Soft brake pedal fix

10925 Views 23 Replies 16 Participants Last post by Worn Out F150, Jan 15, 2010

kf4amu

Discussion Starter · Oct 13, 2009

Been chasing a soft pedal ever since my disk brake swap. F-350 booster/MC swap, made it worse. Bled gallons of fluid through it...no change. Swapped to stainless steel flexlines, no change. Had Dave'sBronc90 touch it...didn't help.

I built a panel for my center console with 2 line locks, a bias controller and pressure gauges for my brake system, but was loathe to install it and add complexity to a brake system that was not working properly. So 300 dollars worth of parts has been sitting for months...

until yesterday...

On Dave's advice I decided to adjust the pushrod that engages the master cylinder. I had never messed with it since my 1 ton swap. I unbolted the MC from the booster, and lengthened the rod about 4 turns, which equaled about 1/8th of an inch. I reinstalled the MC and pushed the brake pedal with my hand and could immediately tell a difference. Cranked it up and with the first pedal application, I could tell it was cured. Took it for a couple hard stops and it locked up all the wheels (36inch Hummer tires on 16.5 inch steel Hummer rims...heavy beasts) no problem. Now I have a nice firm pedal, and it was all as a result of me lengthening the pushrod a few turns.

Just thought I'd post that tidbit up here. It's been very frustrating knowing I had a kickass brake system but it wasn't performing correctly. Now I can hook up my brake controller without worrying about a problem elsewhere in the system.

1 - 20 of 24 Posts

waltman

· #2 · Oct 13, 2009

So you are giving a heads up to say that your problem was solved by lengthening the actuating rod? Cool.
I will file that away in my need to know one day folder of my mind...only problem is I have a weird way to file stuff and sometimes miss file important tidbits of info. One day I may try the dewy decimal system.

kf4amu

Discussion Starter · #3 · Oct 13, 2009

waltman said:
So you are giving a heads up to say that your problem was solved by lengthening the actuating rod? Cool.
I will file that away in my need to know one day folder of my mind...only problem is I have a weird way to file stuff and sometimes miss file important tidbits of info. One day I may try the dewy decimal system.

Yea it was simple and quick. About 3 minutes. I edited my post to be a little more direct about what the fix entailed.

Mr. Death

· #4 · Oct 13, 2009

Thanks for posting this. I've been having the same problem as of late so I'll have to try this out tomorrow.

Dave's Bronc 90

· #5 · Oct 13, 2009

Like Will said, this adjustment can make an amazing difference. You want to adjust the rod out long enough that it just touches the master cylinder piston without actually pushing it in at all. Just a little short won't cause a problem, but just a little long will hold the brakes to be partially set all the time, so take your time and be careful with the adjustment. In Will's case it made his brakes go from disturbingly soft to very tight, pretty much because he was never able to fully apply the brakes with the rod as far out of adjustment as it was. Before his pedal would go half way through it's full travel before it engaged the brakes at all, and now he can make you kiss the windshield if he feels like it.:thumbup

MajSuckelton

· #6 · Oct 13, 2009

The simple method is to adjust the pushrod out about 1/2 turn at a time until the m/c will no longer fit flush on the booster without forcing it and then back it off a 1/2 turn. They are supposed to ship pre-adjusted when you buy a new booster though.

Dave's Bronc 90

· #7 · Oct 13, 2009

I can't argue with how they are supposed to be shipped because I really don't know, but I can tell you that mine needed adjustment right out of the box.

XDAILY

· #8 · Oct 13, 2009

Interesting. Thanks.

locopny

· #9 · Oct 13, 2009

I may check that on mine. it stops good...but if I can make it stop GREAT...I'm all for it.

thanks for the tip.

A1Fiddler

· #10 · Oct 13, 2009

So THAT'S what happened when I swapped booster/MC. Thanks! Will check that out when it stops raining.

wv85bronco

· #11 · Oct 14, 2009

good info thanks ...

i can lock up all four so i'm not gonna mess with mine ...

but i've always thought the brakes were a little soft ...

78'460

· #12 · Oct 14, 2009

I can just break free 32's in gravel.. Im going to adjust mine in the next hour. I also got a super squishy break peddle and brakes have been bled

kf4amu

Discussion Starter · #13 · Oct 14, 2009

wv85bronco said:
good info thanks ...

i can lock up all four so i'm not gonna mess with mine ...

but i've always thought the brakes were a little soft ...

For me it wasn't so much a lack of braking availability, but the slight delay in brake application, and the extra pedal travel made panic stopping quite disconcerting. I could still lock up all 4 tires but it wasn't very precise.

Has anybody adjusted their pushrod yet? I'm wondering how many people need or don't need this.

reptillikus

· #14 · Oct 15, 2009

Ive done this before. Im on my second one-ton booster in my truck (first got water in the back & effed it up), and this one needed to have the pushrod extended 2½ turns to get it right. I can just about lock up my 42s, which is pretty good if ya ask me.

The boosters are 'supposed' to be set right when they boxed up, but usually they tell you (in the instructions) to check them to make sure.

A1Fiddler

· #15 · Oct 15, 2009

kf4amu said:
For me it wasn't so much a lack of braking availability, but the slight delay in brake application, and the extra pedal travel made panic stopping quite disconcerting. I could still lock up all 4 tires but it wasn't very precise.

Has anybody adjusted their pushrod yet? I'm wondering how many people need or don't need this.

I did today. Worked great!

locopny

· #16 · Oct 15, 2009

kf4amu said:
Has anybody adjusted their pushrod yet? I'm wondering how many people need or don't need this.

had planned to do it today.
Hadn't planned on 2" of 'wet' snow.
it'll wait. :thumbup

Drilim

· #17 · Oct 16, 2009

kf4amu said:
On Dave's advice I decided to adjust the pushrod that engages the master cylinder. I had never messed with it since my 1 ton swap. I unbolted the MC from the booster, and lengthened the rod about 4 turns, which equaled about 1/8th of an inch. I reinstalled the MC and pushed the brake pedal with my hand and could immediately tell a difference. Cranked it up and with the first pedal application, I could tell it was cured. Took it for a couple hard stops and it locked up all the wheels (36inch Hummer tires on 16.5 inch steel Hummer rims...heavy beasts) no problem. Now I have a nice firm pedal, and it was all as a result of me lengthening the pushrod a few turns.

What does this mean? I did the booster swap, and out of the box, i had brake drag. Whats the easiest way to check how and when the pushrod is touching the MC? right now my pedal sucks.

So irritating.

Dave's Bronc 90

· #18 · Oct 16, 2009

The way to check it is really easy- when you put the master cylinder back on if it touches the rod before it seats on the front of the booster it's too long, which sounds like the problem in your case. Shorten that rod up just a little and it should be good.

MajSuckelton

· #19 · Oct 16, 2009

Drilim said:
What does this mean? I did the booster swap, and out of the box, i had brake drag. Whats the easiest way to check how and when the pushrod is touching the MC? right now my pedal sucks.

So irritating.

Read much? Check post # 6.

Andy351

· #20 · Oct 17, 2009

tweaked mine today, brake drag gone. i just put a new booster on the other week and didn't even think to do it then lol

1 - 20 of 24 Posts

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