Motschrocker Posted September 27, 2014 Report Share Posted September 27, 2014 So i just put on a new master cylinder for a 73 610. I bench bled it and bled the system once on. The pedal was solid and i had good stopping power. My problem now is that brake fluid from the rear resevoir of the MC is being pumped into the front resevoir and overflowing through the cap. It does this when i pump the pedal. What would cause this. Do i have a bad MC? Quote Link to comment
datzenmike Posted September 27, 2014 Report Share Posted September 27, 2014 Likely the 'new' master is 'bad'. It should not do this. Rather than try to fix it I would return it for a replacement. This is the brake system not a radio knob that falls off. Quote Link to comment
Motschrocker Posted September 28, 2014 Author Report Share Posted September 28, 2014 I thought it might be the MC but i dont understand how fluid would leak from one reservoir to another. Could it be another part of the system malfunctioning like the proportioning valve? Quote Link to comment
datzenmike Posted September 28, 2014 Report Share Posted September 28, 2014 You are under the assumption that because something is new it can't be the cause of a new problem. The opposite is true. The reservoir didn't over flow before the new part was added, but now it does. The new master is a total unknown quantity, worse and even more suspect is it may be a cheaply rebuilt (cheap parts and labor) or a cheaply manufactured knock-off from China. Both are not anywhere near to the original equipment quality demanded by Nissan. There is no proportioning valve on the 620 brakes. Quote Link to comment
Motschrocker Posted September 28, 2014 Author Report Share Posted September 28, 2014 I guess i just am not familiar with the internal workings of the master cylinder and wanted to understand how the fluid would flow into the other resevoir. Ill return it this week and hope the next one functions properly. Quote Link to comment
datzenmike Posted September 28, 2014 Report Share Posted September 28, 2014 Well there are two systems inside the master sharing the same cylinder. They are separated by rubber seals. It's not a stretch to see that one could be forced into the other. It's been reported time and again the $19 knock offs are 50% bad in the box. They have been taken apart and found to have aluminum 'chips' from the machining process inside. Dollar an hour workers put part A onto part B and stuff into part C. 1 Quote Link to comment
Motschrocker Posted October 21, 2014 Author Report Share Posted October 21, 2014 So i ordered another master cylinder and installed it. Different brand this time and it is doing the same thing. Fluid is taken from the front resevoir and overflowing out of the rear. Is it possible i got 2 bad mc or is there something else causing this. I can upload pics if that would help anyone Quote Link to comment
datzenmike Posted October 22, 2014 Report Share Posted October 22, 2014 Often after market parts are only made by a few makers and sold under many brand names. If the quality is poor they will all be poor. Still two in a row is odd. Why did you change the master in the first place? Quote Link to comment
Motschrocker Posted October 22, 2014 Author Report Share Posted October 22, 2014 I changed the original because fluid was leaking out next to the brake booster. The first mc did not move fluid from one resevoir to the other or at least not that i noticed. Once i saw the leak i replaced it. I will take some pics of the set up tomorrow and maybe that will spark some new ideas. Quote Link to comment
Z-train Posted October 22, 2014 Report Share Posted October 22, 2014 You are under the assumption that because something is new it can't be the cause of a new problem. The opposite is true. The reservoir didn't over flow before the new part was added, but now it does. The new master is a total unknown quantity, worse and even more suspect is it may be a cheaply rebuilt (cheap parts and labor) or a cheaply manufactured knock-off from China. Both are not anywhere near to the original equipment quality demanded by Nissan. There is no proportioning valve on the 620 brakes. This^^^^ Quote Link to comment
Motschrocker Posted October 22, 2014 Author Report Share Posted October 22, 2014 I am not ruling out that i could have gotten another bad mc, but i cant seem to find anyone who has experienced an issue similar to mine. I should mention too that the fluid only transfers from one reservoir to the other when i let up on the pedal and not when i push down. Quote Link to comment
datzenmike Posted October 22, 2014 Report Share Posted October 22, 2014 The dual hydraulic brake system is designed to keep the two systems totally separate so if one fails the other will work. The only place they are close is at the master. 1 Quote Link to comment
Motschrocker Posted October 27, 2014 Author Report Share Posted October 27, 2014 I haven't got any pics uploaded yet but let me ask another amateur question. My brake system has both a brake pressure warning switch and an NP-valve in the lines. Could a malfunction in either of these cause my problem. If not i have seen some new old stock MC on ebay. Would i have better luck with one of those? Quote Link to comment
Motschrocker Posted October 27, 2014 Author Report Share Posted October 27, 2014 Here is a link with some pics. I cropped one old photo to show the np valve right next to the coil. Ill try and get better pics soon. https://picasaweb.google.com/103137401177043918465/66L18Roadster Quote Link to comment
datzenmike Posted October 28, 2014 Report Share Posted October 28, 2014 I suppose that the pressure warning switch is one other area where the two systems are close together. Possibly one could bleed into the other. Quote Link to comment
Motschrocker Posted March 19, 2015 Author Report Share Posted March 19, 2015 Well i did not my car all winter but im back at it to solve my brake issue. I pulled NP-valve and took it apart. Gave it a good cleaning, but for the most part the internals seemped to be in good condition. I also took off the brake pressure switch. Took that apart and i could look straight through it and no valving or springs were in it. Im not sure if that is right. Maybe that is where i am having issues. So i am wondering if my best option is going to be a universal proportioning valve and just run new lines. I put some pictures in the following link. https://picasaweb.google.com/103137401177043918465/66L18Roadster Quote Link to comment
datzenmike Posted March 19, 2015 Report Share Posted March 19, 2015 Pretty sure the 610 did not use a proportioning valve. The front to rear brake bias was designed into the system by using the correctr size rear wheel cylinders. This saves parts and time by the maker of the car. Quote Link to comment
Motschrocker Posted March 19, 2015 Author Report Share Posted March 19, 2015 I downloaded an old 610 manual and according to it they did have this NP valve. Either way it was on my car as well as the brake switch. Something is causing my mc to overflow. Shouldnt the brake light switch have some sort of internals to it? Quote Link to comment
ggzilla Posted March 19, 2015 Report Share Posted March 19, 2015 You need a good master cylinder. This exact same symptoms have been reported before and the solution is to replace or repair the master cylinder. Take your MC apart and examine the seals. One may be put on backwards. Quote Link to comment
ggzilla Posted March 19, 2015 Report Share Posted March 19, 2015 Early Datsuns used fixed proportion brakes, but in the 1970s some were fitted with a "Load Sensing Valve Assembly" called the NP-Valve. This allows good braking whether fully loaded or empty. It is a proprtioning valve. 610/B210 NP-valve was integrated into the splitter/pressure differential switch. In the 510, it replaced the 2-way connector which all 510s have. * 46400-A1100 "P" VALVE ASS'Y (op.) DX * 46400-A1100 ASS'Y-VALVE, proportioning (op.) S&C JDM Quote Link to comment
Motschrocker Posted March 19, 2015 Author Report Share Posted March 19, 2015 Thanks for the advice. Ill attempt to take the mc apart. Any suggestions on a good mc brand or place to buy? The two i have bought have had the same issue thats why i have questioned if another part of the system malfunctioned Quote Link to comment
ggzilla Posted March 19, 2015 Report Share Posted March 19, 2015 Good brands are new Tokico or NABCO. About $200. Not Remanufactured ones. Most everything else is cheaply repaired or made. Which can be OK but has a good chance of defects. Quote Link to comment
datzenmike Posted March 19, 2015 Report Share Posted March 19, 2015 A Nissan rebuild kit would be cheapest. Quote Link to comment
Motschrocker Posted March 20, 2015 Author Report Share Posted March 20, 2015 Well i took apart both master cylinders. The original one that was on it is a nabco and it is is really cruddy on the inside. I compared it with the new one i had gotten and they look essentially the same as far as how the piston assembly is set up. I am not really sure what to do at this point. Rebuild the old one? Try another new one? Is it possible something else in the system is causing this. Quote Link to comment
Motschrocker Posted March 20, 2015 Author Report Share Posted March 20, 2015 Again i put some pictures in the link i gave before. And keep in mind this is a custom brake job on my datsun roadster using 610 parts Quote Link to comment
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