clogged wheel cylinder

[waveandwen]

Folks, a little of your vast experience is requested.

My BN4 has a chronic air in the brake line issue. I am about to rebuild all cylinders. However, past attempts have identified a blocked front wheel cylinder bleed screw orifice. With the bleed screw entirely removed (obviously clear) the opening within the cylinder is completely clogged. Many attempts, short of drilling it out have failed to clear the lodged obstruction.

Any reasonable method to clear this or am I into a new cylinder ? Plan to try again this weekend.

Thoughts ?

Dave.

 

[Randy Forbes]

At the very least, you should consider rebuilding the wheel cylinders. If debris is clogging that one, you likely have "stuff" floating in the rest of them too.

Once you're down to that point, clearing the obstruction should be a simple task.

This may sound dumb, but you do have the tube connecting both cylinders (on one wheel) in place, don't you?

Talking strictly about one wheel; the feed from the master cylinder comes into wheel cylinder "A" and then a tube leads from it (at what would be a bleed screw location) to wheel cylinder "B" and only this wheel cylinder has a bleed screw to exhaust any trapped air in the circuit.

I only mention this to be certain that you're not expecting something to come out of a wheel cylinder that doesn't have anything going into it

 

[aeronca65t]

If it's *that* clogged, you'd best remove it and clean it properly in parts cleaner, hone it, and then rebuild it with new seal (or better yet, buy a new one if they're reasonable).

Be sure that your flex line to the front brake isn't collapsed and internally clogged....I've seen this happen twice on Sprites.

 

[Dave Russell]

Dave,
On some of the early cars there was a steel ball under the bleed screw. It may be that the ball is stuck to it's seat & this is the obstruction that you are seeing. If so, try to work the ball loose & push it out from the inside. Air pressure or a soft wire might work.

As an aside, when you reassemble things make sure that the ball is not under the brake line fitting instead of under the bleed fitting. This can happen if you interchange front & rear cylinders on the front brakes.

Good luck,
D

 

[waveandwen]

Randy,

Thanks for the thoughts. The clog was found during the last rebuild of the cylinders. It's in "wheel cylinder B"; the one with the bleed screw. Rather than damage it, I honed it, replace seals and bled it by "cracking" the fitting leading into the cylinder where the tube from the other cylinder enters. Worked OK; a little messy though. However, now that I'm doing again, I thought I would try more dilligently to remove the obstruction.

Whatever it is, it's stuck pretty good. Last time had me attempting to pick it out from the outside, push it out from the inside to no avail. I am considering a small drill bit this time. If this fails, sounds like a new wheel cylinder.

Thanks, Dave.

 

[waveandwen]

Thanks for the input. Drove to Moss and picked up a new wheel cylinder (immediate gratification is wonderful thing). The ball bearing providing the seal for the bleed screw was firmly lodged in place.

Everything now fine after a full day of bleeding. Only issue is the new bleed screw of the purchased wheel cylinder is of the metric variety. Not a big deal I guess; but now there is one, and only one, metric wrench required to service. Oh well, the price of progress ?

Thanks for the help.
Dave.

 

[Randy Forbes]

<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by waveandwen:
Thanks for the input. Drove to Moss and picked up a new wheel cylinder (immediate gratification is wonderful thing). The ball bearing providing the seal for the bleed screw was firmly lodged in place.

Everything now fine after a full day of bleeding. Only issue is the new bleed screw of the purchased wheel cylinder is of the metric variety. Not a big deal I guess; but now there is one, and only one, metric wrench required to service. Oh well, the price of progress ?

Thanks for the help.
Dave.<hr></blockquote>

I just replaced the rear wheel cylinders on my car. They too had Metric sized bleed screw heads; the port threads were still 3/8 fine thread. I replaced the Metric ones with some decent old ones I had.

 

[waveandwen]

Randy,
I too thought of replacing the bleed screw with a spare. Problem is, all the old ones around are of the older ball bearing sealing type and not the newer self sealing variety. For now, I'm stuck with the metric wrench requirement.

The master cylinder is next; I'm sorry that I assumed it to be OK, it's not.

Anyone have experience with the "Easy Bleed" system. A pressurized resevoir that attaches to the master a uses this pressure to force barke fluid through the lines onces a bleed screw is opened. The small master resevoir on my BN4 requires refilling so often during bleeding the job becomes quite excrutiating.

 

[Randy Forbes]

<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by waveandwen:

Anyone have experience with the "Easy Bleed" system. A pressurized resevoir that attaches to the master a uses this pressure to force barke fluid through the lines onces a bleed screw is opened. The small master resevoir on my BN4 requires refilling so often during bleeding the job becomes quite excrutiating.<hr></blockquote>

I use an Easy Bleed with good results. I sugest running it off of a spare tire with only about fifteen (15) PSI instead of the left front tire with nearer to thirty (30) PSI though. The higher pressures make it harder to get a good seal at the adapter to resevoir mating surfaces.

I also suggest that you test the integrity of that seal (applying your 15 PSI) BEFORE you put brake fluid in the Easy Bleed bottle. I'm telling you these things as a result of (bad) experience...

Other than that, it works just fine.