Thwaites 3t dumper - tipping problem

[Jonnyt]

Hi Guys,

First post but have read the forum with interest for several years.

I have a thwaites 3t swivel tip dumper. Reg is 'R' so 1996. It has a 4 cyl perkins engine. Has run and worked really well for the last 3 years only issue was a new clutch but seems fair wear and tear to me.

Today though the tipping stopped working. The events were all a bit odd. All working perfectly. Filled another load and went to tip. The tipping ram simply didn't operate but swivel and steering still did and do. Checked hyd oil level and the oil was below the red line - I filled it up and it probably took 4 litres. That was unusual because although an old machine I have never had to put oil in before (except when a hose blew) and I checked the level last Sunday. It is also odd because there is no sign of where the oil has gone - checked over the whole machine and no obvious leaks as it ought to be to have lost that much oil.

Still didn't work so cracked the nut on the tipping ram and no oil is coming out. I should say that the pump is obviously working because the swivel and steering is working (the spool block for swivel and tip are one and have one feed) and when I move the lever to tip the engine goes under load as it normally would and as I say the swivel works.

The fact that the oil has gone is a bit of a mystery but I'm guessing that it has got to be the spool valve?

Any other ideas? If it is the spool valve is it servicable?

Thanks,

Jon

[Jeremy Rowland]

Hi Jon welcome to the forum while I am no expert I would say that yes the spool valve could be serviced, I may be wrong here but it sounds like the hydraulic oil is bypassing the tipping ram as if a pressure valve somewhere in the system is stuck open? I am at a loss to say where your hydraulic oil could have gone are you 100% that there is no oil leaking out when you try and tip the body?

Jeremy

[essexpete]

Has a single ram (although I am not sure it would make any difference)? I am wondering if you have a piston seal completely blown allowing the oil to bypass around the piston.

[Whitlock 505]

Hi Jon
I've had trouble with hydraulic rams and found that the locking bolt that keeps the piston seals to the bottom of the ram had unscrewed itself over time, meant a strip down of the ram and screw it back on, could be a possible cause?

Ian