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So lately, my brakes have been getting softer. Before I only had to pump once to get full pressure (2-3 months ago). Recently, I’d have to pump it twice before I could get full pressure. Now I have to pump it 4/5 times before I get a solid pressure. When it builds pressure finally, the pedal doesn’t sink to the floor. I do believe the brake fluid level does decrease a tiny bit (1-2mm in the reservoir per week). If there was a leak, would it allow me to build solid pressure still? Also, after pressure is built, if I completely take my foot on the pedal, I have to pump to build up pressure again. Thanks! Will get a full line flush and replace what is necessary this Friday when I get paid. And it’s my DD, so help figuring out the issue is greatly appreciated.
Forgot to first mention that it’s an 84 Z31. No ABS. Just a master cylinder and brake lines.
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check for leaks. Remove your pads to see if they are in need of replacement.
If rear drum brakes check they are adjusted correctly. more in this link.Pads were replaced 6 months ago (as well as rotors). All disc brakes (gotta love how Nissan over-engineered their vehicles in the 70’s and 80’s). A bit difficult to check for leaks as my jack is MIA and I don’t have access to a lift till Friday at best (and I’ll have to order parts, so here is hoping I have any brakes by then or I’ll be downshifting and using the parking brake like a b****. And I can confirm that the fluid level in the reservoir dropped .5mm in the past week. If I have a pinhole leak, could it allow my brakes to build pressure by pumping but then go soft again?
Well, I was hoping to get some more ideas about what I could test without access to under the vehicle. Got a mightyvac and going to slowly (seized bleeders) work on replacing all the brake fluid (a flush more or less) and if the problem persists, I can assume its most likely the MC or a leak. I park in the garage every night and I never really noticed any unusual leaks (I know my PS pump leaks and I lose a little oil from my breather filter). And from my house to my work, I only brake twice, so that’s nice.
Beg, borrow, buy a jack and some jack stands. They will seem a lot cheaper after you rear end something and total your car or hurt somebody. Park it like now!
Borrowed a jack from a friend when I got off work a bit ago. Doing a flush myself today. Barely any brakes as of now. Hoping ft a flush to do the trick. Ordering a master cylinder now. Thank god I’ve got a manual and a parking brake. Gonna save my butt this morning getting home. Thanks for the replies guys!
Did you ever look underneath driver side carpeting where the pedals are? MC sits at slight decline and leaks around brake pedal push rod, into the carpet. It does not show itself until carpeting and insulation are peeled away from the floor.
As it will be good to know what exactly leaks.
Calipers can drip inside the wheel and then centrifugal force casts fluid all over and away out in the air. Dirt masks it too.
Don’t forget that rubber brake line hoses stretch over time and can take pressure into them acting like bellows. This may explain, why you still can build up pressure in the system.
But leak it is for sure.As of this morning I wasn’t able to build up pressure. But thanks for the info that a leak can still build pressure. About 1/3 of the way done bleeding. Rear right is done. Working on rear left (about 1/2 done). Thankfully I’m one of the people who have a small stock pile of fluids and sprays. Had 7 unopened quarts of brake fluid.
and I recently had the dash apart for a heater core. Issue began before then. But I felt under the carpet and sound deadening material. All dry.
Doing front right. Found out that the bleeder leaks under vacuum (from the hole, not the threads). Likely culprit? I’ll pump the breaks and see if it leaks then. Did regain a tiny bit of pressure after the rears (not enough to get by though).
Got that fixed. Lines and hoses are good. So no leaks from them. Bled everything. Seem to get a better response for my brakes. Now for a test drive. If the issue persists, would everyone else agree that its the MC? Booster is good (and so is the vacuum, id notice an idle of 2k plus haha).
Got about 70% of my brakes back. With no leaks present, I’m going to go ahead and order a MC and have it replaced by Nissan (surprisingly, my local dealer has a heck of a good price system). $97 to replace the MC and do a full flush (with fluid cost too).
Well, it was the mc. Just replacing it alone improved my brake pressure drastically, and I haven’t bled the lines yet.
If the dealer “full flush” means the entire system why would you need to bleed the system again? Anyway, I have rule of never opening a bottle of brake fluid twice. Brake fluid is very hygroscopic meaning it sucks water right out of the atmosphere. If you get it on your fingers the skin will crack. Brake systems work best with dry fluid.
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