Cat 938g no bucket tilt/curl in cold weather

[promark51]

hoping someone can help me out. Have a 938g cat loader that when temps get cold (16 deg or less), I lose the ability to curl/tilt the bucket. Boom up/down works fine. Just replaced hydraulic fluid and hydraulic filter hoping it would help....no luck. Once temps get in the upper 20s, everything works fine. I am lost, please help.

Like I said it seems that the cold is the contributing factor here. I’ve tried warming up the machine, cycling thru the functions that do work.....nothing seems to help other than a warm up from Mother Nature.

Thanks in advance.

 

[old-iron-habit]

A G series is a bit new for me to understand much about how it works but I offer the following. Just a cold weather dwellers guess but it sounds like you have a bit of water that settles someplace and when it turns to ice it does not allow flow or perhaps does not allow control. Is it Pilot Control? I have seen them with frozen moisture in them on older machines.

 

[kshansen]

As always a full S/N might help determine what type of system this has. Such as are the hydraulics controlled by solenoids that could have ice in them?

 

[promark51]

Thank u for the response. Here is the info for the machine:
Pin: *6w502689*
Eng: 3126dita
6jk08081

 

[kshansen]

I think you have a typo there the S/N should be 6WS02689. that "5" after the W should be an "S"

Not being familiar with this specific machine I'm thinking a place to start might be to check the pilot oil pressure as that is what is used to operate the actual hydraulic valve.

Attached is the instructions on that test. I know the instructions will tell you to do the test with machine warmed up but I would be interested to see if there was a major difference between the cold not working time and the warm working pressures.

 

[promark51]

Thank u again for the reply and information. And you are right about my typo, sorry about that. Any idea where on the machine this pilot might be?

As a side note, this machine is used to plow snow, and while I was out last nite I tried stalling the hydraulics to warm the fluid quicker. (As recommended by a friend of mine who worked as a tech in the past). Did that for approx. 10 to 15 min then tried moving the lever that controls the curl/tilt functions of the bucket (the boom has a separate joystick.) the bucket slowly started to tilt down. So did some more stalling, then out of nowhere, when I moved the lever again, I heard a rush of fluid, a motor begin to whine, and the bucket curled all the way up with no problems. After that I couldn’t recreate any movement again (in terms of curl/tilt).

 

[Nige]

Quick question. What viscosity of oil are you using in the hydraulic system..?

 

[promark51]

Aw-32.....

 

[John C.]

I don't recall if that series is electro hydraulic and has a computer controlling the implement functions. You can check by looking for hydraulic hoses going to the bottoms of the joysticks. A check on SIS would tell you but I don't have access to that anymore.

 

[kshansen]

I don't recall if that series is electro hydraulic and has a computer controlling the implement functions. You can check by looking for hydraulic hoses going to the bottoms of the joysticks. A check on SIS would tell you but I don't have access to that anymore.

From what I see on SIS this is a straight hydraulic pilot valve system:

 

[Nige]

It would be interesting to measure hook a gauge up to the pilot pressure tap and see if anything changes from the machine being cold to when it warms up.
I've seen slow implement function caused by pilot issues with a really cold machine before although it was much bigger than a 938G. The problem was related around the fact that the pilot lines between the cab and the main control valve effectively dead-headed at the control valve. For that reason it was impossible to rapidly warm up the oil in the pilot lines between the levers and the main control valve. It may be worth looking at the hydraulic schematic to see if this system also dead heads the pilot oil at the control valve. Check out SEPD0370 "Improve Implement Movement Response in Extremely Cold Weather", it will give you an idea of the problem.

 

[kshansen]

Never had one of the 988B's not work when cold but you did have to be careful to not run cylinders too close to the end of stroke before warming them up good. Seems there was a very slow response delay in the controls. Bucket would keep moving for several inches after you moved control lever back to hold position.

Worst problem was in the steering, would blow a hose before neutralizer valve could react.

Must be my SIS access is too low as I can't access "Improve Implement Movement Response in Extremely Cold Weather" SEPD0370!

 

[Nige]

Try a media Search for SEPD0370. You might have to trawl through all the articles. That's from back in the day when a Service Mag had more than one article in it..!

 

[kshansen]

Try a media Search for SEPD0370. You might have to trawl through all the articles. That's from back in the day when a Service Mag had more than one article in it..!

That's what I did and it just says:
SEPD0370 NOT FOUND

And just for kicks I did an "Advanced Full Text Search" and get this:

Sorry, but no documents were found that matched your criteria

So it's either not in SIS or I don't have proper security clearance! I know someone who worked for the NSA, maybe they could help? Okay now I have to wait for the knock on the door in the middle of the night!

 

[promark51]

Thanks again everyone for the help. Unfortunately I won’t be able to access this document either.

Just a small update....we received a new blanket of snow here in Michigan and while I was onsite I warmed up the machine and starting cycling thru the controls again. Was able to get the bucket to start curling and tilting (although it was minimal movement) and continued to cycle the controls until I got things to move fairly smoothly. Now, the functions are not as fast as normal, but I am getting movement. I also noticed lots of lag and delay with the joystick control for the tilt. I would release the control and the bucket would continue to curl or tilt.....until things warmed up further.

Interestingly, I’ll notice that if I am fully articulated, I’ll get no function. But when I straighten out with the steering, I’ll regain function. I think this goes along with the pdf supplied by kshansen where it describes that the pilot valve is supplied oil by the steering.

Once the storms pass I plan and digging deeper and getting this resolved. Couple of questions:

1. I mentioned that I did a hydraulic fluid/filter change hoping to resolve this problem. Is aw32 an acceptable fluid.....or is there a more appropriate fluid especially for cold weather?
2. Is there an additive that can be used for the oil to help the fluid? I know Lucas oil makes a stop leak/booster, not sure is that would be an option.

Thanks tremendously!

 

[Nige]

Dyslexia strikes again.... SEPD0730..

 

[kshansen]

Dyslexia strikes again.... SEPD0730..

The SIS gods still won't let me see that one!

 

[kshansen]

1. I mentioned that I did a hydraulic fluid/filter change hoping to resolve this problem. Is aw32 an acceptable fluid.....or is there a more appropriate fluid especially for cold weather?

Best I can find as far as the Viscosity of the oil is:

Cat calls for a 10 weight hydraulic oil for temps from -4ºF to 104ºF

I looked up some oil viscosity and find that a Chevron AW32 comes in at 33.6 cSt@40ºC and a Mobil 10W hydraulic oil at 37.7cSt@40ºC so from that I would say that your AW32 is plenty "light" enough for "normal" winter use in Michigan!

Where I worked we used Mobil DTE 25 for hydraulic oil and that is rated at 44.2 cSt@40ºC and other than a little sluggish action for a few minutes during warm up when down in the single digits ºF never had any problems.

 

[Mark250]

hi here is a copy of Niges SEPD0370

 

[John C.]

Little bit of difference between a 994 and a 938.