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changing hydraulic oil and maybe hydraulic pump for convertible top

withlibertyand's Avatar
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08-08-2010, 03:47 AM   #1  
changing hydraulic oil and maybe hydraulic pump for convertible top

I had one problem and now I think I've created another.

Preliminaries: I did a boneheaded thing. My 1999 93 convertible top wasn't working as designed. I took it to my independent Saab mechanic who found 3 of the 4 hydraulic cylinders were leaking. He quoted me something in the neighborhood of $3000 to replace all 4. I balked. I decided to just keep topping off the reservoir instead.

Here's the boneheaded thing: instead of using the Saab hydraulic fluid, I used 30W motor oil. That worked for a while and then one day it didn't. I think I probably killed the hydraulic pump. (Ok, so along with spitting into the wind, I won't ever do that again.)

So I took a smart pill and found this site and another one like it. I learned that there is a product that people have been using to fix my first problem: the leaky cylinders. (See I'm hoping I can undo the damage I've done and try that repair.

Here's where i need some guidance:
1) How do I drain off the offending oil from the convertible hydraulic system?
2) Is there any easy way to tell if the hydraulic pump (motor) is indeed dead?
3) If the pump is dead, is it easy to replace and get me back to where I started (leaky cylinders and a top that works when I add the correct hydraulic oil)? Do I just swap the lines, mount it, and plug the thing in?
4) What's the right way to introduce the new fluid? Do I have to flush it out with the good stuff?
5) How do I prevent cavitation?
6) Is it likely that I have created other problems in using the 30W motor oil instead of the spec hydraulic oil? What might they be? What symptoms would tell me that I had another new problem?

It's maybe a tall order and I appreciate any guidance you would share -- many thanks. I must say that for me one of the best things about the Internet is having access to so much expertise. Thanks for sharing yours.

withlibertyand's Avatar
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Join Date: Aug 2010
Posts: 2

08-24-2010, 08:15 PM   #2  
progress update

Here's an update:

I found a "previously enjoyed" hydraulic motor on eBay for $375 delivered. After some head scratching, I swapped out the old one for the new. Fortunately, the hydraulic lines have letter codes corresponding to the locations where they go on the hydraulic motor. The lines are attached to the motor via flanges which are held to the motor by screws. This is a fairly involved procedure and very doable for a capable novice like me.

I added hydraulic fluid and bled the system by loosening the upper hydraulic hose on the left 5th bow cylinder. To access this line, open the roof so that the 5th bow and the soft-top cover are raised. (There are additional procedures for bleeding the system if this does do the trick. They involve the soft top cover's cylinder and require two people to do. I was lucky.)

Stage 2: I added some Lucas 100% Petroleum Hydraulic Oil Booster & Stop Leak (see So far, the cylinders are still leaking, which is to be expected at this point.

keilysmith's Avatar
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Join Date: Aug 2010
Posts: 5

08-25-2010, 05:59 AM   #3  
Most new cars in the ATF 1967 and use, from 1962 to 1967, was able to use the automatic transmission fluid or brake fluid. Brake fluid can be detected by its strong smell and the transmission fluid smells more like oil. Pre 1962 cars are often supplied with brake fluid, but must be controlled by the type of fluid in the system may have changed, the combination of different types of liquid lead to component failure. If you change the whole system, the use of automatic transmission fluid, it is recommended to never use silicone brake fluid will void the warranty.

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