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  #1  
Old 07-17-2017, 06:42 PM
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Location: South Florida
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84 300TD Brake question

Hi Everyone, long time.

Was driving the wagon with in town traffic for about 45 min. When I got out I could smell brakes on the back left. Touched the rim and yes, it was hot. Not "leave finger tip skin on the rim" hot, but enough to realize there is too much friction for rear brakes. Went to the right rear and it too smelled and was hot to the touch. Front brakes were warm/hot to the touch, but no smell. Normal in town driving might cause the fronts, especially since no smell.

My immediate thought was the e brake.

So I set the e brake and released it again, really never use it in South Florida, and started home. Everything seemed normal. Then, about a half mile down the road the brake pedal goes almost to the floor! I can brake but with only what felt like an inch to 2 inches of pedal left. I could pump up pressure and it would hold at this point. Very cautiously I continued home. About 15 min of driving and slowly the pressure built back up and my brakes were functioning normally!! Now nothing fixes itself! When I got home, I could still smell brakes. I turned the car off and put it in neutral and it rolled freely, no brake noise or dragging. When braking there is no pulling in any direction.

Is this a fluid overheat fading or am I looking at a master cylinder problem? Would a faulty mc cause fluid to not evacuate and cause binding. With the car off, no vac applied, would it release this fluid allowing it to roll?

The brakes have plenty of meat on them and all 4 wheels were done at the same time along with 4 new rotors and replaced seals on all pistons and new soft lines. There are no leaks and the fluid is topped up. This was done about a year ago, the car is garaged and it is not an everyday driver. Maybe 4 to 6 thousand miles since brake job.

Sorry for the long post but I wanted you to have all the facts before posting to the forum. Thanks guys

__________________
1980 300TD, SOLD
1984 300TD, 275K
1999 C230 K Black & Tan
2013 C250 Black
1974 CJ5 Red
You might faint from the fight, but you're gonna find it. Every challenge could have paradise behind it. -John Popper-

Last edited by firstdiesel; 07-17-2017 at 06:44 PM. Reason: clarification
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Old 07-17-2017, 08:10 PM
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Welcome back to the forum - in case it is the master cylinder, I'm attaching a link to a DIY tech article from our site on the procedure to address the issue. Please let us know if you have any questions!

Mercedes-Benz W123 Brake Master Cylinder Replacement | W123 (1977-1985) | Pelican Parts DIY Maintenance Article
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Old 07-17-2017, 09:32 PM
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If a seal or something rolled on one of the pistons in the MC it's plausible that you could get the type of behavior you describe. If the brakes go to the floor without any external leaks, it's time to look for air in the lines or a failure in the master cylinder.
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Old 07-17-2017, 09:58 PM
firstdiesel's Avatar
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Quote:
Originally Posted by Dmitry at Pelican Parts View Post
Welcome back to the forum - in case it is the master cylinder, I'm attaching a link to a DIY tech article from our site on the procedure to address the issue. Please let us know if you have any questions!

Mercedes-Benz W123 Brake Master Cylinder Replacement | W123 (1977-1985) | Pelican Parts DIY Maintenance Article
Thanks Dmitry, think I'm gonna need that!!

Todd
__________________
1980 300TD, SOLD
1984 300TD, 275K
1999 C230 K Black & Tan
2013 C250 Black
1974 CJ5 Red
You might faint from the fight, but you're gonna find it. Every challenge could have paradise behind it. -John Popper-
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  #5  
Old 07-17-2017, 10:02 PM
firstdiesel's Avatar
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Quote:
Originally Posted by Diseasel300 View Post
If a seal or something rolled on one of the pistons in the MC it's plausible that you could get the type of behavior you describe. If the brakes go to the floor without any external leaks, it's time to look for air in the lines or a failure in the master cylinder.
Thanks Diseasel. So, based off of what you are saying, I can rebuild my master cylinder?

Been here a long time and I've driven to NC to see VStech and rebuilt my transmission with help from Stretch, just to name a few, and I still have the same car. I welcome the help, and thanks for the reply!!

By the way, love the Diseasel thread!! Thanks!

Todd

__________________
1980 300TD, SOLD
1984 300TD, 275K
1999 C230 K Black & Tan
2013 C250 Black
1974 CJ5 Red
You might faint from the fight, but you're gonna find it. Every challenge could have paradise behind it. -John Popper-
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