brake help 88 p/u
#1
brake help 88 p/u
brakes went out do to loss of fluid the other night added fluid bleed the breaks, they only work when you pump them 3 or so times then they work awesome. replaced the master cylinder and the problem wasnt fixed. brought it to les schwab for a break test they told me at first i didnt bleed them right. so they ran about a gallon of fluid through and said the master was bad... i really dont think thats the problem so i went to orileys where i bought the cylidner and they said they would replace it but they dont think thats the problem. any ideas? im stumped
#5
i found a leak where the master cylinder meets the brake booster.. could this allow air to enter and not probably bleed them? even when i replaced my master cylinder the problem stayed the same. which makes me believe it is not the master cylinder and possibly the brake booster.
#6
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When you replaced the m/c, did you bench bleed it? Did you see the leak on the outside at the joint btwn the m/c and booster or did you see the leak only after separating the m/c from the booster? Is there brake fluid in the booster?
The booster itself cannot cause a fluid leak. Its the seal around the primary piston in the m/c that would result in fluid in that area - reman'd m/c I am guessing. As much of a PITA as it is, I would exchange the m/c with another one if you have brake fluid exposed around the mounting flange area.
Does the pedal slowly go to the floor when you hold the brakes at constant pressure (engine on)?
The booster itself cannot cause a fluid leak. Its the seal around the primary piston in the m/c that would result in fluid in that area - reman'd m/c I am guessing. As much of a PITA as it is, I would exchange the m/c with another one if you have brake fluid exposed around the mounting flange area.
Does the pedal slowly go to the floor when you hold the brakes at constant pressure (engine on)?
#7
When you replaced the m/c, did you bench bleed it? Did you see the leak on the outside at the joint btwn the m/c and booster or did you see the leak only after separating the m/c from the booster? Is there brake fluid in the booster?
The booster itself cannot cause a fluid leak. Its the seal around the primary piston in the m/c that would result in fluid in that area - reman'd m/c I am guessing. As much of a PITA as it is, I would exchange the m/c with another one if you have brake fluid exposed around the mounting flange area.
Does the pedal slowly go to the floor when you hold the brakes at constant pressure (engine on)?
The booster itself cannot cause a fluid leak. Its the seal around the primary piston in the m/c that would result in fluid in that area - reman'd m/c I am guessing. As much of a PITA as it is, I would exchange the m/c with another one if you have brake fluid exposed around the mounting flange area.
Does the pedal slowly go to the floor when you hold the brakes at constant pressure (engine on)?
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#8
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Don't forget to check the Load Sensing Proportioning Valve. It is on the passenger side above the axle on the frame. My '88 had no brakes and I changed the m/c and nothing happened. I then noticed the ball of rust above the rear axle.
Although the LSPV may have something to do with it, I would go ahead and bench bleed first. LSPV's are very hard to find. Only place I found mine was from a junk yard in Wisconsin. good luck
Although the LSPV may have something to do with it, I would go ahead and bench bleed first. LSPV's are very hard to find. Only place I found mine was from a junk yard in Wisconsin. good luck
Last edited by bassbro1; 11-21-2011 at 08:32 PM.
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Good luck.
Last edited by angrybob; 11-22-2011 at 02:49 PM.
#10
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I just had the most frustrating brake experience ever and it kind of sounds along the same line as yours.
Last week my pedal got really soft and would only work after I pumped it a few times. This past August, I redid the entire front (wheel bearings, seals, pads rotors etc.), but never touched the back. So my first check was the back breaks and found my right wheel cylinder leaking very slowly. So I replaced both sides and put new shoes on. Still had a soft pedal. I did not suspect the MC because if I pumped the breaks, the pedal would hold steady. So I just kept bleeding and bleeding and it got me nowhere.
In frustration, I got a new OEM MC and put it on and bled the brakes. Well my soft pedal went away and the brakes work fantastic now. I took apart the MC to see what was up and I could not see any apparent failures in the seals. I can only guess it was leaking internally somewhere. I have no idea what went out, but it was a bad MC.
I bench bled the MC just by plugging up the outlet holes with my fingers. When the pedal was depressed, I let the air escape past my fingers. When the pedal was released, I plugged the holes so no air went back in. I did this about 5 times before I got pure fluid out of the MC.
Hope this helps...Breaks are one system that I would not hesitate to replace parts until it’s fixed. Just for the principle of safety alone.
Last week my pedal got really soft and would only work after I pumped it a few times. This past August, I redid the entire front (wheel bearings, seals, pads rotors etc.), but never touched the back. So my first check was the back breaks and found my right wheel cylinder leaking very slowly. So I replaced both sides and put new shoes on. Still had a soft pedal. I did not suspect the MC because if I pumped the breaks, the pedal would hold steady. So I just kept bleeding and bleeding and it got me nowhere.
In frustration, I got a new OEM MC and put it on and bled the brakes. Well my soft pedal went away and the brakes work fantastic now. I took apart the MC to see what was up and I could not see any apparent failures in the seals. I can only guess it was leaking internally somewhere. I have no idea what went out, but it was a bad MC.
I bench bled the MC just by plugging up the outlet holes with my fingers. When the pedal was depressed, I let the air escape past my fingers. When the pedal was released, I plugged the holes so no air went back in. I did this about 5 times before I got pure fluid out of the MC.
Hope this helps...Breaks are one system that I would not hesitate to replace parts until it’s fixed. Just for the principle of safety alone.
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make sure the rear brakes are adjusted first. then bleed the m/c followed by left rear, right rear, left front, right front then the LSPV. you'll probably go through 1-2 quarts of brake fluid.
#13
turns out it was the wheel cylinder. the leak most have been small at first because i saw no fluid. but i got home last night from work i pulled it into the garage and noticed my rear driver side tire was covered in fluid. so i getting my rebuild kit today and hopefully this will solve my problem
#14
okayy im really stumped now! the wheel cylinder did not fix it so i put on another m/c bleed it . and it still feels the same.... could my calipers be letting air in. they are not leaking and my brakes work great when i pump them . this could be a job for a professional
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bleed everything again, and this time, include the LSPV. Be sure to bleed the line in the LSPV that comes from from the front brakes. Basically, every connected joint in the brake lines will need to be cracked open during the bleeding of the entire system, and eventually, you will be able to work out the air.
Read this entire post for more information:
https://www.yotatech.com/forums/f120...eeding-244093/
Read this entire post for more information:
https://www.yotatech.com/forums/f120...eeding-244093/