Hello everyone, I'm new to this and pretty new to the world of accord ownership. I have a 99 ex sedan 5 speed and i have had a spongy brake pedal now for about the past month. I have bled the brakes more times than I care to mention, have replaced a seized Lf caliper and the car is presently on her 3rd master cylinder (original failed, 1st replacement defective). As of now the brakes do feel better than before, but the pedal is still soft and travels about halfway before anything really happens. As I said before the brakes have been bled very well and all lines hard and soft are very good. I have consulted my father who's been a tech since before I was even a twinkle in his eye (has little to no experience with Honda however) and we have reason to believe the culprit to be a bad proportioning valve. I unplugged the abs and made a few panic stops with a couple of friends watching the wheels and no matter how hard I hit the brakes the rear tires would at the most BARELY lock up while the fronts would without fail. Before I go ahead and replace the proportioning valve I was wondering if there was A) anything else I could be overlooking, and B) is there any procedure to reset the valve so it sends the proper pressure to front and rear. I'm sorry for this being a little bit wrong, I just felt it helpful to add as much detail as possible. Thanks in advance.

 

Are the bleeder valves on the calipers on the top or the bottom?

You may need to adjust the push rod on the new master cylinder.

Watch this video:


This is for a clutch master that has the push rod adjustment.

 

I'll give that a shot tomorrow, It can't hurt anything. As for my bleeders, they are on the tops of the calipers and I always make sure that they are tight before I put everything back together.

 

By "soft pedal" do you mean the pedal is spongy and goes all the way to the floor unless you pump, or perhaps just excessive pedal travel w/ hard brake pedal at a very low pedal position?

Trapped air will usually mean no brake action w/o pumping several times. Is this the case?

A soft brake pedal might occur due to soft ballooning brake lines. Suggest inspecting each line under pressure for bulges. It would not take much of a bulge to soften the pedal.

Regarding the proporitioning valve being the cause/solution, this seems possible, but unlikely. I did some reading on how the proportioning valve works (Proportioning Valves) and a damaged proportioning valve might soften the pedal. The rear brake pressure build rate when applying brake pressure is supposed to slow compared to front brakes (how was not described, possibly a spring loaded relief valve), but if faulty the valve might result in too much softening of rear brake pressure build. This is strictly speculation, and I've never heard of a faulty proportioning valve.

Also, when searching for a solution, the simplest explanation (air in brakes) is the most likely. When you bleed, did you bleed for 10-15 brake pedal press/hold/release cycles. It sometimes takes many cycles to clear all air.

good luck

 

the pedal doesn't get as hard as it's supposed to be, but there is excessive travel before the brakes start to noticeably apply and pumping the brakes has not helped with anything. When bleeding the brakes I have done at least 10-15 cycles per wheel, honestly I lost count. As for the rubber lines I have not seen the lines do anything that would even resemble ballooning.

 

You would have to watch the rubber brake lines as someone presses the pedal. They only balloon under pressure.

Many times, I've been bleeding brakes, and the fluid comes out nice & clear & new. But the pedal is soft. Keep bleeding, like a 1/2-pint (250ml) at each wheel. Can't think of how many times the fluid comes out clear & free of bubbles for awhile, then I finally get the last 2 or 3 air bubbles.

 

I will try and double check the rubber lines during the daylight hours, going back to how the brake pedal felt, I just took the car out and it does firm up, but again more than halfway down. I will also try bleeding the brakes again if I can find someone who isn't sick of it yet to help me. While I was out I tried a few successive 40-0 panic stops (on empty side roads) and that did get the pedal to firm up a bit, however that effect went away rather quickly. I am aware that when the abs kicks in it does make the pedal hard as a side note, the pedal felt better when I got going and tried tapping the brakes a couple of times.