Packard Forum Index » Post-War (1946-54)

Drove my Clipper today in the rain. First time. Noticed that when engine is under stress, wipers slow way down or stop. Let up on accelerator and they resume. Is this normal operation? Thanks

To an extent. Open throttle or an engine load reduces intake manifold vacuum so the wipers do slow but the vacuum supply to the wipers should be going thru the upper vacuum pump section part of the fuel pump.

Normally intake manifold is strong and just pulls thru the pump keeping the pump valves open. When the intake manifold drops the valves in the vacuum pump start working and lets the pump take over. That should provide enough vacuum to prevent the wipers from stopping but will not provide enough volume to keep them going at the same speed as the large manifold vacuum supply provides.

It could be the wiper motor is borderline in need of a rebuild and currently needs every bit of vacuum it can get just to move or it could be the vacuum pump section has been bypassed or is not functioning properly. Old dry cracked or poor fitting hoses could also be providing a small vacuum leak which would cut down the available supply.

Howard's answer was, as usual, right on the money. As an aside, Trico, the manufacturer of the wiper motor, offered an electric booster pump. I had one in my 1953 Clipper Deluxe and with it the wipers would work even without the engine running!

I had forgotten about those electric vacuum pumps. There are several on ebay now including one for a 6v car. Also a couple that don't have electric motors but have a flat pulley that must rub against a fan belt. Says that one is for some Fords. Several 12v units that might work for anyone that has an Olds oil pump conversion and no more vacuum pump. Unless someone is determined to stay as stock looking as possible and wants to hide a pump, for that application I like Peter Packards mod of the combo alternator/vacuum pump. to address two items with one mod. If I ever go back to vacuum wipers in the 56 would seriously give his mod a consideration. The US available version of his alternator/pump combo seems to be fairly reasonable.

There is another electric vacuum pump that the seller said was for a 54 Buick and was used for cars with power brakes. Didn't Buick use the GM version of the BTV? If so am curious if they had a vacuum reservoir or is there something different with the Buick that they would need a booster pump rather than running the brake booster directly off the manifold as Packard did.