Convertible top slow to come up on 1968 - Impala Tech
Troubleshooting Diagnosing problems

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post #1 of 11 (permalink) Old 06-18-2014, 11:11 PM Thread Starter
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Convertible top slow to come up on 1968

My convertible top is super slow to come back up on my 68 about 3 weeks ago it was ok, and I mean just "ok" but now it wont budge without someone out helping it while I work the switch. It goes down fine. I have read somewhere that is could be the fluid level? If so how do I access the mechanism? What transmission fluid should I use for a 68. If you please step by step instructions to get to the access. Thanks so much!
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post #2 of 11 (permalink) Old 06-19-2014, 07:29 AM
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There is a rubber plug that gains access to the fluid. You have to pull or pry it out. Make real sure you have tranny fluid not brake fluid in there as they do not mix well. Gm fluid is fine. Your motor could be going out if fluid is full.
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post #3 of 11 (permalink) Old 06-19-2014, 10:23 AM
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Bear in mind that if the fluid is low - you've probably got a leak which could also be in the lines or in the hydraulic actuator hidden behind each rear seat side-panel.
If you can, it may pay to remove the lower of the rear seat to ensure no leaks collecting in the floor there. Ditto around the pump in the trunk.

My money is on an old, worn-out pump though. They aren't exactly cheap, but they are sold at plenty of places.

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post #4 of 11 (permalink) Old 06-19-2014, 02:34 PM
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I'll bet on the pump, too. On my 65, it died between me buying the car, and when I picked it up. The seller replaced the pump for me. Put 12V to the pump, you'll know right away what the problem is...

Two doors, four doors, wagons, and ragtops.
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post #5 of 11 (permalink) Old 06-19-2014, 11:57 PM Thread Starter
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Convertible pump how to access it through seat?

What is the best way to access the convertible pump? Should the top be up? I don't want to wreck the new well vinyl. Any advice? Thanks
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post #6 of 11 (permalink) Old 06-20-2014, 08:30 AM
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Check it with the top up. On my 65 it was the cylinders leaking. I still run my original pump. To fill the pump, use a squeeze bottle with a nozzle on it. Run the top up and down a few times. If you overfill it it will purge the fluid out the fill hole. it can get messy, so keep some rags handy.
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post #7 of 11 (permalink) Old 06-20-2014, 11:08 PM Thread Starter
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Cylinder Access?

How exactly do I get to the convertible hydraulic cylinder? Through the trunk? If so how? Through the seat? How are they fastened?

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post #8 of 11 (permalink) Old 06-21-2014, 06:22 AM
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The cylinders are located behind the side panels ( where the ashtray is ) and all work is performed there. To get them out you have to remove the rear seat's, the lower side panel is attached by 2 screws at the front of panel where the windlace is and 1 screw where the seat back is mounted. There is where the lower mounting is for the lift cylinder. I think they're a shoulder bolt type of can't miss it.
My pump did the same thing, there is a guy in Columbia SC who rebuild's your pump and he give a lifetime warranty. He told me most issues the pump seals dry out and leak fluid from pump into the motor. Another is when pump is overfilled and fluid also gets into the motor.
I'll have to dig up his receipt if you want to check him out. He does his work out of his garage and I have no complaint's about him.
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post #9 of 11 (permalink) Old 06-21-2014, 08:26 AM
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Fluids need to constantly wash over the seals in your power steering, transmission, and in this case the hydraulic mechanism to raise and lower the convertible top. If the car sits idle these seals will dry out and leak when you again attempt to use the car. Once they are cracked and separating from the steel retainer they will not stop leaking so while you have it apart it is best to rebuild what ever part of your car that is leaking.

This is due to the factory relying upon primitive plastics and natural gum rubber to seal things and to transport fluids (such as your rubber gas line connectors). Everything has to be replace with new parts designed to work with the new formulation of new hydraulic fluids.

The earlier 1960's era DOT 3 or the 1980's era DOT 4 brake fluid, and the newer DOT 5 brake fluid are not going to work when mixed together. The mixing of these two incompatible brake fluids results in a plastic resin that will plug your orifices in the master cylinder and the brake lines). This is because DOT 3 is polyalkylene-glycol based and DOT 4 is polyglycol based while DOT 5 is silicone based and the elastomers in DOT 5 react with the basic (high pH) DOT 3 and DOT 5 fluids (not to mention DOT 3 brake fluid will peel paint down to the metal if spilled on the fender).

Power Steering Fluid and ATF has been reformulated (as in the new stuff no longer contains additives to preserve the old style seals) as well since the sixties, but as far as I know they still mix together without anything bad happening. like the chemical reaction with brake fluid. Additionally you can hardly even find Dextron III ATF on the shelf anymore; and GM recommends using the new Mercon /Dextron ATF sold in stores near you. Problem is once again these new ATF formulations do not contain softeners and lubricants for the older rubberized seals found in your PowerGlide transmission.

Not only has modern metallurgy allowed cars to be built out of thinner gages of sheet metal that results in a car that is stronger than the sixties lead sleds, but chemical improvements in brake fluid results in higher temperature boiling points that do not absorb water, and new plastic seals that last longer and resist higher pressures. Gas lines are now Teflon lined to accept gasohol, V-belts where replaced by serpentine belts that do not slip roll or stretch like the old V-belts that are no longer being made with a horsepower rating high enough to drive your accessories (most belts you find now hanging on the wall at your corner cheap priced auto parts store were designed for lawn mowers or washing machines, not automotive applications).

Time moves on so you have to be aware of the changes made over the decades to know how to adapt your car to live in todays environment. You don't want it to go extinct (or burn to the ground) over a cup or two of alcohol in your gas.

Big Dave
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post #10 of 11 (permalink) Old 06-21-2014, 10:08 AM Thread Starter
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Big Dave and 68imp much appreciated info.
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post #11 of 11 (permalink) Old 06-21-2014, 03:11 PM
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Joe...sent you a PM
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