Jim Yergin Posted September 21, 2009 Report Posted September 21, 2009 I had a thread about my four wheel disc brakes occasionally binding up in my '41 Plymouth. It was suggested that the problem was the 10lb internal residual valve in the original master cylinder. I removed the internal valve but now can't get the brakes to work properly. I have repeatedly bled them but can not get them to work properly. They slow the car down but will not completely stop the car. I have also extended the master cylinder push rod to the fullest extent possible. Would the removal of the internal residual valve be the source of the problem? I have 2lb residual valves on the front and rear lines. The only thing I did was remove the internal residual valve and before that the brakes worked fine except for the binding. Is it a bleeding the air issue? Any suggestions would be appreciated. Jim Yergin Quote
PatS.... Posted September 21, 2009 Report Posted September 21, 2009 I've read that if the master cylinder is below the calipers that there could be a problem. MP Power brakes have a valve and an explanation for that situation. I'm not sure if you are still using the underfloor master but it may be something to consider. Quote
Plymouthy Adams Posted September 21, 2009 Report Posted September 21, 2009 the one article from MP brakes if I recall correctly was to pull the internal residual but KEEP the 2 pounders on the disc and 10 on the rear...you just did not want to combine them with the master's own valve..do you have a 10 lb'er for the rear? Properly adjusted brakes should give a high pedal..properly bled brakes will not feel spongy when applied nor fade if left to sit...smaller the bore of the master the more feel the brakes have, the larger bore makes the pedal firm and as such need a bit more pressure from you.. Quote
greg g Posted September 21, 2009 Report Posted September 21, 2009 Tim Jims car has discs on the rear also. Quote
Plymouthy Adams Posted September 21, 2009 Report Posted September 21, 2009 my error...I read that on the first thread and had forgot till you just mentioned it... in the case of 4 wheel discs..while the movement of the piston is minimal..the displacement for this movement is quite large in volume for all 4 callipers combined...not sure if a larger bore master may not be in order.. Quote
Jim Yergin Posted September 21, 2009 Author Report Posted September 21, 2009 Tim, Thanks for the reply and yes I do have discs in the rear too so I have 2lb residual valves on both lines. What has me puzzled is that the brakes had a good feel and stopped the car fine before I removed the internal residual valve so wouldn't that mean I had adequate volume of fluid? Would removal of the valve change that? I am thinking about replacing the valve but then I am afraid the binding would reoccur. Since removing the valve there has been no binding but then again the stopping power is greatly diminished. Jim Yergin Quote
Plymouthy Adams Posted September 21, 2009 Report Posted September 21, 2009 in my set up, each individual disc calipher had its own 2 lb residual valve..so I have in effect two 2 lbs for the disc up front, one per calipher and a 10 lb shared for the rear drums brakes would not guarantee this is your probleebut I do believe each has have it own 2 lb residual after the common 'T' Quote
Jim Yergin Posted September 24, 2009 Author Report Posted September 24, 2009 I finally got my brakes to work. Because of Tim's suggestion about having separate residual valves for each front caliper I did some searching on the internet. I found that it looks like just one residual valve is adequate for both front calipers. However I did come across this information about removing the master cylinder residual valve: "Note that there is a thick rubber washer in the far end of the master cylinder tube, that probably did not come out when the other components were disassembled. This is the washer that the residual valve previously sealed against. It is important that this washer be left in place in the master cylinder. Because of it’s thickness it will provide proper spacing for the length of the return spring to properly operate with the new disc brake assembly." When I removed the residual valve from my master cylinder, I failed to reinstall the rubber washer. I have since reinstalled it and now the brakes work. This whole process has convinced me that I want a dual reservoir master cylinder designed for disc brakes so I have ordered one from ECI Brakes along with their bracket to install it in my '41. Jim Yergin Quote
Plymouthy Adams Posted September 24, 2009 Report Posted September 24, 2009 excellent Jim and as for the tip on the washer..good note for us all to ear mark.. Quote
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