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Discussion Starter #1
Hi Everyone,

I have a 1997 Corolla, which is still going very strong. I had it in for a front brake job about 3 months ago because one caliper was seizing and locking up the brakes. So, I had one caliper replaced, new rotors, pads, etc.

{I should mention that this is a mechanic that I have largely trusted for several years now.}

The brakes have been great until last Thursday I started smelling that burning pad smell and a light sense of them starting to lock up again. I brought it back to the shop hoping for warranty coverage and I was informed:

- the lines are shot
- the proportioning valve is shot
- the master cylinder is shot
- none of this is covered under the warranty for your last repair

The reason everything is supposedly shot is that they told me some sort of foreign petroleum based substance got into the brake system and it has been deteriorating anything rubber inside the system, including parts on the master cylinder, proportioning valve, etc

I had just paid around $400 back three months ago when I had the other work done. If I have them do this work, it's another $800, which I simply can't afford right now. I have done brake work plenty of times, so I decided I would try and tackle this myself. I have a secondary vehicle, so if the Yota has to be down for a week or whatever as I slowly make it through this process, I will be fine.

I started scouring the web for how to replace proportioning valve for this car and I am finding nothing. I am also searching for the part on all auto parts websites, ebay, etc and I am not finding it for this car.

The only thing I found is several mechanics (even on Toyota Nation) say that they have never seen a bad proportioning valve even when they have removed the nastiest brake fluid. And again, I am find nothing about my model or year car in parts or in repair info.

Does my car not use this part? If it does, does it seem possible that petroleum whatnot got into my system? I said to the mechanic, the only person other than me who has worked on it is you. And I have never put anything but DOT 3 fluid into my master cylinder. He said it could have been in there six years or longer if it was a small amount and just started damaging things, which is why they didn't see it or wouldn't have seen it before.

I just want to know what I really need to replace. I had them flush the fluid just so I could get the car home and it actually drove and braked perfectly fine all the way home. Which in a way I found ever more irritating.

Sorry for the book, folks. Any help would be appreciated.

Thanks!
 

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Don't go back there. Check to make sure your calipers are able to slide on their guide pins. I would suspect this before I'd think it was a piston sticking in the caliper. Then maybe go and bleed it all out again, to be sure that it's OK.
 

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Couple of not so black&white, all-or-nothing items:

- The proportioning valve never goes bad. Not in the 30-years I've had Toyotas have I seen one that's failed, not from wear-and-tear or any kind of contamination.

- The amount of petroleum solvents needed to destroy seals of entire brake-system is huge. You'd need to flush your entire brake-system with pure acetone and use it for a week before you'll damage the seals.

Most likely the initial lock-up issue is either a guide-pin seizing up due to drying-out grease or less likely a piston sticking in the caliper. Test the front calipers:

1. remove caliper, use C-clamp to squeeze in piston about 1/8". Should go in without too much effort, especially the new one that was replaced.

2. inspect the guide-pins & their rubber boots. Grab the pin with pliers and see if you can move it in & out. Inspect the boot for rips. You can get replacement pin bushings & seals pretty easy to repair. Also only use high-temp silicone-grease to lube the pins.

Most likely it's the caliper that wasn't replaced that just needs to have the pins lubed. And perhaps also have the boots/seals replaced. That shop isn't exactly shady, as in they don't do what they promised. But it seems they use the shotgun approach with replacing way more parts than necessary as an alternative to troubleshooting and finding the specific problem part. Saves time, makes them more money.
 

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But it seems they use the shotgun approach with replacing way more parts than necessary as an alternative to troubleshooting and finding the specific problem part. Saves time, makes them more money.
Too bad they're not the ones who eat it when the car comes down off of the lift, and the problem is still there...
 

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I thought I had a bad proportioning valve once.

Yep, I was wrong. Its proabably the ONLY part on a car that never does go bad.

Change all your rubber hoses. They swell shut. I'm not sure if its something in new formulations of brake fluid, or poor compounding in the brake hoses. (If you are using the valvoline product I think this fluid is a cause)

Of course make sure your sliders are all free. If the hoses are the problem you wont be able to push the pistons back in, but they will move when you open the bleeder.

-SP
 

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If you are using the valvoline product I think this fluid is a cause
I switched from OEM Toyota fluid to Valvoline DOT 3-4 fluid last year. No ill effects thus far. I also switched the Outback from Subaru OEM fluid to the same Valvoline fluid.

What makes you think it's a cause of swelling? It seems to get great reviews as far as I can tell.
 

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Discussion Starter #8
Love all the feedback so far. Thanks guys.

Anyone else with tips or comments - I welcome them. As someone said in another thread, you don't want to guess when it comes to brakes, so the more assurance and tips I get, the better.

It's nice to know what you suspected is probably correct.
 

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Discussion Starter #9
In regards to replacing brake lines or hoses as someone mentioned above. I assume you are referring to just the rubber hoses on the front brakes and not the metal lines running to the rear?

If so, how tough is it to replace these? I imagine replace and bleed, but are they tough to access and affix on their route from master cylinder to caliper?

Thanks again.
 

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Yes, just the short rubber sections at the ends of the hard-lines to the calipers. Very easy to replace once you've got the calipers off, about 2-3 minutes each. You can test how fluid flows by opening the bleeder 1-2 turns and having an assistant step on the pedal. Should squirt-out easily with pedal going to floor.

Although I have seen a lot of clogged bleeders as well. Caused by not having a rubber-cap on them. The dirt and water that collects in the opening causes a rust/mud compound that's very hard.
 

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Realize you MAY be replacing the hard line too if you are in a rust belt area. Often the fastener wont come loose from the tube and you just break the end off.

Bleeders- Its a rare occasion when I cant clean out the holes in the bleeder with a couple of small drill bits. Your biggest enemy is it rusting to the caliper and it breaks off instead of unscrewing. Use some never seize and it will never break off again.

-SP
 

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Discussion Starter #12 (Edited)
This could have been a different thread, but since I started this thread and it is all related to the responses I received from you fine folk, I figured I might as well continue here.

I decided just to replace the front rubber brake hoses and the master cylinder. I estimated that if everything went smoothly (ie - no rusty bolts) I could get all of this done in two hours. I was absolutely correct -- if there had been no rusty bolts, two hours would have done nicely, but alas -- not the case. I am three hours in, halfway through the first break line and I got one of the two fittings off of the master cylinder.

ONE THE LEFT BRAKE HOSE -- using a 10mm open ended wrench and then later the 10mm flare wrench I saw recommended in a Youtube video, I could not get the connector between steel line and hose off. Finally, in a true hack method, I used an adjustable pliar and got that broke free. The connection to the caliper was smooth as silk and took about five whole seconds to get out. The biggest problem is the mounting braket mid-line. If I try to loosen this ridiculously stubborn bolt (with wrench, pliers, socket) the entire bracket is so weak that it just bends. I finally sawed the line out of there, but I am stuck with the mounting for the old hose along with the big stubborn bolt still in. I cannot get this.

Any ideas? Or is there some acceptable method of just getting rid of that and tie-strapping the line in some other fashion. I can just see burning another whole day on this mount and still not having that bolt free.

Thanks.
 

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I you referring to where the hose is held to the strut? There is a flat clip that holds the hose in place. You pull it out with pliers. There's no bolt to loosen.
 

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Discussion Starter #14
I wish I had a picture to post.

So, the brake hose connects (at the top of its journey) to the steel line that runs to the master cylinder, that requires a 10mm nut to be loosened and also a clip to be slid out to release the hose that is being replaced.

Then you follow the hose down to the part I am talking about, which connects to the strut as you indicated. The new hose comes with a metal loop (for lack of a better word) already attached to it. The new hose sits in a slot in this mount bracket (that attaches to the strut) and the hole on its loop lines up with a hole on the bracket which has a big bolt through it. If that bolt doesn't need to come out, I am not sure what it would even be there for. And if there is a clip to slide out that releases all of this, I would feel really dumb as I never saw it in the entire three hours I stared angrily at this area looking for a way to beat it.

Let me know if you know something I don't regarding this connection. Again, this is the middle connection where the new hose mounts to a bracket on the strut simply as support, this is not one of the two connections for fluid to travel to or from.

Thanks.
 
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