1952 (and before and after) "dual action" fuel-vacuum pump

[Philippe M. Ruel]

The vacuum-actuated windshield wipers on my car have been very weak for some time, they stopped working a few weeks ago. Their motor is connected to the mechanical vacuum pump ("dual action" fuel-vacuum pump lower part) outlet. When I connect it directly to engine vacuum on intake manifold, it works well again.

So I removed and disassembled the pump, I found out the lower diaphragm destroyed and everything inside covered with engine oil. It is true that the pump is bolted to engine oil filling tube side, therefore it may get liquid oil upon filling and some oil vapor when engine is running.

My question is, why have Cadillac people allowed engine oil access there ?  Is this a well-known problem ? Are there any well-known solutions but replacing diaphragm from time to time or switching to electric wipers ?

[P W Allen CLC# 20193]

Philippe, Does your car have an oil filter? If so, is it piped up as below? This was a problem for the 53's at least, because the oil filter return dumps back right on top of the fuel pump arm. Some of the returning oil would run down the arm and get into the pump. Cadillac recognized the problem and redesigned the gasket where the fuel pump bolts on to the filler tube. See Service Bulletin below. I tried this on mine and it helped a little, but oil still made it's way into the pump and eventually it comes out the small vent hole in the pump casing making a mess. I ended up using a piece of plastic pipe and epoxyed it to the filter return fitting. The plastic pipe was flexible enough so you can work it along side the the fuel pump arm and still screw the fitting in. The return oil from the filter now dumps past the arm, keeping the oil out of the pump.

According to the service Bulletin, this was a problem only for the 53's, but I have to believe that with this design, oil WILL eventually get into the pump just from the vapors that are present when the engine is running. It will lay on top of the vacuum diaphragm, eventually destroying it. What can you do? If your set up is like mine, you can do what I did. If not, replace the diaphram from time to time, OR, go with a single stage fuel pump and get your vacuum directly off the intake manifold as you have already tried.

Paul.

[P W Allen CLC# 20193]

Philippe, Here's a third photo that shows a single stage pump that can be used.

Paul

[Philippe M. Ruel]

Well, my car didn't have an oil filter until I found a used canister on Ebay and new elements through my friend Roger from Switzerland. I re-painted the canister and installed it, but never connected its lines to the engine, it is only here as a decoration - anyway, I know now the way I should NOT connect it, thanks Paul !

I'll cut a new paper gasket like the illustration you show from the service bulletin, for a further protection against oil leakage. It is very surprising this issue hadn't been noticed until 1953.

[P W Allen CLC# 20193]

In 53, the poblem got much worse because of the oil return location and triggered the Service Bulletin. As I said, I tried the new gasket design, but it didn't seem to help much. I was going to try making a gasket out of rubber and fit the square hole tightly around the pump arm, but the plastic pipe trick worked well, so I never did it. Without a funtioning filter, (you really don't need one anyhow) the new gasket design may do the trick for you. Good luck with it.

Paul

[Philippe M. Ruel]

I'm about to rebuild the pump, using an "extended-type" gasket like the one shown by Paul, cut in a tire tube, that will feature a tiny square hole for the actuating arm only.

Just wondering : what if the diaphragm wasn't destroyed by engine oil (after all, these are supposed to resist chemicals like fuel), but if the destroyed-by-age diaphragm made the way for oil vapors to be drawn by manifold vacuum through the pump ? The pump lower body inside was heavily coated with oil ; the pump-to-manifold tube was dry, however.

My car has had hot-starting problems for some time, could it be linked with a vacuum leak, and/or engine oil breathing ?

[Otto Skorzeny]

wHATEVER MATERIAL YOU USE TO MAKE A DIAPHRAGm, be sure it is of the modern rubber which can tolerate the damaging effects of ethanol.

You're in France if I remember correctly, right Phillip? Do they use an ethanol blend over there?  If so, it will distort and degrade rubber parts made of the original type rubber.

[Philippe M. Ruel]

be sure it is of the modern rubber which can tolerate the damaging effects of ethanol.

Well, I purchased my rebuild kit from an eBay seller in the U.S. back in 2005. It looks to be "new new stock" (as opposed to "new old stock"). The description made by the seller specified that it could be used with unleaded fuel, but said nothing about ethanol.

You're in France if I remember correctly, right Phillip? Do they use an ethanol blend over there?

Yes, fuel is blended with 5% ethanol in France, this ratio is to be increased to 10% very soon.