I think my idea about air in there was probably not right. I hope Seawind will tell us how things worked out; I can't picture what would cause the symptoms as he described them (including the latch working fine prior to the shower & new hoses).

 

The system is self purging so priming it is not necessary! As for Seawind he has an electrical issue we are working on.

As for the new hose I hope they took in consideration the 1600psi and temperature range when offering the hose to you.

 

Could someone with the requisite chops take me through how the latch hoses purge themselves?

What is wrong with this model? Air can escape only through the return hose, out into the reservoir (each hose is the return at times). Start with only air in the hoses. Do a raise-latch operation. The volume or air expelled from the return hose can't exceed the volume of piston travel in the latch cylinder. There's still air in the return hose, and when we reverse flow (retract-latch) that air is pushed back toward the latch (chased by fluid supplied by the pump). The air seeks a high point(s) in the system; most or all of it ends up back at the latch.

Do another raise-latch. Whatever air is trapped up at the latch ... as before, the volume of piston travel can't force it all the way through the hose and out to the reservoir. It remains trapped in the hose.

If the hoses really do purge themselves, as it seems they do, there's something wrong with this picture. I just don't know what it is.

Is SteveInFrance around ?

 

Hi Dennis, My excellent industrial hydraulics expert told me I needed to bled the system so I lowered the centre panel down with a piece of string either end and cracked open both unions and proceeded to power up the pump.After a minute nothing happened so I closed off the unions and raised the centre panel. Powered up the pump and within 5 seconds the whole system worked first time perfectly. The latch needs to be in the correct position for the electrical system to sense that it can operate so it seems.The system is self bleeding because you have no access to purge at the latch cylinder which is contrary to what I would have thought.My industrial hose supplier tells me the problem on the longer of the two hoses is not uncommon in the hose world. In very simple terms the fluid at this point can emulate " Sandblasting" inside the hose which it then proceeds to destroy. Notice it is always the same hose in the same place on these Jags that the problem exists. Hopefully the new more modern hose will fix my problem. Cheers John

 

Thanks for that, John

I agree that the lack of a bleed point at the latch indicates that the system somehow purges itself. But I can't for the life of me see how it gets done.

Your hose guy's comments are interesting. We were all naive to think of this as a static problem: x pressure kills a hose. It more dynamical than that ... the pressure gradient, how pressure changes with time, plays a role too as dissimilar materials in the fittings try to react to changing pressures. Testing standards and commercial hose testing equipment take all this into account.

Agreed: here's hoping the newest replacement hoses really are bullet-proof.

 

I just installed my rebuilt convertible top hydraulic cylinders from Top Hydraulics. I also replaced the rear hoses even though they weren't leaking. The black covering on the old hoses was cracked and falling off so I figured it was just a matter of time. I have not seen anyone else mention this problem with the black covering chipping off. Mine was so extensive I needed a shop vac to clean up all of the pieces. Has anyone else had this problem?

Also, the hoses going to the front latch appear to be newer. I know someone posted how to read the codes on these hoses but I can't find it now. Can someone refresh my memory?

By the way, thanks to everyone for all the information in this forum which allowed me to tackle this job myself.
Dennis
1999 XK8

 

I had the same issue with old hoses - bits of cracked black plastic all over the car!..

 

Use this link to my page it should help.

Link JagRepair.com - Jaguar Repair Information Resource

 

hello,

I had an issue with green shower received too :-) . Now I have disasembled all of my interior and new hoses are on the way. But I made a mistake. I did not marked positions of hoses on the pump.

could someone please tell me, what is correct position of hoses on the pump? I do not know which one is on the top (if closing hose or opening hose) and which one is on the bottom.

As I know, closing hose is on the right side of top latch cylinder (actuator) and opening hose is on the left side of the cylinder (actuator). Thank you for answer.

 

This will help you.

JagRepair.com - Jaguar Repair Information Resource

 

thanks, thats exactly what I need.

 

Gus,
Can you or anybody let me know why Jaguar decided to take the long and convoluted route for the hoses that operate the latch on top of the windscreen?
If they had rooted the hoses via the right side of the windscreen top and A pillar, it would have a direct route via the right hand sill to the pump in the boot, not needing to take out the front seat and center console to replace them!
Also if I could use this "right"side route to replace the original hoses and just leave the two old rotten ones where they are, just emptying them of hydraulic fluid?
I plan to use brake lines of circa 9mm wide vs the 7mm original ones, but able to withstand over 7,000lb/sq of pressure.
Thanks

 

Who knows why Jaguar did what they did for the roof operation. Your guess is as good as mine.

 

I am going to jump onto the discussion on purging the system for air.

When I replaced the ram cylinders I believe one contained more hydraulic oil than the other as they were installed in the car; the other was not fully topped off and contained a bit of air. As a result the LH side of the top lags a bit when raising, and sometimes need a friendly hand to clear the front catch. Similarly it doesn't immediately go all the way down, and needs a moment to slowly settle in the down position. Not so much a problem as an annoyance.

I have gone through many cycles, but this doesn't seem to sort itself. Any ideas beyond disassembly and manually topping up the cylinder with fluid?

Thanks,
Lars

 

I thought that maybe there would be a known technical/physical reason for Jaguar routing the hoses through the less direct and at 1st, most obvious way. Otherwise it makes no sense to do it the way they did it.

 

After reaching wits end and no resolution to a CAT TOP problem in sight, which would you use to commit suicide? An SAE caliber or a METRIC caliber? Not at that point yet, but I can see that it is a distant possibility. TIC (tongue in cheek of course, but you do feel my pain, right?)

 

When I replaced my hoses it took about six or seven cycles of the system to purge. I assumed the self purging is because air is compressible and liquid is not, and both rams and top latch are double acting hydraulic cylinders.

 

Haven't put my top down yet but have seen dealer pictures with it down and he said it works but I am afraid to try in cold weather as this may put more stress on the hoses. I've seen replacement springs for the pressure regulator in the pump. Should I replace the OEM springs for the latch mechanism and the lift cylinders and will this reduced pressure significantly slow the top operation?

 

Not to say your hoses will not give out because of the cold but I have dropped the top in the winter as I do in the summer without a second thought. If the fluid is green that means it is synthetic and should not be an issue your concern should be if the hoses have been stressed.

This is a link to the first pressure relief valve for the roof system. Link JagRepair.com - Jaguar Repair Information Resource

 

A word of advice...never modify the top (or anything in the vehicle) until you know it is operating properly to begin with.

If you were to make a modification to a non-working system, determining the problem can become a confusing and daunting task.