Pacific coast Datsun Posted January 31, 2007 Report Share Posted January 31, 2007 I noticed a problem recently on my 74 620. When i step on the brakes i notice the idle goes way down almost to the point that the truck dies. When i let off the brakes it goes back up. Could this be caused by a bad brake master? Bleach told me it could be a bad vaccum assist. can this part be replaced or should i just buy a new brake master?? Quote Link to comment
datsunaholic Posted January 31, 2007 Report Share Posted January 31, 2007 Not a bad master- a bad booster will do that. The master cyl doesn't have any connections to the engine. I had one car with a decent-sized short in the taillight wiring that loaded the alternator and dropped the idle though. The voltage drop was pretty obvious- lights dimmed and the voltmeter went from 13.5 to 11 when I hit the brakes. But I'd be more inclined to think it's the vacuum booster. They eventually do give out. Quote Link to comment
BEEBANI Posted January 31, 2007 Report Share Posted January 31, 2007 I noticed a problem recently on my 74 620. When i step on the brakes i notice the idle goes way down almost to the point that the truck dies. When i let off the brakes it goes back up. Could this be caused by a bad brake master? Bleach told me it could be a bad vaccum assist. can this part be replaced or should i just buy a new brake master?? You can Mark, but they're so damned expensive that you might as well replace the whole thing. That is if they have one, you might have to j/y hopping. If you're gonna replace it, you might just get a newer generation one so you're already set up for when you put discs on her. Quote Link to comment
Pacific coast Datsun Posted January 31, 2007 Author Report Share Posted January 31, 2007 Ok Kragen [shucks] carries the booster http://www.partsamerica.com/ProductList.aspx?parttype=250&ptset=A&searchfor=Power+Brake+Unit I was thinking of replacing the master cylinder too just to be sure. http://www.partsamerica.com/ProductDetail.aspx?mfrcode=BAR&mfrpartnumber=0722678&parttype=230&ptset=A I know they are expensive but i dont wann ago cheap on the brakes..! Jason..if I do want to "upgrade" what year Datsun vehicle booster should i buy? Quote Link to comment
Bleach Posted January 31, 2007 Report Share Posted January 31, 2007 I'd suggest a 1979-83 280ZX master cylinder and a 1978-79 truck booster. Quote Link to comment
BEEBANI Posted January 31, 2007 Report Share Posted January 31, 2007 I'd suggest a 1979-83 280ZX master cylinder and a 1978-79 truck booster. I've got one from a '87 sentra, it's a 7/8 bore I believe? I'm thinking of using it because it has the single res. like on the hb's. Quote Link to comment
Bleach Posted January 31, 2007 Report Share Posted January 31, 2007 280zx is 15/16" bore and is a joined resivour.... although I don't see how that is a plus. If you have a leak in only one caliper, all your fluid for front and rear brakes will eventually go dry. :eek: Quote Link to comment
datsun76_620 Posted February 24, 2007 Report Share Posted February 24, 2007 280zx is 15/16" bore and is a joined resivour.... although I don't see how that is a plus. If you have a leak in only one caliper, all your fluid for front and rear brakes will eventually go dry. :eek: Thats when you grab an ARM FULL of emergency brake and make like the 'fast & the furious' :D Quote Link to comment
datzenmike Posted February 24, 2007 Report Share Posted February 24, 2007 I'm pretty sure there is a small partition to keep one side or the other covered in fluid. Quote Link to comment
71-521 Posted February 24, 2007 Report Share Posted February 24, 2007 I've got one from a '87 sentra, it's a 7/8 bore I believe? I'm thinking of using it because it has the single res. like on the hb's. Take my advice and go Dual circuit! I lost a line and it could have been disastrous as i was on the freeway the day before bringing home a motor... thank goodness I had fixed my e-brake.. Quote Link to comment
datzenmike Posted February 25, 2007 Report Share Posted February 25, 2007 I had a '71 521 and seem to remember it was a dual system. My previous '68 dime was a single. I did get a dual and separate the front from the back. The lines were a different shaped flair and wouldn't seal against the M/C properly. I used a file to re-shape the taper and all was good.(geez... I can't believe I did that and lived to tell it). Anyway, the brakes worked at least as good and I knew if there was a sudden leak, I still would have some brakes. Dual systems were an innovation of the late '60s. Prior to that you would often hear of accidents involving brake failure, when do you hear that now? Kids today will say they remember when cars didn't have Anti Loc brakes! Quote Link to comment
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