*pop* the both rear wheels lock - PeachParts Mercedes-Benz Forum

squishware · #1 10-05-2010, 06:09 PM

I was driving on the Interstate and I heard a pop then the car could barely make 60 mph at 3k rpm. I got off at the next exit and parked. Both back wheels were hot as the dickens. I had it flat towed home. I was able to drive it up on the tow bed after it had cooled. I am entirely unfamiliar with brake repair (other than bicycles). I jacked it up and tried loosening the hose to see if that released it(it did not).
I can not tell for sure if the caliper is locked or the emergency brake. Short of taking off the caliper is there a way to test? Thanks for all replies.
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thayer · #2 10-05-2010, 06:13 PM

My "guess" is that the emergency brake would not have caused that symptom. the emergency brake is not going to survive 3000 rpm straight gear. Sounds like the calipers have seized. After the flat tow home the brake fluid would have had enough time to stop boiling and return to normal temp. If there are still stuck thats beyond my experience.

vstech · #3 10-05-2010, 06:25 PM

rust from water in the brake fluid corrodes the piston and or the sleeve, and causes the brakes to sieze in place. sometimes they can be rebuilt, but it's much simpler to get a set of rebuilt calipers.
does your parking brake pedal push and release?
jack the car up, and remove the wheels, and see if you can pry each pad away from the rotor with a screwdriver.
if they move freely, disconnect the calipers from the two 19mm bolts, and push them off the rotor, then pull the rotor off and see if you have parking brake action.

squishware · #4 10-05-2010, 06:36 PM

The thing that is still making me curious is the fact that both wheels locked at once. It seems logical to me that maybe its something both have in common? I just want to throw that out there. Also the pop.

vstech · #5 10-05-2010, 06:42 PM

could be a differential problem, but you said the wheels were hot. I'd focus on brakes for the moment.

squishware · #6 10-05-2010, 06:51 PM

I meant more the master cylinder or booster. Is that possible?

dude99 · #7 10-05-2010, 06:55 PM

Where you using the brakes at the time? A blown booster cannot lock the wheels, and I've never herd of a master cylinder locking in the pressurized position, although I suppose it's possible, seems more likely to be the parking brake though... pull er apart and find out..

squishware · #8 10-05-2010, 07:00 PM

Will Do in the morning. Thanks for the help.

layback40 · #9 10-05-2010, 07:53 PM

The pop could have been some junk on the road being bounced up & jamming the park brake cable.
You do need to look at the calipers though.

jonbobshinigin · #10 10-05-2010, 08:26 PM

When was the last time you flushed the brake fluid?

When was the last time you did any maintenance with the brakes? (Pads, calipers, hoses, etc)

squishware · #11 10-05-2010, 08:32 PM

I've had the car for about a month and a half. I haven't got around to brakes yet.

tangofox007 · #12 10-05-2010, 08:57 PM

There have been reports of flex discs coming apart and snagging the parking brake cable.

Yak · #13 10-05-2010, 10:29 PM

Or maybe he hit a mattress?

Post 20.

http://www.peachparts.com/shopforum/showthread.php?t=205055&page=2

whunter · #14 10-06-2010, 02:00 PM

Quote:

Originally Posted by squishware

I was driving on the Interstate and I heard a pop then the car could barely make 60 mph at 3k rpm. I got off at the next exit and parked. Both back wheels were hot as the dickens. I had it flat towed home. I was able to drive it up on the tow bed after it had cooled. I am entirely unfamiliar with brake repair (other than bicycles). I jacked it up and tried loosening the hose to see if that released it(it did not).
I can not tell for sure if the caliper is locked or the emergency brake. Short of taking off the caliper is there a way to test? Thanks for all replies.
__________________

If the hoses are damaged inside = acting as a one way valve = brake friction heat builds until:

* The brake fluid flashes to vapor/steam generating a massive 1/10 second over pressure forcing back past the restriction = blowing back through the master cylinder = the small fluid return port can make an audible pop.

* The brake fluid flashes to vapor/steam generating a massive 1/10 second over pressure Hyper Extending/jamming the corroded piston/housing = hose or caliper seal pop/burst = pressure relief leaving the corroded piston/housing Hyper Extended/Locked on the rotor.

* Brakes, bearing grease and/or tire catch fire.

Brake:
http://www.peachparts.com/shopforum/showthread.php?t=142411

Some Facts About Brake Hoses:
#1. The the industry standard average safety life of a brake hose is six years. FYI data SAE: J1401, J1703, J1705, J1873, J1406, J1288, J1403, J1833, J1402.
#2. Brake hoses deteriorate from the inside as well as the outside.
#3. Moisture is absorbed into brake fluid systems through brake hoses.
#4. Contaminants in brake fluid act abrasively on the inner wall of brake hoses.
#5. The brake hose reinforcing fabric deteriorates through expansion and moisture.
#6. High operating temperatures contribute to the deterioration of hoses.
#7. Brake hoses swell with age and restrict flow.
#8. Generally all brake hoses on a vehicle deteriorate at the same rate, So all hoses should be replaced if one is found to be faulty!
Brake hose failure mode:

#A. Rupture (burst hose) = age, exercise (too many miles) or impact are the typical cause.

*B. Partial internal collapse = the inner ply becomes damaged/detached acting as a partial restriction and/or one way valve.

#C. Full internal Blockage = the inner ply becomes damaged/detached acting as a plug = brake pedal still feels good but there is no brake application.

Brake:
http://www.peachparts.com/shopforum/showthread.php?t=142411

New brake hoses on a used car are cheap life insurance.

Brakes caught fire 1999 C280 (with pictures of damage)
http://www.peachparts.com/shopforum/showthread.php?t=208962

Tell my dad my tire is on fire!

http://www.peachparts.com/shopforum/showthread.php?t=105730

Industry Adopts Brake Fluid Replacement Guidelines By Bill Williams, Technical Contributor
http://www.babcox.com/editorial/bf/bf50412.htm

Brake flush every two years?! U'r kidding right?
http://www.peachparts.com/shopforum/showthread.php?t=96852&page=1&pp=15

Why should I flush my brake fluid every year, you ask?
http://www.peachparts.com/shopforum/showthread.php?p=220599

Have a great day.

squishware · #15 10-06-2010, 08:18 PM

WHunter- Is your prediction that I'll need, Master Cylinder, brake lines and 2 new Calipers? 4 calipers? Thanks for your help this would explain both at once going.