Thought I pass on some bits I figured out this past weekend. My top was running slow so I figured it needed some fluid. A couple of searches turned up the info that GM says to switch to mineral oil instead of ATF. I still haven't seen the TSB on this so if anyone has it I'd appreciate a copy. In one of the earlier posts someone suggested that you can look up the procedure in the owner’s manual. At least in the 2002 version there isn’t any information on how to fill the pump. There is info on using the manual control valve but that’s pretty much the extent of the info. Perhaps I am missing a convertible top supplement? If so someone let me know.
This applies to a 2002 Firebird so it is probably good for 98-02s. I started with a quick look with a flashlight through the little cover flap on the inside left panel to confirm that the valve was fully in the correct position to operate and the fluid in the tank looked low. When in the run position the valve should be 90 degrees to the block on which it sits. When the valve is moved 90 degrees to the right (clockwise, it only moves one way) the system pressure is released and the top can be operated manually. The valve should always be fully one way or the other depending on what you need. As a note I started this process with the top up.
Next I carefully removed the cover on the left side by sliding it out from under the edge and behind the other cover pieces. Hardest part was getting it out from behind the CD player as the wiring harness could be damaged if you aren't careful.
An inspection with the flashlight showed some oil on the pump base plate and in the well. Either I had a leak or someone missed the hole when previously filling the pump, I wasn't sure. I decided to remove the two nuts that held down the pump base plate and was able to gently lift the pump and base plate off of the studs and out of the well while still connected to the wiring and all of the hoses. I sat the base plate on some towels to protect the rest of the trunk area (CD player ended up being a great place to set mine while checking it out).
I wiped down everything and found probably a couple of tablespoons of ATF in the well. The pump tank has two lines for min and max fill (not labeled but makes sense). Using a line wrench I carefully snugged up each fitting on the pump being careful not to stress any of the fittings or lines.
I decided that I wanted to remove as much ATF as possible and replace it with mineral oil. From what I have read in several places GM decided that the ATF was not the best for the top ram seals and has recommended mineral oil. I moved the pump valve to the manual position to release the system pressure then using a hex wrench I removed the filler cap that is on top of the pump tank just in front of the valve.
I used my Mityvac with a long thin hose to suction out as much of the AFT as I could get. You could probably get away with a suction bulb and tubing but it would be messier. Then I released the top and manually lowered it to the fully down position which pushed more fluid out of the system. I removed this fluid as well then refilled the tank to the max line with mineral oil that I picked up in the pharmacy section of a local store. I then manually raised and lowered the top several times to circulate the fluid. The fluid that returned to the pump looked more like ATF than mineral oil at this point so I went through the drain and refill process several times to get as much of the ATF out as I could. In the end there is still some ATF color to the fluid but I’m satisfied that it is better than 90 percent mineral oil and the two fluids don’t seem to be separating.
When I was done with the fluid change I switched the pump back to the run position and with the top in the down position had an assistant start the car and push the button to raise the top. It took a moment then the pressure seemed to come up and the top went up just fine. Watching for leaks while the top went up and down several times I found none. I also had my assistant stop the top in the half way up position for a moment so I could check the top seal of the rams (looked with a flashlight between the folds on each side of the top mechanism) to ensure there were no leaks there, good to go.
With the top in the full up position we shut off the car then replaced the pump and base plate back on the studs and snugged down the nuts. Note that the studs go through rubber grommets that reduce the vibrations when the pump is running. These are a common size and should be replaced if deteriorating. There are several grommets on other spots on the base plate that do not sit on studs and if one of yours at the grommet position is worn you might just be able to swap one around to the more critical spot.
Last I filled the tank to the max position. It is important to do this with the top up. If you fill to the max with the top down, when you raise the top you will end up below the min level. When you lower the top the fluid will show above the max level but not more that the tank can handle so my assumption is that you check the pump level with the top in the up position. Do not fill above the max level with the top up as you could end up with more than the tank can handle when you lower the top, it’s pretty close when all of the fluid is pushed back into the tank when the top is down.
Final report is my top now works better (responds immediately when the switch is pressed and is faster in each direction) than it has since I bought the car and I cannot see any leaks.
Hope this helps.
Steve
