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  #1  
Old 07-20-2003, 03:28 AM
mike690003's Avatar
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Join Date: Apr 2003
Location: Miami,FL
Posts: 807
Brakes are going nuts!! HELP!!!

Hello Board, I have a problem with my 1987 300E. My brakes will work fine at 15-30 MPH, but below 15MPH, the brake pedal "shudders" when I try to stop. The brakes also seem to lose firmness after a 15 minute drive. Afte the drive, I have to push the brake pedal down ALL the way to the floor to get the brakes to work. It is very scary because I have press way down to get any brake response. Sometimes I pull over on the highway and repeatedly press the brakes in hope of building up pressure in the brake system. I had the car checked out and found that:

-->the right front brake sensor is broken
-->my rotors are worn out
-->my brand new pads are now worn unevenly


The mechanic also said my ABS is "over-active".

Does anyone know what is ACTUALLY causing my brakes to function like this.

I plan on switching to cross-drilled rotors, but I do not want to spend big $$$ and have to spend extra $$$ if my brakes still end up acting funny.

HELP!!!
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1987 mercedes 300E
1995 e320 conversion(hated the 300e grill)
HID/Xenon (D2S)
Keyless Entry
Monochromatic Paint (Custom Blue)
Smoked Tails
Flat Badged (front)
Debadged (rear)
custom "carbon fiber" console
18 inch HP EVO rims
Sold! Now I drive a Monte Carlo SS
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  #2  
Old 07-20-2003, 03:38 AM
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Join Date: Apr 2002
Posts: 3,469
Sounds like a lot is going on.

The fluid is probably getting hot because the rotors are either warped or the wheel bearings are worn out.

Id upgrade to late model brakes because the early model brakes always get hot and consequently squeak (at least for me).

It is possible that your wheel sensors are bad which would cause the problems under 15mph.

So Check your wheel bearings, check to see the run out of your rotors too. Then go from there.

Do a flush of the brake fluid when you do all this work, its probably bad from being hot so much.
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No Benzes in the stable at the moment, but itching for one again.

Former Mercedes in the Stable:
1983 300CD Turbo diesel 515k mi sold
1984 300CD Turbo Diesel 150 k mi sold
1982 300D Turbo Diesel 225 sold
1987 300D Turbo Diesel 255k mi sold
1988 300 CE AMG Hammer 15k mi sold
1986 300E Amg Hammer 88k mi sold
1992 500E 156k mi sold
etc.
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  #3  
Old 07-20-2003, 03:50 AM
mike690003's Avatar
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Location: Miami,FL
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Thanks a lot, should I switch to cross-drilled rotors?? Any drawbacks to the cross-drilled. I don't race, it would just basically be for looks. But, I dont want good looking brakes that don't work good.
__________________
1987 mercedes 300E
1995 e320 conversion(hated the 300e grill)
HID/Xenon (D2S)
Keyless Entry
Monochromatic Paint (Custom Blue)
Smoked Tails
Flat Badged (front)
Debadged (rear)
custom "carbon fiber" console
18 inch HP EVO rims
Sold! Now I drive a Monte Carlo SS
http://memimage.cardomain.net/member.../352975_67.jpg
http://memimage.cardomain.net/member.../748335_24.jpg
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  #4  
Old 07-20-2003, 04:55 AM
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Join Date: Apr 2002
Posts: 3,469
Spend the money getting late model brakes. Crossdrilled arent as good at slotted, if you want holes in them, they need to be cast into the rotor, slotting the rotors doesnt affect the hard spots in the rotor as much.
__________________
No Benzes in the stable at the moment, but itching for one again.

Former Mercedes in the Stable:
1983 300CD Turbo diesel 515k mi sold
1984 300CD Turbo Diesel 150 k mi sold
1982 300D Turbo Diesel 225 sold
1987 300D Turbo Diesel 255k mi sold
1988 300 CE AMG Hammer 15k mi sold
1986 300E Amg Hammer 88k mi sold
1992 500E 156k mi sold
etc.
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  #5  
Old 07-20-2003, 03:51 PM
mike690003's Avatar
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Join Date: Apr 2003
Location: Miami,FL
Posts: 807
Is flushing the brakes a simple DIY?? I don't want to get any bubbles into the brake system and have my brakes fail. If its easy, I'll do it. I'll just need some instructions. Help!!
__________________
1987 mercedes 300E
1995 e320 conversion(hated the 300e grill)
HID/Xenon (D2S)
Keyless Entry
Monochromatic Paint (Custom Blue)
Smoked Tails
Flat Badged (front)
Debadged (rear)
custom "carbon fiber" console
18 inch HP EVO rims
Sold! Now I drive a Monte Carlo SS
http://memimage.cardomain.net/member.../352975_67.jpg
http://memimage.cardomain.net/member.../748335_24.jpg
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  #6  
Old 07-20-2003, 06:53 PM
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Join Date: Aug 2001
Location: Evansville, Indiana
Posts: 8,150
A sticking piston will cause one wheel to slow faster than the other, even grab. This may cause the ABS to operate, causing the vibration. It's working normally, the brakes aren't.

Loss of pedal after driving sounds like warped rotors -- they will also cause vibration on braking at low speed, and will push the pads back too far, causing the loss of braking after driving -- you have to push the pads back out.

Loose front wheel bearings will do the same thing.

If your rotors are too thin, chances are they are also warped. Get new rotors, pads, and plenty of fluid.

Uneven pad wear is usually a result of a sticking piston -- that pad will be thicker than the others. Remember that the outer pads wear more than the inner ones, too.

Change the pads and rotors (I'd stick with factory ones, the cross drilled and slotted one are for racing, they only reduce braking on the street with so little effect on suspension you won't feel it). Install rotors and pads, check front wheel bearings, and the bleed the brakes. Clean the slots in the caliper for the pads. Put some antiseize on the sides and back of the pad (NOT on the brake material, please!).

Get a piece of clear plastic line that will fit over the bleeder valve on the caliper.

Put the plastic tubing on the bleeder valve with the master cylinder cap off. Put the free end in a clear container so you can see what comes out. Open bleeder. Gravity will slowly run the fluid out. Let it run until you get clear fresh brake fluid out (this works best when the pistons are pushed all the way back). Close bleeder, move to the next wheel, and repeat.

Rears will be very slow, but you can do this yourself, no need for a helper.

You can also use the bleeder accessory that comes with the MitiVac, if you jdo, be careful not to suck all the brake fluid out of the master cylinder!
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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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  #7  
Old 07-20-2003, 11:56 PM
AF300E's Avatar
Don't Mention the War!
 
Join Date: Jul 2003
Location: Melbourne, Australia
Posts: 181
It is usually the leads fromt the speed sensors in the whele hubs.
Most of the time the abs light will not even come on. Remove the leads and test the resistance (i'm sure someone here will know the correct values).
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300e 294,000mi
380sel 185,998mi
380se 309,980mi
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