Power Steering (hydroboost)

[JOHNFAK]

So guys.

Have loss of power steering fluid (none left) . So Im guessing I need to pull the vaccuum pump/PSP assy out and reseal etc. 

However when I was thinking about it - I realized I dont get how the whole system works ...... someone shed more light ?

 

Some questions.

 

1) Most people replace for the oil leak that occurs for the oil feed line to the vacuum pump. I'm sure I probably have this also ..... but I'm talking about loss of PS fluid in resevoir. So ? Do the seal replacements generally take care of PS side leaks ? Dont want to pull the assay only to find PS leak is something else.

 

2) How does this tie into larger system of steering gear and hydroboost. I have no PS fluid ...... so why do I not notice anything in terms of steering and braking. Im guessing the master cylinder is till producing enough power from brake fluid to stop truck with no funny pedal feeling. Just not getting the extra stopping power of hydro assist ?

 

3) Whats the flow of fluid. Is it from the hydroassist to the steering pump then to the PS pump or other way around ?

 

 

Things like that

 

[dripley]

 I am equally as ignorant on this system and how they interact with each other.

[IBMobile]

1. The seal in the vacuum pump seals engine oil not the power steering pump.  Look further for the P/S leak: at the pump itself, the steering box, the hydro boost, the pressure/return lines or fittings. 

 

2. If the power steering pump is low on fluid there would be brake peddle pulsation with the steering not being smooth.  If the reservoir was out of fluid than you would lose all power steering and power brake function with the power steering pump being damaged and noisy.

 

3.Flow is from steering fluid reservoir to pump where it is pressurized up to 1200 psi.  At the hydro boost there are three fluid lines:  one line supplies the pressurized fluid to the hydro boost,   one line supplies pressurized fluid from the hydro boost to the power steering box,  the third line is low pressure fluid retune to the power steering reservoir.  On the reservoir is a second low pressure return line for the power steer box.

[JOHNFAK]

Thanks IB ^^^^ 

 

Weird I dont get any pulsing or any symtoms with pump being noisy etc.

 

Tracking down the PS fluid leak seems a bit harder as its a semi clear color ..... and mixes with oil on engine pretty quick making it look like oil leak not PS.

 

How would you tell if PS pump is damaged (apart from noise). 

 

Might hvae to clean her all down and fill it back up and go for a block drive.

 

Edited April 30, 2016 by JOHNFAK

[IBMobile]

You're going to have to clean all the potential leak areas IE: PS pump. Steering box, Hydro boost unit, all hoses and fittings.  Now start the engine and start looking for a leak.  Use a bright flashlight take your time. If it's not a gusher it will take awhile to appear.  Have a helper turn the steering wheel from full lock to full lock this will cause the pump to produce full pressure in the system.

[JOHNFAK]

How to tell if PS pump is damaged needs replacement.

 

So flow is OUT from the PS pump behind the vacuum pump to the hydroboost behind the master cylinder.

It supplies regulated/pressure hydraulic to the steering gear box (return back to PS pump resevoir).

 

How is the hydraulic boost help braking since that all comes from the master cylinder and break fluid. How does it "boost".

 

I have a new steering box so doubt that's the issue, and pretty sure not coming from the hydroboost as think it would be evident with leak that high. Got to be coming from the PS pump itself somewhere (most likely) or the lines that go to the pump.

 

 

 

 

 

[Haggar]

John,

 

Yes,  A high pressure hose goes from the ps pump to the hydroboost.  A high pressure line goes from the hydroboost to the steering gear.  Both the hydroboost and steering gear have separate low pressure return lines to the ps pump reservoir. 

 

The hydroboost helps your braking by storing hydraulic power.  When you push your brake pedal, you release some of this stored pressure it forces a piston in the hydroboost to help push the master cylinder piston. 

 

If the hydroboost leaks, it usually leaks on the firewall or into the cabin behind the brake pedal.   The steering gear can leak anywhere there is a seal.  The return lines can leak and there are O-rings on the high pressure lines that leak pretty easily.  The pump can leak from the front seal and from the reservoir O-ring.

 

Hope that helps!

[JOHNFAK]

"  it forces a piston in the hydroboost to help push the master cylinder piston.  "

Awesome - guess that's the basic part I was missing.

What does it phsyically do to "assist "

 

No Leaks on firewall or behind pedal.

New Steering box ..... still leaks.

Guess its got to be the lines or fittings or reservoir oring ...... Ill clean everything down and see if I can track her.

 

thanks guys for the insight. Was useful. 

 

You and IB should collate that info together and have put it at top/bottom of mikes hydroboost rebuild doc.

 

 

[dripley]

I would like to double that thank you. I have walked away more educated.

[Haggar]

Here is a great picture of how the hydroboost adds pressure to help you actuate the brakes.

 

Here is a great explanation of the hydroboost operation specifically.  http://www.brakeandfrontend.com/operation-diagnosis-and-repair-of-hydro-boost-power-assist-systems/    The pictures are just crazy small.  

 

Here is where I found the operation picture.  It looks like a great basic explanation of braking systems in general.  (I have not read through it for technical accuracy though.)  http://www.winbrake.com/training_autofundamentalsbrakes.html

 

Notice when you push the "input rod end"  the assembly moves forward.  This opens a valve letting hydraulic pressure to help you push the "power piston" forward.  The hydraulic pressure on the added area of the piston is what helps you "push the brakes harder".

Edited May 3, 2016 by Haggar

[JOHNFAK]

ok - bringing this back from the rear.

 

How do I know if my hydroboost/Power Steering is working properly. Heres my deal.

 

I put on a brand new aftermarket Steering Gear. Was ok but kind of had some slop in the steering under certain conditions that wasnt there before. Not the normal 12noon 15 degrees each way ...... more like 45-120 area.

Spoke with the shop after taking video and they sent me another gear. In between I noticed my PS fluid was low.

 

I put on the new gear, and fresh PS fluid and it was great. It felt like I could steer with 1 finger, and apart from steering wheel slightly out of alignment 95 % of the slop I mentioned was gone.

 

2 days later the steering feels more like it did before. The "feedback" pressure that seemed to come from the PS/hydroboost wasn't as good. Kinda feels like I couldn't turn as easily and the steering is a little less controlled. Under this scenario it feels a little more "loose" in steering. I thought this must be loss of fluid (as it was low before) - so I checked - NOPE. It seems lower ....... but its 4/5th fill.

 

There's definately something going on ........ but I can't put my finger on it. Anyone got any ideas on how to validate or things to look at / for ?

 

[JOHNFAK]

Think Im going to pull the valve and filter and clean up.

 

 

[Haggar]

John,

 

The power steering pump just helps you do the things. 

If you are feeling "loose"  that is usually a mechanical issue, unless your power steering pump pressure is changing.    Is "loose" a place where the wheels are not following the commands of the steering wheel, or is it pressure fluctuating making it easier to turn and harder to turn.  (whether you have power steering pressure, the wheels should follow the commands of the steering wheel.)

You are in a tough spot...  which came first the chicken or the egg?

I would do what you suggested.  Clean the filter and regulator.  You can also try a thin washer behind the spring.  This should increase your PS pump relief pressure.  You could do a complete flush too.  If that doesn't fix it you are going to have to try a pressure test and see if it is going wonky on you.

 

GL!!!

Hag

[JOHNFAK]

Hag - thx.

hard to define it more than that.

Basically when the power steering was working and was able to turn with 1 finger - everything seems more repsonsive like teh pressure was helping the steering feedback to my hands

 

Now its harder to turn - like before I could easily turn in a parking spot ...... now I have to do 2 turns as it doesnt push the steering far enough on a tight turn.

 

So yes - think Im going to pull the valve/regulator  and check the filter........ I have heard of teh washer behind spring - does it go on the backside slipping over the valve/regulator ?

 

Will do this and update.

 

 

[Dieselfuture]

Make sure all of the air is out

 

[Haggar]

John,

 

We may need to re-think.  I have found a couple articles that have said if the pressure to operate is enough, then it is more flow rate is needed.  (I realize that flow and pressure, while different, are highly dependent on each other in a small system like this.)

 

Here is a neat how to. http://www.gmtruckcentral.com/articles/2013/powersteeringmods/

 

I would only concentrate on the flow aspects.  The FSM seems to confirm this:   The 01FSM shows no pressure difference between all the pumps for all Rams. EXCEPT that Diesels and Hydroboosts (which in that year meant the same trucks) Had a HIGHER flow than all the others. by as much as 30%  See page 19-5.  and that goes along with DF's statement, if you are foaming oil, there could be trapped air totally messing up flow rate.

 

GL   HTH

 

Hag

 

 

 

[Haggar]

Wow John,

 

Look what I found too!  An article by Cowboy on helping the flow!!!  Nice write up Cowboy!

 

 

[JOHNFAK]

Yeah this is great stuff ^^^^ 

 

Been meaning to get it done .... but have been away.

Will update soon.

 

Thanks Hag

 

[John Fak]

Pulled the value and center section and spring.

Size was 9/64 I drilled out to 5/32 and stretched the spring to around 2".

Small modifications.

Didnt pull the center section apart.

Will drive tomorrow and see.

 

Cleaned filter with brake cleaner.