Thread: My 88" Series 3

I get what you're saying Rod, but with the dual circuit system, even if you lose one circuit you should still have one working circuit? Is the idea of the PDWA valve, (as well as activating the warning switch), to restrict the flow to the failed circuit so you still have pressure at the master cylinder?

Which leads me to the question, does the rear (back) piston on the master cylinder get activated by mechanical force from the brake pedal, or hydraulic force from the front piston?

Cheers,

Both pistons are activated mechanically by the pushrod as both circuits are used. The pdwa resricts the failed circuit but does not stop it completly. The pdwa is designed to let u know theres a failure and to allow the good circuit to still stop the vehicle. Its a failsafe. When the brake fluid has gone from the failed circuit the good circuit will still have fluid as the master cyl has 2 reservoirs, one for each circuit so when u have total fluid loss from one circuit u will still have effective braking on the other curcuit as u will still have fluid in that circuit. A dual circuit system is just that. Two seperate systems that work in tandem with each other. If u go into a well established brake place they should have diagrams on how the system actually works so u can see it. Its easier if you look at pictures of how it works than trying to imagine how it works, at least it is for me. Hydraulics are a weird thing sometimes. Not as straight forward as some ppl think. Thats why there are hydraulics specialists.

Maybe there is training vids on utube that explain it better.

Cheers Rod.

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The shuttle in the PDWA moves back and forth as necessary to ensure equal pressure in both circuits. If it moves too far it operates the warning light switch. The only reson it will move this far is loss of pressure in one circuit (or on the early 110s the rear drum brakes need adjusting, presumably the same could happen on a S3, but adjustment will be needed roughly symmetrically where front and back are both drums, so you just get more pedal movement).

John

Thanks for the info on the PDWA valve everyone, it helps to have a better understanding of the system, there seems to be lots of contradiction etc about whether or not its needed. The one on the Series 3 will be staying.

Another question, does anyone have a reason why it would be a bad idea to weld a nut onto the trackrod, what for easier adjustment, (and so the person doing the alignment doesn't rip the paint straight off with some vice grips)?

Cheers,

Tim

I think i would not be painting a small section of the rod so the wheel alignment can be done then paint it afterwards. AFAIK, Welding onto steering components is against the law unless its been xrayed and inspected and all that jazz to ensure there is no weakness or microfractures which would lead to failure.

Cheers Rod

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That's a pretty good reason. I'll deal with the scratches when they occour.

Cheers,

In Vic, it's just illegal full stop. They won't even allow X-ray and engineering to pass welded steering components.

Thanks again for the quick info guys, just need to wait for the paint to dry on the track rod clamps and they can go on the car.

I was going to put the starter motor back together today, but the bearings have to soak in engine oil for 24hrs first apparently, so here they shall stay till the morrow





I was lucky to get genuine replacement bearings, goodness only knows how long this box has sat on a shelf!





So, seeing that the starter was a no go, might as well have a go at this bit





All stripped down, (tape is on the windings to protect them from the soda blaster), and the bearings are 6202's if anyone is interested.





Casings cleaned up and given a light coat of clear to keep them somewhat clean





Nearly all back together





And ready to go back on the engine





The replacement steering relay also turned up, I had to "settle" for an aftermarket (Bearmach) unit as genuine ones are NLA, (for a sensible price anyway). Looks to be a good quality unit, and prefilled with oil.





Gave it a light coat of antisieze, hopefully it comes out easier in the future!





And in it's home Long may it stay!





Cheers,