Master Cyl Help - 72 442

[ed1948]

I'm helping my friend of 51 years with his (original owner, no winter

) 1972 Olds 442. Front disk OEM conversion.
His recently replaced master cylinder went bad over the winter. - pedal to the floor.
I bench bled his new master. It has bleeder screws over each of the two lines and since his brake lines were capped and there is only 1" horizontal that would be full of air. We installed the master, slowly bled the air out of the top of the two lines by gravity. That was followed by pedal pumping until the air was bled from the two bleeders. we did three extra pump cycles to ensure there were no more bubbles. The fluid remained topped up.(cast iron master cyl.)
The brake pedal was firm with short travel. The engine (beautiful exhaust sound by the way - that Olds idle!!) was started and the pedal dropped and went soft???/ Now what - fluid level is up, no air out of master bleeders.
The car does have a proportioning valve that shows no brake warning on the dash.

 

[fleming442]

I'm helping my friend of 51 years with his (original owner, no winterView attachment 72508 ) 1972 Olds 442. Front disk OEM conversion.
His recently replaced master cylinder went bad over the winter. - pedal to the floor.
I bench bled his new master. It has bleeder screws over each of the two lines and since his brake lines were capped and there is only 1" horizontal that would be full of air. We installed the master, slowly bled the air out of the top of the two lines by gravity. That was followed by pedal pumping until the air was bled from the two bleeders. we did three extra pump cycles to ensure there were no more bubbles. The fluid remained topped up.(cast iron master cyl.)
The brake pedal was firm with short travel. The engine (beautiful exhaust sound by the way - that Olds idle!!) was started and the pedal dropped and went soft???/ Now what - fluid level is up, no air out of master bleeders.
The car does have a proportioning valve that shows no brake warning on the dash.

You have to bleed at the wheels as far as I'm concerned.
Also, make sure the rear drums are adjusted properly as they provide the pedal height.
Did he get a disc/drum prop valve? Drum circuits have a residual valve in them. It needs to be removed for disc operation.

 

[ed1948]

RE brake system....A very knowledgeable tech did the conversion more than 10 years ago. The Olds has no more than 300 miles since then.

 

[ed1948]

The fluid leak originally was at the rear seal of the cylinder - some fluid leaked on the outside of the booster.
Once we get the space to properly work on the car we'll check the rear brake adj first.

 

[ed1948]

Problem solved. Due to lack of space we were unable to bleed all four corners. We made the room around the car and bled the system...simple .as that. He's still running last year's gas.

 

[pontiacgp]

fleming442 wins with his suggestion the brakes have to bled at the wheels...🙂

and that is really nice of you to help him out.....

 

[fleming442]

I thought that's what we were here for....?

 

[pontiacgp]

I thought that's what we were here for....?

I was ambiguous with the second part of my post......I meant it was nice of Ed to help him out but it was nice of you also and although it's all about helping each other on here it's nice to show appreciation.

 

[fleming442]

Sorry, I just get a little salty about internet car repair. There's a bunch of misinformation out there, where sometimes past experience or just plain common sense should prevail.

Thanks for the props, yo!