New SMC and brake bleeding blues

SMSW said:
Looks like a good tool. My preference is for something that pulls fluid out of the master cylinders. I can see using the reverse bleed procedure to over fill the master cylinder and spilling brake fluid all over everything. Of course I put plastic, an old towel, and more plastic on top of the tank and painted surfaces, but spilling fluid out of the master cylinder reservoir would still make a mess. My pref only.
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If you bleed through the front caliper all the way to the rear caliper and use the bleed screw on the rear caliper with the Motion pro or other bleeding device with a check valve you will not overfill the master cylinder. You can always take the fluid out of the master cylinder reservoir if you are worried about over filling. I don't have any problem spilling. I have both vacuum and pressure bleeders, on the linked brake system the pressure bleeder works better than anything I have used before. Both vacuum and pressure bleeders have their applications depending on the type of system.
 
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After reading this thread, I decided I needed to finish bleeding my 2004s brake system. I started working on it two years ago, but due to my move and all that's happened since, every time I got close to doing it, something else got in the way. But I finished it yesterday, took me a couple of hours, since trying to get anything done in my "shop" right now is next to impossible! :rolleyes:
 
I think that the tool pressures fluid through the system from the reservoir. If that is correct, it should work well. I had one that someone gave me years ago, but it had no adapter which would fit the cap on either the front or rear reservoir, so I never got to use it. The link seems to indicate that this device has adapters for motorcycles.


Regarding the pressure bleeding method from a bleed valve to the cylinder. Some thoughts that are worth considering :

There are a few places in the system where flow through the lines is a tad restricted in the reverse direction, and a few places where fluid cannot flow through the normal channels.

1 - All master cylinders and pistons will only allow fluid through the compensation port in the 'wrong' direction. The primary seal does not yield to pressure coming from the caliper. This means that filling from bottom up will move fluid slowly through the tiny compensation ports, and will not move fluid at all between the inlet port and the primary seal in all three master cylinders. There will be a pool of old fluid surrounding the piston which will remain unflushed. This is a crucial area to exercise and refresh - particularly in the SMC. The one way valve in the filter of the inlet port of the SMC will prevent any fluid passing through in the 'wrong' direction. That filter needs to be properly flushed with fresh fluid, which won't happen using the pressure method.

2 - The delay valve that turns off the flow to the front right centre piston is only operated by pressure from the pedal.

3 - The release of pressure from the rear outer pistons - which is the safety mechanism provided by the proportional control valve - is only operated by pressure from the pedal or SMC.

I'm not saying that it would be wrong to push fluid through from the bottom, but you need to be aware that this method will likely leave old fluid in places that you really need to flush out. So finishing off by pumping fluid in the normal direction, for me, would be a necessity.

It is also worthwhile noting that fluid pumped up from below is still capable of leaving air bubbles trapped in certain places. I hate using the vacuum pump, but it maintains a good steady flow of fluid while I exercise and tap the places wher bubbles are likely to be hiding - with no risk of the bleed tubes being blown off.
 
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bdalameda said:
If you bleed through the front caliper all the way to the rear caliper and use the bleed screw on the rear caliper with the Motion pro or other bleeding device with a check valve you will not overfill the master cylinder. You can always take the fluid out of the master cylinder reservoir if you are worried about over filling. I don't have any problem spilling. I have both vacuum and pressure bleeders, on the linked brake system the pressure bleeder works better than anything I have used before. Both vacuum and pressure bleeders have their applications depending on the type of system.
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My dad made us a similar device ~50 years ago out of an thumb oiler and a piece of rubber tubing when we had a particularly difficult time bleeding the brakes on an MG roadster that was my first car. He was an aircraft mechanic and there were certain hydraulic lines on airplanes he worked on that were bled from the slave cylinder back to the master cylinder so we cobbled one up to see if it would work. It worked and there is no reason one couldn't use one today if the traditional method is not yielding results. Sometimes with a new or completely empty master or slave it's the devil to get enough fluid through so that you can even begin to bleed the system. If you are concerned about points that John raised then rigorously bleed the system from the top after getting the system working in the first place.

If you don't remember what a thumb oiler is it looks like this:

1650468478067.png

A piece of hose the right ID slips over the bleeder on the caliper or slave cylinder and the tip of the oiler and you pump fluid uphill under pressure instead of down hill. My dad worked on everything from Model Ts to F-105s and he probably forgot more about wrenching than I'll ever learn.
 
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dduelin said:
My dad made us a similar device ~50 years ago out of an thumb oiler and a piece of rubber tubing when we had a particularly difficult time bleeding the brakes on an MG roadster that was my first car. He was an aircraft mechanic and there were certain hydraulic lines on airplanes he worked on that were bled from the slave cylinder back to the master cylinder so we cobbled one up to see if it would work. It worked and there is no reason one couldn't use one today if the traditional method is not yielding results. Sometimes with a new or completely empty master or slave it's the devil to get enough fluid through so that you can even begin to bleed the system. If you are concerned about points that John raised then rigorously bleed the system from the top after getting the system working in the first place.

If you don't remember what a thumb oiler is it looks like this:

1650468478067.png

A piece of hose the right ID slips over the bleeder on the caliper or slave cylinder and the tip of the oiler and you pump fluid uphill under pressure instead of down hill. My dad worked on everything from Model Ts to F-105s and he probably forgot more about wrenching than I'll ever learn.
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Yes I have used these oil can pumps before. The old oil can pumps were made well and good quality. Unfortunately the only ones available now are made in China and are just junk. I've tried using them with limited success.

Funny you should mention that you father did this on aircraft. I used to have a Bellanca Viking that I had to reverse bleed the brakes as this was the only way I could get the brakes to bleed properly.

You are right about starting to bleed a completely dry system, especially with an SMC and linked brakes. This is how I discovered this other method for bleeding as I had replaced the foot pedal master cylinder as well as rebuilt the SMC and all the calipers. I was have the devil of a time getting the SMC circuit to bleed properly. I have this pressure bleeder that I use on my Wife's new Volvo for bleeding the brake system so I decided to try it. I was amazed when I bled all the way through to the rear caliper. It flushed the system very well and removed a lot of debris from the whole system. It bled immediately and had a firm pedal right away. In the literature for this bleeder it says that often a reverse bleed can more easily remove air bubbles or trapped air from the system as you are bleeding from low to high which makes it easier for the bubbles and trapped air to migrate out of the system. Trying to either push or pull the trapped air down and out in the conventional way can be difficult in some systems.
 
dduelin said:
While I agree the Honda combined braking system is overly complex it never gave particular trouble to maintain in the ST1300 or Goldwing which is also a similar Rube Goldberg 1980's design. Flush and bleed every 12,000 miles or 12 months and inspect rear wheel free rotation OFTEN if not every ride in the pre-flight routine by giving the rear wheel a foot shove while on center stand. Any dragging is apparent before it becomes a serious problem.

I am glad that I used then copied leo7x24's tech article Brake/Clutch Hydraulic Fluid Flush/Bleed to a pdf when it appeared in 2006. That tutorial is easy to follow and gives outstanding results. I still share copies of it a few times a month when someone asks for it.

My NC700X and RT both have linked ABS systems and it adds NO complexity to a flush and bleed.
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Would you be so kind as to send me that tech article PDF? jvojir9@gmail.com Much appreciated!
 
Some articles of mine that you may find useful.

I used to find the Vaccum pump very useful for getting fluid through the system - but it is useless for bleeding air out - because it sucks air past the threads. I always finish off with the tube and the one way bleed valve. Also the technique of pumping up the pressure in the line, holding the lever in and then opening the bleed valve is well worth using - the residual pressure pushes fluid out while keeping the route back to the reservoir closed.

The first link is all to do with the plumbing and ways of chasing the air out of the system. The others are also related to brake maintenance and service.


Article [13] - ST1300 - Brake Maintenance - Getting all the air out of the brake system | ST1300 Articles

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Article [13] - ST1300 - Brake Maintenance - Replacing the Secondary Master Cylinder (SMC) | ST1300 Articles

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Article [13] - ST1300 - Brake Maintenance - SMC Boot Fitting - A Cause of Failure ? | ST1300 Articles

The rubber boot on the ST1300 Secondary Master Cylinder is designed to keep water out. Unfortunately, since you cannot see what you are doing when fitting the rubber boot, it is entirely possible that casual maintenance can result in allowing water to be let in. I made reference to this in the...
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Article [13] - ST1300 - Brake Maintenance - Avoiding the Pitfalls | ST1300 Articles

A close hands-on look at the Honda ST1300 braking system. These are personal observations about the things that can go wrong, why they go wrong and what can be done to keep things working sweetly. Updated April 2020 and to address more recent observations, to include information about the SMC...
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