Hydro boost install not working

[Dleslie212]

Hey all. Just finished up with my hydroboost install. Something's not right and I can't quite figure out where I went wrong. The brakes are even worse than when I started - when in gear, I have to put all of my 220 pounds on the brake just to stop in idle.

The old vac booster was removed and I installed a new hydro boost, master cylinder and proportioning valve. I made sure the pushrod between the booster and brake pedal was the se length as on the old vac booster.

I made all new custom PTFE hoses. Pressure from the 6 month old PS pump goes in one side of the hydro boost, out the hydroboost and into the pressure side of the steering box, out of the steering box and into return of the PS pump. There's also a return off the hydroboost that's teed into the return line between the steering box and the PS pump return.

I removed the factory proportioning valve and ran new 3/16 line from the new proportioning valve to the 3/16" line heading to the rears.

I did the same with the front, except I teed the new line and the two front lines together, and plugged off the secondary front outlet port on the new proportioning valve.

I vac bled all four corners, starting from furthest to nearest until I got clean fluid out and no more bubbles.

I filled the PS pump with ATF, turned the engine on and rotated the steering wheel until it felt normal, and then topped off the ATF in the PS pump.


As of now, I can turn the engine on but with all my weight on the pedal, it barely stops during idle. Also, the return line off the hydroboost gets pretty hot within just a minute or two of idling. Can anyone give me some advice?

 

[Snoots]

I hope these will help.
1. I have heard that ATF fluid is wrong for a hydroboost system. It should be PS fluid only. Something about foaming.
2. A PS cooler should go into the 'return' line.
3. Did you change or alter the pedal?

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[Dleslie212]

Thank you for the reply

1 - I'm going to go ahead and drain that ATF and replace with PS fluid today

2 - I thought about a cooler, but literally idling for two minutes and that hose is pretty warm to the touch. It just doesn't seem right, even without a cooler. I'd think I would at least get a little bit of brake when starting cold

3 - I did not change or alter the pedal. I measured the rod so that my pedal was just pushing in on the brake light switch to keep the brake lights off, but I didn't change or alter the pedal

I plumbed everything in the same as the first picture, with the tee on the return line

 

[Dleslie212]

Just a quick thought - in your first picture above, it shows the bypass on the booster on the same side as the high pressure outlet. I have mine plumbed in as the high pressure inlet on the same side as the bypass. Is it possible to have the high pressure inlet and outlet backwards, or does that even matter?

 

[Snoots]

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The reason the brake pedal location is different is because the non-HB position does not give the push rod enough throw. You also have to be careful with the length of the throw rod to the type of master cylinder you have.

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[Dleslie212]

The hydroboost and master cylinder came pre-assembled and bolted together from Performance Online, so I'm guessing the throw rod should be correct already.

in your experience, is the brake pedal supposed to be changed to a HB compatible pedal? I'll take a closer look at my pedal when I get home but I don't remember it having any possible other mounting points for the rod

 

[Ricko1966]

Reread postv#2. Look at the picture.

 

[Snoots]

You can remove the pedal and drill it for the new pin.

 

[Dleslie212]

Thanks for the great info guys I really appreciate this community.

Bit of an update. I took a closer look at the plumbing diagram above and realized I had the pressure in and pressure out lines backwards at the HB. I went ahead and drained out the ATF I had in there and replaced with PS fluid, and crossed those lines.

The old girl stops now. There's still a few issues. The brake pedal bounces up/pushes back up against my foot - I'm not sure what that's about just yet.

It's also still a little hard to stop - I'm guessing this is because I did a ****** bleed job, and didn't even bench bleed the new master cylinder. I also need to redo a few hoses that are too long/too short now that I swapped them around. I'm also going to bleed the brakes a little more, and flush the PS fluid out one more time and replace

 

[79c10paintedtwice]

I discovered not enough travel on the master cylinder by using a pressure gage. Had to lower the master cylinder to get the 1 inch travel. Worsk fine now. Do you get the push back on the brake pedal when the engine starts?

 

[CalSgt]

The brake pedal bounces up/pushes back up against my foot - I'm not sure what that's about just yet.

The HB on my Duramax started doing this right before it began to fail

 

[Ricko1966]

Thanks for the great info guys I really appreciate this community.

Bit of an update. I took a closer look at the plumbing diagram above and realized I had the pressure in and pressure out lines backwards at the HB. I went ahead and drained out the ATF I had in there and replaced with PS fluid, and crossed those lines.

The old girl stops now. There's still a few issues. The brake pedal bounces up/pushes back up against my foot - I'm not sure what that's about just yet.

It's also still a little hard to stop - I'm guessing this is because I did a ****** bleed job, and didn't even bench bleed the new master cylinder. I also need to redo a few hoses that are too long/too short now that I swapped them around. I'm also going to bleed the brakes a little more, and flush the PS fluid out one more time and replace

Did you change the brake pedal to the correct pedal? Different leverage point,just like switching from manual brakes to power brakes,you have to change the pedal.

 

[Dleslie212]

Haven't done that yet.

Does that involve removing the brake pedal assembly? I've been looking into buying a replacement that already has the correct hole, but can't seem to find any

 

[TPISly-C10]

PS on HB and vacuum got a different pressor valve too keep a eye on this! but pedal trow position is a good way to look at!

 

[Snoots]

I'm guessing the throw rod should be correct already.

Not the throw rod from the booster to the MC; the throw rod from the pedal to the booster.