Author Topic: Blazer brakes go to floor  (Read 6174 times)

Offline 1976blazer

  • Newbie
  • Posts: 14
  • Newbie
Blazer brakes go to floor
« on: September 24, 2018, 11:01:02 AM »
Okay new to this site and doing this but I needed some help with a brake problem I have it's a 1976 Chevy 2 wheel drive Blazer I have replaced the master cylinder the rubber lines to the calipers ,calipers and the front pads also have replaced the proportioning valve, the problem is the pedal still goes to the floor but will stop the vehicle just slowly, back brakes work front brakes work just not like they should I think there is still air in the system but I've bled it multiple times and it seems to come out with no air in the fluid. I have bled all four corners using the two-person pump the brakes a couple of times and then crack open the bleeder valve method what else could be the problem or how do I get the air out if that's really what's going on. I replace the master cylinder twice thinking the first one was bad , bench bled then both first, only to have the same problem, pedal has brakes but goes to the floor slowly like a bad master cylinder. Any help or suggestions would be great I've worked on my cars since I was 16 years old I'm now 45 I've done this lots of times and never had this problem. Thanks  :o
 Ok make sure you read all the way to the second page bottom to get the solution it will surprise you and the back brakes were never adjusted. Unlike some, it was not the problem ever but good job on trying to get me to do unnecessary work lol. Neck braking stopping power now, YA BABY!!!  Thanks again everyone for all the help.
« Last Edit: September 29, 2018, 11:03:08 PM by 1976blazer »

Offline Rapid Roy

  • Junior Member
  • ***
  • Posts: 635
  • Euless, Texas
Re: Blazer brakes go to floor
« Reply #1 on: September 24, 2018, 11:33:08 AM »
Welcome.

Have you checked the booster for vacuum leaks, and or check valve?
1974 Cheyenne 10 LWB STOCK 350 W HEI /TH350/AC/4 BBL Quadrajet
Mopar by Birth
Chevy by Choice

Offline 1976blazer

  • Newbie
  • Posts: 14
  • Newbie
Re: Blazer brakes go to floor
« Reply #2 on: September 24, 2018, 12:11:07 PM »
Vacuum booster seems to be working just fine has vacuum when the engines running and after shut off and the pedal firms up when you take all the vacuum out of the booster and the pedal goes about three-quarters or more way to the floor without the vacuum booster

Offline Irish_Alley

  • Tim
  • Global Moderator
  • Senior Member
  • *****
  • Posts: 13319
  • Family is not an important thing. It's everything.
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline JohnnyPopper

  • Senior Member
  • ****
  • Posts: 2526
  • Old Goof
Re: Blazer brakes go to floor
« Reply #4 on: September 24, 2018, 03:04:38 PM »
Have you adjusted the back brakes to take out any excess clearance?

The oil is going somewhere, could be that.

If there is still air, you would pump the brakes and the pedal would rise. Is it doing that?

And please, for us older guys, please use periods.
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline Henry

  • Frequent Member
  • **
  • Posts: 331
Re: Blazer brakes go to floor
« Reply #5 on: September 24, 2018, 03:17:10 PM »
Hi 76Blazer:
The 76 service manual says that the combo valve must be held open while bleeding...this is the little button on the end of the combo valve. You can either make a tool to hold it open or rig up some clamping tools to hold it open while you are bleeding.
Regards,
Henry

Offline 1976blazer

  • Newbie
  • Posts: 14
  • Newbie
Re: Blazer brakes go to floor
« Reply #6 on: September 24, 2018, 03:18:35 PM »
You can thank the phone I'm using for not adding punctuation I'll try to do a better job. I have not fully adjusted the back brakes, although they do lock up when I press the pedal and I'm traveling on a wet surface.
I have never had to have the back brakes fully adjusted to get the front  brakes to work on a half ton, seems like something the proportioning valve should be taken care of.
 Thanks for the help.
 To the second part of your question the pedal never pumps up it always go to the floor. That is what's baffling me and I'm not losing fluid anywhere the fluid level stays at the same height once the brake is released.
I've been trying to fix this problem going on a year now and I can't seem to find it. It's a project truck so it's when I have time to work on it.

Offline 1976blazer

  • Newbie
  • Posts: 14
  • Newbie
Re: Blazer brakes go to floor
« Reply #7 on: September 24, 2018, 03:26:50 PM »
 Ok, i did check the button on the valve before and after the bleeding and it did not moved but I will try to hold it while bleeding and see if I get any change in results. I assume you mean to hold the button in  not replace the  switch with something else while bleeding the brakes  like the instructions say for the aftermarket proportion valve. Thanks

Offline 1976blazer

  • Newbie
  • Posts: 14
  • Newbie
Re: Blazer brakes go to floor
« Reply #8 on: September 24, 2018, 10:10:59 PM »
Okay here's an update on the Blazer. I'm not sure about the proportioning valve but I did take the Rubber off the button end and have somebody step on the brakes the little Rod pokes out when you step on the brakes. The brakes still go to the floor but not quite as bad as when the vacuum booster has vacuum but they still go most of the way to the floor I would guess 90 to 95%. I was assuming that you wanted to keep the rod IN while pumping the brakes so I cut a nail and wedged it between the frame and that Rod so it could not come out. Now on second examination I'm wondering if I should have had somebody step on the brakes put a vise grip on that rod and keep it out while pumping the brakes to bleed them. I bled the whole system with no change in the brakes. The pedal still goes to the floor. I will try it the other way Tuesday. Thanks everyone for the help.

Offline VileZambonie

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 18980
Re: Blazer brakes go to floor
« Reply #9 on: September 25, 2018, 04:37:15 AM »
Did you check the rear brakes? Are the drums true and shoes properly installed and adjusted?
,                           ___ 
                         /  _ _ _\_
              ⌠¯¯¯¯¯'   [☼===☼]
              `()_);-;()_)--o--)_)

74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline Henry

  • Frequent Member
  • **
  • Posts: 331
Re: Blazer brakes go to floor
« Reply #10 on: September 25, 2018, 12:11:53 PM »
Hi 76Blazer:
Combo valve: on the factory combo valve you should hold the button in while bleeding. If you have an aftermarket combo valve, what do the instructions with this valve tell you to do while bleeding?

On the factory combo valve, pushing the button in overrides the metering function of the valve which insures that full flow of brake fluid goes to the front and rear brakes simultaneously. Not pressing the button allows the metering function to work which closes off the front brakes from the master cylinder until a certain pressure is arrived at. So this could cause a problem while trying to bleed.

Regards,
Henry

Offline 1976blazer

  • Newbie
  • Posts: 14
  • Newbie
Re: Blazer brakes go to floor
« Reply #11 on: September 25, 2018, 03:44:55 PM »
Thanks Henry
It is a factory proportioning valve. And I did hold it in using a nail wedged against the frame into that hole to hold the rod from coming back out when the person pumping the brakes pushed on the pedal. After all that and bleeding everything I did get a little bit more air out of the rear, but still the brakes go to the floor kind of like you're pushing fluid not just falling completely to the floor right away but there is no pressure building up in the system no matter how many times you pump it. I get plenty of fluid out of the bleeder valves at the wheel. The person pumping the pedal told me when it got to the floor but it didn't always go to the floor or barely even moved, though I was getting fluid out of the bleeder valve in the front.
 makes me think that rubber line that goes to the back brakes may be expanding inside somehow and absorbing some of the pressure and throwing off the system but does not explain why the pedal still goes to the floor and can't build any pressure. Thanks again for all the helpful advice ,the more things I try and the more things I do I will let you guys know.

Offline VileZambonie

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 18980
Re: Blazer brakes go to floor
« Reply #12 on: September 25, 2018, 05:41:38 PM »
Did you check the rear brakes? if not you can bleed it for the rest of your life. Pedal travel is impacted by the brake shoe adjustment. Seems like you continue to ignore this advice which is step 1!
,                           ___ 
                         /  _ _ _\_
              ⌠¯¯¯¯¯'   [☼===☼]
              `()_);-;()_)--o--)_)

74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline bd

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 6438
Re: Blazer brakes go to floor
« Reply #13 on: September 25, 2018, 05:55:35 PM »
Did you check the rear brakes? if not you can bleed it for the rest of your life. Pedal travel is impacted by the brake shoe adjustment. Seems like you continue to ignore this advice which is step 1!

OP, it will behoove you to heed this man's advice ^^^^ and diagnose the issue in the proper order!  You won't find anyone more knowledgeable on these trucks.
« Last Edit: September 25, 2018, 05:58:40 PM by bd »
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline 1976blazer

  • Newbie
  • Posts: 14
  • Newbie
Re: Blazer brakes go to floor
« Reply #14 on: September 25, 2018, 09:23:14 PM »
 thanks but the back brakes work just fine that's mostly what stops the truck if they're that far out of adjustment would that fix the front brakes, so the breaks wood we applied pressure and then I would crack up in the bleeder and sometimes the pedal go to the floor other times cuddled wouldn't move yet I would still get pressure out of the caliper what would be the problem with that? that's something new?