see any external signs of a leak, no smell, no standing coolant or puddles. No excessive smoke or vapor from the exhaust. No H20 in the oil or oil on the water.

I'm at a loss and getting ready to drive the car off a boat ramp and report it stolen. Ok maybe not that desperate but getting close.

I just have to say my 98 Explorer is less trouble.

 

Be prepared to have your wits end extended before you say goodbye to your Jag.
No comparisons to an Explorer please. This is a real car not a lightly modified pickup truck.
I suggest one of the heater hoses has a "weep". They run close to the exhaust and the coolant is evaporating off. Check for white/pink salt deposits.

 

LOL, just as the tranny failed in my Jag at 80,000 miles, so did the tranny in my 02 Explorer fail at 80,000. Cars are cars and s**t happens.

 

My read of that amount of coolant loss without external evidence suggests a head gasket leak. I would be performing a cylinder leakdown test and inspecting for bubbles in the coolant header tank. You might get an early indication of affected cylinder(s) when you remove and inspect the spark plugs prior to the leakdown test.

 

An even easier first step is to rent a cooling system pressure test kit from one of the auto parts chains that do such a thing. Pumped up to 12 -15 psi will quickly display where the leak is. The water pump on all cars is famous for leaking only while driving and hot and never dripping. The Jaguar has several common leak areas around the cats that quickly evaporate without dripping but they do leave the above referenced sediment.

Welcome back JTO!

 

+1 on the cooling system pressure test as a first, easy step. I have successfully diagnosed several 'mystery coolant leaks' easily that way.

 

pingj, You might try looking under the intake manifold. I believe you have two coolant lines that run under there. If it is leaking there you would never see it till there was a larger leak. A small leak would just lay on top of the engine and evaporate. Just a thought.

 

Thanks for all the replies.

I have done a pressure test on other cars in the past, but the XJR's cooling system is more complex than I'm used to dealing with. All of the small hard cooling lines from the expansion tank going to the super charger and such.

I hadn't considered the coolant hitting the exhaust manifold. But wouldn't I smell that when burning off?

How do you do a leak down test?

 

A leak down test is really part of a complete cylinder/rings/valves evaluation. The compression test reads the maximum pressure developed by the moving piston minus the leakage past the rings and valves. The leak down test pressurizes the cylinder from an external air source and measures the drop in pressure due to leaks past the rings and valves. See the following for a far more professional description here: http://autos.yahoo.com/maintain/repa...ques057_1.html

Do the cooling system pressure test first.

 

Thanks for all the ideas. My buddy who is a mechanic has a cooling system pressure tester.
The car needed coolant again today indicating to me that the problem had gotten much worse, but after I got home from work I added coolant and ran the engine for about 20 min with no drop or indication of a leak.

I'm going to do a cooling system test tomorrow as well as a compression test.

I will post the results.

 

Looks like not much has changed here.

"About every 7-10 days I have to add maybe 16 oz of coolant."

If you need a cooling system pressure tester to identify a leak of that significance, then your powers of visual perception and olfactory acuity are deficient. Your car would be drippin' and stinkin'.

Simulating combustion chamber pressure with compressed air during a leakdown test will identify a head gasket failure by introducing air into the cooling system. It's often not easy to confirm a failed head gasket by simply pressurizing the cooling system: the pressure loss at 15 PSI can be minimal, and can be dependant on engine temperature.

A compression test will reveal evidence of a big-time head gasket leak, which you ain't got. There is some benefit to performing this test if you completely fill the cooling system and watch for the header tank to overflow when cranking the engine to test each cylinder. The coolant will overflow if a cylinder is experiencing a pressure loss into the cooling system.

 

Thanks for all the replies. And yes jagtech my wife has always accused me of not being able to smell anything.

I have narrowed it down. I know it is coming from near the resevior tank. I thought it might be coming from the overflow tank since when I pressurized the system I got coolant coming from the left front fender well. Removed the wheel well cover and found the overflow tank.

That is when I realized the pressure rig I have didn't seal the overflow tube. But with the system full and the engine running there is a drip hitting the top of the tranny and running down the side on the drivers side. (LEFT) There is staining so I know I'm getting close.

My question is, what is up above the tranny that could be leaking? I know the fill tank and associated hoses, but I can't see much else.

 

The reservoir tank, the associated hose connections and the heater hose Norma connector are all common leak locations. The pressure tester should allow you to feel around for wetness around joints. The Norma connector uses a replaceable 'O' ring seal but I have never been able to get the male/female sections apart in order to replace them. Some have cut the connector completely out and replaced with 5/8" heater hose and clamps. If that is the issue, the alternative is to replace the entire 'octopus' heater hose.

Here is a thread with both good discussions and pictures on the leak issues.

https://www.jaguarforums.com/forum/s...ht=heater+hose

 

I repaired the LH heater hose Norma connector with an o-ring and replaced the RH one with a male-male connector from the hardware store. Neither leak after one year.

 

looks like your getting closer pingj - hope the advice gets this sorted!

 

I'm taking a half day off of work today.

My buddy has a bore scope that will hopefully allow me to find the leak without having to tear to much apart to diagnose.

Repair is another story. The B#$&H of it is, I got wet riding the Harley into work and it's going to rain all day tomorrow.

Once again thanks for all the advice. I will keep you posted. Keep your fingers crossed it isn't the head(s) / intake manifold.

 

Found it.

It is a hose connection right on top of the tranny.

Now who has pencil arms that can reach?

 

Sometimes you have to start taking stuff off until you can reach the problem.

 

Thanks test point that was a great thread.

That is the exact part that is leaking. I'm thinking that either there were problems with it in the past or there is a newer revision of the same part.

The one that is currently in the car has hard plastic elbows and tee's. The new one is more molded than the old one.

 

All,

Thanks for all the help and advice. I have isolated the problem. Picked up the part from the dealer Friday evening. Found out Saturday that the part was not the same as the original. I'm going to try and exchange it for the correct one today.

My problem is, does anybody know how to disconnect the NORMA connector on the right side? The one on the left was easy. Twist the hose 90 deg, break the tee off. OOPS. But the left side has me stumped.