I’ve written a few articles about the issues with Jaguar XK8
Convertible top hydraulics over the years.
I’d like to begin by referencing Jaguar’s own technical service bulletin
on this topic -
TSB 501-33 -
1997-1999 Convertible Top Operating Slowly - Amended April 2003
Issue: early XK8 Convertibles may experience slow operation
of the convertible top, or slow or erratic operation of the latch. These
conditions are caused by a tendency of the Univis hydraulic fluid in the system
to slowly evaporate, and in certain conditions to gel within the hydraulic
system pipes and hoses. From VIN 037189, vehicles in production have been
filled with an improved fluid, Pentosin CHF 11S.
The service bulletin informs us that the fluid may gel, and
the top may stop operating as a result.
On the face of it, the story sounds pretty benign. Lately we have seen things take a turn for
the worse.
During the past six months three early XK8 Jaguar
convertibles came into Robison Service with slow convertible top
complaints. Two cars were leak free; the
third was showing the familiar hydraulic oil drip from the header bar. On each car we found original fluid in the
top hydraulics. Two of the cars were
still in the hands of original owners, and the third had been owned by its current
owner since three years of age. All were certain – there had never been an
issue with the top before.
After changing to CHF11S fluid (and in one case, changing
leaking lines) all three cars developed additional leaks from the ram seals and
lines. Why did that happen, we
wondered?
A close examination of the failed parts offers some
answers. The first clue can be seen in
one of the pump reservoirs, shown after thorough flushing and change to CHF11S
fluid. You can see the fresh CHF fluid
as green liquid in the bottom of the reservoir.
Above that, lining the bottom of the reservoir, you see a slimy mix of
the two fluids. At the front of the
reservoir is a hard lump of what started out as Jaguar hydraulic oil, circa
1998.
We already know the old hydraulic fluid was prone to thicken
and solidify in chunks. What we now know
is that those chunks get into the seals of the rams and latch, and chew them
up. But they do not always leak, because
the chunks of congealed oil act as leak-plugs, which means the problem worsens
with age, while remaining invisible.
All that changes when the fluid is flushed. All of a sudden you have thin, fast moving
oil flowing through the system. As the
chunky old fluid is washed away, leaks appear.
The solution: Replace the lines,
rebuild the rams, and rebuild the latch and pump. All the chunky old oil has to go, as do all
the seals, and total rebuild is the only way to accomplish that.
My takeaway from this:
Change your hydraulic oil, just like any other fluid. It was the chunky deteriorated fluid that
caused the seal damage. If these cars
had gotten top fluid services every five years, there is a good chance this total
failure would not have happened. Having said
that, I must also point out that many carmakers (Jag included) use plastic
hoses now, and those get brittle and fragile no matter what’s in them.
The lesson for owners of pre-2000 XK8 convertibles: If you have trouble with the top, be prepared
for the possibility of leaks after flush, and if that happens, rebuild the
whole thing and have done with it because the alternative will be replacing everything
one part at a time, which will cost you a lot more in the end.
John Elder Robison is a NY Times bestselling author and the
founder of J E Robsion Service of Springfield, MA. Robison Service is a long established Jaguar
service specialist, with expertise in postwar Jaguar motorcars from 1950 to the
present day. Find them online at www.robisonservice.com
or in the real world at 413-785-1665
7 comments:
The problems in hydraulic systems mainy arises due to contamination of hydraulic oils from dust.Dust blocks the filter this happens when you don't regularly service and grease your hydraulic systems.
Thanks
Bruce Hammerson
Hydraulic Hammers
Hi Bruce!
Not only contamination there could be any other reason too but yes agree that contamination of hydraulic fluid is one of the common problem.What should be done to avoid this problem?
Thanks
Henry Jordan
Hydraulic Seals
I've been having problems with my hydraulic system but I don't have the first clue on how to fix it. I was thinking of buying the hydraulic hose fittings and other supplies I'd need and then learn to do it myself. Would you recommend that for a first time mechanic?
I've got some pretty good experience in this area feel free to give me a call with any questions. Mostly years 1997-2006.
FYI, the part number you'll need to replace the hose is Jaguar part HJB8256AB. If your doing the repair yourself, I can be a big help. Call me with your questions.
Marvin
404-759-6600
I have just had my battery changed by a private company which is now closed for today and my XKR CONVERTIBLE 07 Hood has stuck .the roof is now down and the back flap is up.when I opend the hood today it stopped a quarter ov the way.I fiddled about with pressing the window and hood buttons I switched the car on and off and after a bit I got it to go down but now it's happened again as I've tryed to put it back up.I'm in a bad situation because it's getting cloudy and I can't get it down.can anyone please help help help.thanks
Please can anyone help me .my hood is not responding and it's down ..but the back flap is up .I've just had battery replaced today.thinking it might have something to do with that.it's urgent cos I have no were to put car tonight.it started to go up but then stopped.this happened today when I was putting it down but after fiddling with window buttons answer stuff it worked but not working now I'm a bit desperate cos everywhere shut.please help.thanks
What about flushing and replacing with the original fluid to avoid leaks?
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