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Crawlers, Dozers, Loaders & Backhoes Discussion Forum

Komatsu D21P-6 hydraulic pressure buildup

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Jukenut

07-26-2007 19:22:12




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I have a komatsu d21p-6, I have notice a couple of times that when i remove the cap to add hydraulic oil,( it looks like a radiator cap) their is quite of bit of pressure built up. I hear the pressure release as i remove the cap. And this is after the machine has sat for about a week, and not running. Is this normal.

Also how can i test the alternator, it doesn't seem to be recharging the batteries.

thanks

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kc5gxc

07-29-2007 18:40:00




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 Re: Komatsu D21P-6 hydraulic pressure buildup in reply to Jukenut, 07-26-2007 19:22:12  
The manual says it's normal for the hydraulic reservoir to have pressure....I got a machine like yours and it does build up pressure there...no problems.
Good luck with the electrical system.
Pete in MS



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J Schwiebert

07-27-2007 05:05:47




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 Re: Komatsu D21P-6 hydraulic pressure buildup in reply to Jukenut, 07-26-2007 19:22:12  
I know nothing about your Komatsu machine, however a lot of heavy equipment has a pressure cap on the hydraulic reservoir. It serves two functions. One is to keep dust out of the reservoir. This fine dust will kill a hydraulic system due to the abrasive nature of it. The second reason is it helps keep the hydraulic pump filled and helps avoid pump caviation. Now on the alternator. Do you know the make of the alternator and then does it have an internal or external regulator. Have you checked the voltage with a voltmeter at the alternator? J.

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Jukenut

07-27-2007 11:54:22




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 Re: Komatsu D21P-6 hydraulic pressure buildup in reply to J Schwiebert, 07-27-2007 05:05:47  
That is a good thought JS.
No I have done no testing yet with the alternator, no idea what type/make it is. I was going to throw a meter on the batteries and see what voltage it is getting when running. I was also thinking about taking it off and taking to NAPA or autozone to test.
Thanks



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AJK

07-27-2007 14:36:56




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 Re: Komatsu D21P-6 hydraulic pressure buildup in reply to Jukenut, 07-27-2007 11:54:22  
Has your machine no ammeter or volt meter on the dash,put the volt meter between the positive cable and ground,note the reading,start the engine and increase the speed to high idle,if the alternator is good the voltage reading will have increased by 4/5 volts,the voltage from the alternator has to be higher than that of the battery in order to charge it,a drop load test on the batteries may be in order if the voltage checks out,one bad cell is enough to have a no start,the tank pressure is normal.
Good luck
AJ

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jukenut

07-29-2007 19:45:29




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 Re: Komatsu D21P-6 hydraulic pressure buildup in reply to AJK, 07-27-2007 14:36:56  
Well I put a meter on the batteries today, it measured at about 24 volts. I started her up, meter measured 27.9, high and low idle. So I believe it is charging, but the idiot light still comes on though. One thing I should mention, all the exterior lights have been removed by previous owner. I dont see any cut wires though,it looks like they just took the light off and pulled the wires out from thier connectors. Any thoughts ?

Thanks Again/Anthony

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AJK

07-30-2007 12:33:46




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 Re: Komatsu D21P-6 hydraulic pressure buildup in reply to jukenut, 07-29-2007 19:45:29  
The voltage is not as high as I like,over 28V would be better,is the light that is remaining on the battery light,if it is you may have a problem in the alternator,when we test alternators in the shop a 24v should read between 27.8 and 28.4 and should not drop any more than .7V under full load.look at the back of the alternator,see if one of the terminals is marked WL,if you find it take off that wire,switch on the key and check if the light on the dash has gone out,if it has there is a problem inside the alternator so have it off and take it to the repair man.
AJ

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