(hydroboost) brakes locking up at idle

[Quickstop [UK]]

Re: (hydroboost) brakes locking up at idle

It's a waste of time disconnecting Mike's rod. We've al used it and they're great. :tup: Compare the HB casting number with one on here or another truck to make sure the pedal length is correct but otherwise the rod isn't the issue.

You could dx the MC from the HB unit to isolate the hydrobost unit from the equation. With SS lines you could ask someone to hold the master cylinder upright by hand while disconnected from the HB by those two bolts (that hold the prop valve bracket in as well) and therefore find out if your hydroboost is working or if the MC is seized.

If you did that, the expected result would be no brakes. If brakes are not applied then your hydroboost unit is applying them and you have a bad seal or perhaps the accumulator has ruptured or an internal diaphragm has gone.....

Bleed the whole system but it sounds lkike your HB unit has gone bad.

Good luck - I'm curious,

BTW - what happended with your idle issue and the 1000 post thread on the subject?

 

[BoostedSUV]

Re: (hydroboost) brakes locking up at idle

It's a waste of time disconnecting Mike's rod. We've al used it and they're great. :tup: Compare the HB casting number with one on here or another truck to make sure the pedal length is correct but otherwise the rod isn't the issue.

You could dx the MC from the HB unit to isolate the hydrobost unit from the equation. With SS lines you could ask someone to hold the master cylinder upright by hand while disconnected from the HB by those two bolts (that hold the prop valve bracket in as well) and therefore find out if your hydroboost is working or if the MC is seized.

If you did that, the expected result would be no brakes. If brakes are not applied then your hydroboost unit is applying them and you have a bad seal or perhaps the accumulator has ruptured or an internal diaphragm has gone.....

Bleed the whole system but it sounds lkike your HB unit has gone bad.

Good luck - I'm curious,

BTW - what happended with your idle issue and the 1000 post thread on the subject?

I removed the master cylinder and with the truck off the rod is in, as soon as I start the engine the rod presses out... has to be an issue with the hydroboost unit itself. I will try pumping the brakes and pulling back on the pedal to see if I can get it opperate properly.



as far as your last question, that truck pissed me off and it's being parted out. Only problem was I didn't smarten up and I bought another one that I swapped the guts into...

 

[STOUT74]

Re: (hydroboost) brakes locking up at idle

I'd try calling Vanco, 800-256-6295. They helped me out on my Syclone HB unit. They also rebuilt & modified my HB unit on my Scout w/ hydraulic steering. Really knowledgeable guys with HB units. :2cents:

 

[BoostedSUV]

Re: (hydroboost) brakes locking up at idle

Thanks for that info, if I really get stuck I'll try giving them a call :tup:

 

[MRKING]

Re: (hydroboost) brakes locking up at idle

I understand the rod extending at startup but that could possibly just be the unit hydraulically pressurizing . Im not saying mikes rod is bad , just that all syty's arent created equal . On a set sized rod , the adapter plate thickness being off slightly could make it apply the brakes .

Try installing the unit with out the rod hooked up and see if your brakes are still held . If they are , you know the unit itself is bad . If it isnt , try to manually press the hydroboost and recheck brakes .

If all else fails , just part this one out too . lol j/k

 

[BoostedSUV]

Re: (hydroboost) brakes locking up at idle

Lol this one is NOT getting parted! Took me 8 years to finally have the rust free build I always wanted. The other truck just became an organ donor for a better cause. It was rotted beyond repair.

I will try starting it again with the pedal disconnected and see if that's the issue. All I know is with the master disconnected complete the rod presses out with the truck idling. Makes me believe the HB unit is faulty or perhaps the rod is slightly engaged and causing the brakes to apply. I will look at it closer when I can a free night. Thanks for all the help, I'll report back.

 

[BoostedSUV]

Re: (hydroboost) brakes locking up at idle

Messed with the brakes again tonight and I still have the same problem. Soon as start the truck the pedal pulls down a little bit and the brakes lights come on. The brake are applied and the pedal won't return on its own. If I pull the pedal back by hand the brakes will release but as soon as I let go they re-apply. I checked the rod length and the pedal moves free and is neutral with the engine not running. Doesn't appear to be a rod length issue.

Also if I'm stand on the brakes and turn the steering wheel the wheel is very hard to turn like I loose power steering. When I left off the brakes I can spin the wheel with my pinky. I'm out of ideas aside from replacing the HB unit. I HATE buying parts to trouble shoot. Any ideas??

 

[BoostedSUV]

Re: (hydroboost) brakes locking up at idle

New HB unit, same problem waste of time and money I don't have. What's next? As soon as I apply the brakes the it's like I have lineloc, the brake pedal wont return and the brake lights stay on. what gives??

 

[BoostedSUV]

Re: (hydroboost) brakes locking up at idle

Just blew out all of the lines, drilled open the return port fitting to get better flow and bled the unit again according to the manual. Still nothing. No air or foam in the resevoir and the power steering works as it should. Pedal sits about half way to the floor with the truck running and the brakes are appled. When I shut the truck off I can pull the pedal back and it will return slowly. Ready to give up put the vacuum booster back in. Nothing is ever easy with these trucks :rant:

 

[TYTILIDIE]

Re: (hydroboost) brakes locking up at idle

Your pedal shouldn't move more than a half inch when you fire it up. Any way to verify that you do or don't have a 94 Astro unit?

 

[BoostedSUV]

Re: (hydroboost) brakes locking up at idle

Your pedal shouldn't move more than a half inch when you fire it up. Any way to verify that you do or don't have a 94 Astro unit?

I just puchased a reman 94 Astro unit from advance. It was identical to the one I had in there previously.

The brakes apply and the brake lights stay on but the pedal gets a lot of play, I can move back forth an inch or so. With engine not running the brakes are not applied and the brake lights aren't on. The pedal wont return immediately after I shut the truck off though. I need to pull it back and hold it.

any way to determine proper rod length? Although I would think if it was the rod length the brakes would be applied all the time.

 

[Quickstop [UK]]

Re: (hydroboost) brakes locking up at idle

Have you actually tried reversing the lines on it?

 

[BoostedSUV]

Re: (hydroboost) brakes locking up at idle

Have you actually tried reversing the lines on it?

haven't tried that... I have it plumbed according to the sheet that it came with the unit and MRKING's write-up. Kind of figure that would be a waste of time to try. I'm getting frustrated, this a new to me truck and a new build. I hate having hangups I can't figure out. The only reason I put the hydroboost in the truck is because the unit was one of the "goodies" I got with the roller.

 

[TYTILIDIE]

Re: (hydroboost) brakes locking up at idle

For shits and giggles I would reverse the lines just to see what happens. After or before that, maybe take the adapter I sold you off fire it up and see if you have the problem with out the shaft even hooked up.

 

[leadfoot]

Re: (hydroboost) brakes locking up at idle

For shits and giggles I would reverse the lines just to see what happens. After or before that, maybe take the adapter I sold you off fire it up and see if you have the problem with out the shaft even hooked up.

X2 You have nothing to buy if you do this simple thing. -Perhaps the newer steering boxes have opposite ports for the hydraulic lines. :dunno:

 

[BoostedSUV]

Re: (hydroboost) brakes locking up at idle

I will try reversing the lines. Its easier said than done since there aren't swivel fittings on braided lines. I'm going to have to reposition the 90 degree fittings in order to swap them. I'll give it a shot though, but what are the odds that I got 2 different HB units that's both are reverse flow? I have no idea what vehicle the first one came from.

 

[STOUT74]

Re: (hydroboost) brakes locking up at idle

Have you called the guys at Vanco? That's what they do, HB. I'd give them a call tomorrow before you start swapping lines, I'm not sure what will happen besides it not working. Just a thought. Post #23

 

[BoostedSUV]

Re: (hydroboost) brakes locking up at idle

Reversed the lines, same issue except I had zero brake assistance.

 

[TYTILIDIE]

Re: (hydroboost) brakes locking up at idle

Now how about taking the adapter off? I hope you get this figured out. You will be the king of retarded issues if you don't:lol:

 

[Quickstop [UK]]

Re: (hydroboost) brakes locking up at idle

Now how about taking the adapter off? I hope you get this figured out. You will be the king of retarded issues if you don't:lol:

Man I know how he feels - I'd be pissed right now!

Matt - any word?