Loss of Braking

[Anime]

I'm not real sure. The current master cylinder says Bendix on it so I don't think it's OEM. Could a seal blow in it? Autozone has a booster and master cylinder for $120. I may go that route since my current booster is quite rusty.

The original factory master cylinder is a Bendix. I bought a new Bendix MC and they are slightly different than the OE one, but still have the same connections and everything else.

I understood. Just not sure which one is suspect. It's puzzling because I would think with a firm pedal with no vacuum the hydraulic system would be ok. But a pedal that goes to the floor with vacuum and little braking force would point to either an internal or external fluid leak. As I said above nothing external. So fluid escaping around the piston(?) in the MC?

I'd only suspect the booster if there was no vacuum and zero braking ability after the engine has been turned off.

A pedal that goes to the floor with the engine running is a hydraulics issue, usually the master cylinder.

A pedal that goes to the floor with the engine not running is a vacuum issue, usually the brake booster.

When master cylinders 'go', very often it's just worn seals, o-rings, etc that is letting the fluid go by. It's possible to rebuild a MC with a kit, usually just with o-rings, springs, etc.

Came back home and pulled the check valve, it's good. I plugged the vac line and ran it around the block again. The pedal is obviously harder to push but still goes to the floor with minimal braking.

At this point I believe I ruled out the brake booster and am down to the master cylinder. Doesn't this sound correct? I'm really hoping as I can get one locally for $40+some fluid and have it back on the road again.

Is there a special way to replace the MC without getting air into the ABS pump? I really don't want to have to deal with that!

If the pedal goes to the floor with the engine running, it's the master cylinder.

Just be sure to use a good quality one. I would definitely not skimp on something as important as a MC. Not that a cheap one would be inherently dangerous, but it might not last very long. If you can get another Bendix, or something good for $40, go for it.

Standard bench bleeding before installation is the only thing I've seen for these, even in the factory service manuals. There's no special instructions for anything to do with the ABS. Just don't touch the brake pedal or get any air into the lines unnecessarily, bleed the brakes from shortest line (drivers front) to longest (passenger rear), then repeat the bleeding until you no longer get any air bubbles.

You should have a much improved braking system afterwards.

 

[IAmTodd]

Thanks Anime. I'm going to call around to some of the local parts shops tomorrow to see what they carry. Advance has a Cardone one in stock. If all else fails that will get me back into business.

Thanks again for all of your help. If I can, I'll pull the old one apart to see what exactly failed. I'm also curious to see what the inside of one looks like.

 

[Anime]

A1 Cardone is usually remanufactured stuff. Not that it's bad (you might just get a rebuilt factory Bendix), but with first gens, a good deal of the time the brand new stuff is either not that much more or sometimes less.

Also keep in mind the brand on the box means little, a good deal of the time, it's reboxed. Some of AutoZone's Duralast stuff is like this.

Not that it's worth driving around town to check them all out for yourself or to get every parts guy you talk with to open the box and see what brand the part actually is, but shopping around is definitely good, you will probably pay less for something really good at one store, and a lot more for a cheap generic part at another.

Also if you want to replace the booster, now is the time to do it. If you don't want to replace it but the rust bugs you, it's still easier to clean up the exterior and maybe tape it off and give it a few coats of paint while the master cylinder is off and out of the way.

 

[IAmTodd]

I may get out the wire wheel and clean up the booster a bit. I'm at the point of if it ain't broke don't fix it.

 

[willindsay]

Standard bench bleeding before installation is the only thing I've seen for these, even in the factory service manuals. There's no special instructions for anything to do with the ABS. Just don't touch the brake pedal or get any air into the lines unnecessarily, bleed the brakes from shortest line (drivers front) to longest (passenger rear), then repeat the bleeding until you no longer get any air bubbles.

You should have a much improved braking system afterwards.

Bleeding from the shortest to the longest is the opposite from what I've read many times on this forum. I've always read to start at the passenger rear tire and finish with the driver front.

Now I've never done a break job but I've read many threads on doing it so I'm ready when the time comes to do mine.

Not saying you're wrong just wondering what your reasoning is for doing it opposite of what I've heard from most?

 

[Anime]

The reasoning behind starting at the shortest line and ending with the longest is that any trapped air in the master cylinder will be purged out of the system through the shortest line first, so each subsequently longer line will only be bleeding out air from the line itself, and maybe some smaller amount of air from the master cylinder if there is any.

If you start with the longest line first, ALL of the air that is trapped in the master cylinder has to make it's way through the entire length of the longest brake line, in addition to the air in the line itself. This raises the possibility that a good bit of the air will not be purged until the process has been performed quite a few times. If you start with the shortest line, you're purging the majority of the trapped air sooner, and hopefully making things much easier for yourself.

With respect to the Explorer, this way of performing the procedure is in an effort to not throw off the ABS or proportioning systems. I'm sure that plenty of people just bleed brake systems however they feel like it, and perhaps the majority of the time it doesn't affect anything and it all works as it should afterwards.

However, I'm in the subset of people who are really particular about how they do vehicle maintenance, and I'd also rather do things in the most effective way, which hopefully also prevents me from causing problems on whatever I'm working on, that I then have to spend more time fixing.


It's also the procedure that is detailed in the factory service manual, with the warning that if you don't do it this way, and you get a illuminated brake idiot light afterwards, it's likely because the equilization was thrown off during bleeding, and the only way to fix it is to perform it the 'right' way as they specify. Obviously, it's less hassle to just do it the way they indicate from the start and not have to waste time bleeding the system over and over until the light goes off.

Advance has a Cardone one in stock.

If you do decide to get one from Advance, perhaps you can buy online and use their online coupon codes. Usually if the store has one in stock, you can choose pick up in store and get it in an hour. Nice way to save ~40% and/or get some filler stuff for free.

 

[willindsay]

The reasoning behind starting at the shortest line and ending with the longest is that any trapped air in the master cylinder will be purged out of the system through the shortest line first, so each subsequently longer line will only be bleeding out air from the line itself, and maybe some smaller amount of air from the master cylinder if there is any.

If you start with the longest line first, ALL of the air that is trapped in the master cylinder has to make it's way through the entire length of the longest brake line, in addition to the air in the line itself. This raises the possibility that a good bit of the air will not be purged until the process has been performed quite a few times. If you start with the shortest line, you're purging the majority of the trapped air sooner, and hopefully making things much easier for yourself.

With respect to the Explorer, this way of performing the procedure is in an effort to not throw off the ABS or proportioning systems. I'm sure that plenty of people just bleed brake systems however they feel like it, and perhaps the majority of the time it doesn't affect anything and it all works as it should afterwards.

However, I'm in the subset of people who are really particular about how they do vehicle maintenance, and I'd also rather do things in the most effective way, which hopefully also prevents me from causing problems on whatever I'm working on, that I then have to spend more time fixing.


It's also the procedure that is detailed in the factory service manual, with the warning that if you don't do it this way, and you get a illuminated brake idiot light afterwards, it's likely because the equalization was thrown off during bleeding, and the only way to fix it is to perform it the 'right' way as they specify. Obviously, it's less hassle to just do it the way they indicate from the start and not have to waste time bleeding the system over and over until the light goes off.

Thanks for the explanation it makes perfect sense. I now realize one crucial difference between this thread and the others I've read ya'll are talking about replacing the master where most of the others I read were just replacing pads and shoes.

Great explanation and sry to get the thread off topic. I'll sit back and wait to see what the fix is and hope I never have to deal with it myself.

 

[IAmTodd]

I return to this thread with my tail between my legs. I am very stupid.

This morning I went off to get my new master cylinder. A local indy store had a Cardone one for $30. Turned out to be a rebuilt Bendix, good news right? I got home, swapped everything over. Would have been a half hour job except removing the old fluid tank was mighty difficult!

I bled all the brakes working my way from the front to the back, got it all bolted up and on my test drive it was the same issue, zero improvement. With my tail between my legs I limped around the block and back into the garage. I decided that my next step was going to be to check the wheel I worked on before. Turns out I should have done that first as the adjuster dislodged itself. As those who remember my previous brake thread I have to service this side as it wasn't adjusting properly. I guess I didn't put it back together properly.

So with that back in place another trip around the block had a significant improvement but still pretty soft. I decided to take a trip out on the road and with a couple ABS assisted panic stop the pedal is firm once again and i have full braking power. I'm going to do another round of bleeding just to be on the safe side.

I need to learn to be more patient and check the simple things first. All said and done it was only $40 in parts and fluid so not a bad deal.

 

[Anime]

I'll sit back and wait to see what the fix is and hope I never have to deal with it myself.

All brake master cylinders eventually wear out and go, the only thing you can do to prevent it is replace them before they go out. With a high mileage vehicle, it's not a bad idea, or even just buying a new master cylinder when you see a great price on one to keep around as a replacement so you're not hunting one down when the one on the vehicle finally does go out.

Would have been a half hour job except removing the old fluid tank was mighty difficult!

The new master did not come with the tank? It should have. Nothing's really wrong with re-using the old tank on the new cylinder, but it's best to use new seals, putting the old seals in the new master cylinder doesn't always work so well and can eventually lead to a leak.

I decided that my next step was going to be to check the wheel I worked on before. Turns out I should have done that first as the adjuster dislodged itself. As those who remember my previous brake thread I have to service this side as it wasn't adjusting properly. I guess I didn't put it back together properly.

If the same drum adjuster/cable part keeps coming loose, I'd suggest just getting new parts for the rear drums. Full drum brake parts kits, and cables/adjusters are very very inexpensive. There are quite a few kits and cables/adjusters/plates on rockauto.com that are on clearance and very very cheap even with shipping if your local stores want too much.

With a brand new master it's not a bad idea to bleed a few more times even after a few days of use, both to clear out the lines so all new brake fluid is in there, and to release any remaining air bubbles. If you didn't bench bleed the master before installing, I would definitely suggest bleeding the system once every so often over the next few days/weeks.

 

[IAmTodd]

Master was bench bled before installation so no worries there. This was a separate issue with the rear brake. The first issue was a pinched adjuster cable. I had the adjust out when I fixed that and must not have gotten it fully seated. It ran ok for a few days.

It did not come with a new tank but the black rubber seals where the tank meets the master cylinder were new so no worries there. Leaks won't be an issue. I plan to bleed them one more time. I did some running around this evening and all is well, pedal is much firmer than before so this wasn't a total waste.

 

[huntman58]

Sounds like you know what the problem is but I would test yours any way to make sure.

If you replace nothing special just replace then bleed by what option you feel the best doing and or have the tools / help t do. You only have to worry about the ABS system if you already have air in it now and in that case if it was me I would do the MC bleed the best I can and take it in to have it flushed and the ABS bleed but that’s me.

 

[IAmTodd]

Not sure what you're getting at in your post but getting air out of the ABS pump is pretty easy. A quite panic stop on a gravel road will purge the HCU of air, bleed the brakes again and you're set. Starting completely dry might be a different story but not much air actually entered my system.

Been driving two days now and it's perfect as could be....for right now.

 

[ddoucet]

I have a similar problem, lost all fluid in MC reservoir, as well as braking ability. What's very strange to me is I can't find leak! I refilled MC with fluid, continuous pumping of brake pedal has no effect on reservoir fluid level???

 

[Rhett]

I have a similar problem, lost all fluid in MC reservoir, as well as braking ability. What's very strange to me is I can't find leak! I refilled MC with fluid, continuous pumping of brake pedal has no effect on reservoir fluid level???

The fluid could not have simply disappeared. There is a leak in the system somewhere. Your first task should be to find where the leak is. If a visual inspection of all the lines and fittings doesn't reveal the leak, then refill, bleed, and keep an eye out for leaks. Hopefully your MC isn't damaged from dry pumping.

One time I had a leak on the rear lines (going to the drums), and it leaked for a long time before I noticed it (I definitely noticed it when I lost pedal, but that took a while).

Another time I had a leak on one of the banjo bolts connecting to one of the front calipers. There the leak was obvious (fluid on the backside of caliper/piston assembly)

You will find it, just be eagle eyes!

 

[Mike65]

I have a similar problem, lost all fluid in MC reservoir, as well as braking ability. What's very strange to me is I can't find leak! I refilled MC with fluid, continuous pumping of brake pedal has no effect on reservoir fluid level???

Loosen the master cylinder bolts & pull the master cylinder forward a little & look in the brake booster it might be leaking out the back of the master cylinder & going into the booster so you see no leak, but are still loosing fluid.

 

[Centaurious]

I worked on a beautiful old Ranchero that smoked so bad it stopped all traffic behind it till the smoke cleared. Testing the engine showed great compression and everything seemed fine. Talking to the owner he said it just started doing this and it used no oil, but he had a brake leak and needed to add fluid every week or so. As you may have guessed the brake booster was 3/4 full of fluid and it had started sucking fluid into the intake.

 

[natenkiki2004]

Oh wow, I bet that was some good smelling smoke