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#1
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Confused about rear brakes
I have an '84 300d that is having a difficult time off the line. I suspected that it was a back brake problem and when I removed the tire, the caliper cylinders were restricting the rotation of the tire. This is a great development... at least the problem is identified.
Here's the rub - for me at least. I've had front brakes seize before (gotta love cars from New England) and worked the cylinders until they were free to work. On the back brakes, the cylinders don't move independently. When I depress one cylinder on the rear right wheel, the other cylinder on that wheel pushes out. I don't understand what needs to happen... the brakes were so tight that it took some work getting the pads back in once I took them out. Is there a further problem, or is there a way to adjust the difference between the cylinders as they are now? Thanks in advance... V |
#2
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Quote:
If you need to compress both pistons, open the bleeder valve. That will also prevent contaminated fluid from returning to the master cylinder/reservoir. Of course, you will need to bleed the rear brake system if you do that. |
#3
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Hmmm... On the front brakes it seems that the cylinders were able to compress individually. Maybe I just didn't notice.
So, Tango, it sounds like you are saying that there is too much pressure in my brake lines, and I need to bleed off some of this pressure. Is that right? Thanks for the response. |
#4
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Quote:
When you attempt to force one piston back into its bore, the fluid must go somewhere. It can be forced into the adjacent cylinder...........or it can be forced all the way back to the master cylinder. The adjacent cylinder is much easier in most cases and the opposing piston tries to move outward. If you open the bleeder valve on the caliper, the fluid now has a third place to go............out the bleeder valve. The bleeder valve is right above the piston and it's much easier for the fluid to pass out of the bleeder rather than move the adjacent piston. Opening the bleeder has the benefit of extracting the old fluid without driving it all the way back up to the master cylinder. |
#5
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No. There should not be any pressure in the brake line if the brake is not applied. But compressing a piston moves brake fluid out of that cylinder. So the displaced fluid either moves the other piston or flows back through the master cylinder. Opening the bleeder valve just gives the fluid somehwere else to go. And since the fluid in the caliper is likely rusty and gritty, you don't want it going back to the master cylinder or opposite side caliper where it can do unpleasant things.
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#6
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Attempt to determine that your emergency brakes are not the culprit.
__________________
83 SD 84 CD |
#7
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Thanks guys... it's good to understand these things better than my little brain does right now.
TooMany Benz... how would the parking brake affect this deal? I am having issues with it and plan to adjust it through the star wheel, but don't really understand how the two interact. Thanks, V |
#8
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Quote:
I don't know of any adjustment on the disc brake itself. Good luck.
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83 SD 84 CD |
#9
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If you're able to move all the caliper pistons easily, your calipera are probably OK. It's possible for the flexible rubber brake hoses to deteriorate/collapse internally, allowing the brakes to work when the pedal is depressed, but trapping fluid pressure and causing the brakes to drag when the pedal is released.
Happy Motoring, Mark
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DrDKW |
#10
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Thanks all...
Happy and sad ending to the story... Bled a bit of fluid and adjusted the parking brake in preparation for trip. Loosened things up a bit and felt closer to what it should. Got 100 miles down the road and my transmission showed its true colors. The last straw on this car... great engine and interior, but the body is rusty and there are a few other costly parts that need attention (oil cooler). If you know anyone looking for a sweet dashboard or a strong engine from a wagon (with pump) in the Montana area.... |
#11
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Too bad- have you read up on the adjustements of the tranny??
seems most of them are condemned to an early grave, when they prolly just need some adjustments.... but, I gotta ask- which end of montana?? I remember that I-90 is about 700 miles long in that state............
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1984 123.193 372,xxx miles, room for Seven. 1999 Dodge Durango Cummins 4BTAA 47RE 5k lb 4x4 getting 25+mpgs, room for Seven. |
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