After 2 weeks of happy motoring with my new rebuilt throttle body my test driver was greeted with the green shower after work today.

To get familiar with the process I read through all 300 posts in the sticky section and looked at Gus' helpful pictures.

I'm going to replace both lines to the latch - does anyone have the part numbers handy? Is there a particularly good resource for them?

Thanks!

 

If I had to do mine over, I would go with the redesigned hoses that Gus pioneered.

 

I just PM'D Gus and am going down that path...thanks

 

For the record, I installed the Pressure Reduction Valve and flushed the lines in the Spring of 2008.

I may have the only reported instance of line failure after the installation of the relief valve. I have the early version lines. I will note any interesting conditions at the failure point when I get it opened up.

 

Scott, the earliest reference I could find re: the completion of development and launch of the pressure relief valve is October 2009...

https://www.jaguarforums.com/forum/x...luation-27132/

Is Spring 2008 the date you installed it? Am I missing something?

Maybe it burst even with the valve since the top had many years to operate at higher pressure. Pure conjecture. I don't know.

Jack

 

I was looking at an old Post of mine with that date where I mentioned installing the valve, I might have read it wrong however, it could have been 2009.

I agree with you, 10 years of cooking the hoses in the header undoubtedly weakened them to the point that any pressure was just too much.

At best the valve bought me a year or so, at worst it did nothing but was a fun, easy project.

In hindsight and for the money involved, I'd replace the hoses with Gus' beefed up set instead of installing the valve. They are about the same price these days. Then maybe I'd install the electrical-based pressure solution, although I'm not really up on that particular solution.

 

Of this much I feel sure:
- on any given car there is some pressure at which a hose or a fitting will let go. No way to know what that pressure is on a particular car without testing to failure.
- on any given car, the failure pressure will become lower over time, i.e. the system will weaken as components age, and with use.

So the best chance of having the hydraulics survive to the life of the car seems to me to be:
- run the system at the lowest peak pressure consistent with reliable operation. That pressure is known by experiment to be ~ 1000 PSI, which can be achieved through an electrical or a relief valve pressure reducing system.
- don't use the system more than needed: (I avoid dropping the top sometimes if I know I'll be putting it back up in a half hour.)

FWIW ...

 

That's too bad. I have a question about your pressure relief valve, maybe Gus can chime in; I know that the valve is adjustable, does it come preset at the correct pressure, or do you set the pressure after the valve is installed? Is it possible that the adjustment screw got out of tolerance over time? And if the screw were to back out, I wonder if that would increase the hydraulic pressure or reduce it.

I'm not trying to bash the reducing valve method. I've said several times that I think it is a more elegant solution. I'm just wondering if there is routine maintenance that needs to be done on it to make sure it stays within tolerance. I bet it would be pretty easy to add a pressure gauge downstream of the valve which could be checked every once in a while. Even better would be a pressure gauge that records the peak pressure. That way you could just glance at the gauge and know what the peak pressure has been. Something like this would be perfect: DGR-Series, Digital Hydraulic Pressure Gauges | Enerpac You could put a T in the line and run a short piece of hose to the trunk where the pressure gauge could be mounted.

 

LOL..I drop mine just for entertainment

 

You've got the right idea. I just wish I had your sense of optimism. Entertainment for you; fear and loathing for me

 

I believe it was pre-set. For sure there were no instructions for setting the pressure limits or anything like that. It is a pretty robust piece, I doubt it would go out of it's simple calibration.

I prefer to think that my lines were just cooked and any pressure - reduced or not - was just too much for their weakened condition.

It's that or believe that this freakin car is inhabited with gremlins that attack every possible thing that could go wrong. I've been through the wringer this this one but am trying to stay positive!

 

I had also asked about the specifics of the fine-tuning that could be done to adjust the valve pressure and received this answer from Walt (one of the designers of the valve along with Gus):

Each full turn of the valve will adjust the pressure by about 250psi. The valve is spring operated so this is mostly linear. I advocate 1/4 turn adjustments because it is easy to keep track of. This is 60-65psi for each 1/4 turn. If the roof does not have enough pressure to "get over the hump" then a small increase in pressure should fix the problem. There is no immediate harm in adjusting the valve one way or the other but I do recommend keeping track (write it down) of what was done for future reference. My concern is that the valve gets adjusted relative to some other problem like a leaky lift cylinder.

The goal is to let the system operate at the lowest pressure possible. The main problem is at the end of travel on both ends when the controller holds the pump on when there is zero flow. This is when the pressure spikes and is clearly seen on the graphs that Gus posted on his site. We briefly considered a redesign of the controller but went with the relief valve instead because it was easier for everyone involved.

I did not do any adjusting since the top worked fine with the valve installed. But I did find that it would take some effort to actually turn the adjusting screw so I find it unlikely that it would adjust on its own.


Doug

 

That's interesting! I never adjusted mine either, it worked fine out of the box and there were no instructions to do so.

The question still remains, were they pre-adjusted from the supplier or were we, as installers, supposed to calibrate them "to operate at the lowest pressure possible". If we were, Doug's and mine might not be reducing pressure as much as we think or even much at all!

Gus, any thoughts?

 

Unfortunately I agree with you. My car's previous owner had the green shower fixed a year ago. I installed the pressure relief valve. Pretty much nothing else I can do.

But...

I suspect all this effort will buy us a few years of additional use beyond a "stock" setup. Own the car long enough and it will happen again.

Combine that with the tempermental system getting out of sequence, leaking rams, goofy engineering in the pump, Jaguar playing dumb about the whole thing, etc. and I kind of wish I had a manual system like my old Miata. That was all good. Not as entertaining. But NOBODY ever had a problem with it. NOBODY.

I have the "convertible gene", so I am going to drive a convertible. This one is a pain in the can.

Love the car though.

Jack

 

I hope I did not mislead anyone into thinking that there was any adjustment that was necessarily needed to be done. The instructions that are downloaded from the LSI site note that the valve is already properly pre-adjusted for cars with normally working convertible mechanisms but talks about adjusting the valve if needed for more pressure in case your mechanism was not working efficiently.

So I just asked the question regarding how much pressure is changed by turning the adjustment and Walt answered me on this forum. Again, if you install the valve and everything works fine THERE IS NO NEED FOR ANY ADJUSTMENT.


Doug

 

I thought I was the only one who was hypersensitive about using the top. I was using the top regularly after getting the car but soon got the hose leak at the latch. After getting it fixed at the local dealer (thankfully under warranty) I bought the relief valve but it took me a while to get the confidence to start using the top regularly. I finally got comfortable about using the top again and, bingo, the pump fails. I got that replaced at the dealer (again thankfully under warranty) but have not really used the top since then very much as I have become spooked about what might happen next.

I guess I shouldn't be so timid since I have an extended warranty that is supposed to cover just about everything, and it may be that failing to use the top regularly is worse than not using it.


Doug

 

The valve is preset to 1000psi +/- a few and it is adjustable but the problem with the adjustment is that you can adjust it. As for the unit going out of adjustment I would need to refer it to the manufacture. I would first want to know how long the hose was in the car prior to the install of the pressure relief valve. Like I said in the beginning and is stated on the web page the install of the valve will only delay the failure on an already stressed system.

I have been busy and checking the forum was last on my list. I need to read all your comments to see if I need to answer. I can say this I replaced my hose with the Jaguar hose and used my roof many times. When the valve was designed I installed the second one and my wife would drop the top nearly every day coming home from work and I would drop the top going to dinner. And now that I am in OC Md we drop the top and go on. One day it will fail but right now it is working fine. I still feel the pressure relief valve is the right thing to do and the only way to go.

The key to this situation is was the hose ever replaced and if so when? If the hose has never been replaced then I would say it was just a matter of time and the valve or voltage reduction had nothing to do with the failure!

 

After replacing my hoses I increased the pressure by 1/2 a turn due to air in the line and having to run it thru the closing cycle 2 times to get the top up. Now that the sound of air in the lines is gone and the top cycles normally I will be backing the adjustment screw off the 1/2 turn and back to the suppliers preset setting.

 

Jack,

I know just what you mean. The last non-ragtop I bought was decades ago, and that ain't likely to change soon. (Like your Miata, My MGA's top has never failed me. True, it takes 20 minutes to raise or lower, but it IS reliable.)

I'm a little more optimistic about some XKs going many years without hydraulic failure if the pressure is kept down to ~ 1k PSI. Nobody can really predict when any particular car will let go, and every system in use has been in some sense weakened by its prior use and environment (heat seems especially damaging). But some fast-and-loose statistics on observed failure rates with pressure reduction in place are encouraging; some cars may survive for a long time. Only time will tell ...

On the design of the XK's top: What you said. Especially hard to figure is the complete lack of pump control ... no electrical control, no relief valve. The pump is either on or it's off, and it makes whatever pressure the available voltage (12V or 14V) dictates. Just to pick one contrasting example ... every Mercedes system I've looked at has had either a relief valve or, increasingly common in newer cars, electrical control in place of the valve.

 

Most vehicles with power tops also have a dedicated convertible top controller. Not so in the XK8/XKR. Our cars have distributed control across the Body Processor module, Security and Locking module and the Driver door module. I think this made the design a siginificant integration challenge that was never truly perfected, particularly under fault conditions.