Brake pedal gets soft the longer I drive.
Brake pedal gets soft the longer I drive.
Also the engine doesn't shut off with the key(sometimes, you can rev the engine and shut the key off), I understand this is a vaccum issue, but I wouldn't expect this combination of problems to be connected, could they be related. I guess I just want to have any parts needed when I get a chance to go back and work on it.
82 240D
The brake pedal gets soft the longer I drive. The brakes work great(very firm) when we first leave the house, but then after four or five miles or so the pedal gets increasingly softer. This is an 82 240d that's been sitting for a couple of years. Besides bleeding the brakes, what else would be the first suspicions?
Also the engine doesn't shut off with the key(sometimes, you can rev the engine and shut the key off), I understand this is a vaccum issue, but I wouldn't expect this combination of problems to be connected, could they be related. I guess I just want to have any parts needed when I get a chance to go back and work on it.
82 240D
-1982 300D Turbo, 280k miles, ALDA apparently maxxed, fram 8038, 12 lbs boost, non-egr manifolds, W/M injection, 4 brake light mod, Gen II w126 front rotors/calipers, 4-speed swap
In the works: A/W IC, adjust pump, turbo rebuild (w/60 trim comp wheel)
-1980 300SD, 110k, project car. Goal is to get it lookin' like it did on the showroom floor (body and interior wise, not necessarily under the hood )
-1974 240D, FRESH PAINT!!!!!!
sassparilla_kid
11-15-2011, 04:13 PM #2The brakes on these cars are also vacuum assisted, so a vacuum leak could potentially cause problems
-1982 300D Turbo, 280k miles, ALDA apparently maxxed, fram 8038, 12 lbs boost, non-egr manifolds, W/M injection, 4 brake light mod, Gen II w126 front rotors/calipers, 4-speed swap
In the works: A/W IC, adjust pump, turbo rebuild (w/60 trim comp wheel)
-1980 300SD, 110k, project car. Goal is to get it lookin' like it did on the showroom floor (body and interior wise, not necessarily under the hood )
-1974 240D, FRESH PAINT!!!!!!
1987 300SDL 6spd manual om606.962 swap project
1985 300td euro 5spd wagon running
willbhere4u
11-15-2011, 05:42 PM #4Yea with out vacuum they are hard! after it gets full vacuum it it gets softer
1987 300SDL 6spd manual om606.962 swap project
1985 300td euro 5spd wagon running
-1982 300D Turbo, 280k miles, ALDA apparently maxxed, fram 8038, 12 lbs boost, non-egr manifolds, W/M injection, 4 brake light mod, Gen II w126 front rotors/calipers, 4-speed swap
In the works: A/W IC, adjust pump, turbo rebuild (w/60 trim comp wheel)
-1980 300SD, 110k, project car. Goal is to get it lookin' like it did on the showroom floor (body and interior wise, not necessarily under the hood )
-1974 240D, FRESH PAINT!!!!!!
sassparilla_kid
11-16-2011, 12:42 AM #6Could water in the brake fluid cause them to get softer? After a little while of braking wouldn't it get hot enough to vaporize and cause bubbles in the lines? Just a thought. I know the brakes on my friend's diesel rabbit went out on us while we were driving to the hardware store one day, but that just happened because one of the lines had become loose and it was losing pressure through it
-1982 300D Turbo, 280k miles, ALDA apparently maxxed, fram 8038, 12 lbs boost, non-egr manifolds, W/M injection, 4 brake light mod, Gen II w126 front rotors/calipers, 4-speed swap
In the works: A/W IC, adjust pump, turbo rebuild (w/60 trim comp wheel)
-1980 300SD, 110k, project car. Goal is to get it lookin' like it did on the showroom floor (body and interior wise, not necessarily under the hood )
-1974 240D, FRESH PAINT!!!!!!
IE soft/spongy goes to the floor?
or is easy to use like power breaks are working correctly ?
1987 300SDL 6spd manual om606.962 swap project
1985 300td euro 5spd wagon running
willbhere4u
11-16-2011, 11:59 AM #7Is it a soft pedal? or just softer than having no power breaks?
IE soft/spongy goes to the floor?
or is easy to use like power breaks are working correctly ?
1987 300SDL 6spd manual om606.962 swap project
1985 300td euro 5spd wagon running
I'm gonna go back down on thanksgiving weekend and start with a good bleed to purge all the lines and go from there. I wouldn't be surprised if autozone and oreillys don't stock a master cylinder for this car, so if necessary I may pull the master cylinder off my dads wrecked 300. It worked fine when it tangled with a white tail last year.
82 240D
I'm actually loosing the brakes. I wasn't going fast, but after 3 or 4 pumps, I hit the parking brake and continued to pump. never really accomplishing much with the pumping.
I'm gonna go back down on thanksgiving weekend and start with a good bleed to purge all the lines and go from there. I wouldn't be surprised if autozone and oreillys don't stock a master cylinder for this car, so if necessary I may pull the master cylinder off my dads wrecked 300. It worked fine when it tangled with a white tail last year.
82 240D
1987 300SDL 6spd manual om606.962 swap project
1985 300td euro 5spd wagon running
willbhere4u
11-18-2011, 04:22 PM #9there is an O ring between the master and the booster that needs to be there to seal master to the booster or you will have a huge vacuum leak
1987 300SDL 6spd manual om606.962 swap project
1985 300td euro 5spd wagon running
I do have a vacuum problem that hasn't been diagnosed yet as far as it being the pump or a leaky connection in one of the vacuum hoses.
Thanks for all the input, I can't wait to get this thing straightened out and on the road.
82 240D
But, would a loss of vacuum cause a soft pedal? I would expect if it were a bad booster or loss of vacuum, the pedal would get harder to push.
I do have a vacuum problem that hasn't been diagnosed yet as far as it being the pump or a leaky connection in one of the vacuum hoses.
Thanks for all the input, I can't wait to get this thing straightened out and on the road.
82 240D
As for it not shutting off with the key, that's also directly related to vacuum leaks in addition to the brake booster. Somewhere in the mess of vacuum lines that run into the firewall, there is a major leak. By bypassing straight to the brown line that goes to the ignition switch it shuts off every time without hesitation. I understand that those other lines are for the power locks. And the cruise control? Regardless, I have a Benz that starts and shuts off when commanded.
82 240D
Well, I guess I have an update.?.? I believe the brake booster is bad. I attached a vacuum tester to the brake booster and it doesn't even think about maintaining a vacuum. I've driven it with the brake booster detached from the vacuum system and it feels exactly the same. I will replace the booster and report back. The vacuum pump is functioning properly according to the gauge on my vacuum tester.
As for it not shutting off with the key, that's also directly related to vacuum leaks in addition to the brake booster. Somewhere in the mess of vacuum lines that run into the firewall, there is a major leak. By bypassing straight to the brown line that goes to the ignition switch it shuts off every time without hesitation. I understand that those other lines are for the power locks. And the cruise control? Regardless, I have a Benz that starts and shuts off when commanded.
82 240D
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