Hydroboost braking problem- sticking..

C

cartel

New Member
Joined
Nov 27, 2016
got elliotts Hydroboost assy and put a wilwood dual master - have a prop valve to rear but fully open- 1" master.

this is all brand new with 13" wilwood 6 piston fronts and 12" rears

have about 50 miles on the car- brakes were fine until today-- like day 5 of test drives- as working transmission bugs out of it with WOT shifting- so havent driven it hard yet - today was the first time really on it to test shifting

came back from a 5 minute run and the front brakes were smoking - the pedal was extremely hard and the front brakes were on so much that it took 15 psi boost to move the car- put it in neutral and we couldnt roll it -
had to unbolt the master from HB setup to release the pressure so we could roll the car-

is there anything in the master or the rest of the setup that can cause this or is it simply a defective HB assy?

before this the car rolled easily and there was no drag on the pedal that would cause the brakes to hang up
 
got a reply from Elliott and he thinks that the fluid in the wilwood master is too full and is expanding from heat and causing the hydroboost to prevent releasing the push rod.

i took the lid off earlier and its a good 3/4" below the lip of the master, but that is likely touching the rubber seal on the lid- so i doubt much room to expand- pretty lame if the wilwood master is sealed so tight that it causes the brakes to lock on- - i will take some fluid out and see if that makes a difference.
 
I had a problem on a stock reman hydroboost unit I got from autozone with the original master cylinder! Separate the master and put a average size washer on both side and try that
 
Also make sure, if the rod on the hydroboost to pedal is adjustable, it isn't too long or binding. Another issue could be an obstruction or improperly routed return line or a kink. Post pic
 
I agree with elky. The pedal pushrod may be too long.
How much does the pedal move with light pressure and the Engine off brakes at room temperature?

Should have some play in it.
 
pedal has play..
brakes have no drag .can push car easily when cold.
there's probably 4 hours running time spread out.

I have the PSC hb reservoir and braided lines
 
cartel said:
pedal has play..
brakes have no drag .can push car easily when cold.
there's probably 4 hours running time spread out.

I have the PSC hb reservoir and braided lines
Click to expand...
When you start the car, if you have your foot very slightly on the pedal, does it get pushed back? It's possible the internal rod that engages the brakes is too long, hence the mention of spacing MC with washers. Try the washer thing between MC and booster. If it resolves it, you need to take some material off the rod inside the HB. Also, before you put washers to varify clearance, with the MC off, start the car and have someone watch the rod in the HB. If it engages (starts to push out) you have some restriction on the return or a faulty unit
 
I currently have the same issue. I swapped to an 85 regal factory hydroboost. Operated great for a few drives. Just stuck on me the other day and released on its own. I dont have time to dig into it right now.
 
Blkt6 said:
I currently have the same issue. I swapped to an 85 regal factory hydroboost. Operated great for a few drives. Just stuck on me the other day and released on its own. I dont have time to dig into it right now.
Click to expand...
With factory units, biggest mistake is the return line kinked, too long or a bad unit. I had that happen with factory unit. Problem was using a T in the wrong place.
 
I would check the C-clip that holds the piston in the master cylinder on the wilwood unit. The clip needs to be changed out so the master cylinder shaft doesn't drag and hang-up on the clip. I just tossed the factory wilwood clip in the trash the other day or I would show you where it hits. Basicly the circle piece that the tool grabs to compress it and remove it is to big and it hits. You need a clip that doesn't have it or has a very small one. Picture of what I'm talking about attached. It drags on the lips

Sent from my SM-G935T using Tapatalk
36f0ee629ac39c6f73cd915127de59c2.jpg
 
Boost231 said:
I would check the C-clip that holds the piston in the master cylinder on the wilwood unit. The clip needs to be changed out so the master cylinder shaft doesn't drag and hang-up on the clip. I just tossed the factory wilwood clip in the trash the other day or I would show you where it hits. Basicly the circle piece that the tool grabs to compress it and remove it is to big and it hits. You need a clip that doesn't have it. Let me see if i can find pictures online.

Sent from my SM-G935T using Tapatalk
Click to expand...
People do that to the factory unit but it's not the right way. There is a modification kit for the factory unit to replace the rod. Aftermarket units come with a narrow rod to engage the MC. You replaced the factory snap ring with a wire snap ring. Wilwood told me not to do that, gave me a number and I ordered a kit from that place.
 
TURBOELKY said:
People do that to the factory unit but it's not the right way. There is a modification kit for the factory unit to replace the rod. Aftermarket units come with a narrow rod to engage the MC. You replaced the factory snap ring with a wire snap ring. Wilwood told me not to do that, gave me a number and I ordered a kit from that place.
Click to expand...
Glad they make something for that. My snap ring is holding just fine. Lol

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Boost231 said:
Glad they make something for that. My snap ring is holding just fine. Lol

Sent from my SM-G935T using Tapatalk
Click to expand...
I would have done it that way too. A lot of people have. I asked wilwood first though and they referred me over to a hydroboost company. I do a ton of brake conversions and if it's for someone else's car, I have to be sure it's 100% that's all. (y) Hydroboost can be finicky but damn they stop!
 
Got a link for future reference

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ill pull the master and check it-- the PSC resevoir i got has 2 return ports there is no T fitting joining the return-- i will look and see which of the returns is to aux.

im taking the master out anyway as its 1" and i want to firm up the pedal more so going to increase it to 1. 1/8" the brakes worked great but were TOO easy to use before the sticking issue
 
The wildwood cyl should have come w/ an alum plug. I usually have to machine it down to keep the hb from pushing on the mc piston, when brakes are released.
 
cartel said:
ill pull the master and check it-- the PSC resevoir i got has 2 return ports there is no T fitting joining the return-- i will look and see which of the returns is to aux.

im taking the master out anyway as its 1" and i want to firm up the pedal more so going to increase it to 1. 1/8" the brakes worked great but were TOO easy to use before the sticking issue
Click to expand...
Yeah the 1 1/8" bore is what you need. You can probably sell the 1" to someone wanting manual brakes. You'll catch the problem. (y)
 
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