Hydro boost - rock hard brake pedal (1 Viewer)

[Madcrix12]

i need some help pls

i fitting a 2017 f250 sd hydro unit with MC to my 80. i made over lines from pump to run directly to hydro unit and then output of hydro unit goes to steering box ( top bolt) and low pressure of hydro and steering box (bolt to the side of the box) both T up and return to reservoir.

initially i started engine and kept pouring fluid in and kept turning steering wheel. it was HARd when i mashed brakes and the brake pedal rock hard. steering wheel kept pulsing when mashed brakes. figured i had line mixed up on hyro unit and swapped them. steering is super soft now. however brakes are ROCK hard. i equate it to the old vacuum system with engine off and trying to stop the vehicle.


what do i do? the power steering reservoir squirts fluid out every time i mash brakes. do i have air? is it a bad hyro unit? i have no air in brake lines and did not install a proportion valve. is the rod where the pedal hooks up too long? too short? i cut and welded my oem end onto the ford rod.

 

[use2bn83]

I’m not super familiar with Fords hydroboost systems.

If it were a GM product I’d be doing an accumulator test. If the accumulator fails it can cause the symptoms you’re describing.

Are you using the OE PS pump? It’s probably a bit small for this application. But before you condemn that, verify that the accumulator is working as intended.

Also, you may want to increase the size of the fluid reservoir and add in an additional cooler.

It’s also worth looking into making sure that the new MC has the same bore diameter as the old one or is matched properly to the calipers.

 

[Madcrix12]

i noticed that my output line of the hydro boost is 3 times the size of the factory ford lines. it may be that the output line is too large and not enough pressure is being built up in the hydro system.

 

[Madcrix12]

does the bore matter if i am using a complete unit from the FORD? mc and hydro came as one unit from breaker yard.

 

[Spaggyroe]

Do the brakes operate when you hit the pedal? If so, do they act like more of an on/off switch than a gradual increase in braking force?

I'm wondering if you have a master cylinder size mismatch. The SD master cylinder bore is MUCH larger than the Toyota master cylinder.
(I put a super duty hydroboost unit in my early bronco, but adapted it to a wilwood master cylinder with 1" bore as the huge piston diameter of the super duty master cylinder didn't make sense for my application).

 

[Madcrix12]

they operate to slow the vehicle down but i cannot do an emergency stop. i cant press more than an inch and a half

at a stop if i press the brake and accelerator the van stays put so the brakes are semi working

 

[Spaggyroe]

they operate to slow the vehicle down but i cannot do an emergency stop. i cant press more than an inch and a half

at a stop if i press the brake and accelerator the van stays put so the brakes are semi working

I think you have a master cylinder size mismatch then.
The master cylinder bore size has a significant impact.

Larger bore = higher volume of brake fluid per given pedal travel, lower line pressure.

Smaller bore = less fluid displaced per given pedal travel. higher line pressure. (A.K.A., you'll have more pedal travel, but will gain line pressure and therefore clamping pressure at the calipers)

 

[Madcrix12]

funny thing is the unit was a direct rip out of the ford doner so teh mc and hydro unit came as one

 

[PIP]

funny thing is the unit was a direct rip out of the ford doner so teh mc and hydro unit came as one

Yes, but MC must match the vehicle brake system, not the hydroboost.

 

[Madcrix12]

where to go to get the right MC?

 

[Spaggyroe]

where to go to get the right MC?

You'll need to determine what size is right for you. I would start by measuring the size of a stock toyota one. That way you'll have an idea of where to start.

The hydraboost I used in my Bronco came from a 2005-2010, so I can't verify if a wilwood matches the bolt spread of your 2017 unit. Be aware that I had to make a custom insert (often called a bullet) to go in my wilwood master cylinder to accomodate the length of the hydraboost push rod.

Maybe you could even adapt the toyota master cylinder somehow.

 

[Madcrix12]

ok tks

 

[Spaggyroe]

I found my notes. This is the one I used on my Bronco. I have no idea if this is correct for your Cruiser though. Wilwood Disc Brakes 261-13270-BK Wilwood Aluminum Tandem Master Cylinders | Summit Racing - https://www.summitracing.com/parts/wil-261-13270-bk

Wilwood makes them in a variety of bore sizes

 

[Azca]

Baer breaks is where I bought my unit. The truck is not yet operational but getting close. Their site; Baer Inc. - High Performance Brake Systems, Rotor Upgrades, and Aftermarket Automotive Components - https://baer.com/

Sweeting is where I purchased my hydro boost and may also give you a few clews: Hydro-Boost System for 1969-1997 Toyota Land Cruiser 1996-1997 Lexus LX450 - https://www.powerbrakeservice.net/93tolacrhyco.html

Finally, this mud thread may help: Hydro boost brake conversion - https://forum.ih8mud.com/threads/hydro-boost-brake-conversion.1191277/

 

[baldilocks]

they operate to slow the vehicle down but i cannot do an emergency stop. i cant press more than an inch and a half

at a stop if i press the brake and accelerator the van stays put so the brakes are semi working

I explained this to you yesterday in the Hydro Booster thread. Your MC bore is too big for your calipers. Its large diameter moves much more fluid per every centimeter of brake pedal movement. It’s filling your calipers almost instantly and creating the hard pedal feel. The brakes feel weak because the PSI of brake line pressure is now reduced due to the oversized MC bore. The factory MC has a 1 inch bore. That SD MC probably has 1 1/4” bore or even larger. This is basic hydraulics.

I suspect the hydro booster has an internal defect based on the fact fluid shoots up out of the reservoir from the return circuit. I understand the desire to convert to a hydro booster but not with garbage parts.

 

[baldilocks]

Baer breaks is where I bought my unit. The truck is not yet operational but getting close. Their site; Baer Inc. - High Performance Brake Systems, Rotor Upgrades, and Aftermarket Automotive Components - https://baer.com/

Sweeting is where I purchased my hydro boost and may also give you a few clews: Hydro-Boost System for 1969-1997 Toyota Land Cruiser 1996-1997 Lexus LX450 - https://www.powerbrakeservice.net/93tolacrhyco.html

Finally, this mud thread may help: Hydro boost brake conversion - https://forum.ih8mud.com/threads/hydro-boost-brake-conversion.1191277/

I traded posts with this poster on my hydro boost thread over the past two days. I guess I didn’t state the answer this individual wanted to see over there.
I’d like to add to your list of sources. These folks set me up with my conversion back in 2012. I’d go with them if I ever do a third conversion.

Hydroboost Brakes in Downey, CA - Hydro Boosters

Vanco Power Brake Supply is your premier seller of hydroboost brakes and other power brake solutions for cars in Downey, CA. Order your hydro boosters now!

canrockcrawl.com

 

[jjdeneen918]

I converted to hydro boost a few years ago after reading this thread & vacuum booster failed.

I do believe the brakes have improved, but at the same time I feel “meh” with the results.

I went with the same booster in the original post, Corvette MC, I believe has a 1 1/8” bore (suggested by Matt Sweeney), & Wilwood proportioning valve.

I have deleted the LVSP & have original OEM calipers.

I’ve never locked up the brakes. While at a stop, the rig starts to creep forward. I have to apply additional pressure to keep stopped.

My ex refused to drive it. She felt she didn’t have the strength to stop it. But she was a tiny human.

Any recommendations?
I’m thinking maybe getting rid of the ABS unit could help? Im also thinking a rebuild of the OEM calipers could help?

Any thing else from the collective resources here?

 

[baldilocks]

I converted to hydro boost a few years ago after reading this thread & vacuum booster failed.

I do believe the brakes have improved, but at the same time I feel “meh” with the results.

I went with the same booster in the original post, Corvette MC, I believe has a 1 1/8” bore (suggested by Matt Sweeney), & Wilwood proportioning valve.

I have deleted the LVSP & have original OEM calipers.

I’ve never locked up the brakes. While at a stop, the rig starts to creep forward. I have to apply additional pressure to keep stopped.

My ex refused to drive it. She felt she didn’t have the strength to stop it. But she was a tiny human.

Any recommendations?
I’m thinking maybe getting rid of the ABS unit could help? Im also thinking a rebuild of the OEM calipers could help?

Any thing else from the collective resources here?

I also must apply a bit of additional force to the pedal and that’s due to the larger MC bore. However, the braking power is ultimately higher. Creeping while stopped is not an issue I’ve come close to experiencing. Even on the trail crawling g rocks in low range I work the pedal with my toes and always a much firmer pedal with much less travel and none of the “double pumps” I had to do with the brakes in two previous 80’s. So overall I’d say better brakes now and certainly poised to accept larger calipers. If larger calipers isn’t something you are not interested in adapting to your 80 then you can simply hunt down a MC with a 1” or maybe 1 1/16” bore. Pedal stroke will increase but human effort will decrease.

 

[jjdeneen918]

I also must apply a bit of additional force to the pedal and that’s due to the larger MC bore. However, the braking power is ultimately higher. Creeping while stopped is not an issue I’ve come close to experiencing. Even on the trail crawling g rocks in low range I work the pedal with my toes and always a much firmer pedal with much less travel and none of the “double pumps” I had to do with the brakes in two previous 80’s. So overall I’d say better brakes now and certainly poised to accept larger calipers. If larger calipers isn’t something you are not interested in adapting to your 80 then you can simply hunt down a MC with a 1” or maybe 1 1/16” bore. Pedal stroke will increase but human effort will decrease.

I’ve read a few posts about bigger rotors & calipers. It does sound very enticing.

Last one I read was at a price point of $3,800 for the kit. No thanks.

I’ll stick with OEM, rebuild them as they now have over 250,000 miles & have no indication they have ever seen any love or maintenance.

A different MC could hopefully be a cost effective option to reduce the foot force & hopefully eliminate the “creep” issue.

Has there been any consensus on which would be better, 1” or 1 1/16”?
Not opposed going Wilwood, do they offer both of these sizes?

 

[baldilocks]

I’ve read a few posts about bigger rotors & calipers. It does sound very enticing.

Last one I read was at a price point of $3,800 for the kit. No thanks.

I’ll stick with OEM, rebuild them as they now have over 250,000 miles & have no indication they have ever seen any love or maintenance.

A different MC could hopefully be a cost effective option to reduce the foot force & hopefully eliminate the “creep” issue.

Has there been any consensus on which would be better, 1” or 1 1/16”?
Not opposed going Wilwood, do they offer both of these sizes?

Toyota put a 1” MC in at the factory. Now, with the extra help of the hydro booster a 1 1/16” might work. This is a bit subjective. I think the creep you experience may be due to a loss inside the ancient ABS pump because I eliminated my ABS when I installed hydro boost and have never experienced creep when stopped.

As we know, opinions are abound here and how forcefully we should need to push on the brake pedal to stop quickly is subject to opinion.