Something Happened to the Brakes over the Winter

lr172 · 06:11 PM

I packed up the car ('88 3.2) for the last time in November. Got a nice day today and took it out to knock out the cobwebs. As I rolled down the driveway, I realized I have no brakes.

When I step on the pedal it goes straight to the floor without any resistance. After three pumps it is relatively firm, but not as firm as normal. The pedal travel also seems more than normal. However, it has been 4 months, so tough to judge. After pumping up, it will hold the pressure. However, if I wait 10 second and try again it goes all the way to the floor again. 2-3 pumps then somewhat firm (can stop the car, but not as strong as normal).

There are no signs of leaks on the floor or near the master cylinder. I haven't pulled any tires yet to look or bleed. I am guessing the M/C is the logical place to start if bleeding doesn't help.

Has anyone experienced a problem like this? Any ideas on where to start?

Thanks for any assistance you can provide.

Larry

uwanna · 03-23-2010, 01:41 PM

Sounds like a bad master cylinder. Had exactly the same problem after my SC sat for over a year. Checked everything, it was a pain in the butt to replace, but a new MC was the fix!

Targa Me · Targa Me's Garage

Before you bleed the brakes, does the m/c have fluid at the proper level?
Some m/c have a boost that uses vacuum to function, if that's the case with your's, a vacuum leak at the would cause the pedal to go all the way to the floor. And if the leak is bad enough, running the engine won't help.

lr172 · 03-23-2010, 02:00 PM

The fluid is fine (1/2 way between min & max). My car does have a power brake booster. Are you referring to the vacuum that drives this booster or vacuum that drives something in the M/C? I would expect my brakes to operate and be firm without the power booster working. Please elaborate. I believe the booster just adds leverage to the mechanical connection.

Larry

Green 912 · 03-23-2010, 02:13 PM

It is also a great place to hide leaking brake fluid. Are you loosing fluid?

Green 912 · 03-23-2010, 02:15 PM

It is also a great place to hide leaking brake fluid.

lr172 · 03-23-2010, 02:30 PM

No fluid loss that I can find. Without fluid leaving the system, I don't know how I could get enough air into the system to let the pedal go to the floor. It sure seems like a blown seal in the M/C.

Does anyone know where to find a rebuild kit? None offered by our sponsor. Or am I stuck buying a new or Reman?

Let me know if you think my thinking here is inconsistent with your experience.

Larry

lr172 · 03-24-2010, 06:06 AM

Does anyone have any alternate thoughts before I order a new M/C?

Thanks for the assistance so far.

Larry

Dixie · Dixie's Garage

Quote:

Does anyone have any alternate thoughts before I order a new M/C?

It may sound silly, but I'd remove the old one first. By removing it, you'll most likely confirm the problem is the master. But then again, you may find something else is the culprit.

calling911 · 03-24-2010, 07:42 AM

Here is what I believe happened:

Somehow.. not sure how.. your pads retracted.. something to do with the cold? Dunno.. when you have an old master cyl and you run the piston down the bore all the way there is usually old crud and rust in the bore.. when you do that you tear up the piston.. this is why you should really never run it all the way down on an old car... unless you want to risk rebuilding the master..

I really cant explain why your pistons retracted though.. the other possibility is you do have a leak.. but I seriously doubt it.. air would also cause the pedal to go to the floor..

Even when you bleed your brakes on an old car I only recommend going half way down the bore.. or about where your max brake pedal travel would be under hard braking..

Im sure many will disgree with me on this but I have toasted brake cyl's doing this.. so I know it can happen.

Steve@Rennsport · 03-24-2010, 08:14 AM

Larry,

JMHO, but it sounds like the MC is bad.

You didn't say how many miles are on your car or anything about how you've bled the brakes in the past and those are important pieces of information to help make an accurate diagnoses.

I would strongly recommend buying a pressure bleeder (like the Motive ones) to ensure that the new MC lives a long life,......

lr172 · 03-24-2010, 09:40 AM

Car has 125K on it and the booster and M/C appear to be stock. I purchased the car last summer. and the pads have a lot of life on them, so a brake job somewhere in the last few years. It has the blue fluid and I believe someone did a corner balance and several mods for handling, so likely done with care, but don't know.

I have not bled the brakes yet. The brakes have been excellent since buying the car and have had no reason to bleed them, as they were firm and performed as expected. I did bleed the clutch M/C, hence the middle level on the reservior.

Thanks for any insight you can provide.

Given that nothing changed but time since November, when they worked great, I don't see how it could be anything but a blown M/C seal or a leak, which I cannot find evidence of.

Does the fact that they pump up to 50% firmness each time also point to the M/C? That was my thinking.

Thanks,

Larry

Steve@Rennsport · 03-24-2010, 09:53 AM

Quote:

Originally Posted by lr172

Does the fact that they pump up to 50% firmness each time also point to the M/C? That was my thinking.

Yessir, thats one of the major symptoms. The MC is "shuttling"; fluid is passing around the seal that separates the front and rear chambers.

calling911 · 03-24-2010, 10:28 AM

Quote:

Originally Posted by lr172

Car has 125K on it and the booster and M/C appear to be stock. I purchased the car last summer. and the pads have a lot of life on them, so a brake job somewhere in the last few years. It has the blue fluid and I believe someone did a corner balance and several mods for handling, so likely done with care, but don't know.

I have not bled the brakes yet. The brakes have been excellent since buying the car and have had no reason to bleed them, as they were firm and performed as expected. I did bleed the clutch M/C, hence the middle level on the reservior.

Thanks for any insight you can provide.

Given that nothing changed but time since November, when they worked great, I don't see how it could be anything but a blown M/C seal or a leak, which I cannot find evidence of.

Does the fact that they pump up to 50% firmness each time also point to the M/C? That was my thinking.

Thanks,

Larry

I wouldnt hesitate to buy a new one at this point.

lr172 · 03-24-2010, 11:03 AM

Thanks for the advise guys. Much appreciated. I'll order a new one and get to work on it. Does anyone know where to find rebuild kits? also, any special tricks I need to be aware of or just a simple bench bleed and then bleed each of the calipars to clear the air introduced by the process? I'll look into a pressure bleeder as I don't have one.

Larry

chgoburbs · 03-25-2010, 03:25 PM

Hi Larry, Where in the Chicagoland are you located? Let me know if you want to borrow my Bentley manual!
.
Scott

gregwils · gregwils's Garage

I replaced my M/C last winter. It is a pretty straight forward job. Once you peel back the carpet, be sure to take a few photos of how everything is hooked up since you need to remove a few things to access the M/C.

My two tips/reminders. 1 - Do NOT over-torque the M/C to the vacuum booster. The torque value is relatively low, but I don't recall the exact value. Over torquing can toast the vacuum boost. The whole project is spelled out in Wayne's 101 book. 2 - Bleed order far to close - RR, LR, RF, LF

Since you are new to the car, I would replace the flexible brake lines at the calipers unless you specifically know they are new. I think you can buy all four for about $50. You will have greater peace of mind knowing all the rubber is new and it's very little additional work - use flare wrenches.