1850 Hydraulic pressure pulsates - any theories for cause?

[woodlandfarms]

On my computer it is the #1 item on the list I was having upload issues.

It is for the tilt seat circuit.

Now in Uruguay. Feeling very much like an explorer, except I keep running into people from New York. So much for getting away from it for a while

 

[MikeOConnor]

Yep, #6 was there. I just missed it the first time around.

Well, the saga continues. The new Brake Tender is in -- which is good, because the old one was indeed a little wonky. But unfortunately the pulsing still continues. Terry just had me back off the pressure in the charging valve (by loosening the nut at the end of the big spring just a tad). That didn't do it either. So we're still at work.

 

[J_J]

Can you not put a hyd gage in each circuit and see which circuit is pulsating.

It sounds like a relief valve releasing high pressure and reseating.

Could an unstable engine rpm cause the pulsating?

 

[ponytug]

Dear Mike,

I would look at the float servo and the associated electrical circuit. Check with Terry, but I think that you can unscrew the solenoid, and there might be a bit of "crud" lodged under the needle valve.

All the best,

Peter

Yep, #6 was there. I just missed it the first time around.

Well, the saga continues. The new Brake Tender is in -- which is good, because the old one was indeed a little wonky. But unfortunately the pulsing still continues. Terry just had me back off the pressure in the charging valve (by loosening the nut at the end of the big spring just a tad). That didn't do it either. So we're still at work.

 

[MikeOConnor]

The latest plan is to replace the charging valve again.

JJ, the common point in all the circuits that are pulsing is that charging valve. I was amazed to see how many different circuits it's tied into once I ran through all those diagrams. This happened once before (right in the middle of the day, no connection to putting a new filter in that time) and a new charging valved fixed it.

My current theory is that the brake-tender has been slowly failing for several years. As it's been failing, it's been periodically over-pressuring the circuit, causing the charging valve to blow its seals. The PT drives a LOT better with that new brake tender in it and it no longer "hangs up" at 2500 PSI the way it used to. According to this theory, the charging valve has failed again, which is what's pulsing. Putting the new brake tender eliminated the cause of the charging-valve failure, but the charging valve still needs to be replaced too. We'll see how that turns out.

Peter, do you mean the "float servo" or the "draft-control servo"? Just checking -- those cool diagrams don't show a float servo (a few other things are missing too, they're early drawings).

I mowed for a few hours yesterday to see if I could just settle something down or bounce something into alignment. I didn't jar anything back into place, but nothing got any worse either. Terry doesn't think I'll hurt anything by doing that. It was great to get out on the mower again, it was getting REALLY out of hand out there.

 

[ponytug]

Dear Mike,

See the other thread of Woodlandfarms, but it occurs to me that the small (2.5" dia. x 4") hydraulic accumulator on your charging valve may have lost pressure so the relief kicks in, then out, then in, then out, in some harmonic. Either way, I agree with Terry that it does sound like it might be a charging valve, which includes the hydraulic accumulator. (which might be available locally...)

I meant draft control, which is servo driven. Besides the charging circuit, it is the other circuit where there is a pressure regulation.

I'm on my third or fourth rebuild. They are available on the internet, but you would need a pressure gauge to set the pressure.

All the best,

Peter

The latest plan is to replace the charging valve again.

JJ, the common point in all the circuits that are pulsing is that charging valve. I was amazed to see how many different circuits it's tied into once I ran through all those diagrams. This happened once before (right in the middle of the day, no connection to putting a new filter in that time) and a new charging valved fixed it.

My current theory is that the brake-tender has been slowly failing for several years. As it's been failing, it's been periodically over-pressuring the circuit, causing the charging valve to blow its seals. The PT drives a LOT better with that new brake tender in it and it no longer "hangs up" at 2500 PSI the way it used to. According to this theory, the charging valve has failed again, which is what's pulsing. Putting the new brake tender eliminated the cause of the charging-valve failure, but the charging valve still needs to be replaced too. We'll see how that turns out.

Peter, do you mean the "float servo" or the "draft-control servo"? Just checking -- those cool diagrams don't show a float servo (a few other things are missing too, they're early drawings).

I mowed for a few hours yesterday to see if I could just settle something down or bounce something into alignment. I didn't jar anything back into place, but nothing got any worse either. Terry doesn't think I'll hurt anything by doing that. It was great to get out on the mower again, it was getting REALLY out of hand out there.

 

[MikeOConnor]

Hm. Not a bad theory. I wonder if there's a way to re-charge the accumulator. I've never been real clear on how the accumulator is initially charged or replaced, so I've never touched it when putting in the new charging valve.

I'm on my fourth rebuild as well. It seems like it's being over-taxed by something in that giant collection of circuits that it's a part of. I found that I was blowing them in the winter (makes sense -- cold temperature, thick fluid, lots of pressure). So I got in the habit of waiting for a minimum of 25 degrees outside before using the PT. It may also be the problem I was having with the brake tender where it would hang up at 2500 PSI and just sit there for 10-30 minutes if I wasn't paying attention.

The interesting change with the new brake tender is that it now when I turn off the PT it takes a couple minutes for the brake tender to cycle down to zero pressure and lock the brakes. That used to happen instantaneously when shutting down.

 

[woodlandfarms]

Mike, I am a bit concerned about your note on the tender. That is really dangerous. If you have a stall on a slope you are not going to be able to stop yourself. Hayride to ****.

 

[J_J]

Hm. Not a bad theory. I wonder if there's a way to re-charge the accumulator. I've never been real clear on how the accumulator is initially charged or replaced, so I've never touched it when putting in the new charging valve.

I'm on my fourth rebuild as well. It seems like it's being over-taxed by something in that giant collection of circuits that it's a part of. I found that I was blowing them in the winter (makes sense -- cold temperature, thick fluid, lots of pressure). So I got in the habit of waiting for a minimum of 25 degrees outside before using the PT. It may also be the problem I was having with the brake tender where it would hang up at 2500 PSI and just sit there for 10-30 minutes if I wasn't paying attention.

The interesting change with the new brake tender is that it now when I turn off the PT it takes a couple minutes for the brake tender to cycle down to zero pressure and lock the brakes. That used to happen instantaneously when shutting down.

Do you know if the accumulator is gas filled or spring operated?

If gas, then it can be refilled.

Charging & Gauging :: Accumulators.com

Bladder Accumulator Repair Services - Accumulators.com

http://www.accumulators.com/pdf/File/repairandservicecenterbulletinonline.pdf

http://www.accumulators.com/pdf/File/AccuMights.pdf

Be careful if you try and take it apart. It takes special tools, and a way to release the gas if any.

singlehand

 

[ponytug]

Dear Mike,

It shouldn't take awhile. I'd call Terry on it. While it is possible that you have some debris or a ton of air in the brake line, I'd bet on a bad unit. If you have someone cycle the switch, how fast is the spring moving in an out? It should take under a second or two.

As Woodlandfarms points out, this is a safety issue.

All the best,

Peter

Hm. Not a bad theory. I wonder if there's a way to re-charge the accumulator. I've never been real clear on how the accumulator is initially charged or replaced, so I've never touched it when putting in the new charging valve.

I'm on my fourth rebuild as well. It seems like it's being over-taxed by something in that giant collection of circuits that it's a part of. I found that I was blowing them in the winter (makes sense -- cold temperature, thick fluid, lots of pressure). So I got in the habit of waiting for a minimum of 25 degrees outside before using the PT. It may also be the problem I was having with the brake tender where it would hang up at 2500 PSI and just sit there for 10-30 minutes if I wasn't paying attention.

The interesting change with the new brake tender is that it now when I turn off the PT it takes a couple minutes for the brake tender to cycle down to zero pressure and lock the brakes. That used to happen instantaneously when shutting down.