Hydroboost break set up - constantly overflowing/foaming

[Malicious]

Hi all,

I’ve done a custom hydroboost brake set up in my ‘68 coronet and it brakes amazingly.

But, I can’t use the car as the fluid keeps over flowing and I think it’s due to the fluid foaming / frothing.

The set up is a hydroboost from a Silverado or similar. Runs off the stock Saginaw pump, into the hydro, pressure out to borgeson steering box return back to the Saginaw return, borgeson return goes into an oil cooler then into an additional reservoir on the fire wall, then back to an addition AN return nipple in the side of the Saginaw.

I have tried thick steel wool in the reservoir and that seemed to work, but after a short test, I did find the steel wool being sucked into the outlet to the pump.

So I made a baffle set up with a length of all thread and three sheets of mesh. Garage test looked good, but the drive test saw it overflowing again.

After running you can hear the system is pressurised and pushing fluid out of the Saginaw cap.

At this point I am thinking:
do I need to sand which steel wool inbetween the mesh plates?
Do I need to find a way to seal the system? So try and seam the Saginaw pump?
Or if I can’t seal the Saginaw do I need to find another modern pump that either uses the remote reservoir or integrated one but seals?

Also going to try and retighten all the fittings as well.

But I’m struggling here, could really do with some advice/help!

 

[493 Mike]

Hi all,

I’ve done a custom hydroboost brake set up in my ‘68 coronet and it brakes amazingly.

But, I can’t use the car as the fluid keeps over flowing and I think it’s due to the fluid foaming / frothing.

The set up is a hydroboost from a Silverado or similar. Runs off the stock Saginaw pump, into the hydro, pressure out to borgeson steering box return back to the Saginaw return, borgeson return goes into an oil cooler then into an additional reservoir on the fire wall, then back to an addition AN return nipple in the side of the Saginaw.

I have tried thick steel wool in the reservoir and that seemed to work, but after a short test, I did find the steel wool being sucked into the outlet to the pump.

So I made a baffle set up with a length of all thread and three sheets of mesh. Garage test looked good, but the drive test saw it overflowing again.

After running you can hear the system is pressurised and pushing fluid out of the Saginaw cap.

At this point I am thinking:
do I need to sand which steel wool inbetween the mesh plates?
Do I need to find a way to seal the system? So try and seam the Saginaw pump?
Or if I can’t seal the Saginaw do I need to find another modern pump that either uses the remote reservoir or integrated one but seals?

Also going to try and retighten all the fittings as well.

But I’m struggling here, could really do with some advice/help!

View attachment 1525711

View attachment 1525712

View attachment 1525713

View attachment 1525714

What reasoning led to an extra reservoir?
Mike

 

[6872n73]

Foaming is generally caused by:

Overheating
A leak in the system
Or a starving pump.

 

[Malicious]

What reasoning led to an extra reservoir?
Mike

Overflow, basically from when the system was full, engaging the brakes would over fill the system when pressing the brakes. If enough room was left, there wasn’t enough fluid for the booster

 

[Malicious]

Foaming is generally caused by:

Overheating
A leak in the system
Or a starving pump.

Starving could be an issue as it overflows and runs out of fluid.

When stopped it feels like it drains back to overflow. Again part of why I was considering the system needing to be pressurised.

With a cooler in place and a reasonable amount of duos, I don’t think overheating could be the cause.

Air leak, would the lid of the Saginaw be enough or would it need to be at a fitting?

 

[pnora]

System is cavitated with air severely. Add fluid to level cold. Start and do not steer or use the brake. Do this several times letting it sit 1/2 hour or more between starting. When the fluid quits going down then steer one way and back to center. Shut it off and let sit. Keep the level over the pump all the time. Then steer the opposite way and do the same. Then try the brakes doing the same. The more you run it eventually is should tame down and maintain its level. Air is your enemy and the more you aggravate it the worse it gets.

 

[khryslerkid]

@Kern Dog

 

[PlymCrazy]

I had a hydroboost as a factory option in my ‘98 2500 Suburban. Had to replace it once. After refilling, I had to let it idle for some time and then steer it through full range both directions several times to purge air. Afterwards, it took a couple days of normal driving and topping it off regularly before it finally settled back to normal.

 

[Kern Dog]

@Kern Dog

I wish that I could help. My efforts were a failure so I can't offer any worthwhile advice on this one.

 

[Malicious]

System is cavitated with air severely. Add fluid to level cold. Start and do not steer or use the brake. Do this several times letting it sit 1/2 hour or more between starting. When the fluid quits going down then steer one way and back to center. Shut it off and let sit. Keep the level over the pump all the time. Then steer the opposite way and do the same. Then try the brakes doing the same. The more you run it eventually is should tame down and maintain its level. Air is your enemy and the more you aggravate it the worse it gets.

Thanks! I had done a version of this, but if I leave the lid off the reservoir and the pump, the fluid some how drains back to the pump and then over flows.

I can try again by topping up to the top of the reservoir ‘straw’ then sealing the reservoir, and just leaving the pump lid off. And following you guide more exactly.

But

System is cavitated with air severely. Add fluid to level cold. Start and do not steer or use the brake. Do this several times letting it sit 1/2 hour or more between starting. When the fluid quits going down then steer one way and back to center. Shut it off and let sit. Keep the level over the pump all the time. Then steer the opposite way and do the same. Then try the brakes doing the same. The more you run it eventually is should tame down and maintain its level. Air is your enemy and the more you aggravate it the worse it gets.

System is cavitated with air severely. Add fluid to level cold. Start and do not steer or use the brake. Do this several times letting it sit 1/2 hour or more between starting. When the fluid quits going down then steer one way and back to center. Shut it off and let sit. Keep the level over the pump all the time. Then steer the opposite way and do the same. Then try the brakes doing the same. The more you run it eventually is should tame down and maintain its level. Air is your enemy and the more you aggravate it the worse it gets.

Thanks! I had done a version of this, but if I leave the lid off the reservoir and the pump, the fluid some how drains back to the pump and then over flows.

I can try again by topping up to the top of the reservoir ‘straw’ then sealing the reservoir, and just leaving the pump lid off. And following you guide more exactly.

But basically your saying: bleed it thoroughly and it should sort itself out?

Also dumb question, but I am at that stage of wtf is going wrong: reservoir has one inlet with an internal tube. I have return in without the tube, then reservoir out to the pump with the tube. This is to avoid drain back etc as the reservoir is higher than the pump. Seems like this is the standard anyway, but is this fine?

 

[MoparLeo]

You had to get information from somewhere to do this conversion. Was it an article, friend, or what.
If this is based on a GM system and parts, have you looked at a GM FSM to try to diagnose the problem ?

 

[6872n73]

I would try removing the cooler and tank and connect the return to the pump and see what simplifying things does.