I have an 83 300D that I did some brake work on this summer- new booster and master cylinder, front pads and rotors, rear pads and rotors. When I hit the brakes, everything feels great, but sometimes there is a pop to the pedal. I was wondering if anyone might know what is causing this before I go tearing everything apart.

I don't think it is a suspension part as it also happens when the car is not moving. It doesn't happen all the time, only when brakes are depressed firmly. Also, I don't experience any loss of braking power.

Any thoughts are greatly appreciated!

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Rich

83 300D
98 E320 Wagon

Check for weasels.

Did you bench bleed the master cylinder pretty well?

Does it usually happen after backing up, then going forward and using the brakes?

If so. STOP DRIVING and pull your calipers... There is something moving between direction braking.

Usually, it's caliper mount bolts loosening, allowing them to shift fore and aft...

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

My pedal does this too. It feels almost like it's in the linkage from pedal to master pushrod.

I need to investigate. No other symptoms beside the clicking I can feel on my foot when I brake.

I did bleed master cylinder extremely well- took a long time but made sure there was not a trace of air coming from any of the ports.

It does not seem to be directional. I will experience it after pulling forward out of a parking spot. But, I will check all mounting bolts for tightness today.

It really feels like what Manny S said- linkage. But I'm not understanding what it could be catching on.

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Rich

83 300D
98 E320 Wagon

One of my 240Ds used to clunk when I put on the brakes sometimes. A dull clunk. I never could figure out the cause. It did not cause any trouble in driving or braking though. Drove me nuts though!

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

If this symptom did not exist before you changed the brake parts. I might want to re check the end play of the front wheel bearings. Not that I have any real expectation this is the problem.

Did you Bench bleed it ?

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1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/showthread.php?threadid=10414

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/showthread.php?t=156207&highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html

If the brake pad retaining pins (caliper hardware) are worn the pads may initially hang up when applying the brakes. Or a pin may have come loose.

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1986 300SDL 440,xxx

Air in the MC won't cause a pop in this circumstance, ever.

Being it will pop when stationary, there are only a few things to check.

If the car has a proportioning valve for the rear, you are probably feeling that. Does the pop occur at the same brake pressure and can you let slightly and get it to pop when pressed slightly again? Find the valve and have someone hold on to it and feel for a pop. ( Motor off , car blocked )

You could be having the brake pressure warning switch moving off center but I doubt that.

Do you hear the pop as well? There might be an issue with the pedal mounting system shifting. If manual trans, is there any interaction between operating the clutch and brake?

Check the bolts that hold the brake booster to the firewall and carefully look at where the booster cans lock together. There is a slight chance the two cans are moving when the brake is depressed and back when engine vacuum is pulling them together.

There could be a crack on the booster or the firewall that pops when flexed. Look for very fine brown powder. ( rust ) When metal frets ( rubs ) it makes fine slivers of metal that will runs quickly. )

Have someone go to each wheel and listen for a pop. There is a small chance that a pad is catching / too loose in the caliper but that usually only makes noise when driving at low speed FWD or RWD and applying the brakes.