Still need some brake help....slow pedal return.

[Dr. Marneaus]

Okay!

First off, a good note:





First time it's been in the light of day in almost 2 months. Did the axle swap on May 12th.

That being said, she's runnin' like a champ, as always.

So, no the not so good, brakes are still messed up. 2 issues that may be separate may be related.

1. Pedal is soft when the truck is running. Still goes mostly to the floor.

2. Pedal is SUPER SLOW on the RETURN.

Now, In my mind, the pedal may7 be slow to return simply because it's moving so far.

I assume I just need to give it another bleeding, and make sure all is good. I bench bled the master while on the vehicle, using a bench bleeding Kit (the little rubber hoses) until no bubbles showed. I then bled everything 1 wheel at a time, starting at the furthers. Had my girl slowly pump the brakes, hold the pedal, I opened the valve, closed it, repeated 3 or 5 times per wheel. However it seems entirely possible i may not have done enough.

So. I've also been searching and i've read that its possible the booster can not be right, and can be fighting vacuum on the return stroke if the pedal check valves or something arent working.

It the truck is off, pedal returns with normal speed. Regardless of how far its pressed (it doesnt press all the way to the floor).

With the truck running, it presses to the floor (obviously because of the boost), and takes a few seconds to return. I've never driven a vehicle that acts like this. basically as seen below icannot "pump" the brakes because its too slow to return.



If i disconnect the vacuum line while running, it returns like normal.

What could this be and what shall I do? I figure step one is making sure they are bled properly?

[babywag]

Sounds like a bad booster, especially if disconnecting the vacuum line makes pedal rise normally.

Mushy pedal = air in system still.
Long pedal travel = rear brakes need adjustment.

Hang in there you're almost done.

[Carnuck]

Could be bad booster if used. Brake fluid leaks out of the back of the master and swells the seals and valves in the booster. If they weren't together before, the pin between the booster and master may be adjusted out too far. That will keep the plunger partially engaged and block the ports in the master so it won't return correctly. Ditto if the arm from the pedal is pushing slightly on the booster rod. Sounds more like booster or clogged vacuum hose. Vacuum ball reservoir for the cruise isn't hooked to a tee (or anything else for that matter) on the booster?

[Ristow]

a few times each wheel won't do it. let it gravity bleed a while at each corner. pop the top off the MC and let a good 1/4-1/2 of the chamber go thru each bleeder. then see where you are.

may need to bench bleed the MC,or get it level to tipped down via jack the car up in the rear.

[budryzer]

I'm going with booster issues. Disconnecting the vacuum source sold it for me. Make sure it is not spliced into the pcv. It needs it's own source and ensure there are no leaks.

[itselliot]

My question would be ,"what did you change since the brakes last worked properly"? And Definately air in the system as already stated 3-5 times per wheel is not enough. Next , the statement about "pumping the brakes" ........NO........Apply pressure and hold pressure .........as you open the bleeder do NOT lift off the pedal until you close the bleeder. I have a feeling that you sucked air back into the master. ANY , even tiny, bubbles in there, is air in the master and or the system.

Now, one more Idea/ Question..........it IS entirely possible to install the front calipers upside down (on the opposite sides) with the bleeder on top. If so , the air will NEVER get out. I won't get into the details of how I know.

[addicted]

My question would be ,"what did you change since the brakes last worked properly"? And Definately air in the system as already stated 3-5 times per wheel is not enough. Next , the statement about "pumping the brakes" ........NO........Apply pressure and hold pressure .........as you open the bleeder do NOT lift off the pedal until you close the bleeder. I have a feeling that you sucked air back into the master. ANY , even tiny, bubbles in there, is air in the master and or the system.

Now, one more Idea/ Question..........it IS entirely possible to install the front calipers upside down (on the opposite sides) with the bleeder on top. If so , the air will NEVER get out. I won't get into the details of how I know.

He upgraded from drum to disc using the axles and brake parts from/for a late 70's Wagoneer. So he has had the whole system opened up.

[Ristow]

it could certainly be a bad part,be it MC or booster. however,bleeding is easy and by far the cheapest. 3-5 bleeder cracks per wheel is not enough. the pedal is going to the floor,so you obviously have air in the system,which means little pressure build,which affects how the pedal returns.

the pedal goes lower with the engine running to due booster helping compress all the air inline.

so bleeding is where to start. then start looking at hard parts.

[Dr. Marneaus]

Haha yes. I changed literally everything in the brake system. Literally every single part with the exception of 2 lines is new.

The booster is brand new from a 77 j20 and the master cylinder came attached to it. Pulled the MC and it hasn't leaked inside the booster or anything

I will pick up a vacuum pump and vacuum bleed them tonight seeing as I don't have a helper. Ill run a ton of fluid through and see where that gets me.

Are the bleeder screws on the front calipers supposed to face up?

[Ristow]

yup.

[joe]

I will pick up a vacuum pump and vacuum bleed them tonight seeing as I don't have a helper. Ill run a ton of fluid through and see where that gets me.

Though a vac pump is a handy tool to have on hand. For cars/trucks with long line runs I like to reverse pressure bleed the brakes and work the fluid from the nipple up to the MC. Google "DIY pressure brake bleeder". Lots of sites list every thing you need from a hdw store to make a hand pump garden sprayer into a pressure bleeder. I like the 1/2 gal size sprayers. Even at my local expense small town hdw store you can get everything you need less than $50 including a cheap pressure gauge ($6?). Prolly knock that down to $30 if you have a Lowe's etc close by. Pick up a turkey baster while you're there cause you'll need something to suck fluid from the MC during the process. A stash of clean cotton rags works but a baster is neater.

[Billygoat]

For a fresh system I use a speed bleeder screwed into a hose and the hose clamped on the caliper bleeder (cracked open) - I am just to cheap to buy 4 speed bleeders for every truck I work on.

Then hose from speed bleeder to clean catch jar and I run about half the mc res thru, refill and run half again on each wheel. If the fluid is clean I will resue (generally frowned upon).

With 2 speed bleeders, I have had good luck doing the long runs and short runs on each axle together - only benifit to this is you can leave the cap of the mc and not spray fluid all over, but I will follow that up with 5-7 pumps on each wheel with the bleeder just cracked enough that you have to bear down on the pedal to push the fluid out (similar effect to pumping up and cracking, I never have a helper so I figure out how to get it done by myself). I have used a couple chepo 1 person vacuum bleeders, they just broke and did not work...a quality one would probably work, but again I am cheap, my 2 pack of speed bleeders have done me a solid several times.

The booster does sound suspect, but verify the air is out first.

[FSJunkie]

Check out these little things called "Speed Bleeders". They replace the bleeder screws in your wheel cylinders or calipers and all you have to do to bleed your brakes is open them 1/4 turn, pump the pedal slowly a few times, and close the valve again.

I love them. Most NAPA's can special order them. Stay away from the el-cheapos that don't work.

[itselliot]

Haha yes. I changed literally everything in the brake system. Literally every single part with the exception of 2 lines is new.

The booster is brand new from a 77 j20 and the master cylinder came attached to it. Pulled the MC and it hasn't leaked inside the booster or anything

I will pick up a vacuum pump and vacuum bleed them tonight seeing as I don't have a helper. Ill run a ton of fluid through and see where that gets me.

Are the bleeder screws on the front calipers supposed to face up?

Doh! I really mis spoke.....yea on top not on the bottom.

[Dr. Marneaus]

Cool. I installed the bleed screws facing up.good good.

I shall bleed my heart out this evening...well...you know what I mean haha