I have a dual-circuit brake booster and master cylinder from a 1971 142 series car.. mounted to a 1968 122S. The front and rear systems are split (stock setup) but I have a fully boosted system.



Overall it performs pretty well, is 100% volvo and required only one trip to the welder. It is also a plus that it looks like a 69-70 euro amazon.

Anyway, I've been experiencing a slow pedal sinking when stopped for extended lights for a while. The car would start to roll forward or backward even on a modest incline. A quick pedal pump would restore brake hold, but the problem has been persistent.

Given the sum of my past experience with volvos, I assumed that the problem was probably failing seals in the brake master cylinder. I've been looking for a rebuld kit from the local parts stores, but have come up empty so far.

After replacing some of my rear brake line yesterday, I bled the system using a power-bleeder and was shocked to find (on my test drive) that I barely had any brakes. Given that the rears only provide about 20% of the braking power, I was concerned and did not drive the car today.

Today, I decided to check over the whole hydraulic system and to install some braided stainless steel brake flex lines while I was at it.

After installing the new front lines, I again power-bled the system - flushing out most (if not all) of the old brake fluid along with all the air. I re-bled the system to be sure that NO air was left in the lines.

Took the car for another test-drive and again found that I had almost no braking power. The pedal is nearly at the floor before it stops. Pumping the heck out of the system does nothing to improve the hold.

To me, these symptoms strongly suggest at least partially failing seals in the MC. Since is is a dual system, I must be getting some pressure, but it is not nearly what it should be.

I'd like an opinion on whether I'm on the right track here. No air in the system, fading brake hold, inability to pump the pedal to hard. Seems pretty clear cur, but I've been wrong before.

After comparing the prices a new cylinder ($100.00-$200.00) and the price for a rebuilt ($25.00) and the price of a rebuild kit from VLVWorld ($25.00) I opted to get the rebuilt unit. I just ordered and I'm hoping it is not garbage. Anybody have any experienced with the rebuilt 140-series MC from Rock-Auto?

Also, anyone have a good source for the MC rebuild kit? Seems pretty strange that hardly anyone stocks it. The 140-series is still pretty mainstream.

Thanks as always.