We have a 66 Chevelle SS396 and am not sure what the correct oil is to use in the motor for the top. My wifes late husband restored the car in about 1994 and her daughter said she thinks they put hyd jack fluid in it at one time. It seems to work ok but it is low on fluid and I would like to fill it up and purge some of the air out of the lines. Also we installed a new gasket across the top where it latchs to the windshield and it still leaks some, any suggestions on fixing that. I am new here and thanks for any info that will help me as I am sure I will be asking for help alot in the future.

We have a 66 Chevelle SS396 and am not sure what the correct oil is to use in the motor for the top. My wifes late husband restored the car in about 1994 and her daughter said she thinks they put hyd jack fluid in it at one time. It seems to work ok but it is low on fluid and I would like to fill it up and purge some of the air out of the lines. Also we installed a new gasket across the top where it latchs to the windshield and it still leaks some, any suggestions on fixing that. I am new here and thanks for any info that will help me as I am sure I will be asking for help alot in the future.

I don't know about correctness, but mine had trans fluid in it, and still does. I can't look right now but I believe that is what was called for in the service manual.

I think originally it was brake fluid but the early 70s convts had tranny fluid. I run tranny fluid in mine... based on some threads I read on here a few years ago about the tranny fluid being better.

In my old '67 Cadillac convert, the service manual listed brake fluid. But it stinks and stains when spilled. Esp when bleeding the lines. GM switched over to hydraulic fluid by '69. Trans fluid is hydraulic fluid, dissapates heat well, doesn't stink as bad as brake fluid, and mostly does not eat up any finished areas where it gets spilt. What ever is in the pump , cylinders, and lines currently needs to be drained / removed before switching over to trans fluid. That way you know whats in the line. I guess you could also get some limited cavatation with a mixture of all three.

OK, while were on this subject...
what is the proper way to refill the system?
I'm changing out to a new pump.

This is common sence, but use the same type fluid as whats in it now. You can smell the difference between the two fluids.

The popular fluid today is ATF. There was a post awhile back, about the common misconception that it was brake fluid in the power top system. It was a clear hydraulic fluid, but was not brake fluid. It is just a bad idea to put that in your power top system. Stick with the ATF...JMO

You may have already looked into this but if it is low on fluid where is it going?

I helped a friend with his '66 Mustang Conv. that was low on fluid...when I took out the back seat to get to the pump I found where the fluid was going:( ...all under the seat. You may want to check out the connections and lines for any leaks before adding more to the system. (but then again...that was a Ford;) )

Ok after reading this thread I still don't know what fluid to put in! After seeing the bodywork the previous own(s) have done I don't trust to put in just the same fluid they used. So what fluid should actually be used and how do I flush out what is in it?

Take a small amount of fluid and try to mix it with water. If it mixes, it is brake fluid. I've only been around a few convertibles pumps. They have all been hydraulic fluid. My Arrlington, TX built 68 GTO has hydraulic fluid. Good luck.

I'd also like to see a proper procedure for flushing and bleeding the system.

ALL hydraulic pumps of any kind use some form of hydraulic oil. Brake fluid is not oil; the lines and o-rings in the convertible top system are not designed to be compatible with that fluid and will eventually leak. I would use a mid-weight tractor hydraulic oil if you can find it. ATF works in a pinch as well.

The system will bleed itself during use, I usually cycle the top a dozen times or so after replacing parts, as for flushing....crack a line and operate the pump. Make sure to have rags handy.

The propper way to fill the pump as per the 1970 service manual is to get a hose that fits tightly into the hole in the reservoir and put the other end into a bottle of hyd. oil. Operate the top up and down a few times.
The pump will suck the fluid into the reservoir by itself. Make sure the cylinders are retracted and take the hose out and then put the top up and put the plug back in.

The propper way to fill the pump as per the 1970 service manual is to get a hose that fits tightly into the hole in the reservoir and put the other end into a bottle of hyd. oil. Operate the top up and down a few times.
The pump will suck the fluid into the reservoir by itself. Make sure the cylinders are retracted and take the hose out and then put the top up and put the plug back in.
I use a tire valve stem with the valve core removed. Sitck a piece of 3/8 tubing (like fuel line) in the back side of that, and then a length of 3/8 hose over the tubing to insert into a bottle of POWER STEERING fluid. The threaded end of the valve stem is inserted into the top motor where you pulled the plug out, and the other end in the power steering fluid bottle. It's probably best to use about 3 feet of hose so you can set the bottle in the trunk floor. You will have to run the top all the way up, and all the way down several (maybe10) times to purge all the air out. Like Bob said, it will suck the fluid in by itself. When it moves as soon as you hit the switch, you're done. I pull the hose out and plug it with the top closed, but there are diffferent ways to get the same job done. One more thing; don't be alarmed if you kick the circuit breaker on the top while doing this. Just wait a few minutes, you'll hear it click under the hood, and go again. Once it gets hot enough to kick out, you won't get as many cycles out of it before it kicks the next time. It will be OK. It will cool off completely when you're finished.
Hope this helps,
Dan