Vaihlor Posted February 11, 2016 Share Posted February 11, 2016 My 72 monte used to have power front drum brake (strange for a 72 by the way...). After an accident that damaged right front section, i've decided to convert to disc brakes. So i've brought a complete kit from MBM, no kind of problem to install it, but after multiple bleeding, i can't manage to get good brake pressure and good pedal always feel poor. Except if pump it but the pressure seems to fade away easily. -All brake lines are new -Rear brakes have been rebuild (wheel cylinder replaced), and correctly set -New master have been bench bleed, and tested with plugs (pedal get firm fast and the pressure can be maintained) -No leaks in the system -Combination valve have been replaced from the kit and seems to work well I don't really see where is the problem.... The only thing that can be in cause for me is the master cylinder bore size 1" from the kit, insufficient volume displacement for the car brake system, and i need an d 1"1/8 one thanks by advance for the advices and sorry for incorrect English meanings (i'm a french owner...) Quote Link to comment Share on other sites More sharing options...
Rock Posted February 11, 2016 Share Posted February 11, 2016 Did you change the perportioning valve? Quote Link to comment Share on other sites More sharing options...
Leghome Posted February 11, 2016 Share Posted February 11, 2016 I think his combination valve may be the proportioning valve. Quote Link to comment Share on other sites More sharing options...
Vaihlor Posted February 11, 2016 Author Share Posted February 11, 2016 yes i did it, the one inclued in the kit seems to not work well. Quote Link to comment Share on other sites More sharing options...
Leghome Posted February 11, 2016 Share Posted February 11, 2016 Could that valve be installed backwards? They may only go in one way but thought I would ask. Quote Link to comment Share on other sites More sharing options...
Grease Posted February 12, 2016 Share Posted February 12, 2016 Was the car built in Europe? When the Monte came out in 1970 disc brakes were standard equipment . This was before the Chevelle had them as standard . I think another A body needed a brake upgrade and your car got the parts swapped out before a trade in or sale. Sorry this does not offer any help to your question. Quote Link to comment Share on other sites More sharing options...
monte70car Posted February 12, 2016 Share Posted February 12, 2016 Usual 1" bore is used with 4wheel disc set, have installed those on all my 4wheel disc cars with no issue. Now if your pedal fades after its been applied it would be air in the system still or a leak either at a line. Since you switch from drum front brakes to disc you should need a 1 1/8 bore master this is give you the needed pressure for the disc drum setup. Also the proportioning valve can be the wrong one as a 4wheel disc system works differently then a disc drum one. Just my thoughts Quote Link to comment Share on other sites More sharing options...
Vaihlor Posted February 12, 2016 Author Share Posted February 12, 2016 No my car was built in baltimore plant, was export in 2000's The last p.valve i've bought is for disc/drum setup. And that's after complete bleeding (no air bubbles in bleed tube), i've poor pedal, no great difference between before and after, i can't "feel" the brake pressure coming during the bleeding, usualy, when you do it, and works well, the pedal gets a lot firmer after the rear brake're bleed. in this case not... Quote Link to comment Share on other sites More sharing options...
Sam (Bones) Posted February 12, 2016 Share Posted February 12, 2016 make sure the rear brakes are adjusted, loose rear brakes will cause a low pedal the combination valve may need to be reset too Quote Link to comment Share on other sites More sharing options...
Vaihlor Posted February 13, 2016 Author Share Posted February 13, 2016 what do you mean by "reset" ? Quote Link to comment Share on other sites More sharing options...
Sam (Bones) Posted February 13, 2016 Share Posted February 13, 2016 while bleeding the brakes the valve can get pushed to the front or rear, this makes bleeding difficult, the valve needs to be centered and re-bled Quote Link to comment Share on other sites More sharing options...
Vaihlor Posted February 13, 2016 Author Share Posted February 13, 2016 you mean the valve that activate the warning light ? it stays in center after the bleeding Quote Link to comment Share on other sites More sharing options...
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