a question about replacing the caliper on my front brake

How's everyone doing? This is my first post on the site. I have a 1983 XJ550 that I bought six months ago. Everything is going well, and the bike has been great. The front brakes have been making a little noise, and the mechanic who just installed a new back tire for me, said I need to replace the caliper.

Here's my question. Is this a difficult part to order for my bike and how hard is it to install. My friend who knows a lot about cars and a bit about bikes is going to help me, and I have the manuals as well as online help.

The guy at the garage said I'll need to bleed the brake fluid if I want to change the caliper. How hard is that, and do you need special equipment.

Any help/suggestions/advice would be great. Thanks.

 

Im not familar with the 550 but unless it's damaged you should be able to get a rebuild kit for the caliper instead of replacing it. Save alot of money that way. And yes any time you open the brake system up you will have to bleed the air out. You should look in the links section and see about getting the xjcd, has the owners & service manual. Plus lots of other good information on xj bikes. It's not that hard to do but if your not comfortable doing it yourself, remember these are your brakes and your LIFE!! get someone who knows what they are doing to help you out.
I'm sure someone will be along shortly to give more detailed information.
Good luck and welcome.
Be sure to post some pics. in the gallery so we can see your bike.

 

Why do you need to replace the caliper? Did the mechanic say anything specific about why to change the caliper. I rebuilt mine quite easily. No problem and very little money involved. Hard part is getting the piston out.
I spent $30 on a mityvac brake bleeder and recommend it heartily. These systems are bad about trapping air bubbles that are very hard to remove.

 

I asked him if the brakes were making noise because I needed to replace the pads, and then he took a look and said new pads wouldn't do it. He said the caliper was "collapsed," and that he'd have to order a whole new one.

The brakes currently work, it is just that they squeak. He told me they'd be fine for a few more months, but then I'd have to do something about them.

It sounds like the first thing I need to do is figure out if I just need to rebuild the caliper or actually purchase a new one. How would I figure that out?

 

R1/R6 Conversion

These calipers can be had pretty cheap off of E-bay. You'll notice the R1 discs as well. They bolt right on to the turbo front wheel with no mods. Probably would on any XJ actually. Some V-Max rotors will too.

 

I would get the opinion of another mechanic, I can't figure out what he is talking about when he says it's collasped.

 

I second the comment from jdrich48 - Collapsed?

The "noise" from the brakes is the pads vibrating on the rotor. It's annoying, but it means THEY'RE WORKING.

I'll be back in a few with some more tips on how to rebuild.

You can do this - If I can & I have done a couple of my own - YOU CAN.

 

Ok, I'm back. Let's see here... Where to start?

1) The ONLY reason you should replace the entire caliper is if the piston well is galled, meaning there is a corroded or scored patch in the well. To see if your caliper is working properly try this:

Put the bike on its center stand, jack up the front so the bike front wheel is up, & the back tire is on the ground. Look closely at the caliper for leaks or seapage. Hand spin the tire then apply the brake. You don't have to "Jam or lock up" the front wheel, but it should stop when you apply it. Release the brake & hand spin the wheel again. Does it rub? Is it hard to spin? When you release the brake, the brake piston should retract a bit & let the wheel/rotor turn free.

You've just done a quick trouble shoot for your front caliper.
a) no leakage - seals are still good & holding in brake fluid.
b) Wheel turns free after using brakes - piston moving back & forth correctly.

Have you ever had to "top up" the brake fluid in the cup? What's the color of the brake fluid? is it clear or more of an off yellow or amber color?

That should be good for now, then we'll go on to the next.
Isn't this fun?

 

Nice job Sammowry - crystal!

 

Very crystal. Can't say that for the mechanic. I would like to question him more as to what specifically "collasped". Sounds like a good way to get $200 for a $50 brake job! We call them yamarobbers for a reason. I just ordered a "complete" gasket set for my engine for $79. Yamarobber wanted $60 just for the head gasket.

 

Im not buying the 'collapsed' thing either.. The only thing I can think of he means is maybe it got dropped on the caliper and bent it in? I dunno.. But any way, I've overhauled the calipers on my truck, and the easiest way I've found to get the piston out is to use compressed air and a blowgun attachment.

You remove the caliper, take out the pads, and disconnect the fluid line. Then you put a thin piece of soft wood in the 'fork' of the caliper, put the nozzle of the blowgun into the fluid connector, and give it a puff of air. **WATCH YOUR FINGERS! THE PISTON WILL BLOW OUT HARD, AND IT WILL BITE YOU!!** (Thats why you put the wood scrap in there, to cushion the piston when it shoots out). Then you just have to work the piston out of the bore, pull the bore seal and clean everything before reassembling with the new seal.

Bleeding is easy too, especially on a bike.

- Top off the master cylinder so it doesnt go dry. if it goes dry, you have to bleed that too.

- Fill the caliper with clean fluid and reconnect the brake line.

- Attach a length of clear hose (or a one-man bleeder kit) to the bleeder fitting.

- Put an inch or so of clean brake fluid into a jar (or the bottle of a one-man bleeder kit) and submerge the end of the hose in it.

- Pump the brake lever several times, then, while squeezing it very hard, crack open the bleeder fitting VERY SLOWLY, a TINY BIT. Watch the fluid running through the clear hose. There will be air bubbles in it. As the fluid runs through, you will feel the brake lever soften. When it is almost touching the handgrip, close the bleeder fitting BEFORE YOU RELEASE THE LEVER. Make sure you keep topping off the master cylinder with FRESH brake fluid (DO NOT use spent fluid from the bleeding jar -- this will be contaminated). Give the caliper a couple whacks with the handle of a screwdriver to dislodge any stubborn air bubbles. Repeat this step until no air bubbles are visible in the clear hose. ANY air in the system will cause the brake lever to feel mushy, and your stopping distances will be greatly increased, so it is VERY IMPORTANT to to a thorough job when bleeding. Brake fluid is cheap. What's your life worth?

(Another way to bleed brakes is called "Gravity Bleeding". It works on older cars and trucks, but I've never tried it on a bike. All you do is leave the top off the master cylinder, open the bleed screw, and let the fluid fill the caliper. Gravity brings the fluid down, and since the bleed screw is on the highest part of the caliper, the fluid pushes all of the air out. Im not fond of this method, due to the fact that it takes hours. DOT3 brake fluid is extremely hygroscopic -- it very readily absorbs moisture from the air -- so leaving the system open long enough to complete a gravity bleed means it is absorbing moisture the whole time. Moisture in a hydraulic brake system can be deadly. Not only because it corrodes the system from the inside out, but also because when water is subjected to the extreme pressures in a hydraulic system (upwards of 3,000psi), it boils instantly, creating steam. A tube of hydraulic oil is, for all intents and purposes, a solid object. It does not compress, so 100% of the force you put on the top comes out the bottom. Steam does compress, reducing the transfer efficiency of the tube of oil. This creates a spongy feel in the brake lever, just like air will. So use this method at your own risk. Some swear by it, but I dont.)

-Matt

 

That's why I would never take my bike to a dealer for any kind of service.
I wouldn't want their 19 year old high school dropouts touching any important parts like the brakes or the engine.

 

Another Helpful item if you are bleeding the brakes by yourself. Speed bleeder is the way to go. There is a small one way check valve in the speed bleeder that allows you to just "pump" new fluid into the caliper, without having to "shut or close" the bleeder after every pump.

Dennis Kirk & other on-line m/c places have them for a few bucks.

TazManiac covered a "rebuild" very well - sounds like you've done a lot of them!

So what happened to the feller who started this Q & A thread anyways?

Sammowry.

 

Good call.. I forgot about SpeedBleeders.. I've owned all old trucks since I got my license... So yeah, I've overhauled a caliper or two..

 

How do you go about bleeding the master cylinder?

 

You would suck all the air-laden fluid out of the bleeder valve on the caliper. The only way I'm aware of. That or wait a heck of a long time for the air to find it's way back up past the check valve. I don't expect anyone to wait a week or two before riding so the obvious choice is to just bleed the system. With the RH model, the resevoir is very difficult to get at and requires a means to inject fresh fluid into a 6mm hole capped off by a bolt. Royal pain in the patoot. Just remember to keep topping it off as you bleed or you will have to start all over again. Good luck to you!

 

Well, see here's the thing. As I mentioned in another thread, I completely drained my system because there was some serious funk in the existing (I'm starting to think original) fluid. Now that it's all out of there, I tried putting new fluid in in part to flush the system, and in part to push the pistons out so I can rebuild the calipers. I have the reservoir topped off thanks to a 3cc syringe - it takes a while, but it works.

However I can't bleed the air from the system and I can't build any pressure either. What happens is this: If I open a bleed valve, squeeze the handle, and close the bleed valve and release the handle (the steps Haynes says to bleed the brakes - the steps that have worked before) no fluid is drawn from teh reservoir, and if I re-open the bleed valve for another go, it sucks in the air or fluid it just pushed out on the last go. So I'm gettign nowhere.

Searching the system lead me to this thread which mentioned bleeding the master cylinder as if it's different from bleeding the rest of the system, but my Haynes manual doesn't say anything different about bleeding the cylinder. So I don't know what gives.

You're saying I need to suck the fluid through somehow? Edit: Nevermind - MityVac, right?

BTW, waiting a week or two to ride? What's another week or two?

 

I was having a similar problem recently.
I pulled my calipers apart while rebuilding my forks, so my brakes were pretty much dry.
I tried all manner of new ways to bleed them including pushing fluid up form the bottom, but in the end I returned to the tried and true method for bleeding brakes.
There are 4 main steps.

Pump up the brakes,
Hold the brakes down/in,
Crack the bleeder,
Tighten the bleeder,
Repeat

Pump up the brakes, don't worry if there isn't any pressure at first.
After pumping, you hold the lever/pedal down, and crack the bleeder.
Allow the air/fluid to escape until the lever is fully in/pedal is fully down.
Close the bleeder, while holding the lever/pedal.
Release the lever/pedal, and pump it up again.

I had to start my bleeding at the "t" on the bottom of the triples.
I also forced fluid up from the anti-dive to fill the caliper first.
Do one fork at a time, start at the "t" and work your way down.
Bleed until no air bubbles escape from the nipples.
I bought one of those "one man bleeder" bits, which basically is a clear hose attached to a resevoir.
This allows you to see any bubbles coming out, and catch most of the fluid for reuse.
NEVER let the resevoir get empty, or you will be pumping air.
This method always works, every time.
I love to try new things, but always come back to this when bleeding brakes.

P.S. I use synthetic DOT 4 brake fluid, for a higher boiling point.
Do not use DOT 5 silicone fluid.
It only works in fresh systems with all new seals/rubber parts.

Nachoman

 

Thanks Nachoman. That's what I was doing. I guess I'm just not patient enough. Shouldn't I see the reservoir level go down, though? And why, when I crack the valve again, is fluid and/or air getting pulled back in? I really feel like I'm getting nowhere. I'll try again tomorrow.

 

I hated flushing and bleeding mine too, just one big pain. I totally understand why folks ignore it, but this is just one of those things you can't ignore, it's the front brakes for crying out loud. Yahoos. I use the old tried and true method myself, even after the pressure and vaccum methods. It just works better. Never had any luck with those one-way check valve thingies, they just let more air back in on each of the three gambles I took (guess I've got bad luck on these as they were all purchased at different times and from different vendors, or I'm plain retarded). Squeeze and close the valve has always worked for me. I don't have any faith in the process some folks use in cracking open a union half way between the reservoir and caliper. In my opinion, your just asking for trouble. If it isn't leaking before hand, you may well have one after, so why risk it? Take your time Eblo, this is one process you don't/shouldn't have to rush.

 

the easiest way to bleed a master cylinder is to attach brake line of some sort to the master cyclinder (I have an old piece w/ one end cut off) and stick one end in the res. of the master cylinder. just pump until no air bubbles can be seen. also never release the lever when the bleeder valve is open. I rebuilt my caliper and replaced the master cylinder on my 81 xj-550. pretty easy

 

the easiest way to bleed a master cylinder is to attach brake line of some sort to the master cyclinder (I have an old piece w/ one end cut off) and stick one end in the res. of the master cylinder. just pump until no air bubbles can be seen. also never release the lever when the bleeder valve is open. I rebuilt my caliper and replaced the master cylinder on my 81 xj-550. pretty easy

 

The easiest way I know of to bleed a master cylinder is to attach a piece of hose (I have an old piece of brake line W/ one end cut off ,make sure it is clean) to the master cylinder and stick the other end into the res. of the master cylinder. Just pump the lever until you no longer see air bubbles. OF course the master cylinder is kept full of fluid. When bleeding the caliper never release the lever when the bleed valve is open or you will suck air back into the system and have to start over. I rebuilt the caliper and replaced my master cylinder on my 81-xj-550.BTW I'm new (obviously) at this computer thing so i think posted this more than once,OOPS.

 

I don't know if this is good or bad, but its what I did.
When I took my caliper and flushed the system, I wasn't getting any fluid down to the caliper. So I detached the brake line and started pumping till fluid came through. Screwed it back onto the caliper and proceeded with the bleeding proccess. I had to add fluid to the Master Cylinder of couse, but it worked like a charm. I now have great brake pressure.

-Kevin

 

Any one have some advice on "flushing" techniques? I don't see anything in my Clymer.

thanks,

 

See this article for lots of really good information on brake bleeding. You'll have to adapt the procedures for motorcycle, but the fundamentals are still the same.

 

first thing is make sure the brake line goes up all the way to the master cyl
if the line has any down slope to it bubbles will collect in the high spot in the line and get trapped there
then take out the bleeder on the wheel cyl and put a few wraps of teflon tape on it so it can't suck air back in thru the threads
put the bleeder back in with a clear line to a clean container
fill the master cyl and keep it full
pump the lever and you should get bubbles in the master cyl , not many it doesn't pump much, it's going to take a while to fill the whole system
when fluid and bubbles start coming out the bleeder about 50/50, stop, close the bleeder, take a break let the air come up and the fluid go down
leave the bleeder closed and just wiggle the lever, should get bubbles at the master cyl, when the bubbles get very small like foam almost, take another break and move the lines so any air in them goes to the top
turn the bars or use tape or something to hold them there, let them set that way for ten minutes or so
wiggle the lever some more, till the bubbles get real small again, make sure the clear hose is in the brake fluid and open the bleeder
sometimes the fluid will just flow out with some bubbles, this is a good thing, keep the m.c. full and let it drain till the bubbles are gone, keep the clear hose in the fluid and squeeze the lever and let it snap back
it should pump more out the clear hose than it sucks back, when your satisfied no more bubbles are coming out close the bleeder
at this point the only air left in the system might be some small bubbles that didn't make it to the master cyl yet
the more vertical the line the less bubbles, move the lines around to let them come to the top
now you should have pretty good brakes, good enough to ride
try them out then move the lines as vertical as possible let it set over night and wiggle the lever the next day to get the last bit of air out
hay it works for me

 

I wrap the Bleed Nipple Threads with Teflon tape making sure the Bleed Hole is open.

Then, I attach a One-way Valved Bleeder into a Jar of Brake Fluid so NO Air is going back to the Caliper, what-so-ever.

As in the previous Posts ... I start the Bleed process by pumping-up the laever and holding it closed ... opening the Bleed Nipple to expel the air.

Once the Air is expelled, the Pumping will move the Brake Fluid through the system.
At that point ... I leave the Bleed Nipple OPEN and Pump Fluid through the Linds and Caliper until what is coming OUT is as clean as what is being replenished to the Master Cylinder all throughout the Bleeding process.

It takes a few minutes to expel the air ... the Bubbles travel down through the whole system and out the One-way Bleeder.
Once the air is out ... you're home free.
Each pull of the Brake Lever pushes fresh Fluid through the system and eventually out the submerged One-way.

I waste several ounces of Brake Fluid filling the Jar to keep the One-way submerged. But, is worth it for the nice, strong pressure that you develop when the process is done.

 

and i would imagine there are still more ways to do it
but we both overlooked the little geyser that erupts from the master cylinder

 

That only happens when you get too happy with the lever. Nice and slow and it won't shower you or the bike. Polock, Rick, what are your thoughts on converting to DOT5 (silicone) brake fluid?

 

My front brakes are giving the squeal of death, so I'm going to be doing a MC and caliper overhaul and putting some new stainless steel hoses on my bike this week, and I was thinking of this exact subject.. In my research I found this article on brake fluid which pretty much sums it up..

FLUID FACTS
To understand why moisture enters the brake system, you need to know something about the chemistry of brake fluid. Glycol-based DOT 3 and DOT 4 brake fluids are both "hygroscopic," which means they attract water. Leave a bottle of brake fluid open for several days and it will pull moisture out of the air like a magnet. This is one reason why vehicle manufacturers use glycol-based brake fluid: it disperses moisture that enters the system throughout the fluid to dilute the contamination. This prevents moisture from forming puddles in calipers or wheel cylinders that could boil and cause pedal fade if the brakes get too hot. The downside is that moisture lowers the boiling temperature of the fluid, increases its viscosity and promotes internal corrosion. That's why various chemical additives are put into the fluid to help it fight corrosion and oxidation.

All brake fluid must meet minimum performance standards established by the U.S. Department of Transportation (DOT). Most brake fluids usually surpass these standards, but it's important to know what the minimums are because of their potential impact on driving safety.

For all fluids that meet the DOT 3 specification, the minimum "dry" (contains no water) boiling temperature is 401° F and the minimum "wet" (saturated with water) boiling temperature is 284° F.

For all fluids that meet the DOT 4 specification, the minimum dry boiling temperature is 446° F and the wet boiling temperature is 311° F.


How do these numbers compare with most new brake fluids? For many years, Ford has used a special "high temperature" DOT 3 fluid with a dry boiling temperature of 580° F. General Motors, Chrysler and most "heavy-duty" aftermarket fluids typically have a dry boiling temperature of at least 475° F and some go as high as 550° F. By comparison, most DOT 4 fluids start out with a dry boiling temperature of 509° F or higher.

As you can see, most new fluids far surpass the minimum standards required by the DOT. This provides an extra margin of safety to minimize the risk of fluid boil and pedal fade in severe braking situations when the brakes get really hot. But, moisture contamination can quickly reduce the margin of safety.

According to some studies that have been done, brake fluid typically absorbs about one percent or more moisture per year of service life. Many two-year-old vehicles have as much as two to three percent water in the brake fluid. Imagine how much water must be in some vehicles that are six, eight or 10 years old and have never had the fluid changed!

As the fluid becomes contaminated with moisture, its boiling temperature drops. Only one percent moisture can lower the boiling point of some DOT 3 fluids down to 369° F. Two percent water can push the boiling point down to 320° F, and three percent can drag it all the way down to 293° F - which is getting dangerously close to the minimum DOT requirements.

Why don't the vehicle manufacturers simply switch to DOT 5 brake fluid that is silicone-based and repels moisture? One reason is that silicone brake fluid is very expensive compared to glycol-based fluids. Another is that silicone fluid contains more dissolved air and aerates more easily when pumped rapidly through small orifices that can increase pedal travel and reduce pedal firmness (a spongy pedal). Because of this, most vehicle manufacturers warn against using DOT 5 brake fluid in any vehicle equipped with ABS.

DOT 5 also cannot disperse moisture that enters the system throughout the fluid like DOT 3 and DOT 4 fluids. Any water that does get inside tends to "slug" and settle to the lowest point in the system, which is usually the calipers and wheel cylinders. Slugs of pure water are not something you want inside a brake system because they concentrate corrosion and increase the risk of pedal fade if the water gets hot enough to boil (it only takes 212° F to turn liquid water into steam).

Where DOT 5 fluid works best is in vehicles that sit for long periods of time (antique and classic vehicles that are stored during winter months or in a museum), or in vehicles that are operated in extremely wet environments (including off-road).

The best advice is to always follow the vehicle manufacturer's recommendations as to which type of brake fluid to use. For most vehicles, that's going to be DOT 3 or DOT 4 brake fluids.


I think I am going to be changing to DOT 4, since I will be starting with a completely clean and dry system. Seals and other components manufactured for use with DOT3 should be compatible with DOT4 because they are chemically similar, but that may not be the case with DOT5 - it may break down seals and O-rings designed for DOT3/4.

One other very important detail I came across that was left out of that article is that DOT 3/4 and DOT5 are chemically INCOMPATIBLE. If you mix the two, (even in very small amounts), they react with each other and form a thick sludge which will clog up your brake system. So that means you have to start with a completely clean (as in overhauled) MC and caliper(s), and brand new hoses in order to switch to DOT5.

 

don't

 

Upgrading from DOT 3 to DOT 4 is fine, but the rubber components of a DOT 3/4 system are generally incompatible with a silicone based brake fluid such as DOT 5 (New or old). You're best to just avoid DOT 5 all together. As Polock says, don't.

 

Thanks you for the efforts Taz! I appreciate everyones responses.

 

The DOT5 Fluid is Synthetic Fluid with a viscosity slightly higher than DOT4.

This "Brake Fluid" is used on the newer Cages equipped with Stability Control.
The Fluid has to act on hydraulic pressures many times stronger than generated by a Motorcycle Master Cylinder.

The "Pumps" pushing DOT-5 are so fast that their cycle rate is a frequency.
The DOT-5 Formula can be pressurized and released at those high rates without heating-up as much as DOT-3 & 4 do when the pressure allied to them is as fast as the rotary pumps using the stuff to control braking with a computer working the pumping.

The Workshop Manuals just say to use DOT-3 ... a Petroleum Product. Mixing the two wouldn't be a good idea ... some undesirable chemical reaction could mess things up for good.