I'm fixing the brakes on a 621B sn 45P3597 from memory. I can't get the park brakes to hold. The service brakes work fine. There was water in the system when I started. They worked about a year ago. I've replaced the park brake valve, the double check valve, and the quick release valve. The compressor is pumping fine. It'll pump up the tanks at an idle in 3-4 minutes. I've switched brake actuators(rotochambers) around and even put a new one on one side to see if it worked. It didn't work any better than the ones I had on it. I did rebuild the two on the tractor according to the service manual. It has the new style on it. I've routed around the air dryer until the parts to rebuild it come in. When I pull the park brake button, you can hear it slowly releasing the air for about 20 - 30 seconds. When I put the new quick release valve on it, it did help. Before I did that, it wouldn't even try to set the park brakes. I took the air lines off the park side of the actuators after I pulled the park brake button and it doesn't have any air in the park chambers. It seems like it's not exhausting the air fast enough to allow the park springs in the actuators to slam into park position. I put some alcohol in the line going to the tanks when I routed around the dryer. I can't figure out what I'm missing. Anybody got any ideas? Thanks
Made some progress Found that the check valve on the scraper air tank was bypassing back to the tractor causing air to continue to enter the parking brake chambers. Now I gotta get the new check valve put in and see what it does.
Yair...Is there some statuary requiment to get the system working? Most scrapers that I've ran never had brakes at all...and as far as parking brakes, shes going nowhere once you put down the bowl...just sayin' thats all
Yeah there is. Government job(NRCS), park brake has to hold on a 15 degree slope. They test them on the job site. I've never had them either. When I press the brake pedal, I'm getting back feed to the parking brake chambers. The quick release valve on the tractor is new but not working right. After changing the check valve on the scraper, it worked better but still not right. Still getting some back feed to the park brake chambers. What the hell.
Yair...Is'nt that a load of bull****e. I sympathise but cannot help you...I'm sure someone on here can and will. Bloody senseless regulations. We have just had a rule came in on the first of January that all loader attachments for Ag. tractors have to be self-levelling...effectivly halving the value of the tens thousands of serviceable conventional loaders that are out there. Cheers.
I found the problem. The new double check valve had some rust in it from our contaminated system that looked like sand that was locking down the little shuttle valve inside of it. The back feed I was getting to the park brake chambers when I pressed the service pedal is supposed to happen. It's designed like that. Now that I got them fixed, I'll have to keep them working. That'll be the challenge I'd guess. I figure I'm pretty sharp on this brake system after working on them for several days at least.
When you drain the tractor's air tanks, put the fuel tank side tire up on a bump or slight slope.. you might be surprised at how much more crud will come out that way. Wiggling the tractor with the drains open helps too. Found that out when draining the tanks on 627B's I used to run... especially if they hadn't been done in a while. Hope this helps. Alan
Yeah, I'm beginning to wonder if I need to add an air dryer on the scraper or add some kind of alcohol injector in front of the tanks. I'd rather make it a little more dummy proof to keep more of the moisture out. Sure is nice to have brakes when roading them 90 miles on Farm to Market and state roads instead of chaining and trapping a truck tire in the apron to use as a brake on the pavement. Still can't get reprogrammed though. First reaction is to drag my pan. Sorry TxDOT.
on our 623's apply the service brake then set the park brake...When releasing aplly the service brake then release..Seems to help the rotto chamber unlock
They're still workin great after I worked on em.