B25V boom pressure issue.

[V8Druid]

I know he hasn’t said so, but I assumed that he’d left it in the air with the blade at one end and the boom the other? So the entire weight of the machine is supported? If thats the case then it’s actually impressive that it stayed there in that position overnight.

too right if that is the case James ..... now't wrong with ram seals or valve block

 

[GlenM]

too right if that is the case James ..... now't wrong with ram seals or valve block

Yes, blade at one end, boom at the other and tracks about 2 foot clear of the ground. After a second night like that, the boom is still holding it up and the blade has lost pressure.

 

[Storrsy]

We have a Yanmar B25V mini digger which works absolutely fine, except that the boom ram will not hold pressure. It works fine with normal digging work but lifting anything heavy requires the lever to be held back constantly. Is it likely to be a ram seal issue?

What do you mean by heavy. How long does it take a full bucket to drop to the floor on its own?

 

[Storrsy]

too right if that is the case James ..... now't wrong with ram seals or valve block

But lifting the machine of the floor wants to expand the ram if left- whereas holding a heavy weight wants to contract the ram- is there seals for either way?

 

[Shovelhands]

But lifting the machine of the floor wants to expand the ram if left- whereas holding a heavy weight wants to contract the ram- is there seals for either way?

Generally the main piston seal is bidirectional, so it’s the same seal used in both directions basically. But I will be honest and say that I’ve never been inside a Yanmar ram, so I might be wrong.

 

[GlenM]

What do you mean by heavy. How long does it take a full bucket to drop to the floor on its own?

It struggles with 1/4 of a tonne now and drops it almost instantly, unless you keep the boom lever pulled back.

 

[GlenM]

Id be aiming for the ram seals also. But just check that the little plungers in the joystick are all coming up fully also

I have just checked and the plungers are returning.

 

[GlenM]

Generally the main piston seal is bidirectional, so it’s the same seal used in both directions basically. But I will be honest and say that I’ve never been inside a Yanmar ram, so I might be wrong.

Even if it is a bi-directional seal, I wonder if fluid could be getting past in one direction only.

 

[Bri963]

This sounds to me like an issue with the spool rather than the ram seals. If the ram leaks internally the boom would only drop a small amount until the pressures both sides equalises. For the boom to drop all the way the oil has to be able to escape the circuit, either past the spool, line relief or an external leak.

 

[Shovelhands]

Even if it is a bi-directional seal, I wonder if fluid could be getting past in one direction only.

If it’s possible without too much messing around, you could try swapping the boom ram hoses over. I know it won’t be drivable with the boom service the wrong way round, but it would possibly narrow it down to the boom spool on the lift side. From what you’ve said previously, my guess is if you swap those over then you will reverse the fault. It will lift ok and possibly not be able to lift itself up off the floor using the boom.
At that point I think it would confirm something wrong in the spool or possibly the Boon Up ARV is faulty or has a piece of debris in it holding it open?

 

[topkit]

I have a Yanmar B15-3 that had a similar problem the boom crept back down almost as quickly as you raised it, I had a look at the joystick control first as on of the four spools on the underside of the servo joystick was a bit sticky through lack of use, I also removed the boom ram and got it resealed, The boom now stays up with no creeping down at all.

 

[GlenM]

If it’s possible without too much messing around, you could try swapping the boom ram hoses over. I know it won’t be drivable with the boom service the wrong way round, but it would possibly narrow it down to the boom spool on the lift side. From what you’ve said previously, my guess is if you swap those over then you will reverse the fault. It will lift ok and possibly not be able to lift itself up off the floor using the boom.
At that point I think it would confirm something wrong in the spool or possibly the Boon Up ARV is faulty or has a piece of debris in it holding it open?

Good idea on the boom ram hoses. Someone did suggest the joystick connections but this might be easier. an you explain some technical terms? What is the spool and the boom up ARV? I am guessing the latter is the control valve?

 

[GlenM]

I have a Yanmar B15-3 that had a similar problem the boom crept back down almost as quickly as you raised it, I had a look at the joystick control first as on of the four spools on the underside of the servo joystick was a bit sticky through lack of use, I also removed the boom ram and got it resealed, The boom now stays up with no creeping down at all.

So do you think it was the ram re-sealing that made the difference? I have also noticed that my machine does seem to drop the boom quite quickly when you push the boom lever forward.

 

[Shovelhands]

Good idea on the boom ram hoses. Someone did suggest the joystick connections but this might be easier. an you explain some technical terms? What is the spool and the boom up ARV? I am guessing the latter is the control valve?

Changing the pipes on the lever would only eliminate the lever, but you might have to go there yet…
If you can swap the ram hoses (if they are long enough to swap), then it will eliminate the ram.

The spool valve is in the main valve block and is the thing that diverts the oil from the pump to the ram. ARV’s are usually on the valve block and are a safety device really, it’s just a relief valve, so if it’s letting oil past then it could be the issue? Not every service will have an ARV but I think you could safely say that the boom lift service will have one.

 

[topkit]

I would definatly re seal that ram the seal kits are not expensive, i paid about £45 for the kit and I got a ram repair specialist to re seal it which cost me £100 on a same day turnaround, I got it done as I always struggle to get the plastic ring part to go over the gland i guess its easy if you have the correct tools.

 

[GlenM]

Changing the pipes on the lever would only eliminate the lever, but you might have to go there yet…
If you can swap the ram hoses (if they are long enough to swap), then it will eliminate the ram.

The spool valve is in the main valve block and is the thing that diverts the oil from the pump to the ram. ARV’s are usually on the valve block and are a safety device really, it’s just a relief valve, so if it’s letting oil past then it could be the issue? Not every service will have an ARV but I think you could safely say that the boom lift service will have one.

Thanks. I had a quick look this morning and I can reverse the hoses where they attach to the rigid metal pipes on the back of the boom. Will try that later, if I get time.

 

[Mick-the-fitter]

Piston seals and check valve are good on the boom cylinder circuit, in the down position, this is the better side to be able to check the seals, as if the central piston seal leaks it would have dropped, so the ram is good, look at check valves or if it has lifting valves it could be that. Pictures of cylinders and boom please.

 

[GlenM]

Switched the hoses and it now lifts weight better but it won't lift itself up so well, so looks like the spool valve or ARV.

 

[GlenM]

Took the floor up to look at the spool valves today. The boom valve looks to be the second one down from the top of the picture, the two boom hoses are marked with orange tape. I am guessing that I need to take out all of the valves and then separate them. Have applied de-greaser and will pressure wash the whole area tomorrow.

 

[Mick-the-fitter]

Quite a bit of oil all around, the problem you have could be a pilot leak on the o ring at the end of the spool! Wash it off get a better look