Classic/Antique Car Repair: Convertible Top, rear quarter panel, chevrolet bel air

Question
QUESTION: I have a 1955 Chevrolet Bel Air convertible. The hydraulic top fluid has leaked out and I need to repair. Can you tell me what fluid I should buy, and any tips on how to locate and fix the leak?
Thanks, Dave

ANSWER: Dave,

The first thing that I'd do is determine the cause and source of the leak. If it's a loose hose or fill plug, this is one thing, and an easy fix. However, if someone has put the wrong fluid into the system--the most common mistake is to use brake fluid--then you'll find that your seals might have turned to jelly. It's also possible that one or more seals have cracked or perished.

Anyway, the correct fluid to use once you've determined that your system is fluid-tight and operating properly, is this:

http://www.chevsofthe40s.com/detail/9739.html

Although the name of the company is "Chevs of the 40s", this fluid is the proper formulation for your car.

--Paul

---------- FOLLOW-UP ----------

QUESTION: I am assuming that the motor is behind the rear seat? Will I be able to identify the problem by visual inspection, ie if the seals are damaged.
The prior owner of the car said that he used transmission fluid...is this a problem.
If I am putting in new fluid, how can I bleed off any old residual so that I have a new pure fluid?
Thanks, Dave

Answer
The top motor is behind the rear seat, correct. There are also hydraulic rams; one in each rear quarter panel, roughly behind each rear armrest. Then there are the hoses connecting them.

A leak is most likely in one of the hydraulic rams. Hose leaks are also common, as are loose hose couplings. Hopefully this system was rebuilt sometime in the past...if not, these hoses are more than a half-century old, and are not safe.

ATF could be used as a fluid, but a lot also depends upon what type of ATF was used. There are several types, and you can't be sure what additives might be detrimental to the seals. Power steering fluid is sometimes used, too, and, again, depending upon its composition, could be OK or detrimental.

Flushing the system is a good idea. but to do this properly, all the hoses, pump, valve, and cylinders should be removed and blown out, using the proper oil to dilute whatever is still left in there. This really should be done by a pro; it could reveal the necessity for a rebuild of all the parts, as one blown seal is an indication of possible problems with the rest of the system.

--Paul