Power Steering Pump Overflow at Shutoff

[Jeff10]

Hi Everyone,

We're finally getting the '70 Bronco running again. It has been dormant for almost 7 years.

After getting the engine fired up, one of the first things that became apparent was that the power steering pump overflow problem was not corrected by replacement of hoses.

I am attaching pictures for the pump install/setup for reference.

The problem is that the pump is noisy while running. When the motor is shut-off, power steering fluid pukes with some force out the top of the reservoir (with the cap on the reservoir).

We're trying to figure out if this is a problem with the pump, or if the reservoir's volume is too small, or something else. It just occurred to me that there wasn't a cooler on this Bronco when I bought it. Wondering how much of the problem that could be...

Anyone with experiences like this, or thoughts about how to correct it?

Thanks,

Jeff

 

[Digger556]

My guess, something is aerating the fluid, causing pressure to build.

Do you have any sharp turns or narrow passages in the loop? Any fitting adapters?

You may have to swap the pump if nothing is apparent in the plumbing.

 

[Yeller]

Airated fluid depressurizes and expands. Are you sure you thoroughly bled the box?

 

[Broncobowsher]

Air in the fluid. Hard to get out. Start and shut off after 1-second. Wait for the fluid to degas. Top off. Repeat, repeat, repeat, and repeat a bunch more. Once the air is out all will be good.

 

[Jeff10]

Hi Digger,

Replacing the pump was going to be the first choice unless something else stood out to anyone.

The guys who is bringing this back to life for me thinks it may be a volume issue.... he has to add fluid to the reservoir when the motor's running to quiet the pump and try to bleed the system. Then when he shuts the motor off the fluid pukes out and he has to start all over with the bleed process.

I'm wondering if anyone else has used a pump like this on their Bronco.

Thanks again for the input.

Jeff

 

[Yeller]

Fill it and jack the front tires up off the ground and steer back and forth until the fluid level stops dropping and it begins to get quiet, it will work it’s self out. It’s trapped air in the system, the only thing that will cause that issue. The engine running helps this procedure, some just never bleed right if not running.

 

[Jeff10]

Hey Guys,

I understand what you're saying... I want to be a little respectful of the guy doing most of the work. He's got a lot more experience as a builder and fabricator than I do. We discussed the bleeding process last summer with the other Bronco. I'll make sure we try give the bleeding a good go before making life more complicated.

The other Bronco runs a dual return Saginaw, hydroboost brakes and RAM assist. There's never been a problem like this with trapped air... not even close.

The way this system is plumbed, there's very little fluid in the lines or the steering box... We'll give it a good try... a second at a time to see if it will work out before changing out the pump.

Thanks again.

Jeff

 

[Crush]

Cant tell from the pics but are the lines hooked up correctly? You may have the return and pressure in the wrong hole. This may cause that kind of problem

 

[Jeff10]

Hi Crush,

Cant tell from the pics but are the lines hooked up correctly? You may have the return and pressure in the wrong hole. This may cause that kind of problem

The previous owner said he had the same problem (or, that's what he told me after I bought it and experienced the same problem the first time I drove it). But... that doesn't mean that it wasn't hooked up wrong in its previous life.

We'll try to confirm that before doing anything else. (How do we know that the pressure side of the pump is going to the correct port on the box? I'll do some checking... but, I thought I would ask here, too.)

It would be pretty awesome if that turns out to be the problem.

Take Care,

Jeff

 

[Rustytruck]

Return lines above the pump drain down when the engine shuts down. Any coolers have to be in a position to hold fluid when shut off. I had a problem with this when I mounted my cooler

 

[toddz69]

Jeff:

That's a Ford C-2 pump - I ran one for a few years since it's what came on my Mustang 5.0 that I swapped into my truck back in '97. There wasn't a volume issue (seen the pump used on many other Broncos in the intervening years). As others said, I think it's just a air in the system problem. I had the same problem when I swapped in my 4x4x2 box many years ago. Actually, Protofab did because they did the box install for me. Keith called me one afternoon very frustrated because they couldn't get the system to quit puking fluid. They bled and bled and bled and it finally cleared itself out....

If you don't like that pump, I'd swap that bracket and pump with one from an E-Series van that uses the Saginaw pump.

Todd Z.

 

[langester]

I had a similar problem on my truck (79 f150). The cooler line was plugged and was not allowing the fluid to pass through like it should. The second I shut the truck off it would puke out the top of the lid. May not be your issue but took me a while to figure it out.

Good luck!

 

[Digger556]

You can usually purge trapped air back jacking the front end up and cycling the steering lock-to-lock with the engine off. Just be careful. Too fast and you'll blow the cap off the pump and make a PS fluid mess.

 

[patford]

Had the same problems sag pump hydro boost and cooler try all the tricks puke fluid every time i shut the motor off , then looking at one of aftermarket pump sites they said fluid level should never change running or not . So running i cycle the brakes and steering top up the fluid shut it of puke ! So i install a rad hose on top of the pump about 4" hose clamp it on fire up the motor do all the cycles top up the ,and shut it off level came up but all was contain oh and forgot no more pump wine. So i made a cap with a small vent took the bronc out for a short drive and the level drop off when i shut it off , after a few drives all the air puke out and the level stay the same . I remove the hose and all good . Cheap and easy to try .

 

[Jeff10]

Hey Everyone,

Thanks for all the great input.

Pat, we'll give your method a try first (once we confirm that the high and low pressure lines are connected correctly) and see what happens.

I'll post back later today.

Thanks again.

Jeff

 

[Broncobowsher]

High pressure is closer to the pitman arm
Low pressure is closer to the steering wheel
Get them backwards and you will get a VIOLENT steering wheel shake as soon as you touch the wheel. Break your hand violent. Death wobble will be tame in comparison.

 

[Jeff10]

Hey Guys,

Update... Unsuccessful day.

The builder installed a reservoir for the pump to ad more volume. (He liked that idea better than the radiator hose extension.)

He just can't get it to quit puking fluid when the motor is shut off. He has tried vacuum bleeding the lines... pretty much everything he can think of. He's second guessing the line sizes that were used for the high pressure and return side, too.

Long story short, he's out of time available to work with me, so I have to pick the Bronco up tomorrow and I'll just keep it loaded on the trailer until he can get me back in the shop. Hopefully by then we'll have a game plan put together.

I know that the power steering is a closed system from pump to return. If the system is purged of air, and there are no air leaks between the pressure side of the pump and the return (and there's fluid in the reservoir) there should be no way for air to enter the system. Even if the pump is cavitating, it can't create air. (Or, can it?)

Not sure where we will go from here.

Jeff

 

[tirewater]

Hard to tell from the photos, is that pressure hose kinked? Looks like a pretty tight bend.