Intermitant Spongy Pedal

MrDobin · #1 (**permalink**) 04-16-09, 01:25 AM

I recently bought an 85' Seville, gorgeous car. In great condition however lately noticed after the cold left that the brakes were still doing their off and on spongy deal. I know that if the pedal floors and the park brake isn't catching at all its a need for caliper rebuild but its not consistent. The park brake has worked and though I have not used it lately to remember I know it did work recently enough. With the the brakes are generally fine and I have no spongy BS for the most part. When the pedal does completely go down its all the way but with the normal resistance. My educated guess would be that there is for sure some air in the damn lines and I need to bleed them. No there is no line leaks either I checked. Ranger or Carnut fill me in on if I am right or in the realm of being correct. I am hopeful its just a need to bleed. I could do the rebuild myself with some major stubborn effort but rather not if able to avoid. All help is hugely appreciated, you guys have been awesome with aid in the past. Thanks.

Krashed989 · #2 (**permalink**) 04-16-09, 05:50 AM

It could be the master cylinder. A lot of times they get corroded in there in the spots less traveled by the piston. Then when you bleed the brakes after doing a brake job, it scrapes the rubber seal on the piston. This lets fluid go around the seal rather than pushing it into the lines. The intermittent part about it could be from temperatures (slightly thicker fluid when colder) or whatever mud may be in the bottom of the master cylinder.

**Ranger** · #3 (**permalink**) 04-16-09, 10:42 AM

I assume you are talking about the regular brakes and not the parking brake. If the pedal goes to the floor and there is no external leak, then Krashed is right on. You need a new master cylinder.

MrDobin · #4 (**permalink**) 04-16-09, 12:13 PM

Yea I had the concern. Ill look through the cylinder. didn't think it was too likely since its been apart of the park brake too. It looks like the rear pistons are seized and now the pedal is fine. I think it was temperature of the fluid since here in minnesota it was go from 20 below to 30 for a bit. How time consuming do you guys think it will be to disassemble the rear brakes and do whatever to the pistons. And is there a way to easily fix them or will I need to replace parts etc?. Thanks

MrDobin · #5 (**permalink**) 04-16-09, 08:18 PM

Ok new update. I may be wrong.... good chance. But there is a wire feeding off the brake switch. Not sure if thats the right name. But it feeds into the car then meets a juncture to which a wire that comes from it leads to nothing. The guy I bought the car off said this wire came loose when he took out a radio deck, this also is what made the brake warning light come on. Is there any chance this wire is interfering with the component thats apart of the brake lines?. Its the only wire going into the brake system under the hood and the fact that this all happen with the brake light when he took out the deck. Yet there is zero lighting issues or problems else where.... I don't know. maybe I am just hoping its not needing brake jobs. Thanks for any help again here.

**Ranger** · #6 (**permalink**) 04-16-09, 09:19 PM

Your pedal going to the floor is not an electrical problem.

So the guy rips a wire loose pulling a radio and never bothers to find out what is was from of put it back where it belongs?

MrDobin · #7 (**permalink**) 04-16-09, 09:53 PM

Ha. Ya it seems that way. I'm not advanced enough with electrical to see on the charts where this lone line goes. Hard to tell since it looks almost user added from before.
Any ideas on if its still the cylinder if the back brakes are locked?. Did the park brake test and put the car in drive holding the pedal. Does nothing. This still the cylinder or the pistons?. Pedal has zero issues anymore. Its just those rear and park brake bits being troublesome

**Ranger** · #8 (**permalink**) 04-16-09, 11:26 PM

I'm getting more and more confused. What exactly is the problem.

MrDobin · #9 (**permalink**) 04-16-09, 11:40 PM

Yea. I apologize. My typing doesn't keep up with my thoughts at all. Oh well.

Issue as things stand now.
Rear breaks are non existent, including when I tried the "test" in which i started the car pressed both the park and regular brakes and let the regular break ease off. The park break there fore is not functioning either. Front breaks are totally fine though. I found another forum post mentioning such issue and he said it ended up needing a rebuild of the pistons etc because APPARENTLY, its a known issue with these cars since the park break is not used too often and causes the rear to seize??. So my question at this time is does it sound based on the symptoms that I do need to rebuild the rear brakes or still a cylinder issue?. Found no leaks or issue with the lines. Hugely sorry for the confusion, I babble. Thanks for the help as always.

Krashed989 · #10 (**permalink**) 04-16-09, 11:45 PM

Me too.... I can't imagine how both rear calipers would seize at the same time. I think your parking brake cable is sticking for that to happen. reach up under the car and tug on it to see if you can get it to release.

On a side note, seized calipers should never be overhauled: only replaced. Calipers seize because of corrosion and from whatever gunk may be in them. If you simply overhaul them, chances are that the bore is going to be too big for the new piston. Then the piston will eventually go crooked and seize again.

Edit: Wait, the rear brakes are locked up (always fully engaged)? Or are the rear brakes just not engaging at all?

MrDobin · #11 (**permalink**) 04-16-09, 11:49 PM

Yea. The cable could be. Its baffling. I am memorizing the damn car almost down to wiring and more and more the thought "i hate you park brake this is your fault i swear" hits my mind. Ill take a look.

As for the calipers and piston I already found a supplier for replacing if I need to. Not worried there but rather not used my weekend to do that.

carnut · #12 (**permalink**) 04-18-09, 04:22 PM

If the car creeps with the park brake depressed, you need to replace both rear calipers to correct siezed adjuster screws within them. Once replaced and properly bleed, then adjust the park brake cables to just where the levers on the calipers just start to move away from the cast-in rest on the caliper.

carnut · #13 (**permalink**) 04-18-09, 05:03 PM

If you've read my other posts, you know the importance of using the park brake EVERY TIME you park. That rotates the adjusters, keeping them free and the pads adjusted correctly to the rotors. Once the new calipers are on, you can, with your hand, push up on the park brake lever to confirm the pads grip the rotor before you reattach the park brake cables back up. Yes, you can have a faulty master cyl. but all the calipers must work before going any further with parts. If you have a problem retracting pistons and replacing the calipers send me a PM.

MrDobin · #14 (**permalink**) 04-18-09, 08:01 PM

OK.

So an update. I checked the lines again etc to see about faulty lines or leaks and nothing. To make sure.

The rear brakes in fact work. Normal ones that is. I feel like a complete DS for spazzing and not properly making sure the rear were in fact not functioning. HOWEVER, the park brake is still not functioning. I can feel the lines move when I reach under and then engage the pedal. It appears to contract the springs in back on the calipers as well. Is there something in the sequence that would cause the park brake to not operate like this?.
My biggest apologies to all who were assisting. Though there is still half the issue here it is my stupid spaz attack that made me not check properly that the rear brakes were in fact failing.

Any insight to the faulty park brake lines is appreciated. Thanks guys.

carnut · #15 (**permalink**) 04-18-09, 08:31 PM

If this car creeps ahead at all with your foot on just the parking brake pedal then the rear brakes are, in fact, NOT working fully. The park brake cable is adjusted just like any drum brake car. Thread the nut on the cable adjuster till the caliper levers just start to move away from rest on the calipers. When everything is working, the park brake should go down half way and the car will squat in the rear and sit at idle in gear and not creep. This car does not have a parking brake as such. The caliper pistons are mechanically forced out thru the cables to grip the rotor.