Rear Brake Problem

[ActionJax]

Hello Everyone. New memeber here!

 

I've got a problem with my 83' Venture. I put it to bed last season and the back brake worked fine. When I got it out this past weekend I found that I have nothing...nada...no brake pressure nothing. I've tried everything. I've read over the forum, but I'm still puzzled.

 

I've added DOT3 brake fluid to all the master cylinders. I've tried bleeding the rear with a MightyVac and I can get fluid out (along with bubles) but still not brakes.

 

I've taken everything appart. I've blown through all the hoses. They all seem solid, no leaks. The only place that I think might be a problem is the piston on the pump. (if that's what its called.) It makes a strange "sucking" noise. I'm just not sure if that's what its supposed to do. LOL

 

Any help or advice would be great!

 

Thanks,

 

Jack H. in Akron Ohio

[sarges46]

I dont think there is supposed to be any bubbles at all. You may have to keep it up until all you get is fluid.

[bongobobny]

You do know that the back brake is also linked to the front left brake as well, right? It too has to be bled along with the back brake.

 

You may find that the rear caliper is seized up and needs rebuilding...

[ActionJax]

Not to be ignorant, but is there a way that I can figure out how the rear caliper might be siezed up? And are there any instructions on how to rebuild it? Cuz at this point I'm thinking that "might" be the problem. Everything else seems to work.

 

As for the front left one. I've bled that one just fine. Full pressure and a straight line of fluid comes out.

[timgray]

that strange sucking noise is pumping air.

 

if your under seat reservoir is full, then that can mean it's plugged at the bottom and no fluid is getting to the master cyl for brakes. You will need to take it off along with it 's hose and completely and CAREFULLY clean it up. at the same time check the Master for cleanliness. If you bleed the brakes a lot do you have to refill the reservoir a lot? It is incredibly easy to empty the reservoir when bleeding the brakes due to it only holding a tiny bit.

 

I suggest you also getting a new bottle of the DOT3/4 synthetic and completely change the fluid until it runs clear at all points when you are done, then bleed the brakes at all points again in 2 days.

 

Checking the calipers for seizing is simple. remove them, remove the pads, then try to push the cylinders back into the caliper. They should be stiff but move in nicely. DO NOT DO THIS without completely cleaning the calipers with brake cleaner and a toothbrush to remove any and all gunk and dirt from the pistons and the area around them. Pushing in a dirty piston will ruin the seal.

 

Note: you CANT push them in by hand. I use a very large cresent wrench and slow and steady pressure, you are pushing that fluid back to the master that is behind the piston through a teeny hole. If your pads are getting thin, you might as well replace them at this point as you just did 3/4 of a brake job.

Edited April 28, 2009 by timgray

[ActionJax]

I was able to push the rear calipers/pistons in last night. But what was interesting is that they were "almost" flush at the point "before" I pushed them in. They are completely flush now. But "how" do I get them to come back out? Depressing the brake peddle did nothing to the rear caliper. But I was able to get clear fluid to come out, but only as long as I was using a MightVac pump. When I use the peddle itself, I can only get it to spit bubles and some fluid. Mostly nothing happens. I'm really perplexed.

[MiCarl]

If you've got the air out it really shouldn't "spit bubbles" when you push the pedal. You are closing the bleed screw before you disconnect the mity vac?

 

If you pump the pedal (bleed screws closed) will it build up any pressure?

 

Was the reservoir full when you first opened it? If so, I suspect you need to rebuild the master cylinder (pump).

[ActionJax]

Ok, here's what I've done.

 

I filled the resevoir, put the MightyVac on the rear caliper. Pumped the gauge to about 20 and slowly turned the bleeder value. I can get fluid to come out. Now, if I push the peddle down, nothing. I'll close off the value and try pushing the peddle, and no pressure build up. So maybe it is the pump under the resevoir. Is it possible to just rebuild this part? Or will I need to purchase the whole thing?

 

And is there anyway to check the caliper too? I'd like to make sure its not locked into place and causing some problems also.

[Condor]

A couple of observations. If you're able to get the left front caliper bled properly, and it stays that way, and the rear is not responding, you may have a bad or plugged up proportioning valve. Also if you're not getting a pedal how did you bleed the front caliper without generating pressure. Mighty Vac?? On the sucking sound. You shouldn't be getting any. There's a down hose from the reserve to the master. Check to see if you're getting any flow thru it or if it might have developed an leak. It's gravity fed so there won't be any pressure. Also check behind the plastic fitting on the side of the master for obstruction. I suspect you may not be getting fluid to the master. Also if the brakes worked OK when you put'r away, and you didn't get any pedal when you took'r out of mothballs, what happened to the fluid?? Using a Mighty Vac with a leak in the system will suck air in. Check all your banjo bolt connections. You might need new crush washers??? Did I mentiion I'm not too fond of Mighty Vacs....

[ActionJax]

Condor,

 

As for the front left brake, you were correct, I used the MightVac since I couldn't get the peddle to do anything. And I always add more fluid after I'm done.

 

What exactly is a "proportioning valve?"

 

I really am beginning to think that there is something wrong with master. Just shouldn't be making that kind of sucking sound.

[skydoc_17]

Hey Jack,

Here's what you need to do to get that rear brake working again. The rebuild kit for the rear caliper is part # 31A-W0047-00-00 (approx. $20.00)You need one of these kits.

 

The rebuild kit for the rear master cylinder is part # 26H-W0041-50-00 (approx. $50.00)You Will need one of these kits.

 

I wanted to point out that you could buy the rear master cylinder assembly new for $430.00 if you got more money than time!

Get online, go to Flatout Motorsports, send an e-mail to Chris, tell him you are a VentureRider.Org. member and give him the part numbers. Here's the link:

http://www.flatoutmotorcycles.com/

 

Now for the "nuts and bolts" of this rebuild:

Remove the rear caliper, the rear brake line, the master cylinder AND the reservoir, the Proportioning Valve. To get the piston out of the caliper, I use cheap wooden paint stirrers from a hardware store. blow compressed air into the hole where the brake line connects to the caliper with 3 or 4 paint stirrers inserted where the brake pads go. when the piston contacts the stirrers, stop the air, remove one stirrer and do it again, and again removing one stirrer until you can get ahold of the piston and pull it out. (THIS IS VERY IMPORTANT!) Inside the caliper, one O'Ring is a "seal" and one O'Ring is a "wiper", They are different sizes, PAY VERY CLOSE ATTENTION to the order they are in the caliper, If you put them in backwards, the caliper will leak. Any decent auto parts store will have a "brake cylinder hone" for around $10.00 or so, get one. Put the hone in your drill motor, insert the stones in the caliper cylinder bore, add some lube, (honing oil is best, but motor oil works in a pinch) "blip" the drill motor a few times, (one to two second bursts at medium speed) You are trying to clean the bore, not make it a larger size. Remove hone, clean caliper with aerosol brake cleaner. Blow air thru EVERY HOLE in the caliper to make sure there is no blockage. Lightly buff or scotchbrite the piston to remove brake fluid "build-up. Sometimes there is a packet of red lube with the seal kit, Install the seals in the correct order, lube with red lube, (or brake fluid if no red lube) install piston, pads, clips, and you are done with the caliper.

 

Now for the master cylinder: Remove the single Phillips head screw that attaches the right angle black plastic tube that has the reservoir hose attached to it. DO NOT remove the hose from the black plastic tube or the reservoir, it is OLD, and it is pricey! If you damage it you WILL be buying a new one. (approx. $16.00)

HOSE, RESERVOIR Part # 26H-25895-50-00

Remove the Proportioning Valve.

I can not stress enough how important it is to throughly clean every part, hole and orifice, on the very small return pressure hole verify that the hole is clear by physically inserting a single strand of electrical wire into the hole. Do the same on the Proportioning Valve. Don't be "stingy" with the brake cleaner or the compressed air.

Here is where you are going to need a "good" pair of snap ring pliers. I got a set with interchangeable anvils at Sears for $28.00. Some places sell cheaper sets, but I use mine alot. Remove the internal snap ring at the bottom of the master cylinder. (VERY IMPORTANT!) There is going to be a half dozen or so pieces coming out of the master cylinder, PAY VERY CLOSE ATTENTION TO THE ORDER they came out. I personally laid them out in order, took a pic of the Assembly the first time I did it. With the guts out, you will use the brake cylinder hone again, but this time, you will use an "in and out motion" to hone the entire brake cylinder bore, don't forget the oil, slow to medium speed is better. After that , clean, clean, CLEAN! the master with brake cleaner and compressed air. If you have any of the "red lube" from the caliper left over, use it to lube the master cylinder bore, if not use brake fluid. Install the new parts IN THE CORRECT ORDER, install the snap ring, you will get a new boot for the bottom of the master cylinder install that and you are good to go. I found that "Speed Bleeders" helped the bleeding process, here is the link: http://speedbleeder.zoovy.com/

You don't have to have them, but it makes changing the fluid out in the future much easier. Reinstall all of your rebuilt parts, and bleed, bleed, BLEED! If you have questions, PM me. Sorry this got a little "windy"

Earl

[ActionJax]

Skydoc,

 

Thanks so much for the info. This is exactly what I was interested in knowing. I figured I was going to have to re-build something. LOL

 

And thanks for the pics. A photo really helps.

 

I'll order the parts today.

 

I'll let you know if I need more help once they get here.

 

Thanks again to everyone here.

[Venturous Randy]

I am with Condor on this, a Mighty Vac in some cases can hurt you more than it can help you. If you are not constantly keeping the reservior with enough fluid, you may easily start pulling in air.

I have also found that when getting a reservior started flowing that if I take the line loose right out of the master cylinder and use my finger as a check valve, that I can get flow started. This also works on the handle bar masters. That way you know you are getting fluid flow. These bikes can get a little hinky after being parked for a while. One spring many years ago I was ready to go for a ride and had no clutch release. I had plenty of fluid in the reservior and when I tried to bleed it I was not getting anything. I ended up taking the line loose and starting the bleed there and when I started pumping, I reconnected and bled the whole system.

After bleeding, the clutch worked fine.

I had a spare proportioning valve that we put on SGN's bike as his would not work correctly.

RandyA

[Rocket]

I am with Condor on this, a Mighty Vac in some cases can hurt you more than it can help you. If you are not constantly keeping the reservior with enough fluid, you may easily start pulling in air.

RandyA

 

That is why I use a plastic turkey baster, with the squeeze bulb off & the bottom lip filed off. I thread it into the reservoir opening & fill it most of the way up the tube, for filling / flushing the rear brakes. This way I can do more between refills & can easily see the fluid level. Once the brakes are good, I will continue bleeding until, the baster tube is empty, then I remove it.

 

[logan]

Hi:

I had this same problem, I think the rear master cylinder looses prime if you get even a bit of air in it. After hooking up the mighty vac and making sure there is fluid in the reservoir I pumped the rear brake real fast for about a dozen pumps and it finally took a prime. Problem solved. Bleed the rest of the air out.

 

Jim L

[6m459]

Thanks skydoc for the detailed info.

 

I am facing a rebuild like this on my red bike. Some or all of it I guess as the pedal just doesn't feel right.

 

Your write up is a keeper! I'll be printing it off for shop reference as I work.

 

Cheers,

 

Brian H.

[bongobobny]

OK mnobody explained the proportioning valve to you so I will. Bolted to the output of the rear master cylander is a round silver tubular looking device with the line to the rear brake also attached where it bolts into the master cylander thru a banjo bolt. The other side of this proportioning valve has the line that goes to the front brake. It's basically a spring and diaphragm device that, as soon as you build up pressure in the back caliper, the pressure overcomes the spring rate and opens up to the front brake, allowing pressure to build up in the front brake as well. You can take them apart and degunk them, and there are a couple of rubber seals but their replacements are not available. I've heard of people just removing the guts and using it that way. Downside of that is with the proportioning valve there is a slight delay between the rear brake engaging and then the front, a good thing, as opposed to instantaneous engagement without the proportioning valve...

[ActionJax]

Thanks! That's very informative. I took the proportioning valve apart last night too. Everything looks good in there. No gunk and the two rubber stoppers still look good.

 

I order the parts today from Flatout. Hopefully they'll ship quickly. I'm earger to get started on the rebuild, and back to riding.

[1BigDog]

SkyDoc hit it on the head. When I had my 83 I rebuilt all brake calipers and master cyl. However the rear brake would not work. No pressure. And I didnt have an air compressor at the time. What was causing the problem, which I found out many dollars later was a tiny orfice in the master cyl that was clogged. Once it was cleaned out I had brakes again. I now have that compressor.......

[ActionJax]

Ok everybody...I rebuilt the rear master cylinder and the rear caliper. Had a few problems, but I figured it out in the end. Everything looks and feels great now...except for one thing.

 

I STILL DON'T HAVE ANY REAR BRAKES!!!!

 

I even used the speedbleeders that where recommened. Nothing!

 

Its so strange too. I've got a good stream of fluid coming out of the rear caliper too. But no pressure on the peddle.

 

I bled the front brake too. And they work perfectly.

 

Any and all suggestions would be great! I hate to take this to a shop after I've done 90% of the work. LOL

[ActionJax]

OK, OK I guess I'm a bit dense. LOL

 

I went back and "re-read" all the posts, and went back to the beginning so to speak.

 

Wow, it's really funny "HOW" important that front brake really is, in order to get the back brake to work.

 

So, basically I went and bled the front brake...again...and sure enough, I got preasure on the rear brake too. Here I've been working all afternoon on the back and just ignoring the front. (BIG mistake!)

 

I guess you really do need to have both primed in order to get the rear brakes to work. Now the only thing is, I've got the rear to work, but I and they are stopping the bike...couldn't help but take a test ride...but I wouldn't say that they are great! Still seem to be a bit sluggish. So I think I'll wait until tomorrow and bleed the front, and then the rear again, and see if that doesn't improve them even more.

 

Oh, and the Turkey Baster idea...shear brilliance!

 

Thanks for all the help guys.

[Condor]

A lot of MKI owners seem to have a problem with the stopping power of the brakes on a '83. Personally I find them OK. Not 'lock'm'up' power, but they've never let me down...even in a few oh-crap panic stops. When all three calipers are grabbing you'll stop pretty quick, and not lock 'm up. Personally I think locking up the brakes is a not good.

[friesman]

That is why I use a plastic turkey baster, with the squeeze bulb off & the bottom lip filed off. I thread it into the reservoir opening & fill it most of the way up the tube, for filling / flushing the rear brakes. This way I can do more between refills & can easily see the fluid level. Once the brakes are good, I will continue bleeding until, the baster tube is empty, then I remove it.

 

 

Here is one of Rockets little tricks that he used on my bike when he flushed the lines.