Brakes, not quite right.
 

My brakes on my '98 E320W4 aren't what they should be. When I first apply the pedal they start to work but as I gently increase pedal pressure the braking does not increase in a linear fashion. The braking will eventually come on strong, sort of all at once.

The rotors look like normal wear for a 65K mile car. The rotors do look a little shiny. Could the rotors be glazed? I just got the car so I can't vouch for how it was driven.

The brake master has clean fluid and if up to the right level. There is normal brake dust and there is no squeaking or other noises when the brakes are applied. Nothing else out of the ordinary.

BTT.

Has anyone ever experienced these symtoms? If this is an easy or DIY fix it would save me a lot of money.

Thanks.

BTTT Again.

Anyone have any ideas? Don't tell me this is normal. If I were to guess I'd say the problem could be the glazed rotors, a bad master cylinder, or the pads. I haven't found a good local mechanic yet so I need to know more about this before I take it anywhere.

What about the panic stop circut?

If I don't get a response I'll post this again under the topic of naked women or something.

Resguy,

Don't be fooled by clean looking brake fluid. BF is hydrophilic meaning it absorbs moisture over time and thus reduces braking efficiency and will eventually corrode internal brake components. I do occasional track days with my Porsche and am familiar with brake fade caused by hot or old brake fluid. It's a scary situation especially coming into turn 10 at Road Atlanta where you have to pull it down from 110 mph in time for a 90 degree turn. It is recommended to flush the system before EVERY track event, even if the juice is 2 weeks old.

I can't say that this is definately your problem, but, if your records do not show a brake system flush, I'd bet it's never been done. Even if it doesn't solve your problem, you should do it anyway. I'd be surprised if the poor brake performance is related to glaze....especially on a street car. Change out the juice and I'd bet you'll notice improvement.

Just my 2 cents.

Good luck,

Thanks.

I agree, and will do this as a regular maintanence item.

Do you know of a DIY guide for flushing out old BF? I have flushed out the BF on old cars by completely draining and then blowing out the lines with air. This was an extreme case with evidence of rust etc.

What is the best technique for flushing BF. I don't want to introduce any air to keep the bleeding down. Do you refill with DOT 4 or 5?

Is what I am describing actually brake fade? My brakes stop, it is just that they grab and work like an on/off switch. I thought that fade was when the brakes work and then go away. I have experienced this (fade) with other cars when driving down a long hill when the brakes got hot.

Resqguy,

Do a search on "brake fluid flush" or something similarly worded. You'll get numerous responses with 'how-to's', to include the old two man method and the modern power flush (home version ;) ).

As for your initial query, I don't know, sounds a bit like brake fade, except for the grabbing at the end. I am well versed in the effects of brake fade, have never experience the grab you describe.