1967 Convertible Top Cylinder Fluid

[67stripper]

I have a 1967 Convertible with 75,000 miles that has a power top. One of the cylinders is leaking so I'm going to replace both with aftermarket ones. I believe the cylinders that are in the car now are the originals as I've owned the car since 1978. I've never done anything with the system since I purchased the car and it has worked well but has only seen 13,000 miles in 38 years with lots of storage time.

My question is about the hydraulic fluid. The Body by Fisher Service Manual is very good on top mechanism service, repair and rebuild. In the section on hydraulics the manual states that the fluid is AC Delco Hydraulic fluid #11 or Delco Supreme brake fluid. The fluid in my system is clear so I'm assuming at this stage that it is brake fluid. Later models apparently used automatic transmission fluid. Can I change the fluid to automatic transmission fluid without any problems and do I have to flush it completely or will it mix it I get most of it out? I've just been through this with a friends hoist that we moved that has a hydraulic pump. The original installation of the hoist used clear #10 hydraulic oil and all the people we discussed this with recommended we change to transmission fluid. Apparently one of the big advantages to automatic fluid is much better performance in cold weather. Brake fluid is also nasty on paint etc. If I need to completely flush the system how would I go about doing this?

[Mike S]

 I would completely flush it. I don't recall seeing brake fluid in my 67 05B NOR system. It's transmission fluid to this day.
Check the line for signs of brittleness or cracks. Mine were brittle so I changed them last year.

Mike

[67stripper]

Thanks for the reply Mike. My car is an 11B NOR, built on Nov 11th. I read somewhere that 1967 systems could have either brake fluid or transmission fluid but I can't remember where. I thought it might have been in the Body by Fisher manual but I can't find the reference. I remember the note saying that automatic transmission pumps had a sticker on them to indicate that they used transmission fluid as all references in the Body by Fisher manual reference brake fluid. The only other Body by Fisher manual I have is 1970 and all references to fluid in that manual are to automatic transmission fluid. Does your pump have a sticker on it for transmission fluid and if not do you think the fluid has been changed? The only other car I have experience with in the past is a low mileage original owner and it was brake fluid. Don't have any data now on build date as it was many years ago.

I'll check the lines but my initial inspection indicates that they actually seem pretty good.

My question is how would you suggest I flush the system?

[Mike S]

You might be better off to put the top up, open the bottom hoses on the rams to let it bleed out. Then remove the pump from the rubber feet locks and remove the fill plug and drain the pump reservoir. That should pretty much empty it. Add fluid to the pump reservoir and the run the top to go down. It will be very sluggish until the air is worked out of the system. Once down then move top up. All the time you will have to constantly top off the fluid in the pumps reservoir. Once you see the air out of the lines, then you are done and the top should move very responsively.

[67stripper]

Thanks again Mike. Makes complete sense. Since I'm changing the cylinders and the pump is above the bottom of the lines I should be able to drain the system. From what I can see the pump does not look hard to take out. Filling may be another issue with the plug on the side. Any specific suggestions for filling? The Body by Fisher manual method seems complicated. However, they were using brake fluid.

[KevinW]

I am surprised brake fluid was an option.  Spillage is quite common when filling and that would eat the paint, ATF is much better.  The filling process is similar to brake bleeding, but in reverse.  You need make a pump plug with a metal tube sticking out. Put a hose on the tube into jar/can of ATF with the hose at the bottom of the jar.  Put the jar below the pump on the floor.  Once you put enough fluid in the pump reservoir to create a suction, it will pull fluid from the jar and push air out as you cycle the top up and down.  Multiple cycles will be needed to get all the air out if the ram, lines and pump.  Pretty sure there was a procedure in the Fisher body guide in the vert section.

[BillOhio]

my Chrysler had brake fluid in it. it had leaked into an area that stayed wet and made a bad place in the floor pan. I took the pump apart and it had a waxy residue in it that was a mess to clean out. I have clear fluid in it now and can remember if it was transmission or power sterring fluid.

[67stripper]

The Body by Fisher manual does have a section on filling and bleeding. Pretty much what KevinW described. His description makes me feel better though. I'm not sure brake fluid was the original fluid as the Body by Fisher manual does not say what the initial fluid was. It says that maintenance filling or replacement should use "Delco #11 Hydraulic Fluid (GM Hydraulic Brake Fluid Super #11 or its equivalent)". I don't know what Delco #11 Hydraulic Fluid is. Brake fluid? The fluid in my system is clear and the driver's side cylinder developed a very minor leak that ran down the cylinder and dripped on the seam sealer directly below not on any paint. The fluid puddled a very small bit and softened the sealer but that was about it. Nothing major at all. Easy to just wipe up. I'm going to change the cylinder and fluid as a precaution. I could likely use the existing cylinder as is for quite awhile.

I could probably use hydraulic fluid rather than transmission fluid. Hydraulic fluid #10 is a common fluid used in hydraulic jacks and hoists that is readily available at most auto parts stores but the professionals I've spoken to all now use transmission fluid rather than hydraulic oil. I'm told that a lot of new hoists and hydraulic equipment comes with transmission fluid. I like transmission fluid for hydraulic systems because it is dyed red and it is easy to see on a fluid level dip stick. Not easy with clear hydraulic fluid.

Power steering fluid should work also. I believe most power steering fluid is clear and may be just hydraulic oil #10. Although some power steering systems require only manufacturer sold fluid to work properly. Hard to tell whether this is just repackaged readily available fluid or some special concoction.

[KevinW]

I'm sure any type of simple hydraulic fluid can be used.  Its the slight additives for special purposes (power steering may have higher heat additives) that make the differences.  But the top pump is a simple device and does not generate that much heat, so a simple fluid should work fine.

[BillOhio]

I saw the bottle and it was clear transmission fluid

[69Z28-RS]

What 'brands' of transmission fluid is 'clear'

[67stripper]

Thanks to all those who replied. I took the whole system out and cleaned and flushed it. Nothing unusual or really difficult on my car except the driver side cylinder weeped a bit from what looked like a pitted cylinder rod. Changed both cylinders with aftermarket new and put the system back together with automatic trans fluid. Seems to work okay but I haven't put it to a good test yet. Once I have a chance to really use it I'll report back.

For those who are interested Convertible Service in San Gabriel, CA, have a fill system that looks like it would work quite well but $41 plus shipping. However, could not find on their web site what fluid they suggest.

Link is: http://convertibleparts.com/fluid-matic-tool.html

[BillOhio]

The clear atf I used was from napa and I got a big syringe from my vet friend to fill my pump. 

[67stripper]

Great suggestion Bill. Hadn't thought of that. I actually have a a few of those syringes. The ones I have are graduated in CC. I use them for CC heads and pistons etc. Beats the heck out of burettes. I found you can buy them at local pet clinics.

[camaroboy68ss]

The last 67 convertible my grandfather and I flipped had typical hydraulic fluid in it like for a floor jack. We used a long piece of clear hose to fill the pump and then just ran the top up and down to bleed the system. Worked great till the day we sold the car.