OttawaGSR

So here is my two year long nightmare:

I purchased a '92 DA9 GS two years ago. On the first drive, it had very soft brakes, with the pedal nearly dropping to the floor. I assumed it was either a bad master cylinder, or air in the system, or old brake lines, or even a combination of many things. I bought the car with the intention of making it my new daily driver.

Once I had the car home, I did a little inspection and found some serious brake work was needed. I replaced the master cylinder with a remanufactured product from PartSource, swapped in Russell stainless steel lines, four new calipers, Hawk HPS pads in all four corners, and Eurorotors in all four corners. I then bled the entire system with Prestone DOT4.

The master cylinder was bench bled before installation with a bench bleeding kit. After installation, the brake system was bled properly: the brake pedal was depressed, then I open the bleed screw until the fluid stops flowing, then I close it firmly, then the pedal is released. Repeat, repeat, repeat until no air, then move to the next brake. The bleeding process was in the order of: rear right, front left, rear left, front right - with somebody depressing the brake pedal for me.

The pedal feels exceptionally firm, right at the top of the pedal stroke - until you start the engine. With the booster under vacuum, the pedal sinks very loosely 4/5 of the way down, with the remaining travel offering minimal resistance. Driving the car is a nightmare, where I must augment my braking with the handbrake, which provides a dramatic difference, but no more than what you would expect for a handbrake.

I assumed the master cylinder was faulty and exchanged it at PartSource. I bench bled the new master cylinder and reinstalled. I bled the entire brake system with new fluid. The pedal became exceptionally hard, but as soon as the engine was started, I found the same soft pedal as before. I checked all the connections, found no leaks and could see no loss in fluid at the reservoir. I asked some advice, including the staff at PartSource and thought it could be a bad batch of master cylinders, so I returned/refunded the one I had.

I went to my crashed DB2 parts car and pulled the master cylinder off. It worked fine when it drove, so I hoped it would still be okay. I installed by the same process as above, and found the same soft pedal after starting the engine. I then thought it could be something to do with the ABS system.

I (carefully) drove the car to the nearest Honda dealership and asked for the ABS system to be flushed and tested. They called me back reporting the ABS system flushed and tested out okay, but that the brake pedal was soft, most likely due to air in the system. I explained I was having difficulty with it for some time and was not able firm up the pedal; I asked them to bleed the system. The dealership bled the brakes with Honda DOT3 fluid and called back reporting no change to the pedal response. They claimed the master cylinder was faulty and wanted to change it. I explained that the current master cylinder was the third installed, etc., etc. but they insisted that a *Honda* master cylinder, at $350 plus install, would do the trick. Desperate, I initially agreed, but fortunately, a non-ABS master was delivered so they had to reinstall the original, saying there would be a delay until the correct part arrived. I cancelled the job and took the car back.

After a lot of consideration, I ordered a brand new, genuine Honda master cylinder from a dealership in the US for $220ish delivered and installed it myself with the assistance of an experienced Integra enthusiast, only to be back with the same problem.

I began to suspect the solenoids in the modulator were failing, despite the results from the Honda dealership's tests. I removed and replaced the entire ABS's mechanical system as a whole from the DB2 and installed into the DA9 - that is, the modulator, pump, accumulator, etc., without opening either system (took a long, long time). I bled the entire system again, to get the same soft brake pedal.

I examined the calipers closely and thought there was too much play with the guide pins. When the brake was depressed, the caliper was not moving with linear motion, but rather a slightly curved motion. My girlfriend's DB1 needed front calipers, so we agreed to use these calipers to see how they worked on her car. Once installed and bled, her brakes work fine. I installed the second, new (remanufactured) calipers on my DA9, bled, soft pedal. As a note, the rear calipers appear to be functioning normally and the handbrake is tight and responsive.

I then suspected my stainless steel brake lines. I removed them from my DA9 and put them on my girlfriends DB1. Once bled, her brakes work great. I bought new stainless lines, installed, bled, soft pedal.

I removed the master cylinder and inspected everything closely. I found two extra gaskets between the master cylinder and booster, two were old and swelled up, stuffed right into the booster and the one closest to the master cylinder was new and firm, staying on the master cylinder's rod. I pulled the two old ones out, cleaned everything as best as I could and examined the booster for mechanical problems. I compared the booster with another I had handy and found no dissimilarities. I reinstalled everything, bled the entire brake system and got the same soft pedal after starting the engine. I checked the vacuum hoses and check-valve, everything was operating normally.

It's been two years.

Seriously What the hell?

Scooooter7

In my best Jaws impersonation...Da Da Da Da Da Da Da DAAAA

WOW, wish I could help but I have no idea. To me it sounds like a vacuum leak somewhere. Maybe try a good known vacuum line to your MC and see if that helps.

Hopefully someone will chime in that might have had this happen to them and be able to help you.

stocker2shocker91

i see you have changed the master cylinder but what about the brake booster itself? have u looked into that? seems to me this is the only thing you have not tested or replaced. i would see about putting a vaccuum gauge on the hose connecting to the brake booster draw a vaccuum and see if it holds. It could be failiing internally

I know somtimes in my civic if i have the a/c on and alot of load on the alternator to where the engine has a real low idle my pedal will become more soft due to less vaccuum from the motor

if it was something with the abs like faulty solenoids it should put the abs light on

hbcrazy88

i agree, it sounds like vacuum leak fo sho, only reason is you have a good pedal without the booster and engine on...... whenever you turn your car off after having the spungy pedal does it become stiff immediately or do you have to pump the pedal?

dta03cl

vacuum leak for sure. booster bad will give a hard pedal.
check the large line going from the booster to the intake.

OttawaGSR

I've posted this in a few forums looking for answers and realised I should provide additional information:

As I mentioned before, when the brake was depressed with the engine is off, the pedal was exceptionally firm right at the top of it's travel. Once the engine was started (giving vacuum to the booster), the pedal sank 4/5 of the way down, with the remaining fifth of travel providing minimal braking force (aggressive downshifting provides more decelleration).

Now, when I disconnected and plugged the vacuum tube from the intake manifold and drove the car (now with no booster effect) the braking pedal was firm, but brake force still proportional to the pedal location when the booster was hooked up. In other words, unless I depressed the unboosted brake with everything my two legs can provide to get that pedal at least 4/5 of the way down, there was zero brake response.

When I removeed the master cylinder and examine the the pin that protrudes from the booster, its movement was consistent with the pedal, with maybe a millimeter of play. The boosters I have on hand have similar play. The plunger on the master cylinder was also solid, and when I put the two back together, the brake pedal offered about a millimeter or two before becoming solid.

I believe the booster is not at fault because of all this. If the booster had failed, I would hear a vacuum leak, or be experiencing no change in pedal height after starting the engine, or something along the lines of an equally firm brake pedal regardless of the engine being on or off.

Since the brake response is dependant strictly on how far the brake pedal is depressed, I believe the problem is somewhere after the booster - after the master cylinder, even.

I am curious to know what would happen to brake response if the ABS system was not charging itself. If the original ABS modulator had failed then I swapped in a good ABS system but missed a connection, the ABS pump may not be charging the system. How can I tell? If the system is working properly, then it would be charged and the pump would not run.

Furthermore; Honda has a computerized tool that induces ABS operation when they are testing and bleeding the ABS system. How can I induce modulator activity without this tool?

To answer the question as to why I haven't just changed the booster: I have two spare boosters, one from a non-ABS DA9 (wrong booster - too small) and one from the DB2 parts car. Unfortunately, the DB2 was hit on the front driver's side and pushed the strut tower infront of the booster, making its removal less than gentle. In trying to get it out, I severely damaged it. The two and four studs for the master cylinder and firewall resemble modern art more than an engineered auto part. In my efforts to find a new/remanufactured booster I've found it to be a hard to find and very expensive part, especially when I really feel it is not causing the problem.

At this point I have the following options on the table:

1. Take it back to Honda and have the replacement ABS system flushed and tested.
2. Attempt to induce the ABS pump to run on my own (erp... this scares me a little)
3. Replace the booster with a new/remanufactured product (if I can find one - checking auto wrecker next week)
4. Convert to non-ABS (I would like to avoid this as it's a daily driver, not a track car - see below)

Does anybody have other suggestions? Does anybody have advice on what I've listed above?

Thank-you to mirrorimg on clubintegra.com for your suggestion. I would have suspected my bleeding as an issue, if it wasn't for Honda having the same results. As for deleting the ABS altogether, I would prefer to avoid this since it's a daily driver. The ABS in the G2 may not be the greatest, but the ABS in my current DD DB2 has realized a slippery road before I had on numerous occasions.

OttawaGSR

I fixed it. Two years, it took!

cdscivic from G2IC was right on the money with the adjustment of the booster's pushrod. I had already figured it out by the time I read his post.

A few days after my last post, I picked up a booster from a local wrecker for $75. I had changed every other physical component between my foot and the wheel, save for the booster, so I justified it as peace of mind - just so I could say I did it.

While the original booster ended up not being faulty, I never would have figured it out had I not changed it. This is how it all went:

Reading the instructions in the Acura manual along with other sources, I saw how there was a lot of difficulty adjusting the pushrod clearances once the booster was installed. I thought to save myself some time by holding the two boosters side by side and making the replacement's pushrod the same length as that of the original. They were way off, but I figured it was just the wrecker messing with the adjustment to ease removal from the donor vehicle.

I adjusted the replacement part to match the original and installed it into the car. After bleeding the brakes, the pedal was still soft. I did expect it, but was still a little depressed. Talking with friends about how it went, they asked if I followed the instructions exactly. I said I had, except where I adjusted the pushrod *outside* of the vehicle rather than after it was bolted to the firewall. I was encouraged to do it exactly as per the instructions.

So under the foot-well I crawled, only to discover it was, in fact, very much out of adjustment. And everything came together.

The pedal had to be lowered more than 2/3's of the way down before the booster's pushrod would even contact the master cylinder's. After bench bleeding a master cylinder in a vice, I typically install the unit to the booster and run the lines back into the reservoir and "firewall-bench bleed" it again. I do this just in case air works into where the lines connect during the time between unplugging the hoses and attaching the hardlines. Because of the space, I never worked out the last bit of air. Without the extra push from the booster, my foot was not able to compress the air which is why I experienced a firm pedal with the engine off. Once running, the booster would assist and compress the air that was trapped in the system.

This also made bleeding a longer process, which was something I noticed before but dismissed.

Now my brakes are unbelieveably firm - so firm, I have to loosen them a little because they drag after they warm up!

I can't believe that after all this pain and heartache, it was just a tiny adjustment. I feel a little silly, but hopefully some of you out there will benefit from my story and save yourselves two years of agony!

hatmanafro

Hahah. I got halfway down and i was about to. Coment and suggest adjusting the pedal. Haha. Too late now. Glad you got it fixed!

djkobe

glad you got it fixed man, im going to have to try this because my non abs system is also very sloppy.

Jimmy

iTrader: (5)

Sweet man, I'm glad you got it fixed.. Thanks for actually posting an update in the thread.. I wish everyone would do this.

hatmanafro

+1. lol^