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new here, first 521, first Datsun, finding parts?


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#61 rodjr

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Posted 02 January 2018 - 09:37 PM

If the brakes are adjusted and bled correctly, the brake pedal should be higher than the gas pedal on the first push.

it is, but comes right up to the top of travel on the second push.



#62 wayno

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Posted 02 January 2018 - 10:08 PM

But it should be at the top on the first push, mine all are, don't settle when it comes to brakes.

Here is the worst scenario, you are stopped in the right lane at a stop light on a 3 lane road, the traffic starts moving so you start moving right behind the car in front of you, it's a van in front of you and you were maybe 4/5 cars back from the signal, you get moving 15/20mph and all of a sudden the van in front of you completely stops, you were a car length in back of him, well you don't have time to pump that brake, you now have 3 choices, move to the left if a car is not beside you, hit them while your pumping on the brakes, or go right up onto the sidewalk/grass/in the ditch if there are not people there, why did the van in front of you stop, well the car in front of the van wanted to make a right turn but people were crossing the street in the crossing(legally), that has happened to me 3 times in my life, the first time I rear ended the Kaiser van in front of me as I had nowhere to go, I was hardly moving but it so fast, I pushed my radiator into the fan, no damage at all to the van, the second and third times I made a right turn up onto the sidewalk/grass, all three times I was hauling around a small loaded utility trailer that didn't have electric brakes, since then I put an axle on it that has electric brakes, my situations I described above are like you having to pump the brake pedal.

There is no reason to have to pump the brakes, maybe you have a little air in the system, maybe the back or front brakes need adjustment, I expect you still have front drum brakes.


 

 


#63 thisismatt

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Posted 03 January 2018 - 08:13 AM

I bled & adjusted mine after the MC ran low. Pedal was high and very hard over a few days after bless/adjust. Let the truck sit a month and now it's soft again. Seems I have a leak but none of the slaves were wet, but I haven't had the chance to look at it again.
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#64 gene knight

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Posted 03 January 2018 - 09:22 AM

what about rubber brake lines, they could have a pin hole that is not noticeable at first or check fittings on metal lines to see if threads are wet, i had same issue so i replaced all rubber lines and  i made my own metal brake lines. how new is your m/c?



#65 thisismatt

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Posted 03 January 2018 - 04:30 PM

How new?! Possibly original :D
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#66 wayno

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Posted 03 January 2018 - 06:05 PM

OK, keep in mind that my 521 work truck is highly modified, but here is my story.

I have front disc brakes and a dually rear end in my work truck, but for years I used the stock master brake cylinder with the 10lb residual valve removed, I kept getting a soft pedal after 3 or 4 days of driving to my jobs and back home, it was always the right rear brake that got air in it, so every 3 or 4 days I would bleed that brake on the way out of my house on the main side street heading for the gas station, I got tired of that and eventually replaced that wheel cylinder, I kept replacing that damned wheel cylinder and it kept getting air in it after only a month, one time I changed out the axle because the gears went bad and it did the same thing on that axle.

Well one day several months later when I finished a job and I started heading home the master gave up, with a full reservoir I had no brakes, so I used my electric trailer brakes and my e-brake to get home, I put a new master brake cylinder in and bled the system, I never had an issue with air in that right rear wheel cylinder again, it was the master that was bad all along.

I expect that when I let off the brake pedal a small amount of air got by the seal and it took several days for the air to get to that rear brake cylinder, as I said I was still using the original type master brake cylinder with the residual valve removed, I now have 1990 hardbody V6 front disc brakes, and 1985/56 Nissan 720 dually axle brakes, I have since changed over to a 1973/74 Datsun 620 power brake booster and 1979 Datsun 620 master brake cylinder(dual circuit), I should have done that over ten years ago.