"hot" brakes smell at right rear wheel... ?? - PeachParts Mercedes-Benz Forum

86560SEL · #1 01-02-2009, 09:20 PM

UPDATE - replaced brake pads on the rear several weeks and all is fine now - no more issues with the brakes. Thanks for all of the replies.

I have not noticed it until today, but when I stopped today to fill my car with gas, I got a whiff of "hot brakes". I smelled and it was coming from the right rear wheel well area (where I was standing). None of the others have the smell. I put my hand down near the wheel and it did not feel hot... warm, but not hot. My brakes work fine and there is no squeaking/scraping, etc, so wondering what could be going on.

(Yes, I checked and the e-brake is not applied).

Thanks for any information.
Btw - the car is a LWB W126 sedan.

babymog · #2 01-02-2009, 10:13 PM

Parking brake dragging.

Pooka · #3 01-02-2009, 10:18 PM

This is either a dragging parking brake or a stuck brake caliper piston. You need to jack up the wheel and turn it to see where it is dragging. You might have to pull the disc off to see if the parking brake parts have come apart.

Make sure you chock all the wheels before lifting one of the rears.

If this starts to really drag you may not notice the drag but you will soon notice the heat. The heat will discolor your alloy wheel by burning the paint off of it.

You might just need new brake pads.

Pooka

Arthur Dalton · #4 01-02-2009, 10:34 PM

A very common cause on these is a swollen brake hose...they deteriorate inside and swell up, causing the caliper to hold pressure and not able to return after pedal application..very common w/aged hoses.. pedal pressure is high enough to over-come the restriction and apply force to caliper , but return/release pressure is residual, so the hose acts as a one-way valve due to the interior swell/restriction....

Here is a simple diagnostics trick to iso the problem:

Jack the suspect wheel off ground and apply the brake pedal as hard as you can...now get out and try to hand turn the wheel... if NO , open that bleeder..if the wheel then turns freely, you have a swollen hose...if it does not, you have a frozen caliper [ or e -brake bind]

Simple.............opening the bleeder will release any line pressure to the caliper, so you then know the hose is shot...but if you release pressure w/open bleeder and the caliper is stll holding that wheel, it is not line pressure that is the cause b/c there is no line pressure w/bleeder open.............

86560SEL · #5 01-02-2009, 11:39 PM

Thanks for the replies... I will check that, OR have my mechanic check it. Is it dangerous to drive this way? I may have to drive the car for about 120 miles for a couple of days (in town driving on Sunday and Tuesday), unless I drive my Lexus, but I may have to lend that to my mother, as her car is in the shop being serviced.

BTW, that wheel is already discolored, so this has either been ongoing, or its happened before.

I do not think its been going on for long though, because this is the first time I have noticed it.

I cannot feel it dragging. It will roll on even the slightest grade on my driveway, because at first I was thinking sticking brakes, so I give it a quick check that way.

Thanks again.

Arthur Dalton · #6 01-03-2009, 09:57 AM

If yu don't know how to open a bleeder , then bring it to someone.................the brakes could lock up.

babymog · #7 01-05-2009, 11:23 AM

It has been my (limited) experience that a parking brake dragging can smell like hot brakes without creating enough heat to make the wheel hot, nor enough drag to be perceivable when driving.

If the service / disk brake is creating enough drag to smell hot, it will usually make the wheel hot, and create enough drag that putting the car in neutral at walking speed on level pavement will cause the car to come to a noticably faster stop than normal. The service brake is designed to dissipate much more energy/heat than the parking brake.

If the wheel is hot, I'm betting on a rusted/seized caliper or swollen hose. If not, parking brake (usually cable).

Arthur Dalton · #8 01-05-2009, 12:23 PM

I agree...
So, do the bleeder /wheel spin test before assuming anything.
My post is not a diagnosis, it is a procedure test to arrive at the proper diagnosis.

appatula · #9 01-05-2009, 01:45 PM

Quote:

Originally Posted by Arthur Dalton

I agree...
So, do the bleeder /wheel spin test before assuming anything.
My post is not a diagnosis, it is a procedure test to arrive at the proper diagnosis.

Exactly! Not sure if I'm the center subject now

but I will rule out the E-brake....as its the front right disk. I could also suspect the caliper mounting pivots *name*? As I know the two anchoring bolts should allow for side to side movement, I'll add that check to the list. Thanks again Arthur, and babymog!

appatula · #10 01-06-2009, 02:17 PM

UPS should have my lines in by tomorrow........

86560SEL · #11 01-06-2009, 11:50 PM

Thanks. Well, I was forced to drive the car about 59 miles today and there were no issues. In fact, I smelled around that tire at each stop and it did not even have the smell today and was not even all that warm.

We had soaking and I mean a soaking rain all day, so it may have kept it cooler than normal when I was driving since it was probably staying wet/damp, but it was not even steaming with it being wet.

I will still check it out though.

appatula · #12 01-07-2009, 11:26 AM

Still, get it checked. Brakes are not childs play, however, at least it's not happening on the front.

appatula · #13 01-09-2009, 10:14 AM

Put the new hose on, cleaned up the old caliper, pushed the piston out and cleaned that as well. Its the second day now and all seems as if my red hot rotors are gone. Today will be a longer drive so I'll push her a bit hard through the trip to completely confirm the issue was solved. I'm also considering getting the caliper rebuild kits, the rubber on the one I cleaned up looked fine, however, I suppose the rubber inside could swell and also cause unwanted tightness between the caliper wall and the piston. Thanks so very much guys!

appatula · #14 01-10-2009, 10:29 AM

I can confirm the fix, new hoses and a good cleaning did the job. Took about an hour per front wheel in 20 degree weather, not hard. Time to pop the blower motor regulator in

....

86560SEL · #15 01-12-2009, 12:16 AM

Quote:

Originally Posted by appatula

Still, get it checked. Brakes are not childs play, however, at least it's not happening on the front.

I will. I drove it that Tuesday and there was no smell at all. I was hoping whatever it was broke loose, but it didnt. I had to drive the car today... about 15 miles at 55 mph. I stopped to refill with gas and smelled it pretty strong and I could feel heat if I placed my hand by the wheel. I was almost hesitant to pump gasoline right there.

, but I did anyway, but carefully. I headed back home (which was 13 miles). I stopped a couple of times and checked and there as no smell and it was cool. I got home, checked it again and it was cool and no hot brakes smell. Something is screwy. I will either try to check it myself on my day off, or take it to one of the local MB mechanics.

If its only the hose causing the problem, is it easy to replace?

Thanks!