Vacuum wiper motor

[Rogerchummy]

The vacuum wiper motor on my 1927 Chummy had never been connected to the inlet manifold since I bought it so I recently dismantled and serviced the motor (including soldering some small cracks) and it seems to move freely when I operate it by hand. However, when I attach it to the outlet on the inlet manifold it barely moves at all even though some vacuum can be felt at the motor if the regulator screw is removed.

Can anyone suggest why the vacuum might perhaps be too weak. I am using 4 meters of 4mm clear plastic tubing which I am reluctant to cut down to the required length (2 metres?) until I have sorted out the problem. 4mm is the correct internal diameter for attaching it snugly to the motor and to the spigot on the manifold. Physics was not my strong subject at school but I would have thought that the length of the tubing (within reason) should not significantly affect the delivery of the vacuum from the manifold to the wiper motor.

Compression is good on all cylinders and therefore I assume that the pistons are drawing in air efficiently.

Any thoughts/suggestions would be gratefully received

[bob46320]

What sort of contact pressure between the wiper blade and the windscreen - it doesn't need to be much.

[AustinWood]

What is the engine doing? No hope of it working unless there's good vaccuum.

[Dave Mann]

    I use our vacuum cleaner to test vacuum wiper motors, it doesn't give as much suck but if it works then I know it will be OK on the car. The hose adaptor is from a home brew shop.

[Rogerchummy]

Thanks for this. In fact I am testing it off the car so there is no load on the motor at all.

Regards

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The engine is on tickover which normally creates a good vacuum but there is no improvement if I rev it.

Thanks for the suggestion

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Hi Dave

Brilliant idea ! Why didn't I think of that?

First thing tomorrow I'll be in the garage with my Henry.

Regards

Roger

[Pearls not a Singer]

The most likely causes are a leaking valve or worn leather washers that seal to the cylinders

If you work it manually with the "handle" it should go click or clack at the end of each stroke and there will be a puff of air from the inlet tube

If you don't feel confident contact donb4wipers@yahoo.com

[Rogerchummy]

Hi David

Many thanks for this. The leather washers are in good nick (after 93 years !!) and I have soaked them in oil to keep them supple. There is indeed a click at the end of each stroke but I didn't know about checking for the puff of air - I'll do this tomorrow.

Thanks too for the contact details of the repair guy - definitely my next port of call if I can't fix it soon.

Thanks again

Roger

[Joss]

you say that you are using clear plastic tube of some length, not vacuum tube.
could the tubing be collapsing ?

[Rogerchummy]

Thanks Joss. The tubing is pretty sturdy so I doubt that it is collapsing but I will check next time I try it.

[Dave Mann]

With old but flexible cup washers it is sometime necessary to encourage them out towards the cylinder walls on assembly with oil on assembly. Once in that position the vacuum tends to pull them out.