Hi Folks,
As a follow on I had some trouble with my 674 steering and thought I’d update this thread to keep all info in the same place.
- · The steering from when I bought the machine was always slow / sluggish / and required a lot of effort to turn, especially when loaded.
- · Deteriorated over the years to the point where there was no power assist
I know the hydraulic pump is ok because the loader and rear end hydraulics all work well. I went through the following diagnostics:
- · Dead headed loader hydraulics to activate main hydraulic relief valve and shock the MCV flow diverter / director - no improvement
- · Dropped the MCV Flow Diverter / Director valve – no improvement:
o It wasn’t so easy to pull out. I ended up using an M10 expanding bolt (concrete anchor bolt) in the end of it so I could pull it down.
o I found one little piece of swarf but nothing significant. All ports were clear
o I polished any scores on it with 600 wet and dry
o As per some other guidance, I ground two very small slots in the base of the diverter in case the spring had weakened and it was bottoming against the plug and preventing flow.
- · I replaced the hydraulic filter and cleaned the screen – no improvement
o I think the screen was in the wrong way so I corrected it. I refitted it as follows: MCV block, new filter, screen then steel cover and bolt.
- · I stripped the steering cylinder and rebuilt – no improvement
o Stripped and all looked good and clean, ports all clear, piston in the right place
o I rebuilt with new seals.
o For the piston PTFE seal I recommend the following. Use two small zip ties to pull it over and on to the piston (this will stretch it). Then wrap a number of layers of PVC tape on top of it. Then squeeze it back down to size with a jubilee clamp over the tape. The tape helps compress it and prevent damage. Drop it back in to the cylinder.
o When putting the end cap wiper seals in, press them on the nose in the vice with the back of a socket, nice and square, they’ll pop in. Don’t heat or try to put one side in then the other, they’ll deform.
o For putting the end caps on, use Knipex Gas pliers to turn them rather than hammering at the two holes in the face.
- · I lifted the front end and checked the steering was free – all free – no improvement
o Pumped a load of grease in and moved freely by hand
- · I stripped off the steering supply elbow with check valve / non return valve at the front of the MCV – no improvement
o I pulled out the check, cleaned it (no blockages) and reassembled, note it should look like my photo for correct orientation, it has a habit of popping out by itself.
o Have a big container ready since the full transmission oil will start slowly flowing out
o If you suspect this is the issue, you can refit the elbow without the valve. It’s only there to hold fluid in the steering circuit so you can turn the wheels without the engine on.
I forgot to add that i also tried bleeding the brakes to see if that helped - no improvement
- · I then (finally) pulled out the Steering Safety Valve / Steering Relief Valve – Problem found!
o It pulled out easy with a magnet (which implies the O-ring was shot). The only way it should come out is with one crank of the engine (with the stop lever down!) so the hydraulics push it out.
o It was not looking healthy, pulled it apart and the spring is bent!
o I fitted the one from my 475 to try and the steering worked perfectly. It had a much better O-ring fit.
o I’m sourcing a replacement valve from the scrap man.
Thankfully I didn’t have to strip the Oribital or start looking at the pump! I’m hoping the above helps others when diagnosing problems with the steering. It’d be easy to pull out the relief valve and think all is ok, when in fact the O-ring is leaking and hence bypassing the steering. I’d go so far as to suggest that with steering issues, the sequence should be in terms of easiness:
- · Check MCV
- · Check Steering Relief valve & O-ring!
- · Change Hydraulic filter
- · Test pump pressure
- · Check steering isn’t seized
- · Strip steering Ram
Thanks for reading!
Cheers
Michael
