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644C JD Loader brakes don't work in freezing weather

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stanzuray

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Apr 13, 2016
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Location
Tanana, Alaska
New to forum. Live in an interior Alasakan village of 200 people and have done years of snow removal with graders and Cats etc. Just took over mechanic work on them now however and not to experienced fixing them. Got an old 644C JD and brakes work fine when warm but after a short while out of the shop in freezing temps there are flat out no brakes each and every time. Back in shop they are fine again. What I need to be looking at to fix them?? Thanks for any help, Stan
 
mg2361

mg2361

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Welcome to HEF stanzuray;)! Serial number? Also do you have a tech manual (TM1229)? If not I suggest getting one. You need to start with a brake system pressure test. Does everything else work fine (hydraulics, engine, transmission)?
 
S

stanzuray

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Location
Tanana, Alaska
mg2361 said:
Welcome to HEF stanzuray;)! Serial number? Also do you have a tech manual (TM1229)? If not I suggest getting one. You need to start with a brake system pressure test. Does everything else work fine (hydraulics, engine, transmission)?
Click to expand...
Got the technical, parts, and operator manuals but no gauges or much money to fix. Not much on trouble shooting in manuals. Were a mess here. Do what we can. Hydraulics work okay and transmission moves it fine.
 
mg2361

mg2361

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Is the hydraulic oil milky? Most likely there is ice forming inside the brake valve. Those machines have had some icing issues with the brake valves (see picture below).

Bluox said:
Does it have air brakes?
Click to expand...

Brakes are hydraulic with the brake discs internal to to the inboard side of the axle's. Stan, if have have TM1229, page 1011-02 and 03 shows a picture of the brake discs and pads. Cross section of the brake valve is on page 1060-06. All diagnostics for the brakes are in the 9025 section.

644C Brake valve.png
 
fast_st

fast_st

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yes, and if its like the E model, there are two independent brake pedals/valves/accumulators see if they both operate the same. Pump them down all the way before removing the valve.
 
S

stanzuray

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Location
Tanana, Alaska
MG and Fast st
took the 3 lines off the brake unit you sent the picture of and sure enough lots of foamy white oil came out. Blew it out clear and tomorrow will bleed lines at differentials and try it. Thank you. Town needs to get the loader going good.
 
fast_st

fast_st

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If you open the bleeder fully and hit the brake, make sure your drain bucket is about 30 feet up
 
S

stanzuray

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Joined
Apr 13, 2016
Messages
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Location
Tanana, Alaska
Thank everyone for comments and help. I understand much more now and know what I need to do next. I went with good brakes for 2 days in 20 below and today they froze again. However a look at the milky fluid in the steering and brake hydraulic tank on top a day ago made me realize the brakes were going to accumulate water again and probably freeze again which they did today even though it was only 10 below. I'm going to drain the system and all new fluid. Any hints on that procedure appreciated but got the TM manual and should have the procedure in that. Every day something breaking around here and no brakes is the least of my worries often.
 
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DB2

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Oil viscosity improper for the temperature? Had a Cat that someone put heavy oil in the braking system to slow an internal leak. Worked ok warm but wouldn’t stop the machine when cold.
 
S

stanzuray

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Joined
Apr 13, 2016
Messages
8
Location
Tanana, Alaska
DB2
When these brakes freeze they are nonexistent and you can't push them down. The fact I drained all the foamy oil out and they worked for 2 days seems to tell me they have water accumulating in them. Now need to drain whole system and put clean oil in I think.
 
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