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Well, today was a real thrill here in western CT... 4-6 inches of wet snow made my 40 mile commute a nightmare. Driving on straight level road - no change in throttle or steering - and just ice on the roadway beneath the slush made the car go nearly out of control. Reduced speed and attentiveness kept the car from going off road. I also had several occasions to do a functional check on the ABS system!
But here's the question. Since I replaced rotors and pads a year (and 30K) ago, after driving a while the first push on the brake pedal requires a longer stroke than subsequent pushes. The pedal is not spongy at all, it just goes lower on the first push and then seems to be consistently higher for the following pushes. Today, after a slide-for-life toward the back end of an F150 with the ABS pulsing away for all it was worth, I noticed that the brake pedal went even lower on the first push. Immediately subsequent pushes are OK height-wise, but the time interval until a long pedal stroke is required has seemingly decreased. Any ideas as to what's going on? Again, brake performance is apparently unaffected, but the pedal now goes lower than I'd like for the old heel-and-toe double-clutching drill. I'll do a pressure bleed to be safe, but I'm wondering about why the ABS involvement today should precipitate this new condition.
Not sure if this is understandable, but - any ideas?
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It could be that the master cylinder is getting weak.
The low pedal is not necessarily a sign of a problem. Also, on most cars if you push the pedal twice in rather quick succession, the pedal will be higher on the second push.
Some ABS cars have a slightly more mushy feel. Depending on brake fluid temp and outside temp, the pedal could feel slightly different. Also, the ABS can actually make the pedal feel as if it's lifting, because essentially it fights pedal pressure by releasing the pressure at each line that is attached to a slipping wheel (or rear axle). If the master's seals are getting weak, you might notice a subsequent drop in pedal height, although it might go back to normal after a while.
When you REALLY make the ABS work hard, like on sheet ice where it's thumping turns to a solid growl, and the pedal all of a sudden goes rock hard, it is creating a lot of stress on the master. Not that the master should not be able to handle it (it should) but after years and miles, they are no longer perfect.
Since master cylinders are rather inexpensive, you could replace it. Usually they come with a new reservoir too, which is nice. IF you are careful, you won't have to bleed the lines either. A new master is often a fix for similar problems.
--
1992 940 wagon, low miles
as well as others.
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Chris, thanks for your reply. In general, I attribute the longer first pedal stroke to the brake pistons having retracted (or being pushed back), thus requiring more fluid volume to displace them to the 'deployed' position. As the pedal seem quite hard once the pads are on the rotors, I'm not overly concerned, but since the car just passed 150K I'll probably replace the MC when things warm up a bit. We just had a white Thanksgiving delivered yesterday, and on the lee side of the front it's 14F now. God and I share the same garage, so I'll wait for Him to turn up the thermostat.
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Personally, I wouldn't be worried--I'm just throwing out ideas.
If the pedal doesn't have any mysterious sinking or suddenly go soft at weird times, I wouldn't really be too concerned. Although at the mileage it couldn't hurt to replace it.
Typically MC problems start after a panic stop or "testing the brakes" by slamming them on (lots of people do this, believe it or not). So if you notice substantially different pedal pressure, then worry. Otherwise you could probably hang on until spring or maybe even longer.
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Chris Herbst, in Wisconsin.
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That's sorta what I had in mind. Thanks again!
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On my '92, my brake pedal does basically the same thing on the first push, it always has since new. Changing the brake fluid or pads had no effect on the behavior. I only really take notice of it when I haven't driven the car in a while. However I've never experienced the pedal going "even lower".
The 240 is by far the best poor weather car I've driven, they've all been exceptional in rain, ice and snow conditions 
In all the years I've driven my '92 I've only triggered the ABS twice, and I drive it pretty hard and like to brake as late as possible.
--
'92 240 @45k & '96 960 @41k
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While I'm not sure that the 245 is the best poor weather car I've driven, it is far from the worst. Leaving out the family Chevies I drove in the late 60's, that honor - gasp - goes to my '91 Jetta. Even with good snows all around it was a quirky little rascal with a mind of its own. Probably the best snow car I had was an '80 Saab 99 with unfashionably skinny rubber, but with 60% of the cars weight on the drive wheels it knew its way thru snow.
What I can't understand is all the people who had 145's and early 245's who tell me those cars were the worst in snow! While yesterday I could not negotiate one steep, icy hill because my snow tires were in the shed and not on the car, in over 250,000 miles including about a dozen winters I have never gotten stuck in my Volvos.
Re the ABS, I have yet to trigger it on anything except snow or ice.
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