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Hi guys,
i have a brake pulsation that i cant get rid of.
The car is a old 230.6 w114 mercedes benz (no abs or other kind of electronics).I tried a lot of things up to now but i am kind of stuck and dont know where to go next.
The pulsation only seems to be there when the car is warmed up or the brakes are warm, thats the first thing i dont get.So far i replaced the brake fluid, replaced all 4 of my brake disks, replaced all brake pads, checked all the wheel bearings. Everything seems to be fine. When replacing the disks i made shure to clean every mating service really well.
The pulsation started a few months ago and i am not quite shure whats caused it, i never went over a extreme bump with my car so i woudnt except a shaft to be bent.
I dont feel the pulsation in my brake pedal and dont feel it in the steering wheel and it seems to be coming from the back. The car also does not pull in any direction while doing this.
The pulsation changes with speed and doesnt seem to be related to anything to do with vacuum (checked for vacuum leaks as well), the pulses seem to be on every wheel rotation.
When i brake really hard the pulses smooth out.Any suggestions are welcome, i dont want to trow much more money at this, its becoming quite expensive right now. I find it weird that this only happens once the car is warmed up.
Kind regards,
Hendrik
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I would check the suspension in the rear end for worn parts. It could be something like a worn bushing/rubber part that when you press the brake pedal, it’s creating a different set of stresses on the suspension–and any worn part might go off kilter just enough to cause the ‘pulses’.
I would also drive the car around until the issue returns. Get things good and ‘cooked’. Then do a full inspection of the suspension and brakes. When things are good and hot, that’s when parts expand slightly. Could be bearing, brake caliper mount, brake caliper piston getting hung up just slightly. Just need to catch it in the act.
Just a guess on my part. It’s a tough one.
S-
edit: Wear gloves and/or take safety precautions. Hot brake rotors and such CAN cause nasty burns.
Thanks for your suggestions, i will try checking the car while its warm.
Ill also try getting the micrometer set out and check for runout on my hubs (thats one thing thats still on my list).As for bushings, probably not the issue since i dont find any play in the suspension at all.
Have to throw it out regardless. I’ve seen some really oddball stuff that can create issues in other systems when you think it should not.
It’s there somewhere….just a question of what’s causing this.
Best Regards!
S-
Your rotors could be warped. If the lug nuts were put on too tight that could cause the rotors to warp. You could also have a bad caliper which isn’t allowing the piston to retract slightly causing the pads to rub on the rotor which creates heat. You can check the temperature of the rotors with a heat gun after a drive to see if you have one or both rear rotors overheating.
[quote=”rsawyer05″ post=113469]Your rotors could be warped. If the lug nuts were put on too tight that could cause the rotors to warp. You could also have a bad caliper which isn’t allowing the piston to retract slightly causing the pads to rub on the rotor which creates heat. You can check the temperature of the rotors with a heat gun after a drive to see if you have one or both rear rotors overheating.[/quote]
rsawyer05 took the thoughts out of my mind. If the wheels were not tightened evenly to the correct torque it could cause the problem you are having. I find that German cars are very sensitive to that.
Again thank you for the suggestions,
i always do my wheels myself so they are torqued to specification 110 nm. Heat is not a problem all brakes get warm evenly and certainly not hot.
I checked my runout yesterday evening, and i think it might be bearings after that. Weird thing is, i dont feel any play and dont get any noise from the rear. But when i turn the wheel one direction and then the other i get some runout on the rotors, if i only turn in one direction i have a tiny bit which should be in spec.This is gonna be fun, the bearings on this car are a hell to replace at the rear, special tools + 1.5 meter breaker bar.
Place hand onto spring while turning wheel. If you have vibration in spring, it’s your bearing.
Also, lubricate caliper pins. Someone here had odd vibration with all kinds of suggestions followed, to the last post that said – his mech lub-d pins and vibration went away.Ill give that with the spring a try tomorrow, as for the pins, i also replaced those since its 2 bucks more and put some antiseize on them
I may be wrong but from the description of the symptoms you wrote I get the feeling this is happening all the time not just when braking. If that is true I would suspect a flat spotted tire.
barneyb, it does not happen all the time, its only when braking and above that only when braking while the car is warmed up.
No one hardly ever does this but it is recommended that new rotors and drums be machined prior to installation on a vehicle. Part of the reason for this is to prevent issues like what you’re having. In your case however, I would have the rotors machined on the car to eliminate any issues with runout. In situations like yours, I’ve found this to be the most effective way to deal with the problem. Call around to local shops to see if they have an ‘on the car’ brake lathe. That’s what will be needed in order to machine the rotors on the vehicle.
I’m very encouraged to hear that you’re torquing the wheels because this can also contribute to the problem. More info here.
http://www.ericthecarguy.com/faq/solving-brake-problems
Keep us posted.
Might as well take the whole spindle of the car with the disk on it and machine it myself (got a lathe and milling machine).
Also i did another check, seems my right bearing is getting warmer then the left. I also noticed with a friend in the car and the windows open that my friend can hear the right disk rub on the brakepads when i make a sharp hard corner left. Corner to the right does not generate the sound.
What surprises me that i have no other noises when driving at all (like a typical bearing sound).
Another question that i thought of right now, how does machining on the car work with driven wheels?
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