89 240 Wagon- Had a failure light on and a pedal that went way down. The arrows pointed to the master cylinder. New MC, bench bled, bled the wheels, pedal hard with ignition off, engine on pedal still goes way down. The Failure light stayed off, though, so I guess thats good. What are the symptoms of a leak in the diaphragm of the power booster? And can the diaphram be replaced? Thanks! Dave

 

If you have ABS the there is a special procedure for bleeding the brakes. I worked on a Volkswagen Rabbit just recently and we had way soft brakes. A local shop looked at it, replaced some things in the front, the problem persisted and said it was a bad master cylinder. We replaced it and rebled it all and there was no difference. We inspected the rear brakes and found a broken spring and way worn out shoes. Replaced them and now it works like a charm. I don't know if the 240's even come with drum brakes or not, but at least have a look at all the pads (or shoes) and make sure everything is fine on that end of the system (no uneven wear etc.). (Just don't press the brake pedal while any calipers or drums are off) The brakes should be very stiff if the booster doesn't work. That just assists you to press the pedal more than anything.
Look for leaks to see if a line burst

 

Titan- Thanks for the note. Well she does not have ABS, nor does she have drums in back. All pads are about 2 months old, there are no leaks. New Master Cyl. New calipers front and rear (thanks to the NAPA warranty on crappy parts). I read in my Haynes that if the booster isnt working it would be hard to push brakes. The pedal easily goes almost to the floor. I think I'm gonna bleed again tonight.............Dave (former Rabbit owner)

 

you cant compress a liquid simple as that...hydraulic theory is just that. if it doesnt work there is either air in the system (you can compress gas) or you are bypassing pressure (fluid leak between seals)

http://www.familycar.com/brakes.htm

 

I realize my last post was neither informative or usefull other than the link maybe...

My guess is you need to bleed the system further or suspect that your master cylinder has a problem still. even a minor nick on one of the "o" ring seals can cause problems. Here is a link to an informative site about master cylinders.
http://www.tegger.com/hondafaq/maste...ace/index.html

also

http://www.swedishbricks.net/faq/brakes.html

 

jpravi-I went over to Auotzone today and got a hand held vacuum tester thing. 20 bucks. It hooks up to the bleeder and sucks the fluid / air out. went around the car (twice) on each of the 8 bleeders and I think we're back in business. Failure light off too. Still doesnt feel like a rock, but way better and drivable. Now to get my steering problem sorted out. (see other post) Dave

 

The pedal should not feel hard when the engine is running. The brake booster applies extra force to the hydraulic system when the engine is running.
The pedal should be hard when engine is off and after pedal is pumped several times to destroy vacuum in teh booster.
It is perfectly normal on a car with vacuum bosted brakes, to feel the pedal drop as the engine starts and vacuum is applied to the brake booster.

Regards, Andrew.

 

Typhoon, others- the hand held pressure thing did it. Brakes feel great! hope they stay that way for a while. Dave