Hydroboost brakes sticking

[lotzagoodstuff]

My converted hydroboost brakes have been sticking in the "on" position. Not every time, but once in a while I can tell the car won't roll the same as it should. When I crack the bleeders, there is pressure in brakes, confirming that they are sticking.

I have a guess that the rod out of the booster might be incorrect as it was bought as a rebuilt and not pulled off a hot air car physically. I had a Ford that had an adjustable brake pushrod on it, and if it was too "long" it would create a check valve effect on the brakes.

Anybody have any other ideas to check?

 

[Fast4Ward]

i just did this conversion and it took a while to get the air out and for the pedal to rise up..at first it would take some time to come up.
when you say "sticking on" ...is this on the street when applying the pedal and now the car won't move?
i was afraid of the rod adjustment myself when trying to get them to work but its fine now.

 

[lotzagoodstuff]

Yes, the brakes are staying on, pretty tight actually depending on how much I pump them when they act up. Is the pushrod adjustable? I didn't really look at it.

Any help would be appreciated.

Thanks

 

[Fast4Ward]

Yes, the brakes are staying on, pretty tight actually depending on how much I pump them when they act up. Is the pushrod adjustable? I didn't really look at it.

Any help would be appreciated.

Thanks

the Cardone MC came with instructions to adjust it. i didn't and installed it as is.

 

[lotzagoodstuff]

Dragging brakes update, length corrected

So I pulled off the m/c this weekend, and I did notice that the hydroboost seemd to be pushing on the master cylinder plunger quite "early". That is, when I loosened the two bolts there was considerable travel before the hydroboost rod and m/c plunger were not engaged. There was a small bullet shaped rod that was held into the hydroboost pushrod with an oring. Although it was not adjustable, and nothing in the directions said otherwise, I ground off about .100" and my brakes now appear to be working correctly.

I would be interested in getting the correct plunger "bullet" if anybody knows what the part number and/or a source for it is, but for now the ground down length seems to have fixed me up.

 

[1quick6]

That's interesting. Which master cylinder / booster were you using? I have not heard of this problem with the cast iron master specifically specified for the 83-85 hot air cars. That's the one I am using on my car and it is a Cardone rebuilt unit (Part No: 10-1984).

 

[lotzagoodstuff]

Yes, that's the same cast iron Cardone master cylinder I used, should have worked without any modification, I have a feeling the small rod that was held in with an o-ring was incorrect as it appeared to be pushing on the m/c plunger very early.

Alls well that ends well I guess.

 

[POWERBRAKEBOB]

Hydroboost conversions

We have NEW Hydroboosts that come with the correct pedal rod and master rod. We also prefer our alum master cyl. The Stainless hoses are all designed to connect well and look clean. IF the pedal rod is wrong, cut or welded, or a junkyard unit is used, many problems can occur. IF the pedal rod is wrong by virtue of wrong booster or a wrong pedal, then the hydroboost could be partially applied which will over heat the P/S fluid. Grinding the tip off the Early style "Internal" accumulator unit is risky, because that nub is need to give the control valve it's "feel". The pedal rod is probably binding, causing the sticky pedal. Check the length and angle of the pedal rod.

 

[lotzagoodstuff]

Thanks for the input. I tried to buy all the correct factory parts for a hot air car according to everything I researched and cross referenced. I never removed my factory 87 pedal and the booster rod hooked in easily and the angle looked perfect to the hydroboost. I don't believe I have any pedal bind, just "check valving" on the master cylinder.

I have adjusted the actuator rod going to the master cylinder before on vaccuum units for other applications and I know the length is very critical. I was really just hoping somebody could tell me what the corect length is for the small nub. I ground it down as I know if the length is too long it will cause the m/c to not retract fully causing no release of the fluid pressure.

 

[POWERBRAKEBOB]

sticking

You have to check to see if the pedal is jammed up against the Stop light switch or cruise. ANY pressure against the booster rod, because it is the wrong one, or the braket is wrong, will cause many problems. The H/B bracket is angled at the same angle as the P/M booster/rod. IF you used one of those "Van" brackets, the rod will be too long, AND on the wrong angle. The booster piston will scrub on the bore, gouging it.

 

[lotzagoodstuff]

I am confused: I don't know what "van" piece you are referring to.

The parts I purchased were:

Master Cylinder
Cardone 10-1984

Hydrobooster
Cardone 52-7211

I didn't change any bracket, pedal, or anything on the interior side of the firewall. It's all stock 87 GN pedal wise, so I'm not sure how I would have any issues on the interior side of the firewall.

???

 

[POWERBRAKEBOB]

Small rod

I don't have cardone's catalog here. I use new Bosch. The stub rod you are referrring to are all the same measurement on those early internal accum uinits. It should be retained by a steel lock ring. The original rod was retained by a STEEL lock ring. If they used a rubber lock ring, then Cardone could have made their own replacement for a piece missing from an old core. Those units were used on 84's, maybe 85's. Either the pedal rod/bracket is not right, or the stub rod was a made-up piece by the rebuilder.