I was talking this afternoon with an acquaintance who owns his own auto repair shop. He works exclusively on high-end cars, some in the $250,000 range. He is familiar with a number of different motorized convertible top systems (including the XK8), and always recommends to his clients that they drain their Pentosin hydraulic fluid and replace it with DOT 5 synthetic brake fluid....

While he cannot say that DOT 5 fluid will eliminate or even mitigate the hydraulic hose failure we all dread, he emphatically states that DOT 5 fluid will not cause the catastrophic damage to the car's interior (leather, fabric, paint, plastics, carpet, etc.) that the Pentosin hydraulic fluid does when the hose decides to blow. He believes this fluid switch-a-roo is a no-brainer and has replaced many a convertible's hydraulic fluid with DOT 5 fluid over the past three or four years. He says that no client has ever returned to him with a failed convertible top issue after doing so....

Thoughts / Comments / Rebuttals ??

 

Pentosin CHS-11 is primarily mineral oil based and does not cause interior damage from spills that cannot be cleaned up from all the reports that I have heard.

 

Hello folks,

I would like to introduce myself to this forum. I am a convertible hydraulic cylinder and pump rebuild professional, but will try not to refer to my company or services while posting here as a regular member, as that may be against forum rules. If this forum is more tolerant of professionals actually referring to their own services, please let me know. (My company is already sponsoring a few other auto forums, which gives us the right to make commercial posts in those forums, but we cannot sponsor every convertible forum at the same time. Moderators, I don't think I'm violating any forums rules here, but please let me know if you are uncomfortable with my posts before erasing them. In some Mercedes forums, my posts have actually made a big difference for the members, and we ended up sponsoring those forums after they brought us some decent business. For example, I have posted some 500 DIYs or troubleshooting responses on BenzWorld, and that has turned into a win-win situation for all parties involved.


Your XK8 and XKR convertible hydraulic cylinders and pumps are very similar to those of most European convertibles made in that period. It appears that Pentosin CHF-11S is approved for Jaguars, which is an "LHM" fluid. I know that it is used as a compatible fluid to the following, as well:
BMW 83 29 0 429 576
Porsche 000.043.203.33
Bentley RH5000
VW/Audi G 002 000 A2

Mercedes approves a fairly inexpensive fluid that is clear in color, and that I would recommend without reservations: FeBi 02615. You can get it online for some $11/quart. Try autohausaz, for example, and enter "02615" in their search box. I don't see any reason not to use it on Jaguar systems; it is approved as top hydraulic fluid in MB convertibles from '90 to present. As a matter of fact, I recommend the same fluid to owners of BMW, Audi, VW, Bentley, Porsche, and others. The late 90's Jaguar convertible hydraulic system is quite similar to that of the Mercedes CLK series. Mercedes' own fluid is p/n 0009899103, and it has a green dye in it. In Australia and Asia, it is distributed under the brand name Meyle with the same part number, I believe. Mercedes also uses fluids with a red dye in it, but I'd like to keep this response fairly simple.

The Mercedes convertible top fluid is actually a "ZHM" fluid, as opposed to an "LHM". ZHM is more highly refined, and it is required for more recent model years.

I have heard that a long time ago, Mercedes actually took a Citroen fluid off their list of approved fluids because they found that the dye in the Citroen fluid affected the seals. That is hearsay as far as I'm concerned for now, and Citroen fluid may well be okay for MB systems again. Fact is, almost all car manufacturers use the same suppliers for their convertible top cylinders...

As far as brake system or self leveling suspension fluid is concerned, there is certainly some overlap. DO NOT USE REGULAR BRAKE FLUID IN YOUR TOP SYSTEM, EVER! I personally don't know if DOT5 fluid is okay for your hydraulic top system, and it may very well be. However, there is a better alternative with ZHM.

The important attributes for the hydraulic fluid in most top systems are the following: fairly even viscosity (thickness) over a wide temperature range, no additives that would harm your system (especially pump and valve seals in this case), and no emulsifiers that would suspend water in the fluid (you want any water to sink to the bottom of the reservoir).

A few remarks about using the wrong fluids or additives:

Unfortunately, "Stop-Leak" type products won't do any good on a Saab convertible system. Stop-Leak is designed to make certain seal materials swell up and thus seal cracks that have developed in the system. The seals in late 90's Saabs do not react to Stop-Leak; they are inert to it. However, once your seals are leaking, there is nothing you can do about it. On the down side, we have seen additives destroy hydraulic pumps, and that is an expensive loss for you. If the additive seems to have worked before for any of you, then it was likely the result of some other particles having temporarily clogged a crack in a seal.

Using thicker (more viscous) fluid might slow down the leaks, but it will ultimately kill the pump and it will slow down your system. If your cylinders are leaking, then you need to get them rebuilt. (Or spend the extra bucks and buy new ones which will develop the same problem again in time - proper rebuilds will last longer than new OEM cylinders on account of better seal material being used...)

I hope this helps, and am looking forward to interacting with many of you.

-Klaus

 

Oops, my apologies for referring to Saabs in the paragraph about Stop-Leak additives. I copied that paragraph out of a post I made on a Saab forum a while ago. Didn't mean to insult anyone - '99-'02 Saab systems have a lot in common with the XK8 and XKR hydraulics. I don't think any of you would want to try a red-colored additive when you are fearing the "green bath", anyway...

Klaus

 

Klaus welcome to the forum.

I would ask you to follow forum protocol and introduce yourself in the "New Member" section of this forum. With your introduction please explain the reasoning that you would like to add to this forum. Thank you

Sorry guys back to the OP....

 

+1 on the welcome Klaus

Back to the OP comments..............

 

Klaus,

Thanks for your input. We've owned our 2006 Jaguar XK8 convertible for nearly three weeks now and with top-down season approaching in our neck of the woods, my wife has come to fear the "green shower"....

Please provide more details on how and why you believe FeBi 02615 is superior to Pentosin CHF-11S. The hydraulic hoses on our XK8 convertibles are notorious for leaking at the top latch fitting after a few years. Most folks seem to believe this is due to inferior hose material combined with excessive pump pressure. I would like to know if superior pump fluid could help to mitigate the hose failure issue....

Thanks again for contributing here. Please provide more details....

 

Dear Jon89,

Thank you for response - it made me aware that my wording may have raised some false expectations, and I must apologize for that. I was looking at the hydraulic system mostly from the standpoint of keeping the pump and cylinders fully operational, and I was also referring to the color of the fluid that I almost universally recommend. Let me start with the following clarification:

ZHM fluid (such as FeBi 02615) will not prevent your hoses from bursting or leaking any more than LHM (such as Pentosin CHF-11S).

ZHM is clear, so a potential bath wouldn't be green, but clear. I don't think that makes you feel much better.

In any other convertible I know (we are working on cylinders for almost 20 brands now), the primary reason for people getting oil dripping on them, is that the front latch cylinder(s) themselves are leaking. The latch cylinders (and the top lift cylinders) in XK8s/XKRs will more than likely eventually leak, and that can be taken care of with a good rebuild using better than OEM seals. However, the bursting hoses in your cars that I am only now becoming aware of, are a very serious problem.

The worst hose problems I was aware of so far, are in late 90's Bentleys and Saabs. We are gearing up to manufacturing replacement hoses for those makes. In Saabs, for example, a contributing problem is insufficient strain relief where the lines are exiting the pump, and that doesn't seem to be the issue in your case. I need to understand the Jaguar problems a little better before making comments on possible fixes. Some members seem to have put a lot of effort and ingenuity into a fix for the bursting hoses, and I wouldn't want to interfere before I have hands-on experience with your hoses. If anyone had a failed hose available to send to me, that would be great! Just how bad would the job be of pulling a hose and replacing it with a higher quality version, for example? I would appreciate any expert's input on that question.

On the upside, the Mercedes R129 SL-Series was made from '89 through '02, it has about a dozen hydraulic hoses going to the myriad of cylinders in those cars, some 200,000 of those convertibles have been produced, and hose failures are practically non-existent at pressures comparable to those in your cars.

I just started reading about including a pressure reducer in your system, and thought that was an intriguing approach if the hose upgrade is too difficult. Fact is, the hydraulic systems develop full pressure only when they are at the end of a cylinder's motion, which means the speed at which your top moves is mostly limited by how much flow the pump can produce at medium to lower pressure. Usually, the highest pressure is needed for latching and unlatching, so the pressure reducing remedy needs to be (and maybe already has been) fine-tuned to the pressure needed to faultlessly latch and unlatch front locks even in aging systems with consideration given to contamination in the latch mechanism, wear, misalignment, and changing resistance from aging or replaced weatherstripping on the soft top's front end.

Hope this helps,

-Klaus

 

I am not an expert on the system but I have provided a great deal of information on why this system has a lot of failures. As for the fluid I do not know if it stains the leather but I think others on the forum can answer that question. As for the cleanup use Dawn liquid dishwashing stuff does the job.

Hose evaluation JagRepair.com - HydSystemEvaluationXK8XKR

CHF 11S Information sheet JagRepair.com - HydraulicFluid

As for changing the fluid I do what I was told when dealing with aircraft you do not substitute. The cost of replacing the pump, rams, latch because of compatibility issues could be high. I would not take the chance but that is a choice you can make. Jaguar wants about 3 times the price for the same fluid you can get at AutoZone for around $20.00

 

Klaus-
I and am sure many other were not aware that the XK8/R cylinders can be rebuilt.

If this is true, I think many of us would be interested in the details of what you offer and if you have actually rebuilt the specific cylinders for these models.

 

I do agree with Steve I would like to see if the cylinders can be rebuilt. I do know that the latch can be done it was just a matter of finding the right seals. In my many years dealing with the roof problems I only found a few latches that were leaking but now we are seeing many rams leaking. Most of our failures have been related to the hose then the rams and only 2 pumps.

 

Gus and WhiteXKR,

thank you for your questions and remarks - I will comment below.

WhiteXKR,

Top Hydraulics rebuilds many thousands of convertible top cylinders per year. Our motto is to make the cylinders better than new, and we like to use the term "upgrade" as opposed to "rebuild".

Your own, used cylinders can be made better than new by replacing the failing seals with seals of a different design and/or material. Keep in mind that the only wear parts are the seals and wipers (we add oversized wipers, as well). The information is on our website, but I am not supposed to include any link here myself, because Top Hydraulics is not sponsoring this forum (yet).

I am attaching below a photo of some XK8/XKR lift cylinders with our signature stainless steel cap after upgrade. The cap houses the new wiper and holds the new seal in place. We are just about to file a patent application.

Gus,

thank you for providing the statistics. You will see more and more latches and rams failing; it's a function of time and temperature. The warmer the climate, the faster the chemical reaction of seal decay in the cylinders. It could be worse for Jaguar owners: on some Saab and Mercedes versions, we are already upgrading cylinders in '06 models!

In most cases, pumps will go bad only when the motor gets wet, a relay gets stuck, the wrong fluid has been used, or the pump has run dry.

-

I hope this clarifies things a little.

-Klaus

 

What is the going rate for left and right rebuilds and what is the turnaround? Are you setup for a core charge so waiting time is not an issue? What is the duration of the warranty?

 

Gus,

Top Hydraulics is not a site sponsor, so maybe they can't post their stuff here. Against the rules I guess.

Here is their website...

Top Hydraulics | Rebuilt Convertible Hydraulics - Top Hydraulics, Inc

Here is their Jaguar page. I think it answers most of your questions...

Jaguar - Top Hydraulics, Inc

Jack

 

Thank You! I found the pages and asked a few questions by PM. I am excited to see we may have an option for the rams. I have two leaking and might get it done to see how it goes.

 

Gus,

Please keep us posted in your dealings with Top Hydraulics. Your experience here is very important, and we will be interested to learn your perceptions of the company and its products as you communicate or do business with them....

 

Will do!

 

Just when you think there is nothing more to say or learn on the hydraulic system that powers our convertibles something new comes along! It is the gift that keeps on giving.

I wonder how the more recent systems are working out for cars like the newer XK or on cars with the hard convertible top systems (Lexus, BMW, Infiniti, etc.)

Weather is getting nicer here again in SoCal and I am still dreading that first time of lowering the top for the new season (got to get over that).

Doug

 

Folks,

first of all, I didn't expect my technical response to the hydraulic fluid question to turn into a Q&A about our rebuild service; normally that happens by word of mouth and via forum members reporting about their good experience. In any case, I appreciate the interest and am responding to Gus' and Jon89's questions below...

Gus,

we currently charge $150/ea. per left or right rebuild/upgrade. I am not aware of a single unhappy customer, because honesty and customer satisfaction are very important to me. Life is too short to make each other miserable!

The turn-around is advertised as two days, but we have been averaging one day or less in the past few months. We ship by Priority Mail, which takes 2-3 business days. Our shipping rate is a flat $10 per domestic order. Internationally, we ship at cost and normally use USPS Express Mail, which makes it to most parts of Canada in about three days, many parts of Europe in 3-4 days, and the rest of the world up to a week. We are always happy to use our customers' UPS or FedEx accounts at no charge.

We expect to have a core exchange service available later this year. If any forum members have old cylinders laying around, we would be happy to purchase them and thus speed up the launch of a core exchange for Jaguar.

Our warranty is for three years, parts only. Over the past year, our failure rate has been less than 1/1,000. We are constantly working on improving that number.

It is important to note that the polished cylinder shafts must be free of blemishes, as they slide through the seals and a near perfect surface is crucial to preventing leaks. We are already manufacturing replacement shafts for cylinders similar to yours, and should be ready to provide them for Jaguar within a few months, in case we receive blemished cylinders from our customers (it hasn't happened to us yet on Jaguar cylinders, but we would like to be prepared). As a side note, blemishes on the shafts are typically inflicted by close-to-minimum wage labor doing odd jobs for used car dealers, and that can include very careless cylinder removal... ;-)

As I am reading more on this forum, I am realizing just how much Gus has done for the forum, and it is greatly appreciated.

I don't take good business for granted, and hope that I can always be an asset to the forum.

-Klaus

 

Doug,

I have to admit that the threat of a bursting hose in your windshield header is horrible. The only other car that I know of being notorious for that is the Bentley Azure, of all cars... As I said, we are working on almost 20 different brands now, and for the vast majority of convertibles the main problem is that all cylinders will eventually leak. You may regard that as the cost of owning a fancy convertible. Aside from the hose problem, it is normally good to move the top from time to time.

As far as improvements in newer models go, it is amazing to me that the cylinder manufacturers are still using the same old seal material that decays way too fast. On the upside, hoses are generally not much of a problem. With that in mind, preventative cylinder upgrades can keep those tops working flawlessly for decades. In an average late-model convertible, the life expectancy of the OEM cylinders is just over ten years, which is not much different from XK8s/XKRs... Our replacement seals last a lot longer.

On a personal note, it gives me much joy to know that the system in my Mercedes SLs with about a dozen hydraulic cylinders (soft top version and hard top version alike) will work flawlessly when I push that convertible top button several times daily from Spring to Fall. That is what you should be able to expect!

-Klaus