Brake Fluid Change???

[bronsin]

Originally Posted by tmontague

I have tried the mighty vac and no matter what it pulls air in through the bleeder for me. That is even with covering it with grease as well as using thread sealant tape.

I just use the 2 person method which is cheap. Quick and woke well.

Down the road I'll likely buy a pressure bleeder but for now the 2 person works fine

I agree mityvac is overkill. Spend your money on something useful!

[Motzking1]

I imagine it is possible. I have used a Vacuula brand bleeder and if turned up they can produce almost as much vacuum as a vacuum pump. 28+ in. Of mercury. I have not had a problem before but do not normally use it. I still use the old fashion two person down and hold method. I am careful not to travel the pedal much outside it's normal travel ammount. It seems by bleeding the pedal and therefore the master cylinder too far down Beyond its normal range of travel tends to increase the instance of master cylinder failure. My guess is because you're traveling outside of where the normal wear Groove kind of happens inside the cylinder therefore increasing the chance of damaging the Rubber seal. All so funny what you say about the Mercedes as we have sold a massive amount of calipers on some of the late model Mercedes. You know there's a problem when you go to the shop to pick up Part you would normally stock 2 or 3 sets of and there are 60 sets. It's a real High moving part. I honestly have not dove in to what the failures are with the late model MB calipers. In the past the big failures in big numbers where when some manufactures went to phenolic Pistons instead of metal ones. They cracked they chipped they got soaked with fluid and expanded. Most of those issues have worked themselves out. Most manufactures abandoned the phenolic piston design. But there have been others that have tried to make Ceramics and other Exotics pistons for calipers. Each one has their own little quirk

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[Motzking1]

Toyota tends to use time tested parts and methods instead of going for the newest latest and greatest. That makes them reliable and easier to service

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[Motzking1]

Interesting I would really like to see a good write-up or video on brake bleeding I think that's a great idea. You're right being as that it really hasn't changed a lot and over a hundred years there are a lot of people who still must understand it and the whole notion is sometimes a little mysterious as to when and how. It seems the same is true of disc brake servicing. I have seen a lot of brake jobs done and I've seen as many different ways of doing it as I have seen technicians to do it. Some technicians Grease the pad Hardware. Some people put silicone lubricant grease oil whatever on the back of the pad and swear by it. A lot of people misunderstand what a pad shim is what it does. Getting straight answers to these questions has been sometimes difficult. Even out of the manufactures themselves. I of course have some strong opinions on it being in the automotive service business an automotive parts business my whole life. But as strong as my opinion on what to do I still get a lot of people who disagree. Take the pad hardware for example I get people who swear by lubricating the pad Hardware. I strongly believe that grease and oil attract dust and debris. I don't lubricate them. Not to mention all the ones I sell these days come with a pre lubricated Teflon coating to them. But there are many varied opinions on how to do this and what works.

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[Motzking1]

I'm not buying the fact that the mighty vac is pulling air with grease and thread tape. That does not make coming sence. Think about that. You think because you see air in the line it came from ambient air? Not likely. What is more likely is the mighty vac is in a vacuum. All matter and it's state are affected by atmospheric pressure or lack thereof. In other words you don't find a lot of water 4 brake fluid for that matter in its liquid form in a vacuum. The reason being without the atmospheric pressure of the Earth's atmosphere water becomes a gas. When you use the Mighty vac it pulls a vacuum a strong vacuum with the bleeder being the orfice tube in the system. Anything behind that or forced tube is in a strong vacuum. What you're seeing is air. But likely where it came from his lack of atmosphere causing vapor to boil. This is called Boyle's Law

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[dogsridewith]

Mityvac instructions say you will see big spurty bubbles when air is coming out of the system, then steady little bubbles (which are no problem) of air being pulled through the loosend nipple's threading (from ambient air) and mixing with fluid being pulled through the system...into the cup...until the nipple is closed...all the while with the operator paying attention to the gauge and squeezing the vacuum pump handle enough to maintain some vacuum.
There's no vacuum diaphragms to Mityvac check on Yaris? People would have saved millions of dollars tuning the late 1980's Tercel fleet finding broken diaphrams in distributor advances and emissions gizmos instead of buying new or rebuilt carburetors.
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I can see using some grease on bleeder nipples to prevent rusting, but grease or Teflon tape can't be expected to seal straight threads. The seal is at the end of the nipple.

[CoryM]

Air will pull past the coarse bleeder threads when using vacuum on the bleeder. Especially on rebuilt calipers with poorly machined threads. The threads are not designed to seal at all, and are loose enough that even fluid can pass through them readily when the bleeder is loose (which is annoying because it means when I do flushes, brake fluid drips on the hoist). Just make sure to close the bleeder while there is a vacuum still on it and you shouldn't have any air problems. If you loose vacuum while the bleeder is open, it will pull air back into the brake system. The mityvac may be harder to use than a flusher because of this. The best way to use the mityvac for the final bleed is probably to pump the hell out of it with the bleeder closed, crack the bleeder and then close it again before vacuum runs out. Otherwise you may keep getting air sucked back into the system.

Do not use any petroleum based greased where it can contact your brake fluid or rubber. It will swell the seals and destroy them.

[bronsin]

Originally Posted by CoryM

Air will pull past the coarse bleeder threads when using vacuum on the bleeder. Especially on rebuilt calipers with poorly machined threads. The threads are not designed to seal at all, and are loose enough that even fluid can pass through them readily when the bleeder is loose (which is annoying because it means when I do flushes, brake fluid drips on the hoist). Just make sure to close the bleeder while there is a vacuum still on it and you shouldn't have any air problems. If you loose vacuum while the bleeder is open, it will pull air back into the brake system. The mityvac may be harder to use than a flusher because of this. The best way to use the mityvac for the final bleed is probably to pump the hell out of it with the bleeder closed, crack the bleeder and then close it again before vacuum runs out. Otherwise you may keep getting air sucked back into the system.

Do not use any petroleum based greased where it can contact your brake fluid or rubber. It will swell the seals and destroy them.

Sounds like an excellent reason not to use a mityvac.

[tmontague]

The problem I had was that not enough fluid was being drawn down to the bleed nipple to do an adequate flush and bleed. The vacuum was being maintained without issue but I find putting pressure at the main reservoir always flushed way more fluid through the system. I would have a small drop with the mighty vac and a full rush of fluid with the 2 person method.

As long as you have a helper and a block of wood to stop the pedal from going all of the way down it take very little time and gets everything through the brake lines and out.

[dogsridewith]

Originally Posted by tmontague

The problem I had was that not enough fluid was being drawn down to the bleed nipple to do an adequate flush and bleed. The vacuum was being maintained without issue but I find putting pressure at the main reservoir always flushed way more fluid through the system. I would have a small drop with the mighty vac and a full rush of fluid with the 2 person method...

Then your problem was unclogging the system BEFORE being able to bleed it.
I've only seen this level of clog--rusty dirt-- happen inside the tip of the nipple, or maybe just inside the wheel cylinder...resolved by removing the nipple completely and clearing nipple/cylinder with a drill bit(s). Stomping the pedal would certainly produce more system pressure to clear rust in the lines, sticky proportioning valves, etc.

[KimmoKekki]

Why you should not hit brake pedal to the floor ??

[CoryM]

Originally Posted by KimmoKekki

Why you should not hit brake pedal to the floor ??

Because the master cylinder piston only moves around 1/2 stroke in normal use. The bore wears, which leave a ridge at the end of it's normal stroke. So when you bleed and go all the way to the floor, the rubber piston seal has to go over that ridge and it tears. Then you have to replace the master cylinder.

Never go more than 1/2way to the floor when bleeding (unless master cylinder has just been replaced).

[KimmoKekki]

So like said ... pedal to the metal !!

[dogsridewith]

Which reason are you addressing? Air pushing past bleeder threads is irrelevant. I never come close to loosing vacuum with the bleeder open. The gauge is right there to watch and I'm just cracking the bleeder w/ an 8 mm wrench while watching the fluid/bubble mix run through clear tubing...very easy to stop in an instant w/ a tiny movement of the wrench. MityVac has enough vacuum reservoir to do this easily. It helps if everything is attached (the tubing to the bleeder nipple, and all other tubing pieces) and hung/placed (the pulled-fluid receiving cup) sufficiently.

[bronsin]

Originally Posted by dogsridewith

Which reason are you addressing? Air pushing past bleeder threads is irrelevant. I never come close to loosing vacuum with the bleeder open. The gauge is right there to watch and I'm just cracking the bleeder w/ an 8 mm wrench while watching the fluid/bubble mix run through clear tubing...very easy to stop in an instant w/ a tiny movement of the wrench. MityVac has enough vacuum reservoir to do this easily. Lots of auto mechanic work takes two or three hands. This, just one, if everything is attached (the tubing to the bleeder nipple, and all other tubing pieces) and hung/placed (the pulled-fluid receiving cup) sufficiently.

CoryM says one thing and you say the opposite. You guys settle it.

As for me I can bleed my brakes all by myself without a mityvac and usually without help. Ive bled the brake system of the ST1300 motorcycle alone, a VERY Rube Goldberg system with TWO master cylinders one lever actuated one front brake rotor actuated! Very complicated and very nuts!

How nuts? The front wheel has two discs each with its own caliper. When its pads grab the disc, the left caliper pivots actuating a secondary master cylinder, which applied the rear brake. Actually, it applies one piston of the three pistons on the rear caliper. Totally CRAZY! VERY complicated!

I can always get someone to help if needed.