Brakes - not spongy but slow stopping

[milty60]

ABS does not work on my car since I purchased it - dash ABS light is on - tone rings are missing on two hubs. I have replaced all rotors/drums and brake pads/shoes, caliper piston moves easily (old calipers), no fluid leaks, master cylinder appears new - clean fluid. Pedal does not feel spongy (I have not bleed brakes to date) but it takes quite a bit of pressure on the pedal to stop the car and it certainly does not stop on a dime. Any thoughts? 

 

Thanks, 

 

Milty

[Mike104]

ABS does not really have much impact if not working it really only prevents wheel lock up.  Bleeding, bad master cylinder and proper brake pad bedding are the best solutions to brakes.  I find my older Subaru's to need more pressure compared to the 2017 Impreza rental I had the other day.  Just about put my manager through the windshield when I stepped on the brake pedal as hard as I do on my car.

[idosubaru]

Change the fluid

Change it again? Haha

 

Clean and regrease slides

 

Check pad clips and make sure they’re not bent, corroded or massive build up. Seems unlikely those would affect enough of 4 different calipers to inhibit braking that much though.

[idosubaru]

Is there anyway to test MC output? Google it? DIY test, backyard hack test....?

[heartless]

(I have not bleed brakes to date)

 

i would start by doing a proper bleed of the system all the way around.

[CNY_Dave]

My '03 LL bean with the H6 took abnormal pedal pressure to generate good braking power.

Never did track it down, but it wasn't bleeding or calipers or pads/sliders not moving freely.

 

The brake booster was amplifying effort, but could have been below what it should have been doing.

[milty60]

I will start out with bleeding - bummer is all calipers are I think original and I picture snapping off most of the bleeders - they are mostly corroded away too. Was trying to avoid buying calipers but I will soak the crap out of them - maybe apply a little heat and buy new bleeders. Project for next weekend 

 

A thought. I had a Bonneville that had blockage in the rubber hoses at two of the wheels that cased slow braking and sticking calipers. 

 

Also will re-exam all brake components again. I do wonder if there is a DIY way to check MC - will Google it -  it does look new & fluid is clear but who knows.

 

Appreciate all the advice. 

 

....Milty  

[Mike104]

In theory weak brake hoses could cause an issue but those tend to harden with age not get softer so not sure if that is anything to worry about.  If they are original calipers the pistons may be seized or binding that would cause your issue but should show up with pads that have little wear.  May want to bite the bullet and get new calipers if you can't break the pistons free

[milty60]

Possibly caliper pistons - previously replacing all pads I did compress the pistons in the bores and they seemed to move freely but hard to know for sure - I think I will try bleeding brakes first if I don't break off rusted/corroded bleeders in the process - and then replace calipers all the way around. 

 

....Milty  

[montana tom]

 Have you checked the vacuum booster ? 

[Fairtax4me]

If the bleeders are so locked up that you can't change the fluid you really should change the calipers. Only twice have I had customers request to have a broken bleeder screw drilled out rather than replacing the caliper. Both times the car was back in the shop just a few months later, same calipers, pistons seized, ate up the new brake pads and warped the rotor.

In a shop it's a half hour of labor to replace a brake caliper. $40 caliper + $50 labor= $90 And it's done for years.

It's an hour labor and a $10 bleeder screw to drill out a caliper. $110, and then end up replacing the caliper anyway a couple months later. Plus in these cases replace the brake pads again, and replace the damaged rotor.

 

If the pedal is hard, that could be a booster problem. There's a check valve in the vacuum line to the booster that can get stuck and prevent full vacuum from reaching the booster. The booster could also have an internal failure causing it to not provide full boost power.

There are specs for testing the booster in the factory service manual.

[heartless]

have to agree with Fairtax.. if the calipers are in that bad of shape, then replace them. it is not hard to do, and brakes are not something that should be skimped on.

 

just because the fluid in the MC looks fresh, does not mean the lines have been flushed (especially if the bleeders look like they have not been touched in a long time)

[idosubaru]

I would bleed. Then look at the booster.

 

Your description sounds like braking in a Subaru without the engine running. No vaccuum, poor booster performance:

 

1. Check vacuum line to booster. Maybe it’s clogged or leaking?

 

2. Try braking with the engine not running (coasting down a hill), if the performance isn’t a drastic change then the vacuum/booster needs looked at or someone more versed on those cam comment, they rarely fail and I’ve never seen it.

 

Again I don’t know how to test those though. Can you measure MC output or booster performance?

 

Seems highly unlikely it’s the calipers to me, if they’re rusted to scrap then replace but otherwise I’d look elsewhere for your issues.

 

Brake hoses I’ve seen fail on multiple American cars (and I don’t even work on them) but very rarely on subarus, I’ve never seen it happen which is odd because I’m around plenty of 80’s subarus and the american cars I see it happen too are much newer. The hoses collapse internally and during braking the internal collapse functions like a valve and doesn’t allow fluid back out of the MC so the pads keep clamping the rotor even when you take your foot off he pedal. Very funny seeing that for the first time.

 

Jack up car. Brake - let off - can’t turn wheel - crack bleeder - wheel turns - brake - let off - abt turn wheel....etc.

 

I’ve never heard of other failure modes besides leaks and even this internal collapse isnt common.

[idosubaru]

Actually I’d do that test by braking while coasting first, I can’t tell what you’re experiencing but sure sounds like you’re decribimg stopping a non running Subaru.