91 XJS V12 Convertible Top Hydraulic Pump Question
 

I need to top off the hydraulic fluid for my top, as it's low and running slow. I doubt it's ever been serviced. Anyway, how does the cap to the fluid resevoir unscrew? Is it with an Allen wrench?

Not sure, but you will need special fluid. Do not use atf.

I looked more closely, I believe a hex key/Allen wrench, removes the cap to the resevoir. I also plan on using Pentosin to top off. I looked through many other forum posts, and the consensus is that Pentosin is compatible.
https://cimg0.ibsrv.net/gimg/www.jag...8a3e6c3d37.png

That fluid is about twice as thick as what is called for. Aircraft 5606 hydraulic fluid is what you want.

Thanks for the info. I just ordered a pint of the aircraft 5606 hydraulic fluid from a aircraft supply company. It was cheaper than the Pentosin too.

When I purchased my XJS it had a half full tin of CHF 11S in the trunk, so I can only assume this is what is in the roof pump system.
And it works perfectly!

So do I continue to use the 11S? or the aircraft 5606?
That is my question.

I agree with you about using CHF 11S. Although the aircraft spec fluid may work, I have not seen anyone else recommending it. In fact, everyone apparently uses the Pentosin. The fact that you have it in your trunk, speaks volumes.

I just started having trouble with raising my convertible top on my 91 XJS Classic Collection. First time, I thought it might be an undercharged battery, so I charged it up and also tried with engine running, but the top still did not raise fully. I discovered some red fluid on the garage fool wicking along an extension cord and initially wondered what it was. Now, I suspect that is from the convertible hydraulic system.

Is CHF 11S a red color?

i will access the pump area to discover if the system is low on fluid and if I have a mess to clean up. I don’t know yet how the fluid gets to the garage floor from the hydraulic system.

hydraulic fluid would have run down behind the carpeting to the floor of the trunk. There are drain ports there. Might just be round holes but originally would have had little rubber plugs with and open side facing to the rear to let water, etc... out of the trunk.

The CHF that I have used in my xk8 and XKR is a light greenish color...

When I got my XJS I had to replace a rubber bushing in the drive shaft of the pump. It serves as the seal. The bushi a bit of work to find online (I bought 4 for future) and, the gear in the pump had shattered before I got the car. Miraculously, I found a guy who sent me the gear. Found him on eBay. The bush is pretty easy to change out.

Anyways, I won't quote anyone, but I have heard that ATF in this style of pump is fine. I've been using ATF and my top after that first fix moves as smooth as butter, no foam or bubbles in the lines and no leaks. Still,,, with the mis luck I've had in some areas, with my level of experience,,, I might NOT be the best person to listen to on matters.

And yes, I think it's a small Allen key and an Oring for the reservoir fill port. Just be careful in turning it off. I'd imagine in some cases them brass on plastic threads have been touching a while and ya wouldn't want to strip them OR crack the whole threaded mold OFF the top of the reservoir. Finding and replacing JUST the white plastic reservoir after damage can't be an easy find....

Thanks very much for your helpful reply.

when you changed the seal, how did you get the motor-pump assembly moved enough to access the seal.

i believe once the assembly is moved enough, one can just remove the 2 bolts joining the pump and motor and then pop out and reinstall a new seal. My problem is getting all the bolts out of the plate so I can move the assembly. I cannot see what may be a 3rd bolt on the plate.