Soft pedal issue...Master Cylinder or Calipers?

[The Chazz]

Hey whats up?

I have a "soft pedal" issue with my brakes on my 2G, meaning under initial application, the pedal goes to the floorboard, but with a few "pumps", I regain pressure.

In anyone's experience, would these indicate more of a Master Cylinder issue, or the actual brake calipers?

Thanks!

[D Walker]

Sounds like air in the lines or a bad M/C. Lately it seems like we are seeing more and more M/C issues, especially as the weather changes.

[Paul]

Probably neither.

Did you check your FSM?

When did you bleed them last? Cold weather seems to exacerbate having any air or water in the brake lines.

Paul

[ErikW]

hi guys. It's been a while.
I also vote that contaminated fluid is your problem. It is almost impossible to get all the water, air and other debris completely out the first time. Then later is becomes more noticable. It's a cheaper and easier thing to try first.
I was just looking into flushing my brakes and i came upon a simple system that applies presure to the fill resivoir. A one man system. This sounds like a great investment. Winter should be a good time to do this. The climate is very dry.
That, in theroy, sounds to be the best way to bleed the system. And better for ABS systems. Plus, you will not risk over purging the master cylinder by using the typical petal push method.
Motive products created a home version of what mechanic shops use. But I wonder how this system keeps the fluid from over flowing the resivoir when attached. Could it be just the arch in the hose that is in place before the resivior controlling this?

http://store.motiveproducts.com/shared/StoreFront/default.asp?CS=motive&StoreType=BtoC&Count1=886852443&Count2=803992867

here's a good how to: http://www.top4runners.com/ja/brakeflush.html
cheers
ew

[JackM]

If a new master, bleeding, and new lines don't work it could be a damaged caliper. I was pulling the hair out of my head trying to figure out why my pedal is almost hitting the floor before the brakes do anything and found the passenger side front caliper was completely melted on my car.

I would do all that was mentioned above though but also be sure to take a very close look at the rear brake lines as the rear flex section is known to balloon up and break too.

Another thing to keep in mind is the brake system is a closed system. So if this suddenly happened something is wrong somewhere. You shouldn't have water or air in your lines unless something allowed it to get in there in the first place. Yes, many miles and a few years of use may do this, but not over night.

Jack

[The Chazz]

Typically a "soft" pedal is from air in the lines.

These have been properly blead with fresh fluid.

I surmise the Master Cylinder is the main culprit.

I will check the brake lines again, but I appreciate the ideas. This has allowed me to narrow it down to what I first thought.

Thanks .

[JSMCPN]

My 2G has always had a spongy pedal too, it's really annoying and has kept me away from road courses. If I pump the pedal once, it stiffens up and the brakes feel good for one use, then gets soft again.

So far I have inspected the lines, replaced the master cylinder and rear calipers (genuine Mitsu), still no improvement. It might be a bad front caliper - I know how to bleed brakes properly and I've flushed more than a large bottle of Valvoline synthetic through the system. I have wondered if the ABS unit might be the culprit. Unlikely, but my ABS has never worked so it's always made me suspicious. I don't get any ABS light ever, but for all I know it's burned out. I've already tried replacing the ABS ECU under the passenger floor panel, still nothing.

I'll be installing a Baer TrackClaw upgrade soon (which is nothing more than adapter brackets and Mustang Cobra/Vette C4 brakes!) - so I'll know then if my spongy brakes is because of a bad caliper or not. I hope it's just a caliper, I really don't want to replace or remove the ABS system :)

[thiazole]

My brake pedal has been spongy since the day I bought the car in 2003. It will brake fine the first time I push it, but the pedal goes down further than it should - if I pump it once, I get full pedal. I REALLY need to bleed my system one of these days.

[Paul]

My brake pedal has been spongy since the day I bought the car in 2003. It will brake fine the first time I push it, but the pedal goes down further than it should - if I pump it once, I get full pedal. I REALLY need to bleed my system one of these days.

No offense, but that mod list and you can't bleed the brakes?

I mentioned one time Jesse that you should bring it by and maybe we can figure it out.

Paul

[JSMCPN]

Paul, I'd be glad to pop over for a while. The car is on jackstands right now until the Baer brakes go on, which might fix the problem. Either way, you're just down the street from me!

[Paul]

Paul, I'd be glad to pop over for a while.


Those jack stands have wheels! Maybe better if I go there? I could probably do something next Sat late morning?

When do the new brakes come in?

Paul

[thiazole]

No offense, but that mod list and you can't bleed the brakes?


Paul

Yah, yah - the car stops fine, just has a spongy pedal. I actually didn't realize it was that unusual until another DSMer commented on how ****ty my brakes felt a few months ago.

[Paul]

Reminds me of the Sunbeam Tiger at SC. His brakes felt a little funny on his last lap.

Safety
Maintenance
Mods

Paul

[JSMCPN]

Those jack stands have wheels! Maybe better if I go there? I could probably do something next Sat late morning?

When do the new brakes come in?

Paul

I have the calipers installed, but still have to either make or order some custom brake lines, but I'll let you know when I'm ready!

[rx7ttlm]

when in doubt bleed and bleed again, also motul 600 works well...

[Paul]

also motul 600 works well...

A little (or a lot) expensive for a street car.

One thing I did learn that helped was not to wait until the brake pedal was all the way down to close the nipple and make sure the hose it tight on the nipple (said nipple twice in one sentence:) ).

Paul

[Overkill]

You also said "hose" & "tight"