Re: 1934 vacuum wipers lube

Posted by Owen_Dyneto On 2012/12/8 10:10:09

Terry, let me try to clarify. There are two systems on your car which are operated or assisted by engine vacuum, the windscreen wipers and the power brake booster system. Engine vacuum is at it's lowest during engine acceleration or heavy load; this would decrease the performance of the wipers and thus the wipers have a secondary source of vacuum, the vacuum pump which is part of your fuel pump (it's a two-section pump, one for fuel and one for vacuum,both using a rubber diaphram and valves). The vacuum booster section of the fuel pump is not connected to the vacuum power brakes because it's not needed - you don't apply the brakes at the same time you are accelerating, or at least I hope not, and manifold vacuum is at it's highest during decelleration.

So...if only one of the two wiper motors doesn't perform properly as you indicate, it's probably either the motor itself or the rubber hose and/or connections that connects it to the vacuum source. If the wipers slow down significantly (or nearly stop) when you accelerate heavily, then the vacuum booster section of the fuel pump needs rebuilding. With the wiper system operating properly, even under the hardest of acceleration the wipers should just barely slow down - almost not noticeable. I've never replaced the wiper vacuum hoses on my 34, but that doesn't mean yours are still intact - inspect them or just change them. Rebuilding the vacuum section of the fuel pump is essentially the same as rebuilding the fuel section, pretty simple basic stuff.

Another thought has just occured to me as I type this; the two vacuum wiper motors are in series with the one on the right side being the end of the line. So perhaps, if you have a vacuum leak anywhere (and especially think of the booster diaphram in the fuel pump), perhaps it's possible that there is sufficient vacuum to operate the first motor in the series, but insufficient residual vacuum left for the second one and thus the problem may not be the wiper motor itself as I had suggested above. Again, suspects would be the hoses and connections, and the fuel pump vacuum booster section. If you haven't rebuild the vacuum section of the fuel pump within the last 10 years, I suspect it's time for it now.

Keep us posted, please.