Using a different pump for the ATF fluid

[Wayne Venomous]

After reading how many semi-auto Bugs have the engine oil/ATF fluid mix problem due to dodgy seals and how difficult (though not impossible) it is to find replacement seals, I kinda got thinking about if a different pump could be used instead which would eliminate this problem and have more available spare parts.

Well a few days passed and I noticed the power steering fluid level warning light on in my 1986 BMW 320i daily driver was on. No problem, open the bonnet, tip some ATF fluid into the power steering reservoir........... AHA! Most BMWs have power steering and their pumps require ATF fluid! And they're a completely self-contained unit driven by the fan belt.
It just so happens I have a 1989 BMW 520i that I'm breaking for parts (my Baja Bug is getting an IRS conversion using the BMW's rear trailing arms and rear driveshafts - but that's another story!) so I was thinking of using the power steering pump from this 5 series and seeing how it goes on our 1302 semi-auto. I'd quite happily do a how-to article on this if anyone's interested.

Now, my thoughts are that it wouldn't take a lot of doing to fabricate a bracket to hold the pump and you could either fit a second pulley to the crank and drive this off a seperate fan belt or get a larger fan belt and stretch this over the crank pulley, generator pulley and the pump pulley. I did something similar years ago when I fitted a 75 amp alternator from a Ford to my Baja Bug.

The other advantage is you can fit another engine without having to transfer the oil pump over. You could even full-flow the engine using a standard Bug oil pump and something like a Gene Berg oil pump cover.

[volkenstein]

Wayne,
         Certainly worth a look. Bear in mind the outlet from the pump shouldn't exceed 52 psi. From what I understand PS pumps can vary the pressure delivered as resistance is placed on it via turning the wheels, so you'd be up for limiting the output. I'd also think about the speed the pump turns at. The VW one is run @ 1/4 engine RPM as it is direct drive off the cam whereas most PS pumps are driven off the crank via different sized pulleys.

Would be cheaper than trying to modify a dry sump system.

How about this? Electric gerotor EFI pump with regulator running ATF??? Another one for bling time? Hillborn/mech injection crank/belt driven fuel pump running ATF??

Regards
Volkenstein

[Wayne Venomous]

Hi Volkenstein,

It would be very easy to limit the output pressure - a simple hydraulic regulator can easily be used and there's one that's more than suitable from RS components for under £7 ($17 Australian Dollars or $14 US Dollars)

Also you could limit the speed easily by fitting a second pulley on the crank that is 1 quarter the size of the pulley on the pump - e.g. a 10mm dia pulley on the crank and a 40mm dia pulley on the pump would make it turn the same speed as the original ATF fluid pump on the Bug engine.

The BMW power steering pump is pretty much just a pump - there's a hydraulic thingy attached to the steering column that seems to do all of the work as far as I can see. The layout isn't that much different to the Bug's as it also has a reservoir tank for the ATF fluid. Even the pipes look the same diameter.

Hilborn mechanical injection fuel pumps aren't exactly easy to get in the UK but there is plenty of electric fuel pumps. I'm not sure if these would be suitable/capable of pumping ATF fluid though.

[Crasher]

Taking that idea a step further, a lot of modern cars have electric power steering pumps, it's an interesting idea as an electric unit could be pressure governed by altering the voltage.

[Wayne Venomous]

Taking that idea a step further, a lot of modern cars have electric power steering pumps, it's an interesting idea as an electric unit could be pressure governed by altering the voltage.

Interesting!
As long as the VW's electrical system can take it, I don't see why an electric pump couldn't be used. Could be a good point to upgrade to an alternator and/or consider a rewire.

At the moment it seems that belt-driven power steering pumps are easiest to obtain from scrap cars but I'd imagine as the years roll on, there'll be more and more electric power steering pumps available as I don't buy new - it's really expensive for stuff like this as it's usually the high-end German cars like Mercs, BMWs and Audis that have these things in.

[Crasher]

You will find it's small cars like the later Polo and Fabia plus other makes such as Mini, Corsa etc that have the electric PS pump and the current consumption is surprisingly low but an alternator would be a must.

[Wayne Venomous]

That's very interesting - sounds like this would make the process a hell of a lot easier!

Proberbly gonna be a few years before they're easily available from scrap cars though. That said, it shouldn't take too long for scrap Corsas to be made available (judging how long my mate's Y-reg one lasted!)

I like the idea of a Polo/Fabia power steering pump - keeping it in the VW family so to speak.