Long-time reader here, first-time poster.

In the past two weeks, my 2005 XJ8L has been leaking coolant--probably about 1.0 to 1.5 quarts over that time. There is a good bit of coolant leakage under the hood--dripping onto the aero tray, dripping down the back of the engine and onto the transmission, etc. The temperature gauge has never moved off the midpoint, where it always is after warmup.

Diagnosis from the mechanic is a failing water pump that is leaking. The mechanic also wants to rplace the intake manifold gasket (possible additiona leak, or maybe coolant is getting to the back of the engine by being blown around underhood from the water pump leak) and the thermostat (no sign of failure but recommended). Total cost including replacing coolant is $2,100.

My sense is that it is pretty unlikely that the intake manifold gasket has failed at the same time as the water pump, so I am leaning toward just getting the water pump and serpentine belt replaced ($250 for parts, $550 for labor) and seeing if that fixes the problem--then folowing up with the intake manifold gasket if there is still leakage. I am unsure whether the thermostat should be replaced ($100 for parts, $340 for labor).

Any advice on what to do, and reasonable prices for parts and labor for the necessary service, would be much appreciated. I am in the Chicago area, so a recommendation for a good Jaguar mechanic would also be welcome. Thank you.

 

Which version car do you have? Water running down the back of the engine is classic valley hose burst and requires removing the supercharger to replace. I'm not 100% sure if the non supercharged engines have one.

 

Sorry for leaving that out--the car is a regular XJ8L, naturally aspirated.

 

I assume that the mechanic put her on a rack and sees evidence of the leaking water pump. I don't see how the water pump could get coolant to the transmission, but I'm no expert.

Is it characteristic of a water pump to leak that much all of a sudden? Do you know if the mechanic used a borescope or some other method to ascertain the pump leaks?

If the mechanic is a good one, I'm sure he is giving you good advice & that he knows that it is not a hose.

As far as I know, I've never had a manifold leak. The only water pump leak I've had was so small to be imperceptible on a daily basis. 10 or so years ago, I took it to a mechanic to replace the water pump. In the process he broke one of the bolts. I drove it for 10 years with the leak until recently when i replaced all of the hoses. I removed the broken bolt & replaced the water pump then. .

Best of luck with it.,

Steve S.

 

Thanks, Steve. Apparently the mechanic did use a borescope to verify the pump leak.

The theory of coolant getting over the top of the engine and dripping onto the transmission is that with enough leakage, ram air from driving at speed or the cooling fan could push enough leaking coolant around so it would flow over the engine. I think that is more likely than an intake manifold gasket failing at exactly, or almost exactly, the same time the water pump failed--but I am not sure.

Any thoughts on whether the thermostat needs to be replaced although there are no signs of trouble, or whether the labor charges and hours make sense for the scope of work? Thanks.

 

Can't comment on how air gets liquid over the top of engine, though valley still exists on V8 even without supercharger.
On thermostat thing: consider fact you already there after gaining access to water pump. The car is OLD, Thermostat housing is plastic, prone to cracking over time; thermostat is old as well. If you do not do it now, that chances are you will have to repeat disassembly to get access to thermostat. With cost of thermostat and housing about $200-250 US I would replace it without blinking: half a day one time or two half days on separate occasions.
On flip side: you may crack/tear something while doing more work.
I would not go for intake collector. I would try to make sure everything else is order, before going for intake.
But then again, it is me, I do turn my wrenches on my car, I am too cheap...

 

My two pennies worth...
I agree with other posters; in my experience, if the coolant is puddling behind the left or right front wheel (in my case it was the left), it is very likely to be the valley hose.

 

Also believe the valley hose, is more likely your rear leak.
Replacing the water pump, thermostat, with the housing.
Is not a hard job, do it yourself, & save some $$$$$.
The valley hose involves pulling the intake manifold.
Also a very doable job, just more time involved.
Read the manual, look at the pictures, take your time.
Gets it handled nicely

 

Coolant running down the back of the engine is the clue- it's the valley hose.

 

I went through a complete overhaul of radiator and hoses last summer, my experiences outlined here. In a nutshell, after replacing the radiator, I went through a short series of next-weakest-part failures as the system was able to build pressure and said *bleep* it, everything goes! I replaced the radiator initially (cracked side tank,) then the expansion tank (split and sprayed,) and finally saw the water pump seeping badly. I replaced every hose, but the only one that looked like it actually needed to be replaced was the valley hose. It was the only one that had ballooning or soft spots in it.

The intake manifold has to come off to get to it, which means finding the correct metal gaskets to reinstall it. The first FOUR set I ordered were cheap cardboard gaskets, even though the pictures showed the metal gaskets. The cardboard gaskets would be next to impossible to line up, as there are no tabs to bend up to hold them in place as you set the manifold back onto the engine.

Intake manifold removal is a chore. You can't reach (or even see) the connectors on the back while it's on the engine, so you have to remove the attaching bolts, slide the manifold forward to the extent you can with the wiring on the back, and then you can reach those connectors. There is no need to separate the upper manifold from the lowers, just remove the whole assembly to expose the valley hose.

 

+1 on Wfooshee's post.
Be very careful when disconnecting the Brake Booster servo pipe at the back of the intake manifold; it gets very hot and brittle back there; please don't ask me how I know!

 

You might wanna look into this thread: https://www.jaguarforums.com/forum/x...ey-hose-282393

And here's list of all the parts that might POTENTIALLY be in need of replacing:
https://www.jaguarforums.com/forum/x...6/#post2798317

 

I didn't actually remove that hose from the manifold, I disconnected it where it meets the line to the booster, disconnected it before unbolting the manifold to slide it forward. I left it on the manifold, as shown here.

In this picture, the electrical connection for the fuel temperature sensor is on the far left. That connector is one you can touch but not disconnect with the manifold bolted down. The MAP sensor connector on the back of the manifold is in no way accessible with the manifold bolted down.

 

Hello everyone, and thanks for the helpful advice.

I took the car to a second mechanic today, one with better recommendations than the first one. Diagnosis is a cracked housing for the thermostat and EGR valve, which is spraying coolant--nothing wrong with the water pump or as far as I can tell the valley hose. The serpentine belt is coated with coolant, which explains the brief and occasional loss of power steering assist at low speeds. There is apparently a lot of air in the cooling system, which the shop says is fairly typical of Jaguars (but probably related to refilling the system over the past two weeks).

The part is fairly expensive, so the total including various gaskets, labor, and a coolant flush and change will be about $1,300--not cheap but a lot less than the offer from the other shop, and looks like it will fix the problem.

 

Good to hear that the leak has been found!
As the EGR valve is at the back of the engine, if it leaks the coolant can run down at the back of the engine. In any case, if by chance the intake manifold needs to be moved or removed to reach the EGR valve, you should consider replacing the valley hose, as well. Sooner or later it will start leaking, and before doing ajob twice...

Best regards,

Thomas

 

I spoke with the mechanic, and he says the valley hose is in excellent shape--pliable, no signs of distress. So he recommends not changing it at this point. Thanks for the tip.

 

I am in the midst of replacing the thermostat housing on my 04. Its as far as I have dug into this motor so far. Its not a hard job just in depth.

 

If he's actually in there far enough to know that, then he's in there far enough to replace it. A failure of that hose would be catastrophic, as the car will be undrivable. Will you be 400 miles from home when it happens? If he has the manifold loose enough to actually examine that hose and make such a determination, then replace the hose now instead of making another trip in there at some future date.

 

I agree, it does not make sense to save a small amount of money when the expensive part is the labour. Also, for replacing the EGR you need to open the colling circuit in any case.

Best regards,

Thomas

 

Adding to my own post just above, if all he's examining is the end that attaches to the throttle body (which you can reach without removing the manifold,) then he's not actually validating that hose. The section under the manifold is the part that deteriorates, mostly because of the heat there, but also because that hose has a plastic coupler that will be brittle. If he didn't actually remove the intake manifold, he's told you nothing about the condition of that hose! That fat piece is absolutely inaccessible with the manifold on the engine, and you can see how ballooned it was on mine, although the thin section of hose is in pretty good condition. (And BTW, while removing the intake manifold, I did actually break the plastic coupler that connects the two sizes together.)


The replacement hose I ordered is a single piece, with the size change molded in: