Dale1990

I am getting ready to drive this damn car off a cliff! The other brake thread has inspired me to try to try to fix this thing again.

I have been fighting a mushy brake pedal problem for a few months that started because of a panic stop. The problem is the pedal is very mushy. The car can stop and can even kick in the ABS at low speeds (<30mph). The brakes on this car were nice and firm once upon a time. They used to be like my Dad's 86 with J55s (installed b4 we got the car) - stop on a dime and give change. I have no quantitative data to back up the crappy performance - only the feel of the pedal. The pedal goes down really far to get any stopping action. It works - just not very confidently.

So far I have done the following:

Replaced M/C: Currently a rebuild from O'Reilly auto. I also had a new Delco and a rebuild from AutoZone. Bench bled a few times each. No change.

Bias Spring: I installed one at one point but it disappeared and probably was returned in a core. No change, anyway.

SS Braided Hoses: I was going to get OE but I got a good deal off the forum so I figured, what the heck. Bled all corners. No change.

Used ABS valve assy from a parted out 90-91 ZR1: Fixed a minor issue with poor fluid flow when bleeding. Pedal still mushy.

New pads all around: PFC Carbon Met. from AutoZone - crappy pads, only work when warm and suck when HOT or cold. I need a different brand. No change to pedal feel.

New (rebuilt) L+R Rear and right front calipers: I basically decided to start replacing things at this point, hoping for the best. Only have the front left OE at this time. No change.

I have run many gallons of fluid thru this thing with no change. I have used both the cheap-o wallyworld fluid (wet BP 284*F) and the Valvoline synthetic stuff with no change. I have pressure bled, vacuum bled, reverse bled, gravity bled, and also did the old-fashioned 2-man pedal bleed (yesterday, in fact) with no change.

WHAT AM I DOING WRONG! Please, any ideas would be nice.

Can these crappy pads make the pedal feel soft?

The rotors have not been replaced yet but they look OK - no rust, no vibration in the pedal to suggest warping, no abnormal noises.

Should I just toss another $80 down the drain and replace the final caliper?

Please help - I know this car has better brakes than this.

Thanks!

Dale

Tom Piper

http://www.phxsyss.com/proddetail.as...XPRO-205&from=

Tom Piper

Dale1990

I used the V12 from that outfit for most of the work - the RFI, vacuum and pressure bleeding. I would have a hard time dropping $300 for that tool. It does not seem to be much different than the V12 - just a more durable unit. If I am wrong. let me know.

Everybody else gets by with pedal bleeding or maybe the Mity-Vac (POS, imo). I have replaced many a brake part but never had this problem.

Dale

Tom Piper

I bought it new here (http://www.tooldiscounter.com/leftme...category=Brake) for just under $200. It does come with more accessories and is more durable and easier to use.

Since I will be using it on multiple cars, I think it is a good deal.

I don't like vacuum bleeding/flushing -- I prefer pedal flushing (or pressure flushing) and then RFI bleeding. Bleeding and flushing are not the same thing.

Tom Piper

Dale1990

I could try reverse bleeding again but it did not have any noticable change last time. I am also 900 miles from my V12 right now.

I suppose there could still be air in the system somewhere, but I cannot see how.

I am so confused

skateparkdave

You didn't mention if you had bled the MC itself. If not you need to do it everytime you put a new one on or have all the fluid out of one. Do it first then do all 4 corners. You just have someone mash the pump the pedal a couple of time and then mash it to the floor and hold it while you crack the lines at the MC one at a time and then close them tight before they release the pedal. Repeat as many times as it takes to get all the air out. Then do a 4 corner bleed one more time.

If you haven't done this try it. May be the solution.

Other than that have you replaced the booster? If not it may be worth checking in to.

Dale1990

Yup, I've done that a couple times for each M/C I put on. I also bench bled it before putting it on using those little plastic fittings and a bunch of hose. It seemed to get all the air out but there is really no way for me to tell.

The power booster is new. It was replaced a few months before this mess. Could a failing booster make a soft pedal? I thought they always failed with a hard pedal.

Thanks!

hogs29

Check the hard lines very closely. I had this same problem, and could not for the life of me figure out what it was. I had a somewhat soft pedal, I had bled the brakes 3 or 4 times, and I had already put on a new master cylinder and booster. Fluid wasn't going down, and while under the car doing an oil change, I noticed my right front hard brake line had a wet area on it in an area I normally wouldn't have noticed it. Turns out there was a very, very small pin-hole in the line up against the crossmember. This is an area that normally gathers engine crud and dirt/sand from driving, which was enough to hide it until I looked real close. Replaced the line, pedal is back.

BTW, I was losing fluid (obviously), but it was so minimal, I didn't notice it during the time I had this problem.

NJPetes89

My pedal goes down to far before the brakes react, while searching I found this. I am adjusting mine tomarrow.
http://forums.corvetteforum.com/show...m_id=48&arch=1

Dale1990

Had not thought about that. I'll put the car on the lift tomorrow and take a good look at the lines. I have had lines fail but usually it is a big leak. I'll give that a shot.

NJPetes89, I did that the last time I replaced the M/C and it did do something but the problem is still there. Maybe my brakes will be better than ever if I can get this problem licked.

Thanks!!

Tom Piper

Go to this site (http://www.phxsyss.com/manuals.htm) and download the manual and read it -- it is free.

This manual is a 40 some page PDF file and will take some time to download, but it is worth it to read it.


Tom Piper

Pete K

Carefully check the copper crush washers at the banjo fittings. They can leak slightly and let minimal fluid leak out. Drove me nut. I now use new ones every time they come apart. Something else to check with no coin spent.

Dale1990

I checked over every inch of line and scrutinized every splice, banjo fitting and bleeder and there is no evidence of even the smallest fluid leak.

I started the car and pumped the pedal as hard as I could about 60-70 times and checked again and found nothing. No fluid was lost from the M/C cups either.

To better describe the pedal feel I made sure to pay attention while the car was running this time. The pedal is very soft for about 2-3in of travel then gets hard about 3-4in from the floor. The pedal never makes it all the way to the floor and does not seem to sink when pushing hard. If I rapidly pump the pedal, it may get hard .5 in or so higher but not much more than that.

I am going to try lifting the nose end of the car up hoping to force any trapped bubbled in the M/C towards the lines while bleeding.

I am open to suggestions

Thanks!!!

aj1988

The suggestion of adjusting the rod in the booster is what finally worked for me. It has taken several times to get it adjusted correctly but definately worth the effort. The best way to do this is to just keep adjusting till the front wheels won't turn and then slowly back it off till they do turn freely.

Tom Piper

I think you said you replaced the ABS unit.

Some ABS units need a special tool (scan-tool) to open the valves on the ABS unit to allow it to be bled. If the ABS unit has air in it, when it runs its self-test (usually at about 4 mph), it will push the air out into the braking system.

I'm not sure how yours is, but on my '92, there is a "prime pipe" that runs from the master cylinder reservoir ( on the left side of the reservoir) back to the ABS/ASR unit. The ABS/ASR unit has a bleed valve in it too. I have to bleed the ABS/ASR unit first, and then the remaining brake system.

If you have a shop manual for your year car, it will tell you if you need a special tool (scan-tool) to open the valves when bleeding. It will also tell you if you need to open the bleed screw on the ABS unit to bleed it.

Tom Piper

joe3906

Maybe you might want to take it to a reputable brake shop and see what they find. Unless, your a die hard do it yourselfer, and are determined to fix the problem via your own swett, and hands. I respect that. Just a suggestion. LOL.

Joe B.

Dale1990

The 90 does not have a ABS bleeder and the book does not mention any special procedures for bleeding the ABS system - it just says to replace the valve assy and bleed as normal. The book is a little hazy on the brake section in general tho so it would not surprise me that a scan tool would be required.

I may have to take this thing somewhere but there are no shops near me that I have worked with enough to trust. I am getting close to the end of line for my abilities to solve this problem.

I am gonna try a few more tricks while bleeding and see where that takes me but I may be out of luck.

Thanks!!

Dale

Tom Piper

Be careful adjusting that rod; if the primary cup in the master cylinder is past the relief port you will have problems. And, those problems may not show up until you have put some miles on and the brake fluid heats up.
It is better to have that rod too short than too long.

Tom Piper

Dale1990

Update:

Aftet doing another round of bleeding with the nose up and tapping on the MC and lines etc. I finally threw in the towel and took it to the local dealer. They test drove it and basically told me I am worrying over nothing...the brakes are fine. They did run an ABS bleed with their magic scan tool just in case. They said no codes were present and everything appears normal. The pedal does feel more "consistant" now that the ABS is bled but I may be imagining things.

He mentioned to try playing with the adjustment rod if I want the pedal to engage higher but to be very careful for the same reasons Tom Piper mentioned above.

I guess the problem has been solved - the brakes work fine. They just don't feel as firm as I would like.

Thanks for all the help everybody!!

Dale

SupaVette

I've only read the 1st and last post, but i remember when you 1st posted about this. I had a similar thing with my brakes, it wasn't because of air etc, it was just that the push rod needed minor adjustment. It took me a couple of tries to get it the way i wanted it, but afterwards i was very happy with the result. You should give it a try, if it doesn't give the desired results, you can always put it back as it was. my .2c worth

I just read Tom's post on adjusting too far. Mine didn't need to go anywhere near as far as Tom is suggesting. It was just a half turn, then a few tweeks etc etc. It's amazing how much diffrence such a small turn does on that thing