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Unread 12-19-2010, 09:24 PM   #1
mntbikr18
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Default Spongy brakes

I think I need a brake bleed but just wanted to confirm before I got it.

My brakes recently became intermittently spongy. Some of the time (maybe 60 percent) they work normal. The rest of the time they take further into the peddle stroke to engage, occasionally going very close to what I think is the bottom. They never don't work but it has me concerned.

The only thing that has changed recently was I put in shorter rear springs and have wheelers offroad SS lines (front and back). I doubt but perhaps they are now too long and are affecting it? The pads and rotors are all relatively new.

Any input appreciated.

Thanks

Last edited by mntbikr18; 12-19-2010 at 09:27 PM.
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Unread 12-19-2010, 09:48 PM   #2
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Length of the "lengthened" lines is irrelevant compared to the overall length of the existing system. Definitely try a good bleed, make sure you follow the procedure in the service manual regarding having the engine running so the ABS pump cycles.
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Unread 12-19-2010, 09:56 PM   #3
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I don't plan on doing it but I'll point out the ABS thing to the shop.

Its something I should probably learn how to do one of these days buts its below freezing now so this time isn't it
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Unread 12-24-2010, 07:22 AM   #4
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So the shop said it felt like it was the master cylinder that was going bad.

From what I can tell this doesn't happen all that often and shouldn't happen with 95k. Has anyone had experience with this?

I assume the car is unsafe to drive if it is in fact this? Is there anyway to tell if this is in fact the problem?

Looks like its going to be a stupidly expensive fix.

Last edited by mntbikr18; 12-24-2010 at 07:42 AM.
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Unread 12-24-2010, 10:09 AM   #5
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Try bleeding it first with the ignition on, so the electric pumps and solenoids help clear all fluid. Hopefully that solves the problem.

There has been a few reports of the master cylinder going bad, and they are very expensive to fix/replace. Good luck.

How often did you flush the brake system? Cold wet climates probably need it done more frequently, but I try to flush my brakes at least once every 2 years. Helps to keep them healthy.
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Unread 12-24-2010, 10:14 AM   #6
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I don't think I've had them flushed in the 2 years Ive had it but they would have been with the SS lines going on I think?

So bleed them and if it doesn't fix it its prob the master?
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Unread 12-24-2010, 10:19 AM   #7
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Is it hard to do? Can't get it into a shop in time for a trip and thinking I may try it myself.
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Unread 12-24-2010, 10:22 AM   #8
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To flush is not hard. See the maintenance write ups. I used a vacuum device to flush mine.
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Unread 12-24-2010, 01:11 PM   #9
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Well I flushed the brakes but can't tell if its all better or not. I think I lost my sense of what "normal" was.

How do I tell if I have a problem I need to worry about or whether it will be safe? The pedal doesn't feel all that spongy but its possible it still engages at different parts of the pedal stroke. I can also push the pedal all the way to the floor if I really try. I dont however remember if thats normal (not sure I ever tried before).

Thoughts?
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Unread 12-24-2010, 01:30 PM   #10
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Quote:
Originally Posted by mntbikr18 View Post
I think I need a brake bleed but just wanted to confirm before I got it.

My brakes recently became intermittently spongy. Some of the time (maybe 60 percent) they work normal. The rest of the time they take further into the peddle stroke to engage, occasionally going very close to what I think is the bottom. They never don't work but it has me concerned.

The only thing that has changed recently was I put in shorter rear springs and have wheelers offroad SS lines (front and back). I doubt but perhaps they are now too long and are affecting it? The pads and rotors are all relatively new.

Any input appreciated.

Thanks
This does not sound like a bleed issue - it sounds more like an intermittently failing master cylinder check valve.

If you had any air in the lines, the pedal would remain spongy all the time - and depending on the vehicle, your ABS / Brake light might activate from a line pressure issue. Some times the master cylinder check valve gets "sticky", and doesn't close all the way after pushing the pedal, allowing the pedal to sink. A quick pump of the pedal usually dislodges the valve, and the pedal temporarily returns to normal. Be careful, because this intermittent issue can become constant at any time, and then you'll have brake failure without warning.

I would suggest a fluid flush anyway, because contaminants might be the cause of a M/C check valve sticking. But, IMO, you might be due for a replacement master cylinder....
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Unread 12-28-2010, 08:22 PM   #11
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Anyone have a link to a writeup on MC replacement? I can't find anything for our generation. Or does anyone at least know how involved of a job it is?

How different would an earlier generation be if that's all I can find?

Looks like I can get the part from a used parts place for 150 or less. If its relatively simple I may attempt it myself. If not I may have an independent shop do it. It seems to be a dealer only new part but I can't think of any reason why a dealer would "need" to install it.

Any thoughts?
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Unread 01-03-2011, 08:25 PM   #12
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Bump

Still wondering how involved the master cylinder is to replace. Also any other diagnostics to be sure it IS the master.
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Unread 01-03-2011, 10:35 PM   #13
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Quote:
Originally Posted by mntbikr18 View Post
Anyone have a link to a writeup on MC replacement? I can't find anything for our generation. Or does anyone at least know how involved of a job it is?

How different would an earlier generation be if that's all I can find?

Looks like I can get the part from a used parts place for 150 or less. If its relatively simple I may attempt it myself. If not I may have an independent shop do it. It seems to be a dealer only new part but I can't think of any reason why a dealer would "need" to install it.

Any thoughts?
First suggestion - NEVER install used brake parts - you have no way to know if they are better than what you have, or what condition they are in.

Second suggestion - If you are not sure what to check, or how to check it, invest in a factory service manual (Assuming you are mechanically inclined, and have proper tools). It isn't cheap, but it is thorough, and it will show you the proper way to diagnose and repair your rig. Keep in mind many installations require specialized tools, and investing in them could be more expensive than actually getting it professionally repaired, if you're only going to do the job once.

Good Luck
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Unread 01-04-2011, 11:28 AM   #14
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There is an online copy of the service manual in the 4Runner section, or you can go tot Toyota's TIS site for $10 or so a day to get the manuals for your specific model.

Maybe worthwhile to look at the diagnostic and reapir sections to get a good feel of how involved things are.
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Unread 11-05-2012, 01:44 PM   #15
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BTW, if anyone is wondering about the price for a new master cylinder, it retails for about $2,300.00. Wow...that's crazy. the 4th gen master cylinder comes complete with the booster pump, so that's probably why it's so expensive.

Unfortunately, I might need to replace mine. I noticed that my booster pump is running a lot more than it used to. It comes on every single time I hit the brake pedal. I don't ever remember it doing that before, so I'm thinking that the system is losing pressure through a bad seal or something.
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Unread 11-06-2012, 08:44 PM   #16
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Just to update my last post, it turns out that it is entirely possible to purchase individual parts to "rebuild' the master cylinder and/or booster pump & solenoid assembly. Most of the parts are available individually if you want to rebuild it yourself, but if you want to buy an entire unit that's ready to bolt on, it will include everything (master cylinder, resevoir, booster pump, solenoids, etc.) and it will cost a pretty penny. My dealer quoted me $2300.00.
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Unread 11-06-2012, 10:28 PM   #17
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I'm sure you can get a more competitive price online than what the dealer quoted you. Was there perhaps labor involved in that number as well?
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Unread 11-06-2012, 10:43 PM   #18
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Quote:
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I'm sure you can get a more competitive price online than what the dealer quoted you. Was there perhaps labor involved in that number as well?
No, that was strictly the price for the part. Outrageous, huh?

And yes, I've already found online prices that are better than my local dealership's prices....but not a lot better.
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Unread 11-06-2012, 10:44 PM   #19
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BTW, if anyone is interested, I have a printout from the dealer that shows an exploded view of the master cylinder and related components, along with part numbers. I can scan it and post it if anyone wants to see it.
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Unread 11-24-2012, 11:02 PM   #20
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Quote:
Originally Posted by Snowman View Post
BTW, if anyone is interested, I have a printout from the dealer that shows an exploded view of the master cylinder and related components, along with part numbers. I can scan it and post it if anyone wants to see it.
I would very much like to see this and would appreciate it.
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