Author Topic: Losing front brake fluid? (Read 4945 times)

Two-Bit · « **on:** April 12, 2014, 12:53:20 AM »

I have a 1976 CB550k. I lost my front brakes the last ride of last year. I refilled the fluid reservoir, and it lasted one ride for this spring. I can't tell where it is leaking from. I think it may be the brake caliper nipple (or lack there of), but I am not sure? I don't know if I even need one or not? I am learning as I go with the mechanics of this bike, so bear with me. Where should I check for leaks?

PeWe · « **Reply #1 on:** April 12, 2014, 01:02:25 AM »

Master cylinder, pump lever and look for leaks. I found small drops of brake fluid on my front fender, spraying when using the brake in the garage. Check around lever bolt where it pumps fluid.

I ordered new after market master cylinder from David Silver, cost not much more than a repair kit. Brake fluid on paint is not good.
I'll replace it this weekend.

Edit: Done!
http://forums.sohc4.net/index.php?topic=61168.msg1534248#msg1534248

Wollongongwolf · « **Reply #2 on:** April 12, 2014, 01:09:46 AM »

Just rebuilt my callip er a week ago on my 76 550, as no fluid in the master cylinder. Refilled it and found it leaking from the master cylinder. You can see the leak at the lever pivot point.
Ordered a kit to refurbish the master cylinder for $30 on ebay.
I am the worlds worst mechanic and the caliper was easy. This will be my first master cylinder, think it should be easy( touch wood) I have a manual and there are how to do videos on YouTube for the CB 550. I would do both calliper and master cylinder. I was given the same advice here and didn't listen, now it am repairing the master cylinder. Should always listen to the experts here I guess.

Two-Bit · « **Reply #3 on:** April 12, 2014, 01:14:29 AM »

Do I need a brake caliper nipple? I really don't remember having one in the 6 years I have owned the bike, but I could be wrong.

Wollongongwolf · « **Reply #4 on:** April 12, 2014, 02:49:07 AM »

Do you mean the bleed nipple? Must of broken off by the sound of it. You need it to bleed the brakes, you put a tube on the end so the fluid goes into a container so it doesn't go every where. The nut section must still be there, so you can bleed it, but a new nipple should be easy to get. Can you post a pic. I would do the brakes yourself. If you stuff up you can always take it to a professional.
As I said look on you tube.

Wollongongwolf · « **Reply #5 on:** April 12, 2014, 02:58:42 AM »

Hey Two Bit, see your from Iowa, I am frequent visitor to Des Moines from Oz, my favourite place in the States. Spent a great afternoon when last there at the the National Motorbike Museum in Anamosa.

calj737 · « **Reply #6 on:** April 12, 2014, 05:19:30 AM »

Quote from: Two-Bit on April 12, 2014, 01:14:29 AM

Do I need a brake caliper nipple? I really don't remember having one in the 6 years I have owned the bike, but I could be wrong.

Yes, you do need the nipple, or at least a plug in there. Most likely that is the source of your leak. Fluid will leak from there with the system under pressure, and will squirt from there when you squeeze the lever. Odd you didn't have fluid covering your shoes from the latest rides.

Remove any last bit of the old plug if it has broken off. Probably it's fully gone, so replacement is a simple fix. Fill MC, and set about bleeding your brakes. Once bled, snug the nipple back in the caliper and ride safely from there-

Don R · « **Reply #7 on:** April 12, 2014, 07:31:07 AM »

Not everyone knows but when bleeding if you pull the lever all the way back to the bar, fluid can get behind the boot seal on the master cylinder and then seep out/corrode the inside. When bleeding only pull the lever part way, the manual has a measurement.

Stev-o · « **Reply #8 on:** April 12, 2014, 08:26:24 AM »

What is a caliper nipple? You mean bleeder valve??

http://www.westernhonda.com/fiche_section_detail.asp?section=2451177&category=Motorcycles&make=Honda&year=1976&fveh=131088

Dr. Noisewater · « **Reply #9 on:** April 12, 2014, 09:30:59 AM »

Hey Don R, my master cylinder is doing just that. I rebuilt it a month ago, bled it (pulled all the way down) and now it sometimes leaks a little down the lever. What do you mean it will corrode the inside? Do I need to take it apart and re-do it or can I just bleed it correctly and be ok? If I need to take it apart can I reuse the same parts?

Sorry to hijack, had to ask.

sixthwisconsin · « **Reply #10 on:** April 12, 2014, 09:51:28 AM »

Two-bit,
If your bleeder valve is missing, you would not have any brake at all as there would be no line pressure. Take a look at a post I just did of my duel disk conversion and compare what your caliper looks like to mine.
http://forums.sohc4.net/index.php?topic=136241.0
The bleeder valve is the "nipple" with the rubber cap on it. Post up a picture of your caliper. Also, check your banjo bolts and see if you have leakage while the lever is being pulled.

Wollongongwolf · « **Reply #11 on:** April 12, 2014, 01:24:08 PM »

I have rebuild brakes on a couple of bikes and always pulled the lever to the bar and not had a problem, never heard that before. I guess when I rebuild the master cylinder, I will give it a go and not pull the whole way in.

strynboen · « **Reply #12 on:** April 12, 2014, 01:31:16 PM »

if the bleed nippel are broken off..it can be reparied...drill the bits aut..vitaut to dammage the threads...if threads are gone it still can be done..but takes a littel more work..if the seating for the nippel are gone..a new bottom seat must be drilled vith a special cut drill..have same degree as the botom tap..so it seal to the seat

Two-Bit · « **Reply #13 on:** April 12, 2014, 11:36:07 PM »

Quote from: on April 12, 2014, 01:31:16 PM

if the bleed nippel are broken off..it can be reparied...drill the bits aut..vitaut to dammage the threads...if threads are gone it still can be done..but takes a littel more work..if the seating for the nippel are gone..a new bottom seat must be drilled vith a special cut drill..have same degree as the botom tap..so it seal to the seat

I have this part still on. I just don't have the rubber piece that covers the tip of it. I know my terminology has been incorrect. Do I need the cap that goes on?

Wollongongwolf · « **Reply #14 on:** April 13, 2014, 02:36:59 AM »

No, just there to keep the dirt and crap out. All my bikes are missing their caps and they are all dirt bikes, so I would not think that is your problem. Time for a rebuild of brakes me thinks, keep you off the streets for a few hours.

Two-Bit · « **Reply #15 on:** April 13, 2014, 05:12:55 PM »

Quote from: Wollongongwolf on April 13, 2014, 02:36:59 AM

No, just there to keep the dirt and crap out. All my bikes are missing their caps and they are all dirt bikes, so I would not think that is your problem. Time for a rebuild of brakes me thinks, keep you off the streets for a few hours.

Thanks. I didn't think I've ever had the cap on it.

As soon as I get some time, I'll get out to the garage. Looks like I have a learning experience to look forward too.

Two-Bit · « **Reply #16 on:** April 16, 2014, 08:29:41 PM »

I had some time to check out the situation tonight. I filled up the reservoir with brake fluid, pulled the lever several times, and found that the brakes were working. I then looked for leaks but didn't find any. I went for a ride for about 20 minutes. I parked it in a spot in the garage where I could see on the ground if anything was leaking. I went in the house for about 30 minutes and then went out to check for leaks. I saw 1 drop on the ground. It was coming from the caliper area. I also noticed that the paint on the bottom of the caliper was gone. I then looked in my Clymer manual to see if I could figure anything out. I didn't. So... any ideas?

calj737 · « **Reply #17 on:** April 17, 2014, 03:23:39 AM »

If you can't identify the actual leak at the brake line fitting or from the bleeder valve then the only other possible culprit is the piston seal. There's a rubber O-ring inside the caliper that seals the piston. It sounds as though it has failed.

Remove the caliper from the bike (intact). Then disassemble the caliper (should be two large, fine threaded bolts) and remove the pads. With the piston still in the caliper, pull the brake lever and see if the seal leaks. Sufficient operation of the brake will ultimately push the piston out (this desirable anyway).

Examine the piston for corrosion or pitting (often a likely cause of leaks), remove the seal (small, squared edge ring sitting in a groove) and detach all lines. Piston should be shiny and perfect for best operation. If not, get a new one. Many members prefer the Phenolic ones sold by Godferrey.

Caution- brake fluid will eat paint with wild abandon, so protect the bike and catch all the fluid into a baggie or some other vessel.

Replace all worn parts. Upon re-assembly, be very gentle with the caliper bolts. Those fine threaded M10s have 1.25 pitch and will cross thread if you mash them together. A little anti-sieze or blue LocTite is recommended.

trueblue · « **Reply #18 on:** April 17, 2014, 03:42:20 AM »

If it has been leaking for a while follow the trail of missing paint. It will lead you to the leak. If not then fill it up, clean the area up around the leak (remember brake fluid washes off with water), pull the lever back hard to keep pressure in the line, and tie it back. I normally use a good sized lump of rag, but zip ties, rope or anything really will do. Let it sit for a couple of minutes then check. If it is as bad as you say it is, it should be apparent fairly quickly.

The other thing to do is pull the caliper off the bike, but don't disconnect the line at this point. Lift up the dust boot around the piston and see if it is wet under there. If it is dry then the piston seal isn't your problem, if it is wet then you have found the problem.

Two-Bit · « **Reply #19 on:** April 17, 2014, 06:08:57 PM »

Quote from: calj737 on April 17, 2014, 03:23:39 AM

If you can't identify the actual leak at the brake line fitting or from the bleeder valve then the only other possible culprit is the piston seal. There's a rubber O-ring inside the caliper that seals the piston. It sounds as though it has failed.

Remove the caliper from the bike (intact). Then disassemble the caliper (should be two large, fine threaded bolts) and remove the pads. With the piston still in the caliper, pull the brake lever and see if the seal leaks. Sufficient operation of the brake will ultimately push the piston out (this desirable anyway).

Examine the piston for corrosion or pitting (often a likely cause of leaks), remove the seal (small, squared edge ring sitting in a groove) and detach all lines. Piston should be shiny and perfect for best operation. If not, get a new one. Many members prefer the Phenolic ones sold by Godferrey.

Caution- brake fluid will eat paint with wild abandon, so protect the bike and catch all the fluid into a baggie or some other vessel.

Replace all worn parts. Upon re-assembly, be very gentle with the caliper bolts. Those fine threaded M10s have 1.25 pitch and will cross thread if you mash them together. A little anti-sieze or blue LocTite is recommended.

I'll try checking the piston seal when I get a chance. It seems like you may be right. I can't find any fluid anywhere else but under the caliper.

Two-Bit · « **Reply #20 on:** April 21, 2014, 10:49:56 PM »

Quote from: calj737 on April 17, 2014, 03:23:39 AM

If you can't identify the actual leak at the brake line fitting or from the bleeder valve then the only other possible culprit is the piston seal. There's a rubber O-ring inside the caliper that seals the piston. It sounds as though it has failed.

Remove the caliper from the bike (intact). Then disassemble the caliper (should be two large, fine threaded bolts) and remove the pads. With the piston still in the caliper, pull the brake lever and see if the seal leaks. Sufficient operation of the brake will ultimately push the piston out (this desirable anyway).

Examine the piston for corrosion or pitting (often a likely cause of leaks), remove the seal (small, squared edge ring sitting in a groove) and detach all lines. Piston should be shiny and perfect for best operation. If not, get a new one. Many members prefer the Phenolic ones sold by Godferrey.

Caution- brake fluid will eat paint with wild abandon, so protect the bike and catch all the fluid into a baggie or some other vessel.

Replace all worn parts. Upon re-assembly, be very gentle with the caliper bolts. Those fine threaded M10s have 1.25 pitch and will cross thread if you mash them together. A little anti-sieze or blue LocTite is recommended.

I went for a ride tonight. I parked the bike in the garage and went inside for about an hour. I went back out to the garage and found about an inch in diameter of brake fluid. It is coming from the caliper. Now, where is the best place to order an O Ring for a 1976 Honda CB550K?

Stev-o · « **Reply #21 on:** April 22, 2014, 02:43:22 AM »

http://www.ebay.com/itm/OEM-Honda-Brake-Caliper-Piston-Seal-CB550-CB750-CB450-CB500-CB350-CB360-CB400-/261450266012?pt=Motorcycles_Parts_Accessories&hash=item3cdfa6759c&vxp=mtr

trueblue · « **Reply #22 on:** April 22, 2014, 03:16:35 AM »

Before you order parts pull it apart and see if you need a piston as well. I find best for srice and service is Dave Silvers Spares

calj737 · « **Reply #23 on:** April 22, 2014, 05:11:09 AM »

David Silver's is a good place for stock pistons. But I'd encourage you to upgrade to a Godferrey phenolic piston. He's got O-rings too. Perform better and will never rust. Cost is pretty much a wash too.

Two-Bit · « **Reply #24 on:** April 22, 2014, 12:46:46 PM »

Quote from: trueblue on April 22, 2014, 03:16:35 AM

Before you order parts pull it apart and see if you need a piston as well. I find best for srice and service is Dave Silvers Spares

Yes, I will for sure take it apart before I order parts. Now, if I cant just find more time to do it. Where can I order that?

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Author Topic: Losing front brake fluid? (Read 4945 times)