Thread: Excavator Relief adjustment

My little 2.5 tonne post driver digger got a wee bit of love today, a whole new set of track bottom rollers.

However it has another problem that I have no idea how to pursue..... the main boom relief is "leaking" so the main boom loses power and won't hold up a load unless it's getting control input.

So how hard are these to adjust and is there any specialist equipment that is essential?? Or do I have to take it into town to a specialist??

Thoughts??

picture of the relief valve would help.
some you can adjust pressure Others are pre set.
most likely the O ring are needing replaced

Mechanic job. If that is the problem as it could be a multitude of things. Then it needs to be set to the correct pressure. Just winding it up could and most probably will cause other issues.

@Tentman Yep as Harryg said ,but most importantly if you are not experienced working with it be extremely cautious ,while we were in Arnhem Land, the local Aboriginal Land Councils would have gear in various stages of disrepair & twice blokes had to be Flying Doctor evacuated after main lining hydraulic fluid while working on leaks & Valves in hard to reach/see places .

Without some proper gauges playing with hydraulics is a shit fight. Boom lift cylinder.seals could be a bit dodge although a bypass check could identify that.
Also possibly spool on control valve?
You could get really sneaky and swap the hoses from the crowd cylinder over and see what happens.
Then it would prove the relief is cactus

I dont think it would be a relief valve as those control maxumim pressure from the pump.
When there is no control input there is no (or shouldn't be) pressure being supplyed to the ram.....the only pressure in it is as a result of whatever load it is holding up.

I suspect you need a piston seal kit in the ram or maybe it has a leaky spool valve in the control .

Originally Posted by veitnamcam

I dont think it would be a relief valve as those control maxumim pressure from the pump.
When there is no control input there is no (or shouldn't be) pressure being supplyed to the ram.....the only pressure in it is as a result of whatever load it is holding up.

I suspect you need a piston seal kit in the ram or maybe it has a leaky spool valve in the control .

The other thing I have seen in my many many many ram repairs is sometimes the ram tube can be streatched aound the piston in a over pressure situation.

This will present as a barely perceptible even with a straightedge on the tube buldge.....but it will be measureable in the bore.
This type of problem is pretty much impossible to cause threw normal operation of the machine (provided the relief valve hasn't been titued with)
Almost invariably what causes those type of failures is using too small a machine for the job and then the abuse starts to get the job done.
Ie ramming stuff with the bucket in travel mode.

Hey thanks guys. My machine (an IHI 25 NX2) is in good nick (2100 hrs) and I don't think itd been knocked around. The hydraulics schematic shows a relief on the main boom valve. However its beyond me so I shall take on board the wisdom of the forum and get a shop to look at it.

Originally Posted by Tentman

Hey thanks guys. My machine (an IHI 25 NX2) is in good nick (2100 hrs) and I don't think itd been knocked around. The hydraulics schematic shows a relief on the main boom valve. However its beyond me so I shall take on board the wisdom of the forum and get a shop to look at it.

Can you post up the schematic?
If it has a separate relief for that ram? It is possible it could be leaking causing the creap.

Hi Tentman,

Curious to know if you sorted this issue and what it was?

Cheers

would be odd to have a relief on the main lift cylinders.
given that is not an old machine its more likely an anti drop Valve. These became manditory for excavators used for liffting stuff, ie prevents sudden drop in the case of a hose failure, also requires you to positivey drive the cylinder down.
at only 2100 hrs I would not be expecting cylinder seals just yet.
You don't want to start screwing them in or out as this will effect the operation of the unit.

As above my guess would be a damaged o-ring on one of the cartrige valves in the Anti drop valve block.
Again as a 2.5 tonner it should be easy to take into someone who works with this stuff. Even an experianced Hose tech should be able to sort this one.
Just remember the if you start removing the cartridge valve and the boom is not completely at rest unloaded stuff can go flying and or you could get an oil injection injury. They are very bad, rare but bad.
Google,
Often under rated as they can appear as a very mild injury, Treatment is termed as immediate and aggressiver surgical intervention is required to save the limb.
Z

After a bit I found the lock on the restrictor for the bucket tilt (which is on this circuit) had come loose and the valve was practically shut down. There is a relief on this circuit but the old hoses were throwing their toys before it released! I think!

Oops- I see I answered the wrong question . . . The relief solved itself before I got it to a shop haha.

well - thats a relief

Yes, you must have been feeling a little under pressure right up until that point. Ahhh, relief...