M936 hydraulic filter question

Back ground info
I noticed my crane (M936A1) seemed to be running slower (hydraulic operations) yesterday, not sure if governor RPMs are down a bit or not, was running at 1500rpm yesterday, can't remember if it used to run just a bit faster (1600-1700?). could 100 rpm make a noticeable operational difference? (i will check this theory out with the manual throttle when i can), but thought i'd ask.

Actual Question:
i have never pulled the hydraulic filter on the tank as the indicator showed "clean". well yesterday due to the seemly slower operation, i tried moving the needle/indicator by hand and - it will mover to where ever i want it. Tried it with the truck off and running (hydraulics engaged). looked over the parts TM and maintenance TM and did not see any good info on how it reads DP across the filter. So question is, is my indicator messed up? should it not "move" to where DP pushes it when running? and should i pull the filter and check it out? I read how its done and would prefer not to open it up if not needed. looks to be a very messy job.

Have any of you guys had your filters plug up? could this be causing the reduced crane speed (starved flow to the pump)? The TM indicated it is a permanent filter in that you clean it and reuse it, so i assume its a metal mesh or perforations type element.

thoughts?

gstirling said:

Back ground info
I noticed my crane (M936A1) seemed to be running slower (hydraulic operations) yesterday, not sure if governor RPMs are down a bit or not, was running at 1500rpm yesterday, can't remember if it used to run just a bit faster (1600-1700?). could 100 rpm make a noticeable operational difference? (i will check this theory out with the manual throttle when i can), but thought i'd ask.

Actual Question:
i have never pulled the hydraulic filter on the tank as the indicator showed "clean". well yesterday due to the seemly slower operation, i tried moving the needle/indicator by hand and - it will mover to where ever i want it. Tried it with the truck off and running (hydraulics engaged). looked over the parts TM and maintenance TM and did not see any good info on how it reads DP across the filter. So question is, is my indicator messed up? should it not "move" to where DP pushes it when running? and should i pull the filter and check it out? I read how its done and would prefer not to open it up if not needed. looks to be a very messy job.

Have any of you guys had your filters plug up? could this be causing the reduced crane speed (starved flow to the pump)? The TM indicated it is a permanent filter in that you clean it and reuse it, so i assume its a metal mesh or perforations type element.

thoughts?

Click to expand...

They are washable. However as cheap as they are it is easier and better to just replace it. I replaced em in a few low hour wreckers and it was in rough shape. Mostly from the junk inside the hoses coming apart from old age of them. The indicator is just like any other military gauge. Don't always trust or rely on gauges.

You may have a collapsed hose as well. Check them for softness or weak spots with the truck off.

Sent from my SM-G965U using Tapatalk

thanks hadn't thought of a collapsed hose... will check that out.

You can go down each of the lines and tap the hose with a small brass or rubber hammer. You will feel the difference if you tap a soft spot. I recommend doing this while the truck is off. Cause if its running and the rear PTO is engaged and you hit a weak spot on that line and it blows you and half the county will be covered in hydraulic fluid. Ask me how I know.

I will be coming thru your way on sunday when i head back to memphis. if you need anything, let me know.

Simp5782
I looked over the hoses last night, just squeezed them. all big return lines were hard as rocks....will try the hammer trick tonight.
one question - the TM indicates that when you pull the hydro tank filter it self seals the line.... but what ever is in the filter i assume will dump. just don't want 100 gal of hydo fluid to come pouring out... it also warned about a hi pressure spray as you first open the filter? just how bad is that? will a towel over it contain it?

If you have time and/or are not running a schedule - i'd trade you lunch for a quick look at my truck - you might be able to quickly see what needs what? or what is normal/not normal. i can meet at any of the west end interchanges/truck stops...Watt road is an easy in/out and several choices, or your favorite restaurant ...

i had a hydraulic hose on a track hoe go once, yeppers.. in the 3 seconds it took to hit the off switch... it seemed like half my house pad was covered in the stuff... 5 gals makes a big mess...

so how messy is removing the hydraulic filter, the tm indicates it auto seals from the tank??? or do I need to empty the tank first?

gstirling said:

so how messy is removing the hydraulic filter, the tm indicates it auto seals from the tank??? or do I need to empty the tank first?

Click to expand...

Its not too bad just curious what ever happend did you find a collapsed hose my m936 seems to be experiencing the same problems

Jaydog996 said:

Its not too bad just curious what ever happend did you find a collapsed hose my m936 seems to be experiencing the same problems

Click to expand...

I have not solved the issue, did drain the tank and change the filter - it was clean. installed a pressure gauge - but put it on the wrong side, so no info on pump pressure. must drain the tank again to move the gauge. that may indicate a weak pump. or if I have a collapsed line between the pump to valve body.

if you come up with a solution to your issue let me know.

gstirling said:

I have not solved the issue, did drain the tank and change the filter - it was clean. installed a pressure gauge - but put it on the wrong side, so no info on pump pressure. must drain the tank again to move the gauge. that may indicate a weak pump. or if I have a collapsed line between the pump to valve body.

if you come up with a solution to your issue let me know.

Click to expand...

So i did get it to go fast again i think its something to do with rpms maybe cuz it seems like the trans isnt shifts into like 5th or something when it runs slow still not quite sure what the issue is but when it pumps slow im thinking its because the trans isnt turning it fast enough

on the governor (crane PTO engaged) my engine runs at about 1700 rpm can't remember exactly, not sure where the PTO takes off the transfer case (how its geared) - but TM has you put it in 5th which is basically automatic. I've never heard the transmission "shift" when on the governor running the crane. for some reason I just figured it was in first gear.

gstirling said:

on the governor (crane PTO engaged) my engine runs at about 1700 rpm can't remember exactly, not sure where the PTO takes off the transfer case (how its geared) - but TM has you put it in 5th which is basically automatic. I've never heard the transmission "shift" when on the governor running the crane. for some reason I just figured it was in first gear.

Click to expand...

Im pretty sure the reason mines not running full bore is because its not spinning fast enough for some reason duno wheater its cuz like a bearing might be going out or not i think the pto for the crane runs off a 1 to 1 ratio not sure thou

Jaydog996 said:

Im pretty sure the reason mines not running full bore is because its not spinning fast enough for some reason duno wheater its cuz like a bearing might be going out or not i think the pto for the crane runs off a 1 to 1 ratio not sure thou

Click to expand...

might look into adjusting your governor on the fuel pump to govern up a bit. the TM gives the correct RPM, my memory, I think it should be about 1700 rpm, I also remember a warning about not running the crane PTO at less than 1500 rpm, but again check those numbers. when i'm on the crane my RPM never varies at all, never hear the engine load up, even when lifting several tons, the hydraulic system never seems to tax the engine side. but I do notice that when the system is operating "slow" I can only operate one function at a time. if the hydraulics are running "fast" I can usually operate two functions. since the engine never changes, that's why I figure my issue is on the hydraulic side. weak pump or restricted line.

gstirling said:

might look into adjusting your governor on the fuel pump to govern up a bit. the TM gives the correct RPM, my memory, I think it should be about 1700 rpm, I also remember a warning about not running the crane PTO at less than 1500 rpm, but again check those numbers. when i'm on the crane my RPM never varies at all, never hear the engine load up, even when lifting several tons, the hydraulic system never seems to tax the engine side. but I do notice that when the system is operating "slow" I can only operate one function at a time. if the hydraulics are running "fast" I can usually operate two functions. since the engine never changes, that's why I figure my issue is on the hydraulic side. weak pump or restricted line.

Click to expand...

was out running my crane and got some of my RPMs wrong in earlier post, mine runs on the governor at 1500 rpm.

gstirling said:

I have not solved the issue, did drain the tank and change the filter - it was clean. installed a pressure gauge - but put it on the wrong side, so no info on pump pressure. must drain the tank again to move the gauge. that may indicate a weak pump. or if I have a collapsed line between the pump to valve body.

if you come up with a solution to your issue let me know.

Click to expand...

Would you mind taking a picture of where you installed the pressure gauge? Is it inline or did you tap a fitting somehow? I'm not sure where the high pressure and low pressure side is located. Thank you!

Drryan said:

Would you mind taking a picture of where you installed the pressure gauge? Is it inline or did you tap a fitting somehow? I'm not sure where the high pressure and low pressure side is located. Thank you!

Click to expand...

I can take a pic, give me a day or two, i just guessed (wrong) and installed it in a plug on the top of the control valve body that i thought wasthe suply side (its still on the wrong side, haven't had the time to move it). i believe i just need to move it to another plug on the other end. the pain is the control valves sits lower than the top of the tank. so you need to drain down the tank to below the control valves. or be really fast... which does work with nomal mess....LOL

gstirling said:

I can take a pic, give me a day or two, i just guessed (wrong) and installed it in a plug on the top of the control valve body that i thought wasthe suply side (its still on the wrong side, haven't had the time to move it). i believe i just need to move it to another plug on the other end. the pain is the control valves sits lower than the top of the tank. so you need to drain down the tank to below the control valves. or be really fast... which does work with nomal mess....LOL

Click to expand...

How's it going with the crane movement? Asking because I'm having issues on mine. Picked up my M936A2 in November and have been chipping away at it. I think it's exactly the way it came from RSMS MS and the more I work on it the less I think they may have tested before shipping..... For example I had to loosen up all the fittings to the drag winch valves because the valve body must have shifted over and with the feed lever pinned it was slightly activating the winch every time you engaged the power divider. Arrgh. Also 20 gallons of ISO 32 added and I'm still not on the dipstick.....

-So did you have to drain to pull the filter? The TM indicates an auto shutoff in there but I really don't want to be caught by surprise. Also I don't want to drain the whole tank...
-I am finding rpm related issues but 1500 to 1700 doesn't really make too much difference. Lower than that and I lose mutliple function control.
-Having a weird one where with no load it works dandy all over but when I have a load on the boom maybe 2k pounds I can't rotate. Actually I can rotate left really jerky but not right. RPM up to 1700 and I can go a bit right but it jerks like hell. I can hear it hit the relief on the valve block it's not trying or the relief is too low. Ever have this happen? All other functions are good just the rotation is bad.
-Next step is TM 9-2320-272-24-2 section 3-389 "Pressure Relief Valve Maintenance" (page 3-956). This is where the pressure is set to 1350psi. You indicated you were going after this adjustment any tips you can offer? I have a gauge from tuning my Kubota I'll be looking for the proper adapters and will post what I wind up with.

I'll top it up with more fluid but frankly with the suction at the bottom I can't think what difference it would make (I'm just below the fill screen now). Makes me think I have a clogged filter or piece of junk in my relief valve holding it open. It's a common relief on the block though and the boom/hoist/extension hold fine. Just my rotation is whacked. So open to suggestions maybe I'm missing something simple here.....

KN6KXR said:

How's it going with the crane movement? Asking because I'm having issues on mine. Picked up my M936A2 in November and have been chipping away at it. I think it's exactly the way it came from RSMS MS and the more I work on it the less I think they may have tested before shipping..... For example I had to loosen up all the fittings to the drag winch valves because the valve body must have shifted over and with the feed lever pinned it was slightly activating the winch every time you engaged the power divider. Arrgh. Also 20 gallons of ISO 32 added and I'm still not on the dipstick.....

-So did you have to drain to pull the filter? The TM indicates an auto shutoff in there but I really don't want to be caught by surprise. Also I don't want to drain the whole tank...
-I am finding rpm related issues but 1500 to 1700 doesn't really make too much difference. Lower than that and I lose mutliple function control.
-Having a weird one where with no load it works dandy all over but when I have a load on the boom maybe 2k pounds I can't rotate. Actually I can rotate left really jerky but not right. RPM up to 1700 and I can go a bit right but it jerks like hell. I can hear it hit the relief on the valve block it's not trying or the relief is too low. Ever have this happen? All other functions are good just the rotation is bad.
-Next step is TM 9-2320-272-24-2 section 3-389 "Pressure Relief Valve Maintenance" (page 3-956). This is where the pressure is set to 1350psi. You indicated you were going after this adjustment any tips you can offer? I have a gauge from tuning my Kubota I'll be looking for the proper adapters and will post what I wind up with.

I'll top it up with more fluid but frankly with the suction at the bottom I can't think what difference it would make (I'm just below the fill screen now). Makes me think I have a clogged filter or piece of junk in my relief valve holding it open. It's a common relief on the block though and the boom/hoist/extension hold fine. Just my rotation is whacked. So open to suggestions maybe I'm missing something simple here.....

Click to expand...

My m936 the hydraulic filter dose have a automatic shut off when changeing the filter you will lose a little fluid thou when changeing it probably like 1 or 2 gallons maybe also it should be a washable filter that you can reuse my shut off didnt all the way shut it off either it still leaked a little also i found that when running my truck some times it wouldn't shift into 5th gear or 4th so i found that shifting the t case in neutral then puting the truck in gears 1-5 then push that leaver back to engage it and send air to the throttle will usually shift the truck into 5th or 4th hope this helps any

KN6KXR said:

How's it going with the crane movement? Asking because I'm having issues on mine. Picked up my M936A2 in November and have been chipping away at it. I think it's exactly the way it came from RSMS MS and the more I work on it the less I think they may have tested before shipping..... For example I had to loosen up all the fittings to the drag winch valves because the valve body must have shifted over and with the feed lever pinned it was slightly activating the winch every time you engaged the power divider. Arrgh. Also 20 gallons of ISO 32 added and I'm still not on the dipstick.....

-So did you have to drain to pull the filter? The TM indicates an auto shutoff in there but I really don't want to be caught by surprise. Also I don't want to drain the whole tank...
-I am finding rpm related issues but 1500 to 1700 doesn't really make too much difference. Lower than that and I lose mutliple function control.
-Having a weird one where with no load it works dandy all over but when I have a load on the boom maybe 2k pounds I can't rotate. Actually I can rotate left really jerky but not right. RPM up to 1700 and I can go a bit right but it jerks like hell. I can hear it hit the relief on the valve block it's not trying or the relief is too low. Ever have this happen? All other functions are good just the rotation is bad.
-Next step is TM 9-2320-272-24-2 section 3-389 "Pressure Relief Valve Maintenance" (page 3-956). This is where the pressure is set to 1350psi. You indicated you were going after this adjustment any tips you can offer? I have a gauge from tuning my Kubota I'll be looking for the proper adapters and will post what I wind up with.

I'll top it up with more fluid but frankly with the suction at the bottom I can't think what difference it would make (I'm just below the fill screen now). Makes me think I have a clogged filter or piece of junk in my relief valve holding it open. It's a common relief on the block though and the boom/hoist/extension hold fine. Just my rotation is whacked. So open to suggestions maybe I'm missing something simple here.....

Click to expand...

.
Chances are that you have "hose crud" (decomposing rubber) getting sucked through the system. I would expect you to find that in the tank filter in mass quantities. Could be wrong, but hose rubber will eventually clog up the valves and the rotation manifold is going to catch a lot of it. Bad part is that there is nothing in the TM's about those parts because the manifold is a replacement part - not rebuildable - or at least not in the books that we have access to...

KN6KXR said:

How's it going with the crane movement? Asking because I'm having issues on mine. Picked up my M936A2 in November and have been chipping away at it. I think it's exactly the way it came from RSMS MS and the more I work on it the less I think they may have tested before shipping..... For example I had to loosen up all the fittings to the drag winch valves because the valve body must have shifted over and with the feed lever pinned it was slightly activating the winch every time you engaged the power divider. Arrgh. Also 20 gallons of ISO 32 added and I'm still not on the dipstick.....

-So did you have to drain to pull the filter? The TM indicates an auto shutoff in there but I really don't want to be caught by surprise. Also I don't want to drain the whole tank...
-I am finding rpm related issues but 1500 to 1700 doesn't really make too much difference. Lower than that and I lose mutliple function control.
-Having a weird one where with no load it works dandy all over but when I have a load on the boom maybe 2k pounds I can't rotate. Actually I can rotate left really jerky but not right. RPM up to 1700 and I can go a bit right but it jerks like hell. I can hear it hit the relief on the valve block it's not trying or the relief is too low. Ever have this happen? All other functions are good just the rotation is bad.
-Next step is TM 9-2320-272-24-2 section 3-389 "Pressure Relief Valve Maintenance" (page 3-956). This is where the pressure is set to 1350psi. You indicated you were going after this adjustment any tips you can offer? I have a gauge from tuning my Kubota I'll be looking for the proper adapters and will post what I wind up with.

I'll top it up with more fluid but frankly with the suction at the bottom I can't think what difference it would make (I'm just below the fill screen now). Makes me think I have a clogged filter or piece of junk in my relief valve holding it open. It's a common relief on the block though and the boom/hoist/extension hold fine. Just my rotation is whacked. So open to suggestions maybe I'm missing something simple here.....

Click to expand...

when i first started trying to figure out why mine might be running "slower" - many (as in this thread) indicted the filter might have hose debris in it. my filter was super clean, so i'd recommend not buying a new filter untill you pull and inspect your old one. as some other have said i think another possibility is the main return hoses may have internally failed and are colasped. several have indiicated you can squeeze the hoses with your hands and feel if you get to a bad section - my hoses are so hard i could not find anything. I also think they are 30yr old hoses and probalby at end of life, so replacement in in their future either way. all my opertions are affect (speed of actions) so my issue is common, since yours only on the rotation id say those hoses, or the motor itself is bad. there have been sereral threads here in SS on the fact that these motors shoul have a drain return line from their seals - look for that thread to explain the in's and out's and he has pics on how he ran the return lines - this seems to affect leakage rather than performance (my rotator motor is leaking).

gstirling said:

when i first started trying to figure out why mine might be running "slower" - many (as in this thread) indicted the filter might have hose debris in it. my filter was super clean, so i'd recommend not buying a new filter untill you pull and inspect your old one. as some other have said i think another possibility is the main return hoses may have internally failed and are colasped. several have indiicated you can squeeze the hoses with your hands and feel if you get to a bad section - my hoses are so hard i could not find anything. I also think they are 30yr old hoses and probalby at end of life, so replacement in in their future either way. all my opertions are affect (speed of actions) so my issue is common, since yours only on the rotation id say those hoses, or the motor itself is bad. there have been sereral threads here in SS on the fact that these motors shoul have a drain return line from their seals - look for that thread to explain the in's and out's and he has pics on how he ran the return lines - this seems to affect leakage rather than performance (my rotator motor is leaking).

Click to expand...

Thanks yes I agree. I ordered another filter because it was cheap enough to have a spare to swap. Also jaydog indicated his auto shutoff leaked by a bit so having one right there seems the ticket. I'll change it later this month when I get it. Meanwhile I'm going to let the tank settle and do a drain down and look see from the bottom leavings. This might be as simple as condensation from sitting. No idea why my tank is 25 gallons low there are small leaks (it marks it's territory a bit) but not that big. I've seen Harley's leak more.

I did run a drain for the hoist motor as directed in that thread and it worked great! I haven't had it puke out fluid since I did. My rotator motor is different there is no drain port. The rotator leaks a little but I've yet to find exactly where. I'll have to pull the covers around the ring gear and see after running it. It's not the motor though (well it might be if it's pushing through the gear case). It's not much I'm going after function first. Even leaking it should perform.

The hoses are really good. Actually most of the truck LOOKS and FEELS really good but like I said.... I think it was spit out of RSMS in a hurry without testing. Talking to my friends they hadn't seen M939 series trucks in their motor pools since the mid '90's or so. Why this one was spit out by RSMS in 2012 is anybody's guess. It then sat in a field for 4 years but after auction was stored inside a hanger for 6 years out of the sun and weather. The previous owner bought 4 or 5 M939 series and while he did some work just didn't have time for them all. I just changed the fuel filters and I think theye were 2012 vintage. Anyways the hoses and rubber bits are really great. Weatherstripping on the doors is all falling off that rubber cement has a shelf life it seems..... But the weatherstripping itself is great.

I really hope I don't find a bunch of rubber shreds in there. There really isn't any solution to that except a total disasembly and cleaning. Of EVERYTHING. Every damn component in the system. Even then another filter installed in line would be called for. Rebuilding the valve blocks and motors isn't hard: finding the right people is. I live in the south part of SF Bay Area and it's all computer nerds. High real estate have driven all the trades and shops away. Luckily I live in a bit of an agriculture area (best strawberry's and artichokes in the nation!) and have some support.

I'll post up what I find. Looking forward to my manifold pressure test and adjustment. This site has been a great resource thanks for the help!