issues with hydro assist fluid

[missouriman]

as some of you know I have two trucks with the same set up.

but I keep getting air in the system on one of them and can't figure out how it is happening.

some times it will go months with out getting aired up. I watch/ check the fluid level each time we go out.

then out of the blue the pump will make some noise, ( I may be driving it or have been driving it at the time).

there it will be, auto trans fluid running down the inside of the fender. looks like pepto bismal.

I have checked the lines. I have taken the cylinder off and held the fitting up and turned back and forth just short of a million times.

I have started the truck, turned the wheel to the left, let it run until I don't see the bubbles in the fluid. then turn it right and again let it run till there are no bubbles. at this time drive it, even ran it down the interstate at 4k rpms for a few miles. check fluid no bubbles that I can see.

shut it off and there it go's, dang near empties the res.
I have checked to make sure I don't have any high spots in the lines where air could hide.

the other truck doesn't do this.

question:
is there any place in the system where there is a lot of suction.
something that would leak in now and then but not all the time?

my next step when the weather is warm enough is to replace the pump.
ps the pump is quiet when it is not aired up.
I have the Hayden 401 cooler mounted lower then the res.

 

[liljlandon]

You could be sucking air in through your cylinder. We have had it happen many times with tractors. The only thing i can think of is, your cylinder isnt under pressure like a tractors would be. Normally in the winter months we leave the front end loaders up in case we have to pull start the tractor. Thats when it occurs the most.

 

[missouriman]

would it not leak out rather then in? it is a single cylinder.
I thought that they only pushed not pulled.
it is the cylinder from surplus center.

not sure how to check that.

 

[liljlandon]

Single meaning only it actuates on only one side? your cylinder should both push and pull... Otherwise it would be extremely easy to turn one way and not the other. The fluid is directed in the direction you turn. Is your cylinder pitted? Air gets in places that have surprised me before.

I would not know how to test it on the vehicle. With tractors and industrial equipment they are normally load bearing items so when it leaks, your load drops.

 

[missouriman]

Single meaning only it actuates on only one side? your cylinder should both push and pull... Otherwise it would be extremely easy to turn one way and not the other. The fluid is directed in the direction you turn. Is your cylinder pitted? Air gets in places that have surprised me before.

I would not know how to test it on the vehicle. With tractors and industrial equipment they are normally load bearing items so when it leaks, your load drops.

pushes on one side of the inner rod seal to go say left, then pushes on the other side of the inner (center) rod seal to turn right.
pressure on one side move cylinder, passively pushing the fluid out of the other side.
so depending on the direction one side or the other is under pressure.
it is a single ended dual direction cylinder.
like this one.

https://www.surpluscenter.com/item.asp?UID=2232010207594643&item=9-7257-6&catname=hydraulic