Exceptionally well said for the both of you. Those guys at Roadfly seemed to be careening headlong down a path based on hunches and what seemed to me to be a "Rube Goldberg" type of solution. Then the author of the idea takes great offense at someone trying to educate them.

Of all the forums out there, clearly this one (jaguarforums.com) is the best organized, has the best "experts", and has the most civil discourse!

Doug

 

It seems to me that I've read on many boating sites that excessive voltage drop on marine 12 volt systems from either undersized wiring for the length of run, or corrosion on terminals, is the primary cause of pump and refrigeration motor reduced life and failure. Adding resistance to the pump circuit in our 12 volt cars doesn't sound like a great idea. If anything, we should have nice thick cables running there and let that pump crank away. Limit psi some other way. ( GO WALT!)

 

I posted an analogy on the Roadfly forum that makes sense to me. If you have a well with a bucket full or water on a rope that you crank up, the rope sees the same force whether you turn the crank slowly or a bit more quickly. The resistors just result in "turning the crank" slowly--force to lift the top ultimately has to be the same.

Does this make sense to anyone? It obviously does NOT make sense to Mr. Resistor over at Roadfly.

Doug

 

Hi all. I'm new to the site and found these great forums after my wife and her visiting cousin had green fluid come pouring out of the headliner when they tried to put the roof down this past weekend. I've been catching-up on the posts regarding the subject and am hoping someone can e-mail me the TSB on the topic. (I'm stuck in the less than 3 day / 10 post category and can't directly download them.)

My vehicle is still covered under the Select Edition warranty, and I have it scheduled to drop-off at the dealership tomorrow morning. I'm also going to have the head-rests worked on, so that TSB would be appreciated as well. I'm hoping I can get those covered under warranty, but couldn't get a direct answer up front.

I've also got some intermittent issues with the tilt function on the column hanging in cold weather and the service light popping on for what is likely a poor seal on the gas cap - we'll see where those issues go while they have the car.

I don't mean to start of with a list of gripes about the vehicle. I love the car and am looking forward to getting her back in a few days!

 

I hope this helps http://www.gusglikas.com/AutoRepairHydHose.htm

 

gonna send you a PM shouldbeworkin in order not to derail this particular thread. Well, I would, but you may not have authorized PMs.

In short, all should be covered under select, my top was, as well as my steering wheel reach/tilt. The evap code you're getting is most likely a CCV (purge) valve, mine had rust in it from the vent tube. Not sure if that will be select covered or not. But hey, 2 out of 3 isn't bad.

 

Top and head rests are fixed and covered under warranty.

Check engine light went out the day before I turned it in, and the tilt isn't acting up. Seems like those 2 may send me back in for service this winter.

When they had the seats out working on the hydraulic lines, the gouged the leather in 5 spots and busted the plastic motor control module off the bottom. Gotta see what I can get them to do with those now...

 

That makes sense, up until the bucket gets to the top of the well. Let's say that there's a hard stop at the top that prevents the bucket from going up any further. As long as the bucket is free to move upward the force is the same, but as soon as the bucket hits that stop you can continue cranking on the handle and put a lot of strain on the rope. That's what happens in the latch assembly. The pump closes the latch, and then the pump continues to try to pump fluid into a closed line causing the pressure to spike. The resistor would dissipate some of the energy going to pump and the pump couldn't develop as much pressure.

Resistor Guy's idea makes sense to me. It may not be the best way to solve the problem, but it is definitely going to reduce the pressure. It's going to slow down the whole cycle because the resistance affects the entire cycle of the motor, not just the pressure peaks as Gus/Walt's device does. There's a chance it may result in a shorter life for the motor. But the resistors cost less than $10 total. Also, no one has actually put a hydraulic pressure gauge on the line to see how much the pressure is reduced. It may only be reducing peak pressure from 1600 PSI to 1400 PSI. That may not be enough of a reduction to significantly lengthen the life of the hose.

Resistor Guy (I forget his name and I can't read that forum, too much clicking) was pushing his solution as if it was the magic bullet that would fix everything. But he hasn't actually tested it to show the results. Another member (I forget their name, too) was acting as if it absolutely positively wouldn't work, yet he hadn't tested it either. He was using examples of a steady weight on a hydraulic line to prove that the pressure wouldn't be reduced, but as I explained above, the spike comes at the end of the cycle on a closed line. There was some serious animosity going on over there, and I don't quite understand it.

So, if someone (Resistor Guy?) will just put a pressure gauge on the line to measure how much pressure the pump is developing now, we can settle that part of the argument. Then it becomes a matter of people's preference. Do they want a $300 solution that saves the lines and spares the pump, or do they want a $10 solution that may save the lines but shorten the life of the pump? I'm not sure how much a pump costs, but it's probably cheaper than paying the dealership $1500 - $2000 to replace the hydraulic lines. Some people may chose to go the cheap route and take a chance on the pump. Others may choose to go the more expensive route and use Gus/Walt's device. It's just a matter of choice. At this point we don't even know if the pump will really be more likely to fail with the resistor solution applied.

 

Doug, I think a better analogy would be pumping up a bike tire with a hand pump, something that just about everyone has done. If you pump slow or fast the pressure increases as long as the rate of inflow from pumping is faster than the leakage. The maximum pressure in both cases is the result of how fast it goes in versus how fast it leaks out. Anyone who has pumped up a bike tire knows that you must pump fast enough to defeat the leakage at the valve in order to get the desired pressure. The same thing is true regarding the roof pump.

According to resistor guy the pump keeps turning, so there is no stall out, and oil continues to push into the line. Our hydraulic pump is not perfect so there is leakage that bypasses the internal parts. Since the motor is turning slower I am sure that the maximum pressure is lower since this affects the ratio of in to out. However, the reduction in pressure is not proportional to the flow rate of the moving roof and only relates to the relative rates of leakage and inflow in the dead head (zero flow) condition.

I think measurements will show that the maximum pressure is slightly less, but nowhere near what is thought by resistor guy, and definitely not 30%. The pressure relief valve is a solution that has evolved over a lot of years of experience because it is the best solution to allowing full functional operation while still protecting the components. I appreciate the desire to save money but this discussion is another example of people seeing what they want to see regardless of common sense. There is an excellent article about this human characteristic in the latest issue of Newsweek.

People own these cars and are free to do whatever they want with them. We see all sorts of mention of what I see as odd ball modifications discussed on the various forums. If someone wants to slow their pump motor down the worst that can happen is a slow moving roof and some early failure of the pump motor, something that already happens anyway. These problems are easily resolved by replacing the parts and no real harm is done. The valve kit does not prevent the eventual breakdown of the parts either. It does make this eventuality later rather than sooner but everything eventually wears out through use.
Walt.

 

Already got the pressure relief kit last year, but only now fitted it due to time... Silly as it took less than 20 minutes or so, at least quicker than printing the instructions ;-). Am glad to have installed it, and personally think this is the better method then working with resistors (pending full test results and confirmation from an expert that the motor can function on a lower voltage).

Thanks Gus!

PS, Cars with the extra hifi option have a higher bracket to hold the amplifier (my amp was out). So is a tad fiddly to get the motor out, but still easy enough.

 

You did the right thing. Without getting into the effect on the motor, the pressures reported by the resistor people are clearly not accurate due to the type of gauge that was used. No one really knows what that arrangement really does because that gauge can't respond to the short high pressure pulse. This is not worth discussing other than to point out the obvious discrepancy.

 

Good to know that you went in the right direction and got the pressure relief valve, you made the right choice. I was also pleased to hear that you did not run into a problem installing the device. What took you so to get around to it??? Only kidding! Kudos to you!! As for the resister application the more information I get from professionals in the hyd field the more I am convinced that pressure relief valve is the right choice without question.

 

The use of the phrase "fiddly" tells me that someone has been watching Ed China on Wheeler Dealers. That is one of my favorite shows.

 

Cold be true ;-), like the show also.

 

I was blessed with my own personal 'green shower' this very evening...Gus, can you PM me to give me directions on obtaining both the hose kit and the pressure reduction kit you have mentioned? Thank you; it appears I will soon be intimate with the underpinnings of my Jag.....

The irony is that I just got my car back today from the N. Scottsdale Jag dealer after a $2500 tab for work under the hood and the underside. Car runs great, tho, and I'm not surprised at the 'green shower', having read many stories about it on this site.

 

I may have asked this before but nobody provided an answer. I was wondering if the newer aluminum-bodied XK models have any similar problems with the convertible system or if Jaguar went with an entirely new system for the new cars. I notice the JEPC lists a hydraulic pump/motor for the current cars so I am wondering if they did anything different to reduce the leak problem.

Doug

 

Information is available in the FAQ or on my webpage. Take a moment to review the information.
http://www.gusglikas.com/RoofHoseReplacement.htm
http://www.gusglikas.com/AutoRepairNewHydHose.htm
http://www.gusglikas.com/AutoRepairJ...esRelValve.htm
http://www.gusglikas.com/AutoRepairHydHose.htm
http://www.gusglikas.com/AutoRepairH...lOperation.htm

 

Latch operation failures have not been associated with hose failures; and it is unlikely a malfunctioning latch has caused your hose to burst.

Rather, extremely high pressure in the lines created when the latch is cinching down the last inch of a closing top has been identified as the most likely cause of tubing failures. Around here, the conventional wisdom is to use the pressure relief valve to limit that pressure.

Problems with the latch usually end up with the system recycling back to a safe point in the system. While this condition prevents the top from opening, it also avoids that part of the top's operation in which the extreme high pressures are created.

 

I have considered that manually latching/unlatching the latch would be an effective, albeit slightly inconvenient, workaround in terms of avoiding excessive hose pressures and failure at the latch fitting. This would definitely be recommended for someone who does not bother to install the LSI relief valve.

Doug