I have an issue that has me stumped. My 450CLC has developed a squeal whenever the hydraulic system is under load. The machine is a 2006 model. It still has full power on all functions, it just makes a god awful noise when the oil temperature comes up and we start working the machine. It tracks straight and doesn't seem to have lost any hydraulic function at all. We have checked the obvious stuff. Oil level is good. All the filters were checked and had no metal particles or dirt in any of the filters. we also checked and changed the hydraulic tank cap to make sure it wasn't a venting problem. The hydraulic oil is clean and was changed about 500 hours ago, and we used the genuine Hitachi Super EX 46HN oil. I had an experienced heavy equipment mechanic come by yesterday and checkneverything out and he put a stethoscope on it. He says it doesn't sound like cavitation but sounds more mechanical. He thinks the pump bearings are bad. He says that if it was the pump itself coming apart, we should see some metal particles in the filters, but all of the filters are clean, as best as we can tell without cutting them open (we turned them over and banged them on a clean rag to see if any dirt or particles came out). However, I'm wondering if it might not be the pump to engine coupling coming apart? It apparently has a flexible coupling that connects the flywheel to the pump(s) (the pumps are two pumps in one housing)? Does anyone have any experience with this problem before? Any advice or input would be greatly appreciated. BTW: the machine only has 6209 hrs on it. It had 4400 when I bought it last year. I had asked the outfit I bought it from to do an oil change on it and they did, but I have reason to believe they didn't use the Hitachi oil, even though I paid them $2000 extra to do so. If they used another oil, could that have caused this problem?
Just an update. We just cut open the main hydraulic filter and found no metal particles in it. Made sure all of the bolts on the supply/suction pipe were tight, as well as the clamps on the hose. Going to check pressures on it shortly. Will report back on what we find out.
Is the noise pretty much constant or just when you put a load on it?
It only made noise when you put load on it. We worked on it some more this afternoon. We found oil on one of the bolts on the flange on the suction pipe, where it bolts onto the bottom of the pump, like it was leaking slightly. We tightened that bolt and the two clamps that hold the hose coming from the tank, as those were not completely tight. We think that it could be that if oil was leaking slightly out of the suction/supply pipe flange, that air could have been sucked in when the pump loads up, causing the pump to capitate. We cranked it up this evening and ran it for a bit until it warmed up and performed several functions for over half an hour and the noise didn't come back. We haven't really worked the machine yet though, but I will put it back in service tomorrow morning and see if the noise is gone. I will report back with the result.
Just by way of update: we worked the machine today for about 4hrs and it works fine, just still has the squeal when it's under load. I took temperature readings with a temp laser gun and the pump temperature after working all morning was around 176 degrees (working in 92degree weather) with no hot spots, and the intake tube, hydraulic tank etc was around 155-158 degrees. We don't have a new hydraulic cap to hand but I tried an old one off my 800C and the squeal was still there. However, I pulled the hyd tank cap (both actually) apart this evening and found that the vent filter inside the cap was very dirty. Cleaned that with some solvent and blew it out with compressed air, reassembled it and put it back on the machine. Will find out tomorrow if that makes any difference. I have a new cap ordered and on the way. Can't believe that it's the pump giving up the ghost because the machine works fine, just noisy. Will try to get someone to check pump pressure and flow tomorrow. Can't believe anyone else on here doesn't have any ideas on what this could be??
Are you certain the noise is coming from the pumps and not the turbocharger?
Just a quick note. I have noticed when the system relief and the circuit relief are close to the same pressure they pop off together and cause a terrible noise from the harmonics. You may want to check pressures on your dig functions.
True, at high RPM/full load, a relief popping off would make a squeal noise.
Thanks for the input. I will see if I can get someone to check that out for me tomorrow. The problem is finding someone over here who actually knows anything about the hydraulic system on these Hitachi/Deere machines. We have a local Cat dealer with tech support, but nothing for Deere or Hitachi. What would cause this and is it harmful to the machines hydraulic system to run it like this? It's not just the dig functions, it makes that noise when you use any of the tool functions, when you swing and when the machine is crawling. Does it have a relief that would pop off on all of these functions?
Fair point. I will double check that tomorrow. The mechanic I had look at it seemed to focus immediately on the hydraulic pump, but, it could be the turbo. In fact, I noticed that the turbine had a little bit of play when I had to pull it down a couple of months ago to change an injector. It smashed an injector then and I would have sworn that it had spun a bearing or bent a rod, so you never know whats wrong just going by how it sounds...
I was thinking relief too.
Well, I think we inadvertently found the problem. The day before yesterday, after working the machine all day loading trucks, with no sign of any loss of power and no sign of hydraulic pressure loss, we decided to pull the body panel on the bottom of the machine (the one right under the pump), to look up behind the pump for anything that might be causing the noise. We didn't find anything obvious and it was getting so late I decided to leave the plate off the machine so I could look under the bottom of the pump when the machine was running. However, imagine my surprise when the operator called me yesterday morning to ask me what I had done to fix the problem, because the noise was gone! Sure enough, after working it all day again yesterday, the noise is completely gone. Turns out that the bolts on one side of the plate had worked themselves loose (which we only found out when we went to take it off) and so I'm assuming that the vibration caused by the pump loading up when the machine was working must have been causing the loose side of the plate to vibrate at such a frequency that the damn pump sounded like it was coming apart. Either that, or the machine somehow cured itself, at least for the time being... Anyways, I'm keeping my fingers crossed, since the quote from Nortrax for a reman pump is $31,500.00! Good thing I didn't pull the trigger on that order. Thanks again for your all your input.
I've had two different occasions, once on a Hitachi ZX220 and once on a Deere 135C, where I was called to come out and diagnose an intermitant hydraulic pump squeal and it turned out to be the travel alarm going bad. The alarm would let out a long, high pitched squeal and it is located directly below the pump. When it would squeal, even with a stethascope, it sounded like the noise was coming from the pump. You can imagine the owners response when I told them I had fixed their hydraulic noise by unplugging the alarm.
Hey I am really glad you found your solution. I also found HWM was a good source for hydraulic pump questions.