I have been having an issue with my lift function on my dozer. The history is the hydraulic pump was replaced and the valve body was resealed simultaneously. Since that time, the lift function has a very slight delay. No other function has this issue. I have had three mechanics look at it, including Cat, with no resolve. They don't notice it, but I have put about 7,000 hours on it and know I'm not imagining it. The pressures check out. The cycle times are within spec. The leak down tests are showing well within normal. The resolver valves pass all the tests from the manual. The last mechanic I had work on it pulled the pressure relief valve and one other valve on the valve body and said there was no debris or rolled o-rings. We did notice that, although very slight, the blade will drop slightly when the lift is barely engaged at low idle. If it was any other function, it wouldn't matter, but it is a little frustrating trying to finish grade and keep up with a 3 light laser. SN 6gn1845. Any ideas?
While all the repair work was being done did anyone happen to look inside the quick drop valve..?
Hi, for the blade to drop before lifting usually indicates a problem with the load check valve which in this case, is part of the flow control valve indicated below also increasing margin pressure to high end of spec can increase response time
I am the one who resealed the valve body, but I cannot honestly answer that as I wouldn't know where it is. I pretty much replaced the resolver valves and any o-ring/backup ring in the valve body when I had it apart. The only things i didn't completely disassemble were the pressure relief valves, so as not to disrupt any settings. Everything looked good when I was in it. The initial issue was just a pump that needed replacing, but had not scattered. Things got bad when, after having the pump replaced, I ran the machine and lost all functions after about 20 minutes of operation. The mechanic couldn't figure out why and thought something might be stuck in a resolver, so we pulled the valve body. Since it was out... The problem turned out to be the new pumps' pressure set screw didn't have the nylon lock tab in it, so it had backed out, but with two functions engaged, would at least make one function move. This has been going on since September of '15. It is getting old. Thank you for your quick reply.
OK, I thought that maybe the hydraulic system had been contaminated as a result of the pump failure and particles may have gone to distant parts of the system. The quick drop valve is mounted on the upper side of the hardnose, it's the square block that the 4 hydraulic hoses for the blade lift cylinders come out of. However in view of what you posted regarding the pump "failure" Mark is most likely on the right track with the load check valve (circled in the illustration above).
I thought my mechanic (different than the one who did the original work) had the check valve out and looked at when he was in it the other day, but I will pursue that avenue.
Remember that you have a new pump installed now, so system pressures might vary somewhat from what they were with the former pump installed. As Mark says increasing the margin pressure right to the top end of the spec rather than aiming for the centre of the range might fix your problem.
Pulled this apart yesterday and replaced the springs and checked the spool. Everything looked fine, but the control still functions with either a slight drop or a delay in the lift cycle. (My service manual calls this section out a the flow control valve).
Have you found the hydraulic system test & adjust section of your service manual that shows you how to go about testing the margin pressure and adjusting it if it's not within specification...?
I had Cat out and they were supposed to check all pressures. I can only assume they did what they were supposed to, but I have not personally tested that.
Did they not give you a service report with all the test results (and the requisite specifications) all listed..?
Their invoice says, "Inspected machine after new pump was installed and verified signal pressure was correct when blade lift lever was activated. Found no delay when blade lever was activated and returned machine to service." That is all they gave me.
I would have refused to pay that until they gave me a copy of their test results ...... maybe that's just me being bolshie but if something has been tested I want to know what the specification was and also what were their actual results on my machine. Based on the wording of the invoice no-one can prove they even put a gauge on anything. Back to your service manual. Is it a full-fat version or do you just have the Operation & Maintenance Manual..? If the former I suggest you start reading the "Test & Adjust" section for the Hydraulic System and look to see how you go about adjusting the margin pressure.
I feel your pain On the D5M ...Listen to these Guys they are Very Very good ..I had this almost same problem and its circled as showed above ...My question is what did the old spool look like it... has holes in it are they scarred if so inside of bank is a polished cylinder that is scarred rough enuff for spool to hang just slightly.... Now on a different note try this Problem I'm having ...As you try to lift and its slow or delay wiggle joy stick side to side see if it picks up like it should
It's the full version manual. I will have to look into the margin pressure. Might not be until this winter though. I ran it for a few days and think it might be slightly better after replacing the springs. Either that or I am getting good at compensating for the delay. Mechanic I usually use wants to take the valve body out and send it to a specialty shop to have it tested.
Old spool looked good. A little shiny in a few spots, but no burrs or anything out of the ordinary. Was the spool the solution to your problem?
Could the spool be in backwards?
It was for a few months ...Now what I seen with banks apart and spools looking in you see holes in spool take a small screw driver slide it thur holes and push away from cap see if it hangs or any binding....I'm posting a new thread about my d5m I want yours fixed but don't want to steer u away from focus ...
No. I checked the parts diagram to make sure.
Before you start pulling valves to have them sent off and tested at a hydraulic shop (and just how exactly would they do that..) I would strongly suggest that you go through your manual and find the procedure for checking the margin pressure. Get hold of the necessary gauges if you don't already have them and test it. As Mark suggested a few posts back even if it falls within the specification in the manual try adjusting it upwards until it's right at the top end of the allowable range. I've had cases before where in order to get a machine to perform correctly a parameter has had to be adjusted right to one end of the specified range as opposed to the normal way of setting it into the centre of the range. Sometimes you even end up with it just outside the range but the machine runs right. Your machine may be one such case.
I will give it a shot.
Did you get your machine fixed ? ....Lets us know
Nige my friend I was just giving advice .......I love to know he fixed his dozers problem ...My dozer ended up small valve body on the pump compresevator valve ..It has metal gasket and 2 O-rings one tiny was blown and other fits over spool coming from pump blown ...This new pump was replaced last year comes with this valve body..............Life gets better when we think outside the box
Seems better after replacing the springs in the compensator. I probably won't pursue anything more until winter at this point. Thank you for asking. If I tear into it this winter and find anything, I will post it.