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Need ideas on odd braking behavior


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This is coming up on my '85 Brat:

 

If I had to guess, I'd say I've bled each corner and both bleeders on the master cylinder 20 times each, using various methods. The brakes still feel like they have air in them.

 

The weird thing is that when I use the hill holder, I can pump the brakes a couple times, and they become rock solid just like they should all the time. I'm not sure how the hill holder affects air in the system, but I'd like to hear some ideas on what's going on. Is air getting stuck in the check valve or something?

 

Thanks.

 

Jacob

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I've been through 3 master cylinders, including one I rebuilt myself (like that matters:)). I'm going to replace the soft lines at some point. The thing that confuses me right now is how the hill holder makes the brakes feel good. If air is stuck in there, how do I get it out? If it's a leak, why does the hill holder fix it? I need someone to think about this for me. Or a large internet community to brainstorm with me.

 

Thanks.

 

Jacob

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If it works with the hill holder, why not just leave it in?

 

It works with the hill holder activated. I've never even thought of removing it.

 

How about a shop putting a pressure type bleeder on it. I know that doesn't fit my idea of DYI either.

 

I actually borrowed one and did it that way as well.

 

I'm trying to find out what the hill holder has to do with the braking feel.

 

Jacob

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The Hill Holder acts as a Valve that Closes when the Clutch pedal is Pressed (To Retain Pressure sent to the Rear Wheels), so if it is Closed when your Brakes become "Rock Hard" that makes me believe that the Problem is Located on the Rear Wheels only.

So those might Need Bleeding at the Master Cylinder and also, the problem could be on the Rubber Lines... (on each rear wheel)

Kind Regards.

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The Hill Holder acts as a Valve that Closes when the Clutch pedal is Pressed (To Retain Pressure sent to the Rear Wheels), so if it is Closed when your Brakes become "Rock Hard" that makes me believe that the Problem is Located on the Rear Wheels only.

So those might Need Bleeding at the Master Cylinder and also, the problem could be on the Rubber Lines... (on each rear wheel)

Kind Regards.

 

I like your logic. However, on USDM Brats, the hill holder uses one front and one rear brake. If you think about the criss-cross setup, then you'll realize it can't lock up both rears without locking both fronts, and we all know that the hill holder only affects one of the two circuits.

 

You have me wondering, though, if maybe I should bleed with the car facing downhill. That way the little ball in the hill holder would be out of the way. Does that make sense, or is that backwards?

 

Jacob

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I'm not fully educated on the "hill holder" function, so my advice comes with the "grain of salt" disclaimer. I'm not saying hand pump bleeders don't work, but I personally have never had any luck with bleeders outside of this style:

 

http://www.harborfreight.com/brake-fluid-bleeder-92924.html

 

My method is to pop a hole in the foil cover of a bottle of brake fluid, stick it upside down (like a water cooler) in the reservoir, and bleed about 28oz of fluid out of the system (8oz through each rear, 6oz through each front). The pneumatic bleeder keeps a constant vacuum on the lines and almost prevents any back feed that can result in air in the lines.

 

I do a large number of motorcycle brake jobs this way (only guy in the area with his own pneumatic unit, so all my friends hit me up :rolleyes:) and I have yet to not be able to bleed a system out and get rock solid pressure.

 

EDIT: This is the one I own personally:

 

http://www.matcotools.com/catalog/product/BB70850K/BRAKE-BLEEDING-KIT/

 

but I don't see a lot of difference in it and the one that HF sells for 1/4 the price.

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I'm not fully educated on the "hill holder" function, so my advice comes with the "grain of salt" disclaimer. I'm not saying hand pump bleeders don't work, but I personally have never had any luck with bleeders outside of this style:

 

http://www.harborfreight.com/brake-fluid-bleeder-92924.html

 

My method is to pop a hole in the foil cover of a bottle of brake fluid, stick it upside down (like a water cooler) in the reservoir, and bleed about 28oz of fluid out of the system (8oz through each rear, 6oz through each front). The pneumatic bleeder keeps a constant vacuum on the lines and almost prevents any back feed that can result in air in the lines.

 

I do a large number of motorcycle brake jobs this way (only guy in the area with his own pneumatic unit, so all my friends hit me up :rolleyes:) and I have yet to not be able to bleed a system out and get rock solid pressure.

 

EDIT: This is the one I own personally:

 

http://www.matcotools.com/catalog/product/BB70850K/BRAKE-BLEEDING-KIT/

 

but I don't see a lot of difference in it and the one that HF sells for 1/4 the price.

 

Thanks, but I have used that style as well.

 

I'd like to reiterate that I'm not looking for a bunch of different bleeding methods. I want to know how the hill holder comes into play.

 

Jacob

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sorry this isn't hill holder related but is there any rust (non existent out there huh?)

 

friend of mine (you can find the thread probably) had a leak i couldn't track down. i finally just started driving the car and eventually a rear brake line leaked enough to loose fluid and drip down to where i could find it. it was rusted up above the rear cross member and i guess wasn't leaking enough to loose substantial fluid or drip down to where i could see it. i replaced the MC and bled multiple times without ever noticing fluid loss or leakage.

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You have me wondering, though, if maybe I should bleed with the car facing downhill. That way the little ball in the hill holder would be out of the way. Does that make sense, or is that backwards?

 

Jacob

 

The ball would be out of the way facing downward. Since it only works when the front of the car is at an upward angle

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sorry this isn't hill holder related but is there any rust (non existent out there huh?)

 

friend of mine (you can find the thread probably) had a leak i couldn't track down. i finally just started driving the car and eventually a rear brake line leaked enough to loose fluid and drip down to where i could find it. it was rusted up above the rear cross member and i guess wasn't leaking enough to loose substantial fluid or drip down to where i could see it. i replaced the MC and bled multiple times without ever noticing fluid loss or leakage.

 

What's this "rust" you speak of? :lol: I suppose it could be leaking out of the front right or left rear lines, and when I activate the hill holder, it blocks off those lines and makes the pedal feel good again. Am I thinking about it right?

 

The ball would be out of the way facing downward. Since it only works when the front of the car is at an upward angle

 

Right, so far I've been bleeding on level ground or with the front up. I wonder if air is getting stuck behind the ball that way. I'm not sure if that's possible or not.

 

Jacob

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...on USDM Brats, the hill holder uses one front and one rear brake. ...

 

You're Right Jacob... I Forgot it was a Brat and I Wrote thinking about the Loyale... Sorry.

Could I Ask if those Brats use a Pressure Regulator / Distribuitor, usually Shaped as a "Tee" on the Line that goes from the Front Wheel to the Rear Wheel?

If so, it Might be Clogged... Just an Idea.

Kind Regards.

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You're Right Jacob... I Forgot it was a Brat and I Wrote thinking about the Loyale... Sorry.

Could I Ask if those Brats use a Pressure Regulator / Distribuitor, usually Shaped as a "Tee" on the Line that goes from the Front Wheel to the Rear Wheel?

If so, it Might be Clogged... Just an Idea.

Kind Regards.

 

I believe they do, and I had not thought of that. Thanks for the idea.

 

Jacob

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  • 3 months later...
  • 2 weeks later...

can you verify that you are getting air in the system when you are bleeding the brakes?

 

ive heard of the hill holders leaking after a while and sometimes they wont leak if you have the lever in the right position.

 

but ive also seen a few times that soft lines can get soft after a while and they flex under brake pressure. i chased down the same issue on an old dodge 1 ton van trying to bleed and bleed and bleed every possible way but with no luck. replaced the 3 soft lines on it and it was gravy.

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I assume since this is three months old not that this has been resolved. So what was the culprit?

 

Nope, I just lived with it for a while. Now it's in a garage undergoing a 5-lug swap. It'll be interesting to see if it does the same thing with the new caliper setup I'm running.

 

have you adjusted the rear brakes? when adjusted rears will need very little fluid when out of adjustment you may need to pump twice to move parts ( shoes into drums)

 

I'm running rear discs, so there's no adjustment. Good idea, though.

 

can you verify that you are getting air in the system when you are bleeding the brakes?

 

ive heard of the hill holders leaking after a while and sometimes they wont leak if you have the lever in the right position.

 

but ive also seen a few times that soft lines can get soft after a while and they flex under brake pressure. i chased down the same issue on an old dodge 1 ton van trying to bleed and bleed and bleed every possible way but with no luck. replaced the 3 soft lines on it and it was gravy.

 

I didn't notice any air after the first few bleedings. I was thinking about the soft lines, but is that consistent with the rock-solid pedal feel I get with the hill-holder? Same question for the leaky hill-holder. Would that cause a bad pedal feel all of the time except when it's engaged?

 

Jacob

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have you adjusted the rear brakes? when adjusted rears will need very little fluid when out of adjustment you may need to pump twice to move parts ( shoes into drums)

 

+1

 

Stupid manual adjusting brakes.

 

Easy to upgrade to EA82 style w/ automatic adjusting.

 

 

 

*edit for not reading far enough before responding.

 

IDK, but I think you get solid feel from the hillholder because it is locking pressure in the ciruit, so you don't have to "build" it more by pumping.

 

At this point i'd say try a new Master. Upgrade to a Legacy one and you'll have a NICE stiff pedal, as the larger master pushes more fluid.

Edited by Gloyale
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+1

 

Stupid manual adjusting brakes.

 

Easy to upgrade to EA82 style w/ automatic adjusting.

 

 

 

*edit for not reading far enough before responding.

 

IDK, but I think you get solid feel from the hillholder because it is locking pressure in the ciruit, so you don't have to "build" it more by pumping.

 

At this point i'd say try a new Master. Upgrade to a Legacy one and you'll have a NICE stiff pedal, as the larger master pushes more fluid.

 

I actually did "upgrade" the master cylinder at one point, but NoahDL's advice found here: http://www.ultimatesubaru.org/forum/showpost.php?p=497927&postcount=6 proved true. The feel was good, but the performance was worse. I've since gone back to a remanned EA81 master. I'll consider going back to a Legacy one once I have the new calipers on.

 

That won't explain this odd behavior, though.

 

Jacob

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Did you install the EA82 proportioning valve?

 

No - he likes the rump roast end coming around when he leans on the brakes real hard. It's going to have to have aftermarket proportioning valves with the new brake setup though. 200SX rear discs are going to be much too strong if we don't limit the pressure.

 

GD

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