Wierd brake feel....

[BigRigTech]

Ever since I changed out my pedal assembly (5spd swap) my brakes have felt wierd, like there is no vacuum at idle. I reused the pushrod that was in it with the auto pedals. What does that vacuum switch do that's on the brake pedal??? Going through traffic it feels fine, but creeping in traffic the pedal feels hard. I can hear air leaking from that switch until I push the pedal down and it stops touching it. I haven't driven it for a month but I can tell something is not quite right. I have good vacuum, my heater doors work fine.

 

[82F100SWB]

That vacuum switch is the cruise dump valve, I don't have mine hooked up, so I can't remember how it's supposed to work...

 

[BigRigTech]

I think I either have a vacuum leak or my pump is going T.U as my brake light started to come on and my fluid level hasn't gone down....I think I hear a vacuum leak or ticking sound near my V.P. too. How much vacuum does this pump pull down too? I want to install my gauge and check it out. I have a spare pump here with a dented diaphram cover but it will work until I can find a new one cheap.

 

[snatchal]

I started having the same problem as you a couple days ago. Brake light comes on and pedal is really hard to push. The weird thing is that the symptoms come and go. Put a new master cylinder and reservoir on today and also bled a lot of air out of the lines. Still have the same problem. Tomorrow I am going to replace the booster.

 

[BigRigTech]

I tested my vacuum pump, I'm seeing about 8" of vacuum at 1500-2000rpm, about 3" at idle (675rpm).....I think my cruise switch was not in far enough and it was letting the vacuum bleed off?? I shoved it in farther and now the brakes feel normal again.....And the light is staying off....I guess I'll find out where I'm at in the morning when I drive it to work. I took the belt off and the pump feels as strong as my spare 1987 6.9L pump. I threw the spare pump in the truck just in case.......The spare has a dent in the diaphram housing so I don't know how long it would last.

 

[towcat]

big rig tech-
go hydro and don't look back
check out "full monte"'s writeup in "tech articles".

 

[82F100SWB]

Your pump sounds like it's toast... I had to put a new on one my truck a couple years back, it pulled 30 at 1500 rpm when new...

As for hydro boost, it does work great for pedal feel, but, trying to steer at a dead stop with your foot on the brake = no power steering... That is VERY annoying off pavement.

 

[BigRigTech]

I'm hearing the dreaded "phhhtt phhhtt phhhtt phhhtt" sound from the pump when the engine is running....And the pedal is not very consistant.....Time for a new pump I guess. Hydro boost, Haven't I made enough changes to my truck for now....

 

[BigRigTech]

I put my spare pump on - same thing. 3" at idle and 8" of vacuum at 1500rpm....I ordered a new pump ($200 taxes/core in) and I'm going to take the brake booster off my 96 F350 parts rig just incase the new pump doesn't cure it. My pedal is soft as I decelerate but hard and slow to apply when I'm poking along in traffic.....Hard to drive this way as I have to drive right through the city to go to work.

 

[Full Monte]

Your pump sounds like it's toast... I had to put a new on one my truck a couple years back, it pulled 30 at 1500 rpm when new...

As for hydro boost, it does work great for pedal feel, but, trying to steer at a dead stop with your foot on the brake = no power steering... That is VERY annoying off pavement.

I haven't noticed this problem with my hydroboost setup.

 

[BigRigTech]

I don't have time right now to go looking for a hydro boost setup, SD's are not that plentiful around here.

 

[snatchal]

Yesterday I tried a new booster and it only made braking worse. Ended up putting old booster back on and replacing the vacuum pump. That solved all my problems. The old pump made less vacuum as the RPMs got higher.

 

[BigRigTech]

My pump is supposed to be here tommorow, I hope it comes in ....My brakes are the *****.....

 

[DieselChemist]

Big Rig, when the pedal was becoming stiff would you have very little brakes or would they grab and lock up the rear wheels. I've been having a problem my pedal being stiff at times and locking up the rear brakes but only intermittently, also the brake light goes on and off when I am sitting at a light again intermittently.

 

[BigRigTech]

Exactly as you described, the new pump didn't do **** for my problem either. The friggin booster is bad, I pinched off the hose to it and my vacuum shot to 25" from 3" at idle.....Hopefully my spare F350 booster is good.....I guess I should have tested it first, it would have saved me $200.