Zx160 LC weak hydraulics with new pump

[Huffa]

I have a ZX160 LC Hitachi non common rail model 12000 hrs that for nearly two years now has driven myself and the service man nuts. It's performance dropped to about 70% of what it was and it started heating its hydraulic oil. It's since had numerous flow testing, hydraulic pump stripped and inspected which was within spec, valve bank completely resealed and all the usual filters and oil. The Hitachi mechanic who is highly experienced then came to the conclusion it was the regulator on the pump. A regulator was hard to get/expensive on it's own so to take away any doubts with the pump we installed a complete brand new pump and regulator. It's made no difference. Performance is still poor and hydraulic oil is cracking into the 90's easy as on only a 20 degree day doing light digging. Im not a mechanic but does anyone have any ideas on what we should be looking at next ? Mechanic is talking about trying another ecu controller from another machine. Running out of ideas here, thanks

 

[uffex]

Good day
On many occasions we are finding that the issue is with the source that of the engine.
Kind regards
Uffex

 

[Huffa]

Bump, still not fixed, anyone got any ideas? Please

 

[mg2361]

Is there a dash number? ZX160LC-#? Serial number as well.

 

[Huffa]

Its just a zx160-1. Its the last of the non common rail engines

 

[Huffa]

 

[mg2361]

I don't have specs to offer but I would get a service manual and check engine power with a boost pressure check. If that checks out OK, then I would check the engine pulldown spec (both individual and combined pulldown) to see if the hydraulic pumps are adjusted correctly. Just to confirm these are mechanically regulated pumps and not electronic pumps, correct? Maybe post a picture of the pumps.

 

[Huffa]

The engine is making good power and pulling the correct revs under load in all modes . I run in H/P and it boosts up as it should . The brand new pumps have been professionally fitted and setup by the Hitachi agency. The pumps do run a electrical torque control and regeneration system. They have looked at both of these, but they are missing something. The tell tail major sign something is wrong is the hydraulic oil temperature. It can crack 90 degrees on only mild work and not a really hot day. The oil cooler has been out checked and flushed, all good. So this to me points to oil bypass creating heat but where?

 

[Huffa]

 

[mg2361]

Are you using Hitachi oil? If not, what viscosity oil are you using? Has the oil cooler bypass valve been checked? Does your engine operate at normal temperature?

 

[Huffa]

Yes new pump has had all new Hitachi oil in it. Yes the Hitachi service man who is regarded as on of the best checked the bypass valve. He said it was fine. If I remember correctly he did say it was a bit sticky to remove, but he wasn't concerned. The engine runs a normal steady temperature about halfway, other than when the hydraulic temp gets in the 90's, it starts to get up then. I have had the radiator out and cleaned about a year or so ago as it did start to heat up all of a sudden, was sweet as after the rod/clean

 

[mg2361]

Check the restriction valve for being stuck closed?

 

[Huffa]

Ok. What or where is that? Is that the same valve as the bypass?

 

[mg2361]

The restriction valve is located in the steel line at the bottom of the oil cooler. There is a hose that connects the line to the cooler. The restriction valve just slides up into the steel line.

 

[Huffa]

Ok thanks. I'll look into that. The other issue tho that dosen't fit with that is the machine lacks hydraulic performance. It dosen't dig & walk up hill like a digger with a brand new pump. That valve won't affect performance will it?

 

[mg2361]

Any unusual noises like whining or cavitation? Suction screen in the tank been checked? Integrity of the suction hose to the pump? Has the pilot pressures been checked? Has the pilot pressure at the spools on the control valve been checked? How about the control pressures from the pump control valves, have they been checked? Did your Hitachi tech check for codes with MPDr? Did he make sure all the pressure sensors are working? Hopefully someone with more Hitachi experience will chime in??

 

[Huffa]

So no unusual noises, suction screen good, hose to pump appears good, pilot pressures checked, not sure about pilot pressures at control valve and control pressures from pump control valves . Pressure sensors are all working correctly, he has had the laptop plugged into it several times and it says everything is good

 

[Vetech63]

Well, I'm late on this thread so correct me if I am wrong, but has the engine performance been checked? The heating issue may be a totally separate issue but I would think that the engine speeds (high idle no load, high idle stall load, etc....) should be verified and within specs. Just throwing some ideas around at the moment.

 

[rmllarue91]

A main relief valve set to low or one bypassing partial flow without opening would make heat and kill performance. In your case is find some accurate ways to take hydraulic temp and watch them from cab while running to see where the heats being produced or where it's not being dissipated I've never found a non contact temp gun that will give accurate readings for hydraulic or a/c but do have better luck with engine cooling systems go figure

 

[Huffa]

Thanks so much guys for the input, any ideas are appreciated. Vetech yes the engine pulls the correct revs with the pump set to spec and under load so am sure its not a problem with the engine. So the main relief is something I have questioned them about several times. They tell me its good. Do you think I should put another one in to be 100% sure? I have played with a heat gun but like you say I couldn't get any consistency with it . Then Hitachi brought down a thermal imaging gun. I spent quite a while with it. Things were getting bloody hot but couldn't really pinpoint anything. By memory the top of the valve bank was bloody hot and the oil getting back to the tank was like 120 degrees plus or something. I think the oil temperature on the machine is taken from the bottom of the tank where its at it's coolest, in reality it gets far hotter. Just to reiterate the valve bank was removed and fully resealed at the beginning of the year