Fastback50 Posted October 29, 2017 Report Posted October 29, 2017 Hi guys, I've just completed my Scarebird front disk conversion and had removed what the residual valve assembly in the MC. When I say valve assembly, I mean I removed the little metal piece with holes (sort of looks like a salt-shaker top), AND a rubber grommet or gasket that sits behind it. I filled the topside of the MC and was going to bleed the brakes and had no pressure at the pedal....I pumped it up quite a bit with no results and the pedal continuing to just feel loose. When I opened the top of the MC again, I saw that no fluid had gone into the lower portion of the MC. Now this MC worked prior to doing this, so I'm just wondering: Did I remove one too many pieces thinking they were both part of the residual?? Otherwise, what else could have gone wrong? The spring did come out but I was able to put that and piece behind it back into place as they should be. Any ideas? Thanks. Quote
Plymouthy Adams Posted October 29, 2017 Report Posted October 29, 2017 in removing the 10 internal residual valve, did you install a two lb for the front disc and then a 10 lb for the rear drums? Quote
Fastback50 Posted October 29, 2017 Author Report Posted October 29, 2017 No....was thinking I could just run without one for the time being until I upgraded to dual MC and/or boosted dual MC. Still shopping around to see what is easiest/best and wanted to be able to run off old MC until then. Does it need the 10 and 2 to work until I find a replacement? Quote
Plymouthy Adams Posted October 30, 2017 Report Posted October 30, 2017 answer me this...what is going to hold the pressure and prevent the very suction of the fluid returning in the master and stopping it from sucking your cylinders dry.... Quote
Fastback50 Posted October 30, 2017 Author Report Posted October 30, 2017 Thanks Tim. So I need a 2 lb. in line residual for the front, and 10 lb. for the rear as long as I stick with rear drum. Right now, I have the rear circuit of the MC plugged until I get the lines replaced , which I will hopefully get to in a week or two. Still wondering why all the fluid sat in the top of the MC? Judging by the diagram in the service manual, the MC should still push fluid even without the residual valve installed. I'll take it apart and see if something is not as it should be. Quote
Plymouthy Adams Posted October 30, 2017 Report Posted October 30, 2017 point two...did you bleed the master before connecting to the brake lines.... Quote
Fastback50 Posted October 30, 2017 Author Report Posted October 30, 2017 So you think the MC's ability to generate any pressure at all is due to me not bleeding it before I cracked open a bleeder on the lines? Quote
Plymouthy Adams Posted October 30, 2017 Report Posted October 30, 2017 the brakes operate as a system and each component plays it part. The proper steps and sequence of steps is necessary to obtain a good pedal with less amount of bleeding and waste of time as possible. Ascertain at this time if the master is shooting fluid on each stroke, use your finger as a check valve to prevent air from being reintroduced on the return of the pedal to full upright...also...verify the correct free play of the pedal at the master making sure that the internal piston is indeed returning to the very rear stop...of the two holes in the reservoir, verify these are not stopped up and DO THIS ONLY if the piston is at the very most rearward stop so not to damage an internal seal. I am not trying to single you out on this next line but if you have little to no experience with brakes, find a friend in the hobby to walk you through it a bit and maybe lend a hand . But first things first, correct components, correctly installed, proper sequence of steps to bleed. Quote
Fastback50 Posted October 30, 2017 Author Report Posted October 30, 2017 Okay Tim, I will revisit it this week and reach out to a buddy if I get stumped. Thanks for the detailed response. Joe Quote
MackTheFinger Posted October 31, 2017 Report Posted October 31, 2017 Just throwing this out there so if it bores you or think this post is a waste of time I apologize.. I've tried to read everything on this site concerning disc brake conversions. I know it's apples to oranges and I've never put disc brakes on an early Mopar but.. I have run several front disc brake conversions on air-cooled VW's without doing anything to the master cylinder, no proportioning valve, nothing, just bolted 'em on and ran.. I just did a cursory web search and can't find any mention of anything other than spindles, calipers, and rotors being necessary. I don't know that they stopped any better than good, correctly adjusted drum brakes but they worked in the rain and didn't need adjusting. I intend to eventually change my P15 over to disc brakes and a remote-fill dual master cylinder for those reasons if nothing else. Right now I have good drum brakes and don't drive the P15 that much. Hopefully that'll change in the future. Quote
56Alan Posted November 2, 2017 Report Posted November 2, 2017 I went down the disc brake route (rusty hope kit) with the 2lb/10lb residuals fitted,removed the MC valve an although the front discs worked they required a lot of right foot to operate. Changed the MC to a 15/16" bore dual cylinder to reduce right foot pressure and the discs worked well IF I clamped of the rears because the rear cylinders are 1 1/8" bore so the new MC could not produce enough fluid before the brake pedal hit the floor. Fitted Explorer axle to rear which has disc brakes and now the brakes work well without the need for a servo. Hope my experiences are of some help, I only wanted better brakes at the front but ended up opening a can of worms as they say! Quote
Fastback50 Posted November 2, 2017 Author Report Posted November 2, 2017 Mack and Alan--thanks for your valuable insight. I've been experiencing the "can of worms" already just based on the MANY opinions and various experiences on what will really make a disc conversion operate properly or better yet, excellent. The further I open the can of worms (and my wallet), the closer I get to just adding a booster. Even with that though, I'm skeptical that the car will stop on a dime and I haven't heard from anyone that has added a booster. The under-the-floor option MC/Booster looks better because I don't think the firewall mount will work without modifying the firewall. Would love to see pics of guys boosted setups. Quote
Plymouthy Adams Posted November 3, 2017 Report Posted November 3, 2017 the booster will not give you any better brakes, only brakes with less effort on your part... Quote
MackTheFinger Posted November 3, 2017 Report Posted November 3, 2017 @Fastback50 I don't know that I was actually any help. Before joining this forum I contacted Scarebird through eBay about their disc brake conversion and asked about removing the residual valve and adding a proportioning valve. They said to do both but didn't mention residual valves. Since my drums are working fine and I don't drive the car much I haven't pursued it any further. Quote
Fastback50 Posted November 3, 2017 Author Report Posted November 3, 2017 19 hours ago, Plymouthy Adams said: the booster will not give you any better brakes, only brakes with less effort on your part... Doesn’t it give me more braking strength or power though based on the vacuum assist from the booster? It seems like there is no way my right leg could ever produce enough force for a manual brake system to stop like my 2016 Fusion. I recently had the unfortunate experience of having to test the limits of modern braking due to a “texter” that pulled out in front of me and I have to say I was truly amazed. I don’t ever want or expect my Plymouth to “handle” that way, but the braking power I wouldn’t mind Quote
Plymouthy Adams Posted November 3, 2017 Report Posted November 3, 2017 15 minutes ago, Fastback50 said: Doesn’t it give me more braking strength or power though based on the vacuum assist from the booster? It seems like there is no way my right leg could ever produce enough force for a manual brake system to stop like my 2016 Fusion. I recently had the unfortunate experience of having to test the limits of modern braking due to a “texter” that pulled out in front of me and I have to say I was truly amazed. I don’t ever want or expect my Plymouth to “handle” that way, but the braking power I wouldn’t mind Hey..I do not know if you do or do not have spider legs.... Quote
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