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No pressure when bleeding front brakes


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TomM65
New User

Apr 8, 2017, 9:17 AM

Post #1 of 5 (213 views)
No pressure when bleeding front brakes Sign In

1986 chevy suburban 2wd 3/4 ton , petal goes to the floor and I have little or no brakes, tried to bleed the brakes and when I release the bleeder valve there is no pressure the brake fluid just trickles out. My first thought is master cylinder. However I don't want to replace it if it could be something else. Thank you


kev2
Veteran
kev2 profile image

Apr 8, 2017, 10:20 AM

Post #2 of 5 (202 views)
Re: No pressure when bleeding front brakes Sign In

helper presses brake pedal and no fluid from front caliper.
Check combination valve - is front pin extended? valve may need to be reset esp on an old system.


Tom Greenleaf
Ultimate Carjunky / Moderator
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Apr 8, 2017, 10:29 AM

Post #3 of 5 (201 views)
Re: No pressure when bleeding front brakes Sign In

1986: It's not full of trickery for brakes just older now for several items to be on third rounds.
Doesn't really matter but did this just come on quickly or and changeable pedal now and then before. It is a sign no matter what of a bad master which shouldn't be very expensive and is pretty common. Even if not first that the pedal going to floor on an old master wrecks the master with the crust of the bore frequently there with age and hasn't passed by that part of the bore for years and years so kills the master.


Bleeders: Take them out if calipers are OK otherwise and know they are clear. Takes two proper drill bits to clean one out so it works properly or cheap new. They plug up and wasn't the reason just in the way of bleeding if not right.
Was it very low on brake fluid in the larger reservoir of the two at master? When checked last or you don't know? This could easily blow out brake lines possible you didn't see the mess as it's water soluble and washes away even in rainy driving but fluid would be super low or gone.


Don't trust it like this: The idea of two reservoirs was so you have some braking if one end fails doesn't work well. You have almost nothing as you notice.


IMO - a new master isn't a waste on this at the age and could fail if it's another area leaking to finish off the bleeding. Be warned and check the rear bleeders work now as new master really means whole vehicle bleeding and should anyway periodically but even I don't for my own!


T



(This post was edited by Tom Greenleaf on Apr 8, 2017, 10:29 AM)


TomM65
New User

Apr 8, 2017, 11:18 AM

Post #4 of 5 (189 views)
Re: No pressure when bleeding front brakes Sign In

Problem started and got worse very quickly, front Reservoir was low but not empty, filled the reservoir and then tried to bleed the brakes and fluid flows out very slowly. Same thing on both sides of vehicle


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Apr 8, 2017, 1:04 PM

Post #5 of 5 (175 views)
Re: No pressure when bleeding front brakes Sign In

Kev2's post showed before mine just saw that now. Combination valve IMO (we each have different experiences) probably isn't the problem now you already mentioned low fluid.


Know some stuff: Master cylinder can be low but has a rubber cap that is supposed to follow lowering fluid level which is normal for wearing front brakes or disc brakes when all 4 - not this vehicle.


If that isn't good the fluid sloshes and you pump air in just being low plus brake fluid absorbs moisture out of the air and wrecks it. Parts corrode and fail just what you have going on.


Know what combination valve is: It both distributes pressure to front and rear in proportion and most are the source to turn on a red brake warning light if off center which low fluid would do or a failure. They do stick to one end or the other sometimes. To fix that get what pressure you can and bleed off rear brakes even right at the master cylinder should do to center it. It normally self centers but might not and no fluid out the failed end by design.


Do you normally check and work on your own brakes? If this is unfamiliar to you to check and do first time only by yourself I don't suggest it. I strongly think now you need front brakes - whatever they need AND the master cylinder failed. Specific bench bleeding for those is a must and do it right.


Point now is are you confident and have tools to do this stuff? Easy for me to say they are not hard but still need to know exactly what you are doing and some tools to do it right. BTW - Front brakes on this require knowing how to deal with greasable separate bearing and set those right. Wrong is a disaster! Qualified help - no guessing with brakes,


T







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