Hi everyone, I've had my 2006 XK8 for two weeks now and have already put more than 1000 miles on it (bought it with 48K), and I've found only a couple of minor issues. I might mention that I bought this car from Nalley Jaguar; it was sold originally and serviced by them. The car is in pristine condition.

I've read through quite a few of the forum threads by now, and have almost made myself ill! Rationally, I know that the happy owners don't post as often as the ones with problems, and since I've owned a 1991 XJ-S for nearly two years and 7K miles, I know that not all the horror stories come true (i.e., my V-12 has not had an engine fire or dropped a valve seal).

However, I just found out I have convertible top hydraulic problems with the Mercedes that the XK8 is replacing, so I'm gun-shy. In the XK8, is the "green shower" a foregone conclusion? Should I bite the bullet and get the pressure valve installed now? Does using the top only sparingly help the hoses last longer?

Thanks all!

 

I am partial to the valve but one thing is for sure we have seen many hose and seal failures. Can I say that all hoses fail no, but many do. Without any pressure reduction on the system the hoses will have a greater risk of failure because of the excessive pressure on the system. Now what most people do not know is that whatever reduction system you install now will only prolong the life of an existing system. For me to tell you that installing a reduction system on your system would eliminate any failures would be an untruth. If your system has been stressed it is just a matter of time. I installed a new hose to the latch on my 99 xk8 I think in 2006 I installed the pressure relief valve in 2009 and to date we are still operating the roof.

You can find a lot of information on the failed hoses and the pressure relief valve on my page

Hose Evaluation
JAGUAR ROOF HYDRAULIC PRESSURE RELIEF VALVE
Auto Repair

Forgive my unorganized page and poor grammar, I am reviewing my mess and re doing it.

 

I don't believe it's inevitable, although I'm sure some people will disagree with me. If the car is kept in a garage I think the heat will have less of an effect on the hoses. I would still recommend one of the pressure reducing devices, because that will definitely prolong the hoses. I still worry a tiny bit every time I put up the top. I usually do it with the engine off, headlights and high beams on, foot on the brake pedal (to turn the brake lights on), and right when the latch closes I press both "up" buttons on the windows to put as much of a load on the battery as possible at that moment. That seems to be working for me so far.

Other than that, I don't "baby" the top. I put it up and down as often as I need to to be comfortable. My wife and I drove up to the mountains over this past weekend, and I probably cycled the top 10 or 12 times.

 

The hydraulics on any car would surely fail eventually (just like every other part) so the operative question, it seems to me, is: can the system be made to hold together for the life of the car?

Based on the low failure rates we're seeing with presure reduction in place, I believe many will survive that long.

Heat is a known enemy of the system so, in addition to pressure reduction, I think it's worth not stressing it when it's very hot. The highest pressure (most stress) occurs at latch-closure time during the raise-top operation.

Good luck.

 

Heat is an issue on the hoses. However, that does not mean at the time of operation. Yes they fail mainly on the open process but, it is the close hose that fails.

 

Maybe some of the UK owners can chime in but I remember some of them saying that the hose failure over there is almost unheard of over there, probably because of the cooler temperatures and fewer convertibles.

 

Yup, as I recall, that is exectly what several UK guys have said.

We don't really have the data to infer whether the system is weaker, more failure prone, while it is hot. (That heat weakens it over time seems pretty clear.) But I'm inclined to play every angle possible to try to keep this system in one piece. If I thought a talisman would help, I'd install one in a heartbeat.

 

Heat is an issue but by how much?

 

Think about this, how may hose failures do we have in the winter when the car is on jack-stands, the battery is disconnected and in the garage with a cover on it?

 

I agree with Dennis as well. Evidence would seem to indicate that if you have older, original hoses, and the car has been broiling in the sun (getting that little space above the windscreen where the latch is hot as blazes) and you cycle the top with the engine running (voltage up), you-all is askin' for trouble. Our dealer here seems to consider 'green showers' rare up here in the Arctic (Toronto), but I have installed Dennis' voltage reduction system anyway, and never cycle the top with the engine running. And besides, it is SO much cooler to do the whole top thing with the key in the driver's door!

 

Does the technique of using the top with motor off apply to folks like me who have installed the relief valve?

If the valve spills pressure above 1,000psi or so, what difference would it make if the car is running or not? I understand if you have the resistor solution, running the top on battery/motor off would turn the pump motor slower and you would get less pressure. But it doesn't look like the relief valve solution would get any different pressure. Am I thinking right?

If 1,000 psi is needed to close the top, why would you operate the top with less?

Thanks,

Jack

 

The relief valve has no restrictions. You use the roof as if you had no problems.

 

As you said, having the car's motor running or not won't matter with the relief valve installed.

With the resistor solution, we're using the voltage v. peak pressure characteristic of the pump to reduce the peak pressure at its source to something around 1000 PSI. Alternator voltage is of course somewhat higher than battery voltage and so the peak pressure will be higher if the car's motor is running.

 

I can't really add much about the XK8 roof here in the UK as mine is a tin top, but my wife has a 1994 Fiat Punto Cabrio which has all its original hydraulic hoses. I have never heard of a hydraulic hose failure. She drives with the roof off most of the time (yes, even in our climate - it has a good heater), so the hydraulics get plenty of use. If Fiat can build hydraulics that last this long, it must be the heat causing the problems!

 

I spent over 2 years researching the problems and solutions on the XK8 XKR 1997 – 2006 roof operating system so I am familiar with it and how it works. And several years listening to the problems others have with it and it should not be compared to other convertibles. They were designed correctly. Should you want to know a little more about the system go to my page, I cover just about everything I came across including what I was told and what I found.

 

hmmm, would I take those odds in Vegas? You bet!

Call it preventative maintenance and install the valve and/or resistor (your preference) just like future transmission fluid changes. For $250, nobody can really afford to take the chance on a top that hasn't had its hoses replaced...and even then, its more security.

 

Well put!

 

Thanks all. Nalley is sending me a complete service history. If as I suspect the hoses have not been replaced, I will employ one of the solutions right away. I don't want to reopen the debate but the resistor sounds way too good to be true.

 

Replaced or not you should act to overcome Jaguar Engineering's failures.

 

This sort of reminds me of the rhetorical questions asked by the Geico guy:



• Is Ed 'Too Tall' Jones too tall?"
• "Does Charlie Daniels play a mean fiddle?"
• "Does Elmer Fudd have trouble with the letter R?"
• "Did The Waltons take way too long to say good night?"
• "Does a ten pound bag of flour make a really big biscuit?"
• "Did the caveman invent fire?"
• "Was Abe Lincoln honest?"
• "Is the Green Shower for Jaguar convertibles inevitable?"


I think it qualifies as rhetorical, don't you?




Doug