[Chris65LeMans]

I just installed my system, and am having some "hanging up" issues, too. My system is from CPP, and they advise driving it for 500 miles to get all the air out after install. I'm at 600 miles now, and still having some issues.

[David Jones]

Chris, I couldn't drive mine 20 miles, much less 500.

Looking at your picture I see one issue and one possible issue that I think will cure your problem.

The "tee" for the low pressure line is one. From what I've read and what I was told, you want the straight through low pressure line going from the power steering box to the pump reservoir and you want the tee from the low pressure hydroboost line coming in to that. And you want that tee positioned as close to the inlet for the pump reservoir as you can get it. If I'm seeing your picture right you have the low pressure line from the hydroboost going directly to the pump reservoir and the steering box low pressure line teeing into it.

The possible issue is the tee itself. Was it sold as 3/8"? Take the lines apart and measure the inside diameter of the tee. If you bought it as a 3/8" tee, my recent experience is that the inside diameter is actually more like 1/4". Not enough capacity. If that's the case, read my reply in #19 about tee's and go from there.

I'd REALLY like to know what you find out about both things.

[Old Goat 67]

Never had any problems like that "hanging up". The boost unit should release the hydraulic pressure to the wheel cylinders when you release the pedal. You both should make sure that the actuator rod is not too long where it would hold the boost unit away from the full release position. If that "spit tube" to the reservoir is hooked up wrong like David said above, it could be causing the booster to not be able to "spit" it's steering fluid enough to cause that hanging up.

Read the paragraph titled "Adjustable Pushrods" below.

My "T" is probably 1/4" unit, but I have never had any problems like that.

Charles

[goatwgn]

When I installed my hydroboost, it did the same thing. I actually warped a rotor from the brakes dragging. The rod was adjusted out a little too far, so it didn't completely release the brakes. I adjusted about 1/4 inch and it was fine afterward.

[David Jones]

I installed the larger tee and noticed no change in the brake operation. Lightly hanging and dragging as before. Others have found this a cure, so it was $3 well spent.

As noted in post 19, another possible contributor was the brake rod to booster length. Looking at the pedals travel I discovered that the brake light switch was holding the pedal from its full travel. I adjusted it backward about 1/4" and the constantly dragging brakes are gone.
The brakes still gently hold on for about a 2 count after you let the pedal up but then you can feel them let go. I have a long gentle grade coming down to the house. Coasting, I could tap the brakes and then about 2 seconds you could feel it let completely go. They don't hold hard....just enough to lightly hold you back.
I believe that's going to turn out to be air in the hydroboost system so I'm going to drive it a while and see if it works itself out.

The brake pedal feel is fairly amazing. Especially in a 1969 Pontiac.

[Old Goat 67]

Originally Posted by David Jones

I believe that's going to turn out to be air in the hydroboost system so I'm going to drive it a while and see if it works itself out.

I don't think so....

[David Jones]

Originally Posted by Old Goat 67

I don't think so....

And you think it is?

[Old Goat 67]

I think you do not have enough free play in your pedal rod. OR, you have a defective boost unit.

Read this carefully, especially about "RELEASED POSITION (NO BRAKING)".

http://www.classicwinnebagos.com/for...p?topic=9126.0

This picture shows my pedal rod adjustment setup. Fully adjustable set up with about .030 thousands freeplay. If that rod has no freeplay, you are telling the boost unit to keep on using hydraulic pressure to put pressure to the master.

[David Jones]

Originally Posted by Old Goat 67

I think you do not have enough free play in your pedal rod. OR, you have a defective boost unit.

Read this carefully, especially about "RELEASED POSITION (NO BRAKING)".

http://www.classicwinnebagos.com/for...p?topic=9126.0

This picture shows my pedal rod adjustment setup. Fully adjustable set up with about .030 thousands freeplay. If that rod has no freeplay, you are telling the boost unit to keep on using hydraulic pressure to put pressure to the master.

I have freeplay. Have I measured it to the hundredths? No. The brake light switch was positioned so far inward that it was limiting the outward travel of the brake pedal, causing the constant dragging. I took the brake light switch all the way back, so it did not contact the brake pedal at all and then repositioned it correctly according to the rearward/upward travel of the brake pedal as controlled by the brake rod. There is nothing else altering the natural stroke of the brake rod. There is not a stop. No rubber bumper. These are factory 1969 GTO manual transmission pedals.

What am I missing?

The gentleman that sold this to me said that most likely I still have air trapped in the unit causing the momentary light brake hang, after releasing the pedal. Give it a few hundred miles. IF that's not it, he says we'll look at pump pressures.

[Old Goat 67]

David,

When you placed the pin through the clevis and into the pedal arm, did you have slight movement of the pedal? If so you should have freeplay you can feel with your hand indicating there is no residual pressure being exerted in the mechanical travel. That would be good.

Air bubbles in the power steering hydraulic line would not cause would cause a "hold" on the hydro unit IMO. Air is compressible, fluid is not. Do you still have bubbles in the fluid in the pump?

Having the brakes drag, even for 2 seconds is not acceptable in my estimation. If you study closely the way the unit is supposed to operate, you should see how important is is to have it stop using hydraulic pressure when released. That takes away from the pressure to be utilized for steering the car.

Put it up on jackstands and apply & release pedal while someone tries to rotate the wheels after release to see if in fact it is not releasing immediately. Mine certainly does, as I can push the car around in the shop as soon as it is in the rest position.

Seems that spool valve may be hanging up maybe, if you do have freeplay.

Charles

[Old Goat 67]

Was this a used unit or a rebuild?

[David Jones]

Brand new unit.
As I noted, I now have freeplay.
I'm following the advice of the gentleman that sells and installs these things concerning the light initial brake drag. I've also read numerous places where in some cases it takes a few miles to completely purge the air from a hydroboost system...and that air can cause a light brake drag, right after release of the pedal.
A quote from my supplier
"If your PS fluid is clear the air is not currently coming out.... Which doesn't necessarily mean there isn't more that is trapped."
Chris65 noted that his supplier cautioned the same thing.....give it 500 miles.
I have noticed no issues with steering the car when the light brake drag occurs. Is brake drag acceptable? In the long run, no. Will I live with it for a few weeks following what seems to be a normally followed routine endorsed by at least 2 suppliers that do this on a daily basis?
Yes.

[Old Goat 67]

I'm done.

[David Jones]

Just curious, you'd recommend what? Replacing the unit?
The freeplay issue is solved.

[BB70]

It could be a master cylinder issue David. You didn't kink a brake line did you ? Best bet is to get it on jackstands, have someone apply the brakes and release-spin the wheels to see which axle is still applied.
John

[David Jones]

No BB, the brake lines survived in good shape.

[vidguy]

From a fellow hydrobooster. I did mine on 2009. Works fine still. Used mused unit and made my own aeroquip teflon hoses.
Upside down mounting has not been an issue with mine.
Drive mine every day to work and back 15 miles RT.
Works like it did then.. Great.

I dont think it's air either.. Air made noise, it didn't cause issues, for me anyhow..
I did put the car up on 4 stands to run it as I bled it left and right FULLY ..

Did you check the angle on the rod at your brake pedal? Does your pedal have both manual and disc brake holes in it? Try the other hole if your rod is still adjustable..
Maybe the angle is causing the rod to release slowly..
I'd guess Rod, master or unit..

Here is a note from my threads back then when I installed mine..

"I kept checking this and the angle to the pedal pin till I got it real close.
The angle to my pedal rod isn't perfectly horizontal so some tilt worked well.
On my car there was only one pin / no second hole on the pedal. Likely since there was no manual brake option in 75?"


Here is one of my threads if it might help...
http://forums.maxperformanceinc.com/...errerid=145926

Good Luck David.
Dont know if I can help more, but I will try..

[David Jones]

Thank you James. I read your thread a few times actually.
The slow pedal is not completely gone, but it is better than it was.
The pedal angle is one of the 1st things my guy had me check. It's nearly straight in and I see no evidence of binding/dragging on the rod. He was worried about that given the angle of the mount.
Driving time has been a little hard to come by lately, so I've not done many miles and others that have had this issue have noted up to 500 miles before the trapped air purges itself.

We'll see. I'll worry about other possibilities/cures once I've taken the easiest one out of play....which is simply driving it a while.

I'm amazed at how good the brakes feel all the time. Pedal feel is great and when you hammer on them they seem to be very controllable.....easy to come right up to the edge of locking if needed.

[David Jones]

An update of the slow to return pedal with the hydroboost.
All seems well now. I was out driving last night and realized I hadn't even thought about it for a while. The brakes continue to be amazing. Great pedal feel, very controllable.

The set up is......originally a power front disc car. Still retains stock replacement front disc/calipers with Hawk pads (dusty as HELL), the rear has been changed to S-10 (99) disc with Car Quest ceramic pads. The original booster/master cylinder and hold off mechanism has given way to a hydroboost setup from http://www.custompowerbrake.com/ and a 1978 Corvette master cylinder. All rubber brake hoses have been swapped for braided over the past few years. Dot 4 fluid. The original distribution block remains and no proportioning valve was added or needed.
My parking brake install, with the "custom by David at his work bench" cable end buttons, is working like a top.

[MNBob]

Glad to hear your got it all working!