Help - Hydroboost brake pedal returning slowly

[hunter1]

Complete new brake system on a frame off build. Disc in front with drums on the rear. Installed a used HB unit, new master cylinder. Started trying to bleed the brakes today and when depressing the brake pedal with the engine running I get a very slow pedal return. Reservoir is an aluminum tank with dual return ports so not using a tee. I had also resealed my steering gear so it has been completely apart also. Does it sound like air in the system? Tank does not have aeration in it and fluid looks to be circulating correctly. I do not currently have the steering column in it so can't turn the steering gear.
What's the problem experts?

 

[toddz69]

Slow pedal return is usually a symptom of a restriction in the return line somewhere. You don't have a T, so that's a good thing. Anything else obvious in the return that could be restricting flow?

Todd Z.

 

[ba123]

Also just could be that it's new. Drive it for a bit and see if it goes away. I went through this same thing with mine. I checked everything and everything was good and then I saw in the WH instructions that it did say this can happen for the first bit. I had to pull the pedal back with my foot every take-off for a little while. After that it was fantastic.

 

[hunter1]

Slow pedal return is usually a symptom of a restriction in the return line somewhere. You don't have a T, so that's a good thing. Anything else obvious in the return that could be restricting flow?

Todd Z.

I did have a clamp holding the two return lines together that I thought might be restricting the flow so I removed it, but didn’t fix it.

 

[hunter1]

Also just could be that it's new. Drive it for a bit and see if it goes away. I went through this same thing with mine. I checked everything and everything was good and then I saw in the WH instructions that it did say this can happen for the first bit. I had to pull the pedal back with my foot every take-off for a little while. After that it was fantastic.

I’ve read that also. I’m still a little ways off from putting it on the road so will have to wait a while to try that.

 

[ba123]

I’ve read that also. I’m still a little ways off from putting it on the road so will have to wait a while to try that.

Yeah, I wouldn't stress about it until you see it not breaking in. Honestly, learn from my own stress...

and now it's the best thing ever; I did not have to do a thing (other than drive it)

 

[hunter1]

Sounds good. Hopefully late winter, early spring I will have it drivable. We’ll see what it’s like driving.

 

[ntsqd]

You might get another of the H-B's return hose fittings to modify. They're called the "spittor" fitting for some reason. OE they have a pretty small hole in them that some folks drill out. Not sure what the downside to doing that is, but it would speed up the return flow. I figure that Bosch made it that way for a reason, so before modifying one I'd want a way to go back to stock.

 

[OX1]

Also just could be that it's new. Drive it for a bit and see if it goes away. I went through this same thing with mine. I checked everything and everything was good and then I saw in the WH instructions that it did say this can happen for the first bit. I had to pull the pedal back with my foot every take-off for a little while. After that it was fantastic.

Except he stated he put in a used HB unit? Unless you meant a new braking system (and/or MC), which slow pedal return has never been an issue for me.

 

[ba123]

Except he stated he put in a used HB unit? Unless you meant a new braking system (and/or MC), which slow pedal return has never been an issue for me.

I missed the "used" part, good call and not sure exactly which part of the WH HB unit needed to be broken in for the pedal to loosen up and no longer stick, but I would bet it's a combination of the master and the HB unit. I would think the master plays a larger part in the pedal loosening up since that's where the pedal goes and I still wouldn't worry about it until some miles are in, Could be just the master, could be the hoses getting broken in with more pressure from using the brakes... I really am not sure, but regardless, I wouldn't stress about it without being sure it won't go away on its own.

 

[OX1]

I missed the "used" part, good call and not sure exactly which part of the WH HB unit needed to be broken in for the pedal to loosen up and no longer stick, but I would bet it's a combination of the master and the HB unit. I would think the master plays a larger part in the pedal loosening up since that's where the pedal goes and I still wouldn't worry about it until some miles are in, Could be just the master, could be the hoses getting broken in with more pressure from using the brakes... I really am not sure, but regardless, I wouldn't stress about it without being sure it won't go away on its own.

Agree for now. With "Chinese" tolerances, I've had all kinds of issues on stuff "they" found out news ways to make things "just"
far enough out