peakbagger
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Looks like I finally need to learn the ari assist brake system to diagnose the loss of the hydraulic brakes. I was using the SEE last year on a hot day for some hard core trenching and at the end of the day when heading down a steep driveway before heading home, I lost the hydraulic brakes. I was in low gear and made it to the bottom but a 20 minute drive home with no brakes in hilly country was not pleasant. It looks like the air booster system is the issue. When I first press on the brake pedal I feel brakes but then the pedal heads down to the floor with no resistance. My primary air gauge reads like I have pressure but I see the red brake pressure needle jump up and then drops to zero. I didnt have a lot to projects last summer and lived with just running slow and using the cable brakes. In theory these are air assist brakes so there should be hydraulic brakes even without air boost but the pedal goes right to the floor. That seems to point at the hydraulics being involved. If I keep the pedla to the floor long enough the primary air pressure drops down towards zero and I have give it few minutes to build back up. To date I have not aired the system remotely so its hard to hear air leaks but to date I havent heard any. BTW no signs of brake fluid leaks on the ground or at the calipers.
It did not cure itself over the winter and I really would like to have hydraulic brakes. I also think that the pressure in the system goes low enough that the air assisted systems stop working. I do have the student handout sketches which are a start but in general its complex system without a lot of documentation. Looking around initially it looks like I also have the combined brake and clutch reservoir is disintegrating and leaking and was empty after this winter. I must admit, I dont think I checked it last year, After some confusion with the parts numbering from the technical manual which appear to be reversed with the brake only reservoir, solved by Scott at EI, I got them on order. SEEs share brake fluid reservoir caps with a couple of decades of Mercedes, so I have two on order to turn into pressure bleeder caps. I plan to pressure bleed the brakes fairly early in the process to see if I am not dealing with air in the system.
The other thing I am going to do is finally weld up a loader support so I can remove it as doing anything under the hood is a major PITA. I have screw jack on order and will be modding it to fit the fitting on the loader frame.
I do know the engine compressor is putting out air and the tanks appear to have air pressure in them despite the loss of brakes. I have ignored the trailer braking system over the years and have no idea if its working and that is one possibility that some problem with that system has expanded to regular braking system. The 406 series Unimog's do have known issues with brake boosters so that is potential possibility albeit not cheap to fix. The temptation is to buy a lot of threaded plugs and just disable the trailer braking system. The other potential is plugged air lines from the cross body air line rotting out. I had disassembled the air system that could be reached without lifting the cab and did find crap in it a few years ago so some of it may have gotten farther into the system and plugged a key component. There are also those overflow valves that appear to dump air between systems and wonder if they are causing issues. EI does not stock them and it looks like they may be tough to find. They seems to be universal to air assist systems so my guess is I guess need to find a way to cross them a standard component.
Once I got the various bits and pieces delivered, I will air up the system externally through a smaple port and start further diagnostics from there. If any folks have suggestions, I am very interested.
It did not cure itself over the winter and I really would like to have hydraulic brakes. I also think that the pressure in the system goes low enough that the air assisted systems stop working. I do have the student handout sketches which are a start but in general its complex system without a lot of documentation. Looking around initially it looks like I also have the combined brake and clutch reservoir is disintegrating and leaking and was empty after this winter. I must admit, I dont think I checked it last year, After some confusion with the parts numbering from the technical manual which appear to be reversed with the brake only reservoir, solved by Scott at EI, I got them on order. SEEs share brake fluid reservoir caps with a couple of decades of Mercedes, so I have two on order to turn into pressure bleeder caps. I plan to pressure bleed the brakes fairly early in the process to see if I am not dealing with air in the system.
The other thing I am going to do is finally weld up a loader support so I can remove it as doing anything under the hood is a major PITA. I have screw jack on order and will be modding it to fit the fitting on the loader frame.
I do know the engine compressor is putting out air and the tanks appear to have air pressure in them despite the loss of brakes. I have ignored the trailer braking system over the years and have no idea if its working and that is one possibility that some problem with that system has expanded to regular braking system. The 406 series Unimog's do have known issues with brake boosters so that is potential possibility albeit not cheap to fix. The temptation is to buy a lot of threaded plugs and just disable the trailer braking system. The other potential is plugged air lines from the cross body air line rotting out. I had disassembled the air system that could be reached without lifting the cab and did find crap in it a few years ago so some of it may have gotten farther into the system and plugged a key component. There are also those overflow valves that appear to dump air between systems and wonder if they are causing issues. EI does not stock them and it looks like they may be tough to find. They seems to be universal to air assist systems so my guess is I guess need to find a way to cross them a standard component.
Once I got the various bits and pieces delivered, I will air up the system externally through a smaple port and start further diagnostics from there. If any folks have suggestions, I am very interested.
