brake bleeding sequence

I have a 1980 MGB Roadster that I am replacing wheel cylinders, shoes and brake hoses on. I want to make sure I'm on the right track for bleeding the system.

If I understand the Haynes manual . . . I seem to have the tandem master cylinder with PDWA, so I start by disconnecting the wires from said PDWA and unscrew it 3.5 turns, then start bleeding at the wheel closest to the master cylinder. On my left hand drive, that would be the driver's side front. Then move to the passenger side front, passenger rear and finally drivers rear.

Once I'm done bleeding the system screw the PDWA back in and reconnect the wires.

Is that the correct sequence of events?

How come you start at the closest wheel if the car has a PDWA, but at the farthest wheel if it doesn't?

(what's PDWA?)

also look at www.adcomgraphics.com/uploads/brakesyringe.pdf) for a different approach to bleeding brakes.

The pdwa is the little switch that monitors front and rear pressure to make sure both systems are working.
Why you would begin closest is beyond me.
I have always bled from the farthest cylinder and worked toward the closest.

chris Wrote:

Pressure differential Warning Actuator.
Man! You do test one!

RR,LR,RF,LF. That's what I've always done and never have fooled around with the swtich. Fool with that switch and the next thing you have are leaks around the damned thing.

I've always done lr, rr, rf, lf, since the plumbing runs up the right side of the car. And I ignore that switch like it is Satan himself.

Yeah, the manual says to start at the rear if you don't have this switch, but at the front if you do. It doesn't say when the switch was introduced or why you need to start closest.

I was taught years ago (confirmed via many factory and motors manuals) that the proper way to bleed brakes is to start with the cyl furthest from the master and work your way to the closest..ie RR/LR RF/LF.......

michael

I was always taught furthest first too.
This may sound a little unorthodox but I came up with a free pressure bleed system. This only works if you have an air compressor. I found that the cap off a brake fluid bottle screws right on the late MC in place of the cap. I drilled an 1/8 hole in the bottle cap and screwed it on in place of the MC cap. With the reservoir full and my air turned down to 40lbs, I opened all the bleeders and put air pressure to the MC with my blowgun. You have to be careful to trigger the blow gun just a little at a time. The plastic reservoir will bulge a bit to let you know it has pressure. Just apply the pressure in little bursts so as not to damage the reservoir. Once you have fluid flowing out all the bleeders, close them. I then have my lovely assistant/GF pump the pedal while I open each bleeder individually in the conventional manner to make sure all the air is out. I found that very little air remains and it saves a lot of the pumping & holding drill. I also did this on my TR8 which has the same reservoir and it worked great. I was able to do the clutch the same way by putting the air to the vent hole on the cap. Like I said, may sound a little unorthodox but it has worked for me. I'm by myself in the shop most of the time & have to improvise a lot.