91 240 Braking Issue - MC? Vac? BBooster? Pls Help
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    1. #1
      Junior Member
      Join Date
      Oct 2012
      Posts
      8

      91 240 Braking Issue - MC? Vac? BBooster? Pls Help

      Hi, 1991 Volvo 240 Auto Base Model Non-Abs.

      I've been having an intermittent issue with my braking and am hoping someone has had a similar issue or can point me in the right direction....

      Once in a while when I depress the brakes the pedal travels to the floor...release brake and depress and full braking again. right away thinking it's the Master Cylinder by not 100% sure as:

      1. This happens with no discernible pattern (ie gets better & worse over time) and temperature, amount of braking, length of trip, length of issue persisting - none of it seems to be consistent. Some days / week no issue whatsoever, then one day have 3 - 4 episodes.
      2. I may be crazy but if any pattern, seems to happen more when I travel downhill for a period or after a period of extended steady acceleration?
      3. If I stand on the brakes when no issue is apparent, it doesn't seem to diminish and the pedal stays firm...
      4. Has been going on infrequently over the past 6 months and don't think it has gotten any better worse, just still happens from time to time (Not an easy feeling driving sometimes so yes, need to address)
      5. Not losing any fluid

      Thinking master cyl. but then think also may be a Vacuum problem or booster issue? Wheel Cylinder?

      Appreciate any advice as want to fix but don't want to just start throwing parts at it (but if going to do it, do it right & not just put master cyl on to find after bleeding etc. it was booster all along)

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    3. #2
      Member
      Join Date
      Mar 2008
      Location
      Sarsfield, ON
      Posts
      3,126

      The Old Fart's ten second brake test

      I found this a few decades back. It's generic but is still handy for an initial diagnosis:

      An old generic brake test I picked up decades ago:

      The Old Fart's Ten Second Brake Test


      Before you go tearing things apart, do the 10 second brake test:

      1. With the engine off, pump the pedal until all vacuum in the booster is eliminated.
      2. Pump the pedal again a few times until you get a firm pedal.
      3. Plant your arse firmly in the seat and push on the pedal as hard as you can, and hold the pressure for 10 seconds.

      Preliminary Diagnosis:

      If the pedal goes straight to the floor, you have a completely burst brake line.

      If the pedal goes down fairly quickly, there's probably a loose fitting, leaking line or hose, or a blown caliper/wheel cylinder seal.

      If the pedal goes down slowly, it's could still be a fitting, but not as loose, a seal, but not as bad, a pin-hole leak in a line, or the master cylinder seals.

      If the pedal is just mushy but firms up a bit with some pedal pumping, there's probably air in the lines, a swelling brake hose due to a soft cover or worn/frayed wire mesh inner sheath, or the fluid level is low.

      If there are no apparent problems after 10 full seconds, start the engine. If the pedal is mushy or drops excessively with the engine running, check that the booster is not building up excess vacuum (not common, but possible).
      '88 244 auto (parts car), '89 244 5 spd. (daily driver), '92 245 5 spd. (my car) '80 Holiday Rambler/Ford E350 (tow vehicle and track crash pad), '95 GMC K2500 (local hauler/back-up tow vehicle), '83 Mazda RX7 (race car when I have the funds), '99 Miska 20' car hauler.

      The man's prayer: "I'm a man, but I can change, ... if I have to, ... I guess."

    4. #3
      Senior Member
      Join Date
      Aug 2004
      Location
      Temple, Texas, USA
      Posts
      19,952
      Intermittent collapsing/uncollapsing of rubber brake line(s).

      George Dill

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