wtdash Posted March 2, 2009 Share Posted March 2, 2009 (edited) '90 Legacy 160K - AT/AWD/NO ABS. When braking, sometimes I can push the pedal as hard as I can, and the car will slowly come to a stop; Other times, I can lock up the tires (non-abs). I can pump the brakes and it seems to help bring back full stopping power. Also, I swapped in '99 Forester front brakes - calipers and rotors- no difference, although the car seems to stop better when the brakes are working properly. Pads and rotors both good. I've bled the brakes twice in the last 3 months w/this procedure: - Remove most of the brake fluid from MC; fill w/new fluid. - Connect the 'one-man bleeder' kit's hose to the bleed valve w/collection bottle above bleed valve. - Open bleed valve. - Slowly push brake pedal to floor and release. - Check hose for bubbles. - Repeat until no bubbles. - On last brake pedal push, keep pedal depressed, and tighten bleed valve. In this order: right front>>left rear>>left front>>right rear . Also, I tested the MC by pushing the brake w/key off, and holding while starting the engine. The pedal moves very little (maybe a 1/8"-barely noticeable) after engine is running. What's it sound like? Thanks Edited March 7, 2009 by wtdash Link to comment Share on other sites More sharing options...
RallyKeith Posted March 2, 2009 Share Posted March 2, 2009 Does this have Drums or Discs in the Rear? Link to comment Share on other sites More sharing options...
wtdash Posted March 2, 2009 Author Share Posted March 2, 2009 Rear discs (drum parking brake). Link to comment Share on other sites More sharing options...
OB99W Posted March 2, 2009 Share Posted March 2, 2009 [...]What's it sound like? Sounds like it might be a problem related to the vacuum booster. What's the temperature on the days you've had the problem? Link to comment Share on other sites More sharing options...
wtdash Posted March 2, 2009 Author Share Posted March 2, 2009 Temps have been right around freezing. Link to comment Share on other sites More sharing options...
OB99W Posted March 2, 2009 Share Posted March 2, 2009 See this thread: http://www.ultimatesubaru.org/forum/showthread.php?t=93492 Link to comment Share on other sites More sharing options...
wtdash Posted March 2, 2009 Author Share Posted March 2, 2009 See this thread: http://www.ultimatesubaru.org/forum/showthread.php?t=93492 Hmm, that could be the issue as I recently installed a hood scoop for my turbo swap, which lets in air right where the vac line is. I'll give the WD40 trick a try until I can replace the hose/check valve. Thank- you Link to comment Share on other sites More sharing options...
abog Posted March 2, 2009 Share Posted March 2, 2009 +1 brake booster issue. With proper vacuum applied when holding the pedal and starting the engine, the pedal should fall more than an 1/8 of an inch. Verify that you have manifold vacuum at the booster. Check for any signs of leakage from the master cylinder. If all this is ok, you probably have an issue with the boosters vacuum diaphram. Link to comment Share on other sites More sharing options...
OB99W Posted March 2, 2009 Share Posted March 2, 2009 Hmm, that could be the issue as I recently installed a hood scoop for my turbo swap, which lets in air right where the vac line is. Certainly a possible cause/effect relationship on sufficiently cold days. Thank- you You're welcome, I hope that's it. Link to comment Share on other sites More sharing options...
SVX_commuter Posted March 2, 2009 Share Posted March 2, 2009 Cold days could be water in the brake lines. The flushing of the lines has to get all the water out. With the one man bleeder, how do you keep the air from going thru the threads of the bleeder screw when the brake peddle is released? Think about checking with another person for the I need a buddy to bleed method. Link to comment Share on other sites More sharing options...
OB99W Posted March 2, 2009 Share Posted March 2, 2009 Cold days could be water in the brake lines. The flushing of the lines has to get all the water out. Moisture in brake lines isn't good. However, even without the bleeding/flushing procedure that wtdash used, it's very unlikely that there could be enough water in the brake hydraulic lines to freeze, at least under normal circumstances with systems running glycol-based fluid. Those fluids are hygroscopic, and moisture will disperse throughout the fluid, rather than form pockets that could solidify. The chances are much greater that moisture-contaminated fluid would boil under hard usage (and/or cause brake system corrosion) long before it could freeze. Link to comment Share on other sites More sharing options...
wtdash Posted March 7, 2009 Author Share Posted March 7, 2009 (edited) - Tried the WD40 trick on the vac hose - no luck. - Installed another hose from my '93 SS donor and still not fixed. (I don't know the condition of this hose - never drove the car.) But this a.m. it was about 25 degrees F when I started the car and headed out -city driving. I hit the brakes 2x and they seemed OK. I accelerated up to about 35, just got into boost (EJ22T swap), and then hit brakes to slow down and there was almost no stopping power! I pushed harder and still not better. I released the brakes and pumped them a couple times and they felt 'dead' - like they do when pushed w/the engine off. So, I'm thinking there's more to this than just a hose. Also, I forgot to add in the OP, that I also installed SS brake lines on the front. Brake booster? Master cylinder? Calipers? As stated in the OP, I swapped in Forester calipers/rotors of unknown mileage - How would I know if they need a rebuild? Thanks for any more feedback. Edited March 7, 2009 by wtdash Link to comment Share on other sites More sharing options...
OB99W Posted March 7, 2009 Share Posted March 7, 2009 Does the car pull left or right at all when the problem occurs? If not, and the only obvious symptom is the need for substantially increased pedal effort, then it's still likely that there's a failure of brake vacuum boost. The effort goes up dramatically if a vacuum booster isn't working, since it can add a few hundred pounds of pressure to your leg power when it's operating correctly. The vacuum line check valve operation is even more important with a turbo than it is with a normally-aspirated engine, since intake manifold 'vacuum' is replaced by 'pressure' during turbo boost -- if the check valve doesn't close, the vacuum stored in the booster is immediately displaced. If the valve is 'sticky' and doesn't open when vacuum is present, there will be no brake boost even when there's sufficient intake vacuum (no turbo boost). In order to help determine what to concentrate on, you might 'T' a vacuum gauge in the line between the check valve and the booster, and see what it reads when the problem occurs. If it's okay, there could be a porting problem within the booster. Link to comment Share on other sites More sharing options...
wtdash Posted March 13, 2009 Author Share Posted March 13, 2009 (edited) Car doesn't pull when brakes are applied - either when they work well or badly. I've not checked the line w/a vac gauge....don't have one...yet. I'm thinking it's the brake booster, since it's doing it in cold or warm weather. And since there's a different part number for the Turbo vs. NA, my original '90 NA booster may be wrong for the '93 Turbo. I read on LCBBS that a '97 Impreza 'single diaphragm' (my '90 is dual) might be a good replacement/upgrade. And mine is a NON-ABS and has 4 brake line connections...looks like the ABS only have 2? Anyone know what other Subarus will fit? Thanks Edited March 13, 2009 by wtdash Link to comment Share on other sites More sharing options...
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