1985 300td wagon brake issues, brakes overheating? - PeachParts Mercedes-Benz Forum

neumann · #1 08-13-2012, 10:16 PM

I took an 1985 wagon for a test ride the other night and the front brakes were severly smoking after a couple of miles, the rears were hot but nowhere near as hot as the fronts.

Some background: car has predominantly sat for the last year with an occasional move in the yard so the po could mow the lawn and such then relegated to a carport for last 6 months solid. Battery was dead as dead. I was told of the car a couple of weeks ago and knocked on the door to see if they would consider selling it. They said sure so 79mercy and I go over for a test ride. Find the power steering fluid is low, brake fluid is low and 3 tires need about 10-15 pounds of air, drop in another battery. So we drive in the the wagon to the local parts store which is about a mile away and buy some fluids. Brake fluid was the lowest and took about 10 ounces.

On the way to the parts store the burning brake smell started, pulled in and the fronts were pretty, pretty toasty hot as tested by touching the wheels, back brakes were getting slightly warm. I chalk it up to sitting for a long time and maybe they will work loose. Top off fluids and drive to I-10, still dragging brakes, get on then ramp and realize it was a big mistake. Front brakes start smoking real bad, now I am afraid it might catch fire

. Car tops out at 40mph floored. Limp/Drive 1/2 mile to next exit, let the brakes cool for 30 minutes, fronts were very hot to the touch like burn your skin hot, backs were hot as well but nowhere near as the fronts. So we bite the bullet and drive back on surface streets after the cool down. Get back,check brakes, still hot, park the car and make plans to buy it and start pricing brake parts.

I pick up the car tonight, fully prepared to have it towed home but I threw caution to the wind and decided to drive it home..about 1.5 miles. Made it back just fine, no smoke from wheels, no burning brke smell, front wheels pretty normal to the touch as far as heat goes.

What gives? Any armchair feedback? Did something work loose or the brakes may be fine? Or could the low fluid have caused the brakes to overheat?

layback40 · #2 08-13-2012, 10:22 PM

Rusty disks & seized calipers. Your use of it has undone the neglect.
Best keep an eye on the fluids. You may have caliper leaks.

Mark DiSilvestro · #3 08-13-2012, 10:41 PM

If they're old/original, consider replacing all the rubber brake hoses anyway. Even if they look fine, these can swell-up internally with age - acting like a one-way valve to allow fluid pressure to the calipers, but preventing release when your foot is off the pedal.
If you can get the brakes to seize again, you can try to verify if it's a hose or caliper by immediately jacking up the locked, overheated wheel and cracking open the caliper bleeder-screw. If that brake quickly releases, it's most likely the hose. If not, it's the caliper.
Also, sometimes, on a car that's been sitting long, the brake pads will rust into the calipers, preventing release. But usually it's the caliper pistons that have seized.

Happy Motoring, Mark

kerry · #4 08-13-2012, 10:41 PM

Quote:

Originally Posted by layback40

Rusty disks & seized calipers. Your use of it has undone the neglect.
Best keep an eye on the fluids. You may have caliper leaks.

x2

JHZR2 · #5 08-13-2012, 10:52 PM

The lines are shot no matter what (6 years is all that DOT allows for brake lines technically), and the calipers likely have bad condition on the piston seals if they arent seized.

Add water in the brake fluid and things may well be rotted from the inside out.

For cars these ages, replacement of the whole system is smart, IMO.

qwerty · #6 08-13-2012, 11:39 PM

Quote:

Originally Posted by JHZR2

The lines are shot no matter what (6 years is all that DOT allows for brake lines technically)...

Have a reference for that?

JHZR2 · #7 08-14-2012, 12:21 AM

Quote:

Originally Posted by qwerty

Have a reference for that?

"Brake Hose

The average life of brake hose is not forever, as many motorists assume. It is more like six to 10 years, or even less if a hose suffers some type of road damage that causes it to leak. A leaky brake hose is a very dangerous condition because the loss of fluid can result in brake failure."

Tire Review - Sharpen Your Belts and Hoses Knowledge

"The estimated life of a typical 'rubber' brake hose is 6 years, according to BrakeQuip, the manufacturer of aftermarket rubber and high-performance stainless steel braided brake hoses. "

Inspecting Automotive Brake Lines

Quote:

Industry Adopts Brake Fluid Replacement Guidelines By Bill Williams, Technical Contributor

Some Facts About Brake Hoses:
#1. 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.

Stainless Steel Braided Brake Hoses

And I know firsthand that this is what the brake hoses look like on well maintained, low mileage w123 diesels: