Gents'
Good stuff.
Where does the resistor go? Into which wire?
Thanks
Bill

 

https://www.jaguarforums.com/forum/n...reply&p=413925

https://www.jaguarforums.com/forum/x...deo-faq-60134/

http://www.scorekeeper.com/jaguar/jaguar01.htm

 

me aswell

 

Before adding a resistor, please read this thread, too: https://www.jaguarforums.com/forum/x...ake-2-a-61565/

This has obviously been a contentious issue. I still believe the resistor can prevent hose failures, but I want everyone to be fully informed before installing one.

 

Gentlemen,
I know I am a new member with few priviliges thus far. However, as the Honorable Baroness Thatcher once said " Consensus negates leadership " For those of us new to the forum this vigorous debate can be very informative so long as civilty prevails of course.

I think it would actually be interesting to explore bending steel hydraulic lines and replacing the whole hose system. Has anyone looked at that yet?

Cheers All

 

I think that might have been possible if they had been installed in the car before it was assembled, but now it would require the entire car to be disassembled to get the lines installed. It would be a monumental task.

 

Steel hyd lines were explored in the beginning but the problem we ran into was installing a fitting at the other end of the hose. Everyone I took the hose to said they did not have the fittings for it. The hose and fittings on this car are metric and I along with others could not get a reply from PowerPcakers or Parker the only option was to replace the hose. The hose splice kit by PowerPakers Parker sold by Jaguar failed. Use this link to see the hose and seals failure and at the end I have 2 links to the splice kit used for the repairs.

Link XK8/R Hydraulic System Evaluation

 

I thought I would weigh in on this as a quasi-knowledgeable person.

I had the bursting pipe issue and paid the price for my Jaguar dealership to fix it. Given the propensity for recurrence they replaced the entire hydraulic loop and charged me close to $2,000 for the pleasure. I'm happy to say that the issue has not recurred; however this should serve as a strong incentive to those mechanically minded enough to find a more cost effective solution.

Has anyone looked at the pressure rating on the hoses? Could this be solved by replacing them with braided hoses (like we used to do with brake lines back in the day)?

 

Baxkr
You have repaired your car, but you still need to address the problem that created it. A resistor or valve still needs to be installed. The previous owner of my car had the dealer replace the hoses when they failed on warranty no splice kit they replaced hoses, plus the upper console above the rear view mirror. A couple of years after I purchased the car the hoses developed another leak( not a green shower) and had to be replaced, at which time I installed the valve.
Good Luck

 

This issue is the thrill that keeps on giving!

In my opinion, the more direct and cost-effective solution would be to completely eliminate the hydraulic operation of the latch (since that is where all or most of the failures occur) and replace with a manually operated lever.

Alternatively, the hose run could have been broken into a number of segments with decent proper fittings at each segment so that you would not have had to replace the entire damn length of hose from trunk to latch due to a break that pretty much always occurs only at the latch.

Doug

 

This situation has been looked at, evaluated and best results provided and I will provide a link to much of the information you so desire. Keep in mind you will find a lot of opinions on the hydraulic hose failure but the links show what takes place and the why with graphs. I worked hard to find the cause and the solution and Walter developed the relief valve.

Link System evaluation JagRepair.com - Jaguar Repair Information Resource
Link Modified hose JagRepair.com - Jaguar Repair Information Resource
Link Roof latch & Ram Rebuild JagRepair.com - Jaguar Repair Information Resource
Link Pressure relief vale JagRepair.com - Jaguar Repair Information Resource
Link Pressure relief & Resister evaluation JagRepair.com - Jaguar Repair Information Resource

I have a lot of other stuff on my page if you wish to look.

 

Sigh.

Please also see www.scorekeeper.com/jaguar/jaguar01.htm for information on:
- contributors to plastic hydraulic hose failures in general,
- the performance and other attributes of the voltage reduction and relief valve approaches.

 

With all the work Gus and Walt put into this issue, it seems pretty clear that the hoses and seals are not up to the pressure spike from the pump. It seems like a reasonable step to take is to lower the pressure spike. The valve is a sure thing, set for a specific and repeatable pressure. It's a bit like the tensioners.......don't pay and cross your fingers, or be proactive to try and eliminate the problem. The only proof we don't have is whether the valve will save old hoses and seals at a rate high enough to warrant the cost. Those of us who took the plunge are field testing. Stay tuned.....

 

I know this is an older post and much has been said for an against, but check out the pressure relief valve made by LSI (Jaguar Kit | LSI Controls, Inc.), I have no connection with these guys, but it works and is simple to install and very reasonably priced. Main thing is there is the comparison graph of system pressure.Main point worth making is that before you mess with the pump pressure by whatever means make sure you roof is working properly.

 

Look at the pump curves if available and see what happens.

The resistor acts like an electrical orifice (similar to a fluid orifice) where it reduces the (Amps)flow and the (Volts) pressure. A dc motor will not spin as fast if the voltage is reduced, there by reducing the output max pressure at deadhead. A pressure relief valve will reduce the flow and pressure of the unit/pump output by doing a recirculation back to the reservoir or back to the inlet of the pump.

Both dump energy, the resistor converts electrical energy to heat energy, the relief valve dumps mechanical energy through a "waste gate". So all said, almost six of one and half dozen of the other. The pump will last a little longer with the resistor because it is not turning as many rpms with the resistor.

My hoses blew at the pump. It was a combination of flexing back and forth, pressure being applied to the hose and probably some heat. Just like bending the coat hanger.

The hose is made of what appears to be nylon core with a fiberglass reinforcement and the protective outer layer, that does deteriorate and ends up being useless.


My hoses were replaced with 316SS reinforced brake hoses and standard 1/4" JIC flared fittings made at a local hydraulic hose repair shop. The ports in the pump and the cylinders are 1/8"x27 NPT so it made life easier. The passenger cylinder at the bottom as a goofy nipple like fitting with a retaining clip and "o" ring. Fortunately I have a lathe, so I made my own and brazed on the male flared connection.

Then I added the resistor from Brother Marine, Rev. Sam, (Bravo Zulu) as it was snap, snap and done.
All is well after 18 mos.

If I can be of further help, please let me know.

Thanks,

Bill

 

RCSign is completely correct - I am in the most expensive position of having forked out for a new but equally flawed setup to be installed at Jaguar main dealer nosebleed rates. Such is life ...

Living in Southern California I am used to the fact that my car can get extremely hot in the summer. I noted, with interest, the specs. for the OEM hoses and published by Gus on JagRepair.com. It is worth noting that those of us in hot climes are probably exceeding the max temperature rating - particularly if we leave the roof down since the top rail is nice and black. When summer comes I will measure the temperature there and post for those interested. I will also consider painting it white!

The pressure traces published all clearly demonstrate that the system is working right at the published pressure limit of 1600 psi. Combine that with excessive heat and the failure starts to make sense. When all said and done I believe there to be a fundamental design flaw.

At the point when the hood is fully extended and engaged with the catch the main rams stall for 1 - 1 1/2 seconds before the catch starts to close. I suspect this time delay was intended to allow the roof to be closed with the vehicle moving slowly (the manual states less than 5 miles per hour). However the result is the huge pressure spike (and associated load on the motor) that we all see. Far better would have been to detect the position of the roof and trigger the latch to close immediately. (A simple hall effect device and magnet could achieve that for very little cost). Even if there is a desire to wait for a second for the roof to settle into the catch they should at least stop the pump so that the pressure doesn't continue to rise.

So to the various solutions presented thus far:

- Resistor. Inexpensive and simple to fit. Provides some protection for the motor by reducing the peak current (and consequent heat). Slows the operation of the hood (minor user inconvenience only). Provides little or no protection for the hoses since the system continues to pump against the stalled rams causing the same excessive pressure spike.

- Pressure relief valve. Mid priced solution that addresses the pressure spike. It should also reduce load on the motor by allowing fluid to move during the spike - but detailed current plots would be required to determine. Manageable install for the mechanically adept.

- Replacement hoses. Expensive solution and complicated install that adds a safety margin to the hoses - both pressure and temperature. Does not address the design flaw nor does it provide any protection for the motor. Potentially it may add further load to the motor since the new hoses are likely to be even less flexible than the standard ones (i.e. less likely to bulge) so the pressure spike might be higher - again measurements required.

It is worth bearing in mind that our beloved vehicle was designed in England - a land where sunshine and unicorns are about as common as each other and where temperatures never get about 100° F (well not until a couple of years ago).

One final thought - I wonder how hard it would be to do a geographical and time study of failures. If we identify statistically significant grouping in hot climates during summer that would lend weight to the need for better hoses. If there is interest I will put together a simple web survey so that we can gauge the distribution - let me know.

Nick

 

Hey Nick,

Your post pretty well sums up the situation. I wonder what types of problems, if any, show up with other manufacturers' convertibles--both high end like Mercedes and lower end like Chrysler. It could be that these types of boneheaded design flaws are not limited to Jaguar.

By the way, where in SoCal are you? I am in the San Fernando Valley.

Doug

 

Nick,
Just for the record my 2002 just blew out its top hose, the car has been living in PA all its life, only done 33k always garaged and this happened on a cold Jan morning during opening, so the roof was being taken down and the catches were disengaging before the roof itself moved, which to me indicates there is also a pressure spike at the begining of the cycle. Ok so maybe the hoses could have been weakened by its past life...just another part of the puzzle.

 

I'm on the western edge of the Inland Empire.

 

Interesting. I haven't seen mention of the low end of the operating temperature range for the stock hoses. If you look at the various pressure traces posted you will see that there is, indeed, a pressure spike at the start of the cycle. It is shorter and slightly less extreme. It suggests that the main rams may be being pressurized before the catch is fully open (most significantly before the two retaining pins have withdrawn from the alignment lugs on either side of the main catch). Again this could suggest a timing issue with the design - not sure yet.

Thanks for the update

I have a question for the various folks who have posted pressure plots:

- Was anyone able to run parallel plots for the main rams and front catch hydraulic circuits? It would be very interesting to see how long both circuits remain pressurized together.

Nick