Brakes still spongy after fluid change

vmmf · Jul 27, 2021

TomKatt said:
In the "old days", turning rotors was a common, cost effective practice. These days, no mechanic I've spoken to has recommended it - they claim that modern rotors are often thinner to begin with, and the depth of material that needs to be removed results in the rotor ending up much too thin to be worthwhile. I can't comment on how much rotor thicknesses has changed, but I know I've inquired several times about resurfacing and the answer has been the same at multiple repair centers.

As for why your appear to be bad, I think the maximum variation from "flat" on the pad surface area permitted is only around 0.015", and yours appear to be beyond that.

I see, then I would need to replace that caliper, rotor and brake pads all at the same time. Do you have a good opinion of after market calipers?

TomKatt · Jul 27, 2021

That's probably the best solution.

And thinking more about it, it may well be that what you are really experiencing is more pedal force being required because that sticking caliper is not applying sufficient braking pressure, forcing you to press harder for the others to compensate...

paulday · Jul 27, 2021

Replacing in pairs prevents side pull during sudden heavy braking, and going into a spin. The side that hasn't been worked on/replaced will react slower then the new replacement side, causing the car's rear end to swing out.

Good luck.

Have a good day.

vmmf · Jul 27, 2021

paulday said:
Replacing in pairs prevents side pull during sudden heavy braking, and going into a spin. The side that hasn't been worked on/replaced will react slower then the new replacement side, causing the car's rear end to swing out.

Good luck.

Have a good day.

Thank you for the advise. Yes I would definitely replace rear pads and rotors in pairs. But if only one rear caliper is problematic, then I would change that one for now. Do you have experience with after market calipers?

Do you have any thoughts about questions 4 and 5?

vmmf · Jul 27, 2021

TomKatt said:
That's probably the best solution.

And thinking more about it, it may well be that what you are really experiencing is more pedal force being required because that sticking caliper is not applying sufficient braking pressure, forcing you to press harder for the others to compensate...

Well thinking about it that way instead of 100% if I only have 75% of braking capacity that would explain a longer time to brake and needing to sink the pedal deeper to achieve the same braking distance. But I don't understand why the pedal would feel softer, which it does.

Do you have any thoughts about questions 4 and 5?

paulday · Jul 27, 2021

vmmf said:
Thank you for the advise. Yes I would definitely replace rear pads and rotors in pairs. But if only one rear caliper is problematic, then I would change that one for now. Do you have experience with after market calipers?

Do you have any thoughts about questions 4 and 5?

I go with one of the major national caliber rebuilders. They have a better success rate then the big box chains that go for the cheapest supplier. You can find them online. They usually have a $50 caliber return fee with free return shipping.

You can also comparison shop the car parts chains for the cheapest price, but again, beware of quality issues with the cheap reman calibers.

If one caliber is sticking, the other is not far behind. Since the piston seals slowly swell over time, your new one will operate with less pressure then the old one on the other side. It's alright if you're in the habit of pumping the brakes when coming to a stop, but it will be an issue in a panic stop. The new caliber will lockup first, swinging the rear end out. In the rain, you will definitely end up in a spin during a panic stop if you only replace one caliber.

Good luck.

Have a good day.

paulday · Jul 27, 2021

vmmf said:
Well thinking about it that way instead of 100% if I only have 75% of braking capacity that would explain a longer time to brake and needing to sink the pedal deeper to achieve the same braking distance. But I don't understand why the pedal would feel softer, which it does.

Do you have any thoughts about questions 4 and 5?

It's feeling softer because the hydraulic action is at it's max and now the system is exerting force against only one side of the rotor from either a seized piston or frozen slide pins, allowing metal parts to slightly flex.

Have a good day.

vmmf · Jul 27, 2021

paulday said:
I go with one of the major national caliber rebuilders. They have a better success rate then the big box chains that go for the cheapest supplier. You can find them online. They usually have a $50 caliber return fee with free return shipping.

You can also comparison shop the car parts chains for the cheapest price, but again, beware of quality issues with the cheap reman calibers.

If one caliber is sticking, the other is not far behind. Since the piston seals slowly swell over time, your new one will operate with less pressure then the old one on the other side. It's alright if you're in the habit of pumping the brakes when coming to a stop, but it will be an issue in a panic stop. The new caliber will lockup first, swinging the rear end out. In the rain, you will definitely end up in a spin during a panic stop if you only replace one caliber.

Good luck.

Have a good day.

Well I understand your point. In that case it is best to replace both calipers in pairs. So I will replace the 2 rear ones. Although my car is FWD but the front brakes seem to be fine.

I want to ask you

If the master cylinder or booster were defective how dangerous is it not to replace them right away?
What could be the consequences of filling my master cylinder above the max indicating line to see if I can regain some brake strength while I wait for the parts to change the back caliper, rotors, brake pads, etc?

TomKatt · Jul 27, 2021

vmmf said:
If the master cylinder or booster were defective how dangerous is it not to replace them right away?

The booster just provides assistance, so it's more of an aid than a necessity. You'll have to press harder, but the brakes still work. A defective master cylinder can cause loss of brake pressure, but I think they tend to fail more with obvious signs of leakage.

vmmf said:
What could be the consequences of filling my master cylinder above the max indicating line to see if I can regain some brake strength

I'm not sure I understand how overfilling the master cylinder would provide any additional brake pressure... Unless you are somehow emptying the entire reservoir on each pedal press (in which case you've got bigger trouble)... More fluid <> more pressure

vmmf · Jul 27, 2021

TomKatt said:
I'm not sure I understand how overfilling the master cylinder would provide any additional brake pressure... Unless you are somehow emptying the entire reservoir on each pedal press (in which case you've got bigger trouble)... More fluid <> more pressure

My idea was, but I could be completely wrong, that when you press the brake pedal that is a complete sealed system and the only little air remaining is on top of the master cylinder. So I'm naively thinking that if the amount of that air is minimum I would get less brake weakness. However I'm not aware of how the internal seals in the master cylinder work and most likely I'm wrong. I also saw Chris Fix closing the master cylinder cap and opening the brake bleeding valve when he wanted the brake fluid to escape through the caliper while bleeding. I'm not sure if having to close the cap of the master cylinder is just to avoid contamination or to effectively preserve the pressure while pressing the brake. I saw a video in which Scotty Kilmer was heavily criticizing a mechanic for putting a nylon and a rubber band instead of the proper master cylinder cap. So what do you think?

Bigphil555 · Jul 27, 2021

I agree with @TomKatt on the general thoughts today, it is just to give the full picture. I prefer to change the rotors, and I would with yours (and pads) after you have serviced them. I think your rotors are bad just by looking at the poor contact area across the rotor and the general scoring.

Calipers fit either front or rear, and are side specific too, as the bleed nipple needs to be on top (or up high). OEM are good, but may be expensive, but a good quality OE type would suffice too. Not sure what brands are available in Canada - hope another member could help.

Please remind me, what was question 4 and 5 - I have missed those

vmmf · Jul 27, 2021

Bigphil555 said:
I agree with @TomKatt on the general thoughts today, it is just to give the full picture. I prefer to change the rotors, and I would with yours (and pads) after you have serviced them. I think your rotors are bad just by looking at the poor contact area across the rotor and the general scoring.

Calipers fit either front or rear, and are side specific too, as the bleed nipple needs to be on top (or up high). OEM are good, but may be expensive, but a good quality OE type would suffice too. Not sure what brands are available in Canada - hope another member could help.

Please remind me, what was question 4 and 5 - I have missed those

OK so the calipers are side specific? This means when you go to buy them you say I want to buy a caliper for right side and a caliper for left side?

My questions 4 and 5
4. If the master cylinder or booster were defective how dangerous is it not to replace them right away?
5. What could be the consequences of filling my master cylinder above the max indicating line to see if I can regain some brake strength while I wait for the parts to change the back caliper, rotors, brake pads, etc?

paulday · Jul 27, 2021

vmmf said:
OK so the calipers are side specific? This means when you go to buy them you say I want to buy a caliper for right side and a caliper for left side?

My questions 4 and 5
4. If the master cylinder or booster were defective how dangerous is it not to replace them right away?
5. What could be the consequences of filling my master cylinder above the max indicating line to see if I can regain some brake strength while I wait for the parts to change the back caliper, rotors, brake pads, etc?

Calibers are front and rear, with each having a Left and a Right.

4. Not road worthy. Also a liability if you get in an accident and are aware you have a brake issue.

5. Fluid level past the Max level does nothing for the braking power. It's only the brake fluid reservoir. Watch a Youtube video on how a master cylinder works. As long as the fluid level is above the Minimum, air can't get sucked into the system. End of story.

Have a good day.

Just Another Guy · Jul 27, 2021

Just a thought.
You did day your peddle is stiff when motor is off. This should not be instantly, the booster should hold vacuum for 1 or 2 peddle presses when car is shut off.

This is needed to assist in braking when or if the motor suddenly stops. There is a vacuum line going to the booster. That line has a check valve which closes to seal the vacuum line so the booster retains vacuum assist. If that check valve is bad or there are pin holes in the metal case, the vacuum could escape or say leak.

The valve should be cheap and worth a try.

vmmf · Jul 27, 2021

Just Another Guy said:
Just a thought.
You did day your peddle is stiff when motor is off. This should not be instantly, the booster should hold vacuum for 1 or 2 peddle presses when car is shut off.

This is needed to assist in braking when or if the motor suddenly stops. There is a vacuum line going to the booster. That line has a check valve which closes to seal the vacuum line so the booster retains vacuum assist. If that check valve is bad or there are pin holes in the metal case, the vacuum could escape or say leak.

The valve should be cheap and worth a try.

Yes, as soon as the car stops, you count 10 seconds and the brake pedal is rock solid. It won't move. So in your RAV4 you are able to make 2 presses after it is shut off?

I will try this after replacing the calipers and rotors which are bad

Just Another Guy · Jul 28, 2021

I will check again tomorrow because I did not wait 10 seconds. But a properly working system should hold the vacuum longer. I believe quite a lot longer if not until peddle is pushed again, even over night.

I will test mine tomorrow again and let you know for sure. I know my other cars hold but have not had the RAV long enough to know it's quirks.

Bigphil555 · Jul 28, 2021

@vmmf , I agree with what @paulday said to question 4 and 5

vmmf · Jul 28, 2021

Bigphil555 said:
I agree with @TomKatt on the general thoughts today, it is just to give the full picture. I prefer to change the rotors, and I would with yours (and pads) after you have serviced them. I think your rotors are bad just by looking at the poor contact area across the rotor and the general scoring.

Calipers fit either front or rear, and are side specific too, as the bleed nipple needs to be on top (or up high). OEM are good, but may be expensive, but a good quality OE type would suffice too. Not sure what brands are available in Canada - hope another member could help.

Please remind me, what was question 4 and 5 - I have missed those

I just pre-ordered (haven't paid yet) Raybestos new calipers @ 120 CAD each (part # FRC12995N & 996N) + new coated rotors @ 40 CAD each (part # 980483FZN) + parking brake shoes and hardware @55 CAD + ceramic brake pads (mid grade part # TEC 1212) @30 CAD + brake lube tube @ 8 CAD

The premium hybrid ceramic brake pads (part # EHT1212H) were 75 CAD. I just don't know if they would be worth it, I can still change my mind. Also on pictures on internet the coated rotors don't look painted. What is this coating exactly?

Is Raybestos stuff good quality?

vmmf · Jul 28, 2021

Just Another Guy said:
I will check again tomorrow because I did not wait 10 seconds. But a properly working system should hold the vacuum longer. I believe quite a lot longer if not until peddle is pushed again, even over night.

I will test mine tomorrow again and let you know for sure. I know my other cars hold but have not had the RAV long enough to know it's quirks.

Could you do the testing?

Bigphil555 · Jul 28, 2021

@vmmf , I do not know the brand here in the UK - does anyone from Canada know?

Rotors have an oil based coat on them to prevent rust in storage. Make sure you clean the rotors thoroughly before putting the pads in - you will be fine. Watch a SMA video and see how Eric O cleans rotors

Brakes still spongy after fluid change

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