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rodjr, December 16, 2017 in 521
Thanks Wayne, Don't suppose you would know where i can find a matchbox and coil in good condition? This one does work but i would like to find a matchbox and keep this for an emergency spare.
I am actually looking for one myself, they came on 1978/79 Datsun 620 trucks, they also came on the 1980 Datsun 720, they came on some cars also, but there are not that many cars out there them years, but they imported a shit load of trucks.
By the way you need the pedestal also, do not by a Matchbox without the pedestal.
You said your brakes take two pumps to be a solid pedal. Does it hold solid?
If yes, adjust tighter. If no, and pedal is spongy or falls to floor- then you have a bad leak or air.
No power brakes means shoes/wheel cylinders don't stay "energized." If they are just the slightest bit loose it will take a pump for the cylinder to hit the shoe, another pump to push on it.
Your brake drum should not come off without some extra effort.
Nissan used a dual point distributor in the 1970's for controlling emissions. The second set of points was retarded 5 distributor degrees, or 10 crankshaft degrees, in third gear, part throttle. The second set of points is not used any other time. The second set of points is connected in parallel with the first set of points, by a relay. There is are switches on the transmission, the clutch pedal, the throttle pedal, and the carburetor, that control the point relay.
521 wheel cylinders only have one port for fluid to go in and out. You have to use the motion of the brake shoes collapsing when pressure is released to push air out of the wheel cylinders, and out the bleeder valve. Using a pressure bleeder does not allow wheel cylinder air to escape the wheel cylinders, and using a vacuum bleeder on the wheel cylinder bleeder probably will not remove all the air from the wheel cylinder.
You have to bleed 521 brakes the old fashioned way, with two people usually. Pump up the brakes, and hold pressure. While pedal pressure is being held, open the bleeder valve, and keep it open until the brake pedal goes to the floor, and the shoes collapse again. Then close the bleeder, and after the bleeder is closed, then the brake pedal can be allowed to come up, and pumped up again. Three full movements of the brake pedal, and refill the master cylinder.
Daniel I chose not to even talk about the dual points because it is likely none/some of the stuff to make them work is not even there anymore, it is complicated if one knows nothing about the system, fact is I don't know enough myself to explain to someone how to make it work, as you mentioned above there are several things needed.
It is just way easier to buy a matchbox/pedestal/coil, set it up and forget about that and work on other things.
I completely removed the secondary points setup on my truck. I'm sure it worked when new, but now it's just a bunch of stuff that overly complicates things. I went so far as to remove the secondaries from the dizzy, and removed a bunch of wiring back to the firewall. I even cut off the full throttle switch bracket from the carb. Anything to clean up the engine bay and simplify the way the truck works is a plus to me. It's not my daily, but the more reliable, the better.
Good way to store an emergency set of points and condenser.
I went through all the boxes of parts that came with the truck........6 pos distributors but one is a D4k9-08 matchbox with base. I believe it has issues though as the center rotor at times catches the metal points on the outside as you spin it. Shaft is not super loose but obviously has some movement. Does anybody rebuild these things? Can the module be easily tested and are they available if it is bad?
Thanks for the tips on the brakes, they come right up and hold on the second stab. I thought they were adjusted ok as they all had some drag but i will go ahead and re-adjust a bit tighter.
Very nice truck.
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.
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.
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.
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?
How new?! Possibly original :D
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.
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