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  #1  
Old 02-19-2002, 02:33 PM
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Question DISK BRAKE master cyclinder- HELP

As some of you kinow I'm converting to a 4 whl disk system on the runner. I know I'm supposed to remove the Residual pressure valve for the rear drums- which is supposedly behind the lineseat in the master. Problem is- I don't think there is one there. I remember seeing a picture of this done some time ago and it looked like it was a ball/spring check valve behind the seat. When I take a small drill bit and insert in through the seat ... it can go all the way to the piston bore without hitting any resistance. am i right in assuming there is no check valve in the master? It is the same thing on the front side,( rear port) of the master- nothing there till the piston. These are rebuilt masters.

AND would this explain why- after I converted to the front disk system- The first pump on the pedal felt like air was in the system- and the second pump the pedal would feellike it is supposed to- nice and solid.

Thanks.
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Old 02-19-2002, 03:25 PM
George G. Leverette George G. Leverette is offline
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The conversion should include a disc brake master cylinder, the aluminum ones work best of course that requires the adapter from the dealers. If air is trapped in the system then it should be bled to eleminate the pumping to stop the car.
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Old 02-19-2002, 04:36 PM
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Do you need the adapter for the aluminum master on a manual system?
I'm almost positive there was no air in the lines- I bled that system like 4 times with no air being found- it just felt like it. I think what was happening was- because the RPV was not there, it allowed the drum slave cylinders to completely return it's fluid volume to the master, instead of holding a set pressure/ volume in the slave cylinder. It took two pumps to replace that fluid to where the the drums would engage and the sytem acted normal. I'm looking for confirmation on that. There is only an aftermarket proportioning valve in line now after the splitter/warning switch/ seal off "T".
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Old 02-20-2002, 11:40 AM
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The problem is that your master cyl. Can't displace the amount of fluid needed to push the rear pistons out in one pump. That's why the second pump is hard, and the first one is soft. I agree with changing the master cyl.
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Old 02-20-2002, 04:34 PM
kekoakeakane kekoakeakane is offline
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Yes, it sounds like your MC does not have RPV's. That's exactly what happened to me on a 4 wheel drum car when I switched to the Aluminum MC. The fix for a drum brake car is to either install RPV's in the brake line or metal expander cups in the wheel cylinders (which BTW is what the manufacturers did to replace the RPV's in the MC). Either of those will hold a small amount of pressure in the line to hold the shoes out.
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Old 02-20-2002, 05:54 PM
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I will find out for sure tomorrow night. I got a rebuilt master in and went to bench bleed it. Well it no sooner got fluid in the resevoir and fluid started pouring out of the piston by the retaining ring. Jimi was not a happy camper and the parts man heard about it this morning. Thanks guys for your help.
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Old 02-21-2002, 02:48 PM
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I am on my second rebuilt master clyinder in one month too raod chicken. The last one leaked through the top and spilled brake fluid all over the side of the engine bay. Ruined my paint! Damn am I pissed! The Napa guy told me it was the same part number as a ford! That expalins it. The second cylinder was put on 2 weeks ago and it seals fine, but I seem to be suffering from a soft pedal like you. I also bled it and got 4 good squirts out of each wheel. The pedal feels good and stiff when the car is not running, but while running with the power assist it feels a little sloppy. Almost too much play for my satisfaction.
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Old 02-25-2002, 08:56 AM
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this might not be in line with the rest of the replies. i have a 72 dart i converted to 4 wheel disc brakes. i use a master cylinder off of an a 71 imperial with manual 4 wheel disc brakesa dn it bolts right on and works great
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Old 02-25-2002, 10:11 AM
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440dart_72


Hmmm Imperial master..... I never thought of that. Might be just the ticket, since I just got them on and bled- thoughly,( Like three time around the car with no sign of air. I still have the softer pedal. I'm sure it will lock it up, but I would rather have the firm pedal. I will have to check into that and see. Is your car manual or power??
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Old 02-25-2002, 10:58 AM
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my car is has full manual brakes the pedal is firm and it stops great. go to your local parts store and find out what chrysler cars had 4 wheel disc brakes. i think mine was from a imperial. good luck
bill
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Old 02-25-2002, 11:47 AM
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Default IMPERIAL BRAKES

I HAVE A 74 IMPERIAL LEBARON IT HAS 4 WHL. DISK THE ONLY PROBLEM I HAVE HAD IS FINDING REAR PADS. THE MASTER HAS BEEN REPLACED AND I GOT IT NEW FROM NAPA.
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Old 03-07-2002, 10:29 AM
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Well, I headed out and got the imperial 4 disk master. It doesn't matchup with the 71 bolt pattern. To make it work I would have to cut a section out of the pedal support under the dash so that is no go. I called Master Power Brakes and told them the deal- He knew right away it was a Stainless Steel Brake Corp. rear disk kit I was dealing with. I guess he get this all the time from their customers. The Mopar master doesn't have enough volume to drive the rear disk. So I have one comming from MPB. It's a specially modified vette unit with an adapter plate and push rod. Ya I know- not my first choice either ... but ya gotta have brakes. Once I get this all together- SSBC is in for one hell of a time. I'll be submiting a bill for all the time needed to modify their kit, time lost due to bad design and missing parts. should drop in right at $300 buck. Will they pay???? Probably not- but you can bet once I prove out this was the problem everyone on a mopar board is going to know not to buy from them!!!!! Along with a few other places that can hurt their buisness.
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