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
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)?
Water in the brake lines or housings getting frozen??
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.
This is what it seems like (water) just don't understand the brake system. Even though I got the manuals. I'll keep exploring.
Does it have air brakes?
So far it seems to be braking inside the differentials or the transmission and is hydraulic in nature - my best guess. No air compressor found yet. Definitely no lines and brakes going to or at the wheels.
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). 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.
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.
Wow - you guys are great. Heading to the shop soon and will bring all this info. Bet this is it and will let you know.
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.
Let us know how you make out.
If you open the bleeder fully and hit the brake, make sure your drain bucket is about 30 feet up
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.
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.
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.
Sorry I’m not all thar well versed in Deere loaders