Outer Limits 4x4 Board

i have a palfinger pk6700a crane on my hino and it seems to be so slow
every thing works it just moves slow
i have changed the suction hose and the oil but no differernce
i rang palfinger and they didnt want to help me unless i took the crane to them and all he wanted to do was sell me a new crane,it is about an 85model??
does any one have any ideas as to why and what can ido
sorry it is not 4b tech

Checked the filter and by-pass?

Has it lost any power IE: will it still lift usual load? or is it just slow?

http://www.machinerylubrication.com/art ... icleid=531
Jas.

have you checked the filter?

and all hoses, hyd lines to be clear and flowing well, no leaks of kinks etc.

is any part of the arm stiff, bent or not moving freely

do you know if its moving slower than original or do you just think it is slow?

speed will depend on what flow (litrs per min) the pump flows and the displacement of the ram(s) big dia ram will move slower than a samll dia ram same flow.

serg

the mechanics of the crane are ok there is some wear in the pivot bushs
but no binding
when you operate any of the controls it takes 10 to 30 seconds for the
crane to respond
havent changed the filter yet but it is on the return line,does it make that much difference
the crane is slow compared to the others that i have used
it is more the response time that concerns me
havent lifted a known weight yet will be doing that soon
the pump also makes a rattle noise and then the it moans when you hit the relief valve
the main jib rams have a 3.5"ram shaft with 6"body
2 1"long rams on the extension
thanks for the link very helpful
i am trying to find out what type of pump it is as it has no tags or numbers on it
it is a 4 bolt gear pump obout 6-8" long

hey mate,
I would be checking the return filter, from memory it sits on top of the oil tank and usually has a filter guage on it. might be able to pull it out and give it a quick run just to see.
The rattle noise in the pump sounds like it is cavitating, make sure your feed line is free and there is not something blocking the suction point inside your tank.

Have fun

I'd say you have air in the system. The slow response time is while the pump compresses the air: it has to build up the air pressure to whatever pressure is required to lift the load. The "groaning" is probably something to do with air in the system too - pressure bleeding down over an extended time, rather almost instantly? It's probably pushing a large volume of oil as the air expands again - the "groaning" may be this oil flowing through the relief valve?

If it runs a vane pump, the pump could be rooted. Also if the return is blocked or restricted it will be choking te system.

If it has test ports you could check operating preasure is correct, if it has a valve that stops the arm dropping if it blows a lift hose this too could be faulty.

CAUTION HYDRAULIC PREASURE IS EXTREMELY DANGEROUS.

-Scott- wrote:I'd say you have air in the system. The slow response time is while the pump compresses the air: it has to build up the air pressure to whatever pressure is required to lift the load. The "groaning" is probably something to do with air in the system too - pressure bleeding down over an extended time, rather almost instantly? It's probably pushing a large volume of oil as the air expands again - the "groaning" may be this oil flowing through the relief valve?

X2
I'd be checking for air in the system.
ALso a blocked filter in the return line will also slow things down. Remember the oil has to go somewhere.
Does the system have a pressure gauge?
Also lift a weight with it, and suspend it for a while, see if the load drops.
If it does it's a good sign that pressure is releaseing from somewhere or air in the system.

Has the crane always been like it or has it just happened?

Has it just been fitted to the truck?

If it has just been fitted, is it a new PTO and pump, or a s/h one that 'fitted'?

Will it respond quicker when the engine is idled up a bit?

A blocked return filter will make SFA differance (they have bypasses in them)

A too small or restricted suction will cause cavitation (rattle) and can kill a pump pretty quick. An air leak in the suction line will cause airation (noisey and frothy oil). There may be a strainer on the suction (inside the tank), can't remember.

Can it get to relief pressure (can you hear the relief in the control valve opening) when you deadhead a cylinder?

A lot of jap truck boxes can have a very poor PTO ratio (sometimes less than half engine speed) with the wrong PTO spec. Most gear pumps dont like running under 4-500rpm.

It will be either a Powauto or Chealsea gear pump fitted, quite easy to jerk it off strip it. Easy to see it its RS.

Rick

gearbox is roadranger 10sp
just bought the truck ,crane been fitted for long time poor service history
waiting for a new return filter
havent lifted anything heavy but it doesnt drop with light load @500kg
1 ram does leak when arm folded up so at the min im leaving it open
so it dosent leak
when i got the truck the hydraulic oil had leaked out due to a loose suction hose and it was empty
replaced hose and no more leak
cant see the numbers of the pump have to remove it first,but it is a gear type pump
yes the relief valve seems to activate when you deadhead any of the cylinders
there is a small valve/test port on the valve control where the hose from the pump attachs no i dont have any test gauges
will the air bleed out over time or do i have to do a specific action to fix it ?
thanks for all the input been very helpful
i am a mechanic but my knowledge of hydraulics is very limited,its just that i know it should be better than it is
thanks

You vary rarely have air problems in hydraulic systems that require anything special done to bleed them. Use all functions (to full extent) a few times and all air should be out.

If it gets to relief pressure, pump is at least in 'reasonable' condition. Time the main boom travel from right down to right up. Then fully extend boom and time again. It will take more pressure to lift with the all the extension out, and if pump is worn, flow will drop as pressure rises causing cylinder speed to slow up.

Check its operation hot and cold. Good cold/bad hot is usually a sign of a worn pump/internal leakage somewhere. Bad cold / good hot usually points to a suction problem. Blocked suction filter/hose to small/ restriction in suction side somewhere. Give to a rev (15-1600rpm), better/worse?

The pump may just be too small, that dosn't explain the hesitation tho.

revs are 1500rpm
it works better cold than when its hot so im assuming the pump is on its
way out
i did check the suction side for restrictions from tank to pump it is all good
will do wwhat you said in the morning to verify the prognosis
thanks

If you think its the pump, pull it and open it up. If its got 4 x mounting bolts and about 11ish studs/nuts holding the pump together it would be a Powauto (very common). They comonaly blow the pressure plate loading seals inside the pump which causes poor efficiency. If the gears have worn half way around the housing, it pretty much RS, buy a newie.

If its got a 3 bolt mount, its a cheap Italian style (pick a brand) pump which never seem to last very well. Again, if its worn toss it.

v8zuki wrote:when you operate any of the controls it takes 10 to 30 seconds for the crane to respond

Assuming youve run the crane out to full extensions ( out riggers included) to clear any air in the system, and have suffecient oil in the system it leaves only one posibility

Farked pump for sure

V8Patrol wrote:

v8zuki wrote:when you operate any of the controls it takes 10 to 30 seconds for the crane to respond

Assuming youve run the crane out to full extensions ( out riggers included) to clear any air in the system, and have suffecient oil in the system it leaves only one posibility

Farked pump for sure

Bingo.

Bleed air.

Check oil level.

Check filters.

Then pump.