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It's a V240 '89 A/T with Girling front and rear calipers.
I've been struggling with spongy brake pedal on my Volvo for some time now. It all started with soft pedal/poor braking after changing worn front pads. After reading some posts on brickboard.com I followed by changing master cylinder which didn't cure the problem. Since that time I changed almost everything, bled the system several times wasting lots of DOT4 and accomplishing almost nothing.
Until now I have:
- put new master cylinder made by ATE - tested it with plugs and with those installed the pedal is rock hard. I bled it on car using two pipes going all the way from its ports to its container filled with DOT4, once or twice I bled it loosening the screws on hard lines with pressure applied on pedal.
- changed all four calipers to refurbished Raybestos - true beauties. I did check if the front ones didn't have the halves mis-installed and these are fine.
- changed all 8 flexible hoses. I had them custom made at local shop using SAE100-R2 hose.
- changed brake line junction (OEM Volvo) that was leaking from the switch
- tested the check valve on power booster and it let the air pass just one way (at least when I use my mouth as a testing equipment)
- when I realized there was a small leak on those new rear calipers, I bought Rothenberger flaring tool, cut about 5mm of the old line and made new flares. That stopped that leak.
- tested for more leaks leaving the Motive pressure bleeder at about 20PSI for 15min and it kept the pressure
- bled the system about a zillion times spending a fortune on DOT4. I used different techniques: with Motive bleeder, with pedal, applying some pedal pressure while having Motive bleeder produce about 20PSI, having the rear of the car lifted higher than the front, leaving the car for 2 days with the pedal pressure applied. Bled the system when it was cold and bled it immediately after driving about 20km with lots of breaking and shaking over bad roads. No dice!
Right now the car brakes pretty well. After heating the brakes for about 5km (never tried with cold ones), although I try to avoid that I can block the wheels and squeal with tires whenever I want.
I even compared the braking distance with much, much younger Mazda I have and there is nothing to be ashamed of - at some point Volvo had even better results.
The thing is that pressing that pedal feels like stepping into a crap. Like in one of those dreams where you are pushing the brake pedal, it falls into the floor, car is not stopping and you wake up immediately before hitting the other car (am I the only one that is having those?).
There is a "long" distance where almost no resistance is felt, more or less at the height of the accelerator pedal one starts to feel that there is something going on and pressing further from that point brings you to stop. Braking does not feel aggressive, it does not feel like the car is grabbing on that brakes and you're going to crash your skull on the windshield. It's more like slowing down - but on a short distance :) Oh, BTW this car has no ABS.
What's more, even if you block the wheels you still feel the softness, the sponginess at the end of the pedal working distance. It never gets really stiff.
I can't deny there still is some stupid air trapped inside the system. Mostly I was bleeding using the Haynes sequence. Last time I decided to bleed just the rear with about 250ml of DOT4 passing through each bleeder. After not seeing those for a few last bleedings, some bubbles did came out on the rear-right. One was about 5mm long and after some time there was a series of really small bubbles, like 0,5mm each. I was pretty happy seeing them however on a test drive I realized that the only change I noticed was the pedal stiffness. Still, there was almost no resistance until the height of accelerator pedal and only from this point brake pedal got a bit (a small bit) harder.
Front discs are Lucas, rear are Fremax, front pads are Ferodo, rear are Lucas. None of those have seen more road than 500km. On last two test trips I noticed that over the time two symptoms have developed none of which appears with every braking.
First is that kind of middle-low pitch-submarine-type squeal at the end of breaking distance that appears only if you are braking hard (but without wheel block).
Second one is that sometimes (I believe also after heavy braking but am not sure yet) when the car rolls veeery slowly I can hear the other type of squeal - pretty silent and high pitched. It's like squeak-squeak-squeak with every wheel turn and it gets faster and faster with the speed increasing until it completely disappears. After next braking it's sometimes still on and sometimes it's gone. I'm just hoping I didn't bend the discs with all that short distance (10-20km) test drives.
There is one more thing I have to mention. My sensation is that there is no consistency in how the pedal feels. The car was without use for more than a week. Today I took it for a 10km trip and the pedal softness almost scared me at the beginning. After driving about 500m it got better. Then it was more or less as I described above but my conviction is that it doesn't feel the same with every kick. If, when driving at let's say 60kph, I kick the pedal once and then immediately kick it once more the second kick meets with lots of resistance and there is that "pufff" sound. It might point the brake booster as being defective, however I can't imagine how could it fail with such symptoms.
OK, sorry for such a long post. I just tried to write down everything I remember hoping that someone will see any pattern in all that mess and suggest a solution or point out what I'm doing wrong. Thanks for reading, I'd really appreciate any input.
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