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possible clogged brake bleed screw?
Posted by: vairTer ()
Date: January 22, 2022 12:45PM

I've been working on flushing my brake lines after 3 years and I got to the last wheel (LF) and no fluid comes out the bleed screw, even if I open it a full turn. The other 3 wheels had no issues. I'm using a Motive pressure bleeder to pressurize the MC to 15 psi.

The MC is a dual reservoir unit.

• Am I going to have to fully drain the reservoir for the front wheels in order to prevent having a fluid mess created when I remove the bleed screw for repair/replacement? Will fluid immediately start to drain as I remove the old bleed screw?

• Is draining of the MC reservoir going to trigger the need for a bench bleed of the reservoir?

• Am I better off replacing or trying to clean out the old bleed screw? If I get a replacement that can be slapped on quickly, can I avoid draining the MC in advance?

• Can anyone recommend particular bleed screws that might work well as a replacement?

1966 140 Monza PG convertible
Ventura County, CA

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Re: possible clogged brake bleed screw?
Posted by: solo2r ()
Date: January 22, 2022 01:04PM

Just get an appropriate size drill bit and go for it! It will not all leak out ....take the pressure off the Motive!

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Re: possible clogged brake bleed screw?
Posted by: RexJohnson ()
Date: January 22, 2022 01:17PM

If you remove the screw brake fluid will come out. If you first fill up the reservoir and then put the lid on with the clip wire as the fluid drains it will create a suction and slow the draining of the fluid. This will not stop the draining but slow it down. Find a plug to put in the open hole and slow in down even more. I have opened up a lot of plugged bleeder screws. I use small drill bits. Sometimes if the dirt is really packed in there, I will use the bit in a power drill, but I try by hand first. For the outside I use a wire wheel to clean that up and then a little anti-seize to help keep it from happening again. If it takes too long to get the bleeder cleaned up top off the reservoir and don't let it run dry or you will need to bench bleed the master cylinder.

RJ tools
Salem,Oregon

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Re: possible clogged brake bleed screw?
Posted by: vairTer ()
Date: January 22, 2022 01:59PM

Will some of the draining brake fluid make its way into the drum area and possibly foul the shoes?

The Clark's bleeder screws seem cheap enough ($2.30 + shipping) for me to just go ahead and buy one to slap right in when the old one comes out. Does anyone have experience with these:

[ssl.corvair.com]


Another question: is it a no-no to put any anti-corrosion product on the threads of the bleed screw, lest it come into contact with brake fluid?

Terry

1966 140 Monza PG convertible
Ventura County, CA

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Re: possible clogged brake bleed screw?
Posted by: The Stig ()
Date: January 22, 2022 02:09PM

Don't make too big a deal of this. Take the screw out. Clean it with a small drill bit - by hand. Takes thirty seconds. Re-install. Move along.

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Re: possible clogged brake bleed screw?
Posted by: steve c goodman ()
Date: January 22, 2022 02:25PM

It is possibly the small hole in the wheel cylinder under the bleeder screw plugged.

Quickly remove the bleeder valve and use a 5/64" drill bit into the wheel cylinder to ensure the port is open. Only a little fluid will run out if you have the drill bit in hand, the check will only take 30 seconds. Place a paper towel under wheel cylinder to catch any leakage.

best wishes, Steve
Rear Engine Spec. Inc. Golden, Colo.

1962 spyder 3.0L turbo---1965 Crown V8
1967 monza 110/4---1968 monza 110/4
1971 amante gt 110/4
CORSA/RMC/PPCC/V8 Registry

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Re: possible clogged brake bleed screw?
Posted by: vairTer ()
Date: January 22, 2022 06:27PM

a 5/64" drill bit poked into the bleed screw did the trick. didn't even have to remove the bleed screw-the clog must have been in the axial passageway.

thanks, Steve and others, for your helpful suggestions.

brakes are happy again, for 2-3 years.

1966 140 Monza PG convertible
Ventura County, CA

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Re: possible clogged brake bleed screw?
Posted by: Frank DuVal ()
Date: January 22, 2022 08:52PM

NO-no or not, I have put a SMALL dot of never-seize on the threads of bleeder screws here in the rusty est. On every car I work on when I remove the bleeder, drum or disc. I keep the Never-seize away from the first thread, but, it seems to get everywhere.....grinning smiley

On sloppy fitting bleeder screws, I have even put a turn of PTFE tape on them so I can use the Mighty-Vac to bleed the system.eye popping smiley I don't remember this problem on Corvairs. I reason the PTFE shards will never get through the small hole into the hydraulics of the system.

Frank DuVal

Fredericksburg, VA

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Re: possible clogged brake bleed screw?
Posted by: American Mel ()
Date: January 22, 2022 09:29PM

Frank DuVal Wrote:
-------------------------------------------------------
> NO-no or not, I have put a SMALL dot of never-seize on the threads of bleeder screws here in the rusty est. On every car I work on when I remove the bleeder, drum or disc. I keep the Never-seize away from the first thread, but, it seems to get everywhere.....grinning smiley
>
> On sloppy fitting bleeder screws, I have even put a turn of PTFE tape on them so I can use the Mighty-Vac to bleed the system.eye popping smiley I don't remember this problem on Corvairs. I reason the PTFE shards will never get through the small hole into the hydraulics of the system.


I was having a similar problem once when using a vacuum bleeder.
It was simply sucking air from around the bleeder.
I mentioned it to a friend and he suggested that I apply some plain ole suspension grease around the outside of the bleeder.
Worked like a charm, as the grease was too thick to get sucked in there, and it was less resistance to pull brake fluid, than grease. thumbs up

-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
WA. state, 1 mile south of the Canadian border, I am not at the end of the world, but you can see it from here.

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Re: possible clogged brake bleed screw?
Posted by: Lane66m ()
Date: January 23, 2022 05:15AM

I put the anti-seize on, then wipe off with shop towel so a glistening of the compound is left. When finished, I put rubber caps over the bleeder to keep dirt out.


(25 Pack) Brake Bleeder Screw Caps Grease Zerk Fitting Cap Rubber Dust Cover

[www.ebay.com]

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Re: possible clogged brake bleed screw?
Posted by: jjohnsonjo ()
Date: January 23, 2022 06:09AM

They now have SS bleeders for nearly every size. Al the last of those caps I bought turned into a mess after two years. The factory GM ones last almost forever. I want to Russel bleeders, much easier than vacuum bleeding. I will go down to the garage and get the part number if anyone wants it

J.O.

65 Corsa Turbo Vert
79 Honda XL 500S
69 Honda CL 160 D
2010 BMW F 650 GS
2003 Bounder 36D
2013 KIA Optima SX turbo-AKA ZIPPY (wife,s car)
69 Newport Holiday Sailboat
Baja 150 dune buggy cart
Coleman HS 500 UTV
2016 KIA Sorento SXL Turbo

Bethlehem,Pa


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Re: possible clogged brake bleed screw?
Posted by: Lane66m ()
Date: January 24, 2022 03:26AM

I have a set of unknown caps on the More Door bleeders. Still going good after 3 years. But they are not a soft style of rubber.

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Re: possible clogged brake bleed screw?
Posted by: Wagon Master ()
Date: January 24, 2022 05:11AM

Just had one of those aha moments that I seldom get anymore. We've all bled brakes for years and we know how all that goes. Let's look at what happens when you tighten up bleeder screw down the last time. The taper on the end of the bleeder screw seals against the seat and seals off everything on the outboard side of that seat. Which is full of brake fluid including the threaded area clear up to where it exits the screw. What does brake fluid do? It attracts moisture. I wonder if we started giving them a short blast of air with a rag wrapped around them to protect the paint if that would help?

Friends Don't Let Friends Drive Stock
Been Aircooled Since 1973
Northwest Ohio 45840

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Re: possible clogged brake bleed screw?
Posted by: joelsplace ()
Date: January 24, 2022 08:58PM

That is a good idea Wagon. I think maybe a shot of contact/brake cleaner would be better since it would get rid of all the fluid and leave nothing behind.
I usually blast mine with a water hose since it will rinse away all the brake fluid.

Joel
Northlake, TX
5 Ultravans, 138 Corvairs and counting...




Edited 1 time(s). Last edit at 01/24/2022 08:59PM by joelsplace.

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