Initial try. Top stops less than 1/2 way down. I close it and start again. Top goes furthur but will not open all the way. If i hold the button I can hear the motor running, It closes fine (windows go up etc) but it will not completely open. It has new pistons. I took a video but can not upload it here. Any ideas what would cause this? Last week after repeaded attempts it finally opened all the way and did so many times after that (same day)
Any advise is greatly appreciated.

 

Did you double check your fluid level? It may have bled some air from the cylinders and now is too low to open fully

 

New pistons were installed and the reservoir flushed and filled with new fluid not too long ago. It was doing this before I had the pistons changed thinking that was the cause. It wasn't obviously. Levels fine- mechanic had bled the system after installation. Mechanic just texted me and said the motor might be getting weak. Said he can check amperage to confirm.

 

coldpad1,

You have used the correct fluid? If you mix the earlier Jaguar fluid with the later fluid, it will congeal and cause all sorts of problems.

Cheers

Paul

 

Thanks - yes the fluid my mechanic told me to get that he used also when he installed the pistons

 

This is the correct fluid
Genuine Royco 756 Aircraft Aviation Petroleum Hydraulic Fluid Oil, MIL-PRF-5606H | eBay

 

Pentosin CHF11S is the fluid. He's been a Jag mechanic for 30 years. Thats what he said to get and what he uses.

 

coldoad1,

Below is something i wrote on a similar thread 2 years ago:

"The original Jaguar fluid was Exxon Univis j13 which is no longer available.
If you look for a hydraulic oil that matches mil-h-5606a spec (or possibly 5606h?), that will do fine.

As I understand it, Royco 756 is available in the US and meets that spec. That's a red-dyed non-foaming fluid.

Post-XJS, Jaguar changed hood spec fluid for the XK8 to Pentosin CHF 11S. However, the use of that required a proper flush of the system. Mixing of the fluids seems to often cause a jellying of the fluid causing real problems. I know 2 XK8 owners who had that problem."


The later Pentosin has a very different viscosity to the originsl XJS fluid.

I'm not saying it's your problem, but you should be aware of the problems people have had when mixing. Just a thought.

Cheers

Paul

 

Paul
Thank you but this problem started before any fluids were even added. I thought the problem was the pistons. When they were changed the reservoir etc were flushed prior to putting the Pentosin in.

 

Just spitball in’ here.

Is it possible at all that any of the four hoses connecting into the motor are in the wrong place?

If this started happening before any service or work was done, then it’s rather unlikely.

Weak motor could be it. You could tie a multimeter to it and see what happens? No need to take it into a shop?

Its not hitting the top of the back seat, is it?

 

Thats about the spot its stopping at ... top of the back seat... but why would that suddenly happen?

 

Where would I use the multimeter?

 

coldpad1,

Maybe put it into manual mode and just check that it actually can fold all the way down, just to eliminate that it's not fouling on the frame somehow.

Paul

 

Im not in a location to look; however if you go to jagrepair.com, you’ll be able to download the wiring diagrams.

 

Coldpad1,

I didn't see the year of your XJS. My 90 had a computer that controlled the top and quarter windows so that the top had to reach a certain point for the computer to tell the quarter window motors to either go up or go down. This is/was controlled by a set of relays for each component: an up relay and a down relay. The relays are in the package shelf on the right side. The middle 2 relays (mine are white) control the top. The first thing I would have tried is to determine the top-down relay and jumper a wire across 30 and 15, the power set that tells the motor to activate. If you can get the motor to drive the top fully down by jumpering it, then the problem is not in the cylinders or motor, but in the computer itself.

In my own situation, I eliminated the computer entirely. For the top, I continued to use the relays, but for the quarter windows (which constantly failed previously and I had them work on the bench but not via the computer), I installed a separate set of switches for each window with power from the side window switches, eliminating the relays. They work perfectly every time now.

 

Thank you for your suggestions. In manual the same thing happens and it stops. The top of the back window frame hits the seat. Brought it to upholstery shop and he thinks changing the straps will fix it. My mechanic mentioned the stiching around the window but upholsterer said the window sits in a frame. He pulled on the strap and you can see the window tighten. Thank you again...trying it in manual got me on the right track for sure. Its a cheap fix instead of a new top.

 

coldpad1,

Glad to hear you're getting to the bottom of the problem. Mine does a similar thing where it catches the top of the rear seat. Annoyingly, it slightly ripped the seat trim the first time it happened. I just lean back and gently guide it past when I lower the hood. I think the problem on mine is caused by a lack of tension in the hood fabric in the area just below the rear window, where I have a slight rip, which causes the window to lose a bit of tension and drop when the hood is lowered. I'm not convinced that it's the webbing straps but I might be wrong

Good luck

Paul

 

Mine is hitting the back seat on the top of the rear window frame. He pulled on the webbing and it pulled up some slack so may be a different result for me.Fingers crossed..