Hard Brake Pedal

keith107

New member
Hi Lads. Had a look around the forum there and maybe this is in there somewhere but ive missed it. My brake pedal in my forester sg9 STI is very hard. Any ideas on the issue? Brakes seem bad enough due to it.
Also any Sligo lads on here that can work on a subaru?
Cheers.
 
Hi Lads. Had a look around the forum there and maybe this is in there somewhere but ive missed it. My brake pedal in my forester sg9 STI is very hard. Any ideas on the issue? Brakes seem bad enough due to it.
Also any Sligo lads on here that can work on a subaru?
Cheers.

Could be a vac related issue? There's a vac line running from the servo on the firewall to the intake manifold - about 6 inches from the servo is a check valve - they can go faulty apparently and lead to issue similar to yours. Easy to locate and swap out
 
Take the vacum line off, you should be able to draw air through it from the side that pushes onto inlet, and you shouldn't be able to blow back through it from this side. It's a one way valve that's in it... worth checking your calipers aren't seizing, and if all else is ok, it could be servo itself
 
Had similar problems before with brakes and servo. So a test for servo is let car run and see do you get one assisted press and if peddle gets hard and comes back up to you seal in servo could be gone if like what ken says pull v-pipe off and with car on idle should hear and feel it sucking air if it's doing that vacuum pump ok also when pipe off check it's dry inside small cotton bud no fluid. And always follow pipes from A to B make sure all pipes are in good shape hope this helps a bit it's a pain trouble shooting


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Had similar problems before with brakes and servo. So a test for servo is let car run and see do you get one assisted press and if peddle gets hard and comes back up to you seal in servo could be gone if like what ken says pull v-pipe off and with car on idle should hear and feel it sucking air if it's doing that vacuum pump ok also when pipe off check it's dry inside small cotton bud no fluid. And always follow pipes from A to B make sure all pipes are in good shape hope this helps a bit it's a pain trouble shooting


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Thanks lads. Didn't get near it tonight but will hopefully get at it tomorrow. Will let Ye know. Cheers.
 
Hi. So I checked a few bits this evening. Check valve is working. Vacuum pump defo seems ok. Doesn't appear to be any leaks. So really could be down to the servo or maybe callipers. They Don't seem to be sticking but I'll try get it on a lift some evening.
Any mechanical minded Subaru heads on here from Sligo? ????
 
Sticky calipers if stainless steal pistons never swopped in
Be my uneducated guess


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I had problem on type r before where the brake proportioning valve mounted in front of the master cylinder was sticking. If i gave it a tap of a hammer brakes would improve until sticking again , eventually replaced. That was on non abs sti. Would not be familiar with setup on Forrester. Most modern abs equipped cars do away with bias valves but I do see some breed of a valve on the modern Subaru's in same location though different to mine. Like the one in this photo.
You can test vacuum servo assistance by pumping the brake pedal a few times with engine off to empty servo ( or refill with air if you want to be specific). Press pedal hard then start car, if pedal moves away from you half an inch or there abouts servo action is fine.

If no servo assistance measure vacuum with vacuum gauge it should pull 20+ inches of mercury. If vacuum is good use hand vacuum pump to pull a vacuum in the servo it should hold the vacuum if not diaphragm in servo is shot.
 

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I had problem on type r before where the brake proportioning valve mounted in front of the master cylinder was sticking. If i gave it a tap of a hammer brakes would improve until sticking again , eventually replaced. That was on non abs sti. Would not be familiar with setup on Forrester. Most modern abs equipped cars do away with bias valves but I do see some breed of a valve on the modern Subaru's in same location though different to mine. Like the one in this photo.
You can test vacuum servo assistance by pumping the brake pedal a few times with engine off to empty servo ( or refill with air if you want to be specific). Press pedal hard then start car, if pedal moves away from you half an inch or there abouts servo action is fine.

If no servo assistance measure vacuum with vacuum gauge it should pull 20+ inches of mercury. If vacuum is good use hand vacuum pump to pull a vacuum in the servo it should hold the vacuum if not diaphragm in servo is shot.

Cheers for the advise. Will try later after work. There is one of them valves on it alright mounted right beside the servo.
One of my old imprezas had a similar problem but was never sorted after new calipers and servo so could of been that valve also.
Hopefully i will get to the bottom of it tonight.
 
Plenty of advice for checking servo and all suggested checks work fine....one other thing that can cause a hard pedal and rubbish brakes: flexible hoses can soften and swell over time. The swelling occurs on the inside diameter as much as appear on the outside. You end up with a very small hole for the brake fluid to get through.

Take a good look at the 4 hoses
 
Hi. Bit of a late update. So turned out pads were rock hard track type pads. Unsure of make. And there is a brake servo stopper on the strut brace. Loosened this out and changed the pads and the pedal and brakes are perfect now.
 
:clap:Good man fair play for updating it :thumbsup: when pads get old they get hard and useless so might not even be a racing pad . Had this on a set of brembo calipers and 10 year old sti brake pads there was just no bit from them new pads and there were sorted :thumbsup:

is that your white sti forester 2004
 
:clap:Good man fair play for updating it :thumbsup: when pads get old they get hard and useless so might not even be a racing pad . Had this on a set of brembo calipers and 10 year old sti brake pads there was just no bit from them new pads and there were sorted :thumbsup:

is that your white sti forester 2004

Hi. They were red pads so just taught they might be race style. Yes that’s mine alright. Planned on keeping it but I need to sell it regretfully to fund some non car related issues. �� Going to buy a classic scooby after it’s sold though to keep me somewhat happy. ���� it’s genuinely in mint condition if you know anybody.
 
Have been having a similar issue myself. Hard brake pedal on the impreza. Got new pistons, seals, pads and failing that I have a spare servo to try aswell. All lines are braided so no issues there...
 
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