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1970 Deville front Caliper Bleed Screw

Started by colorado4x4, May 22, 2021, 09:36:40 PM

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colorado4x4

So of course, a simple brake pad change can never be go as planned.  The bleed screw on the passenger side caliper of my 1970 Deville broke off.

Tried drilling a hole for an extractor but that didn't work as it broke off also. Was able to get the broken extractor out but now the drilled hole is larger.  I don't think I have damaged the caliper with the drilling. 

The bleed screw in better days takes a 3/8 wrench, any intel on what the actual bleed screw thread hole/tap size is?  What does the inside of the bleed port look like when all is right with the world?

Should I try and re-tap at the original thread size (what ever that is)?  Take the caliper to a machine shop and have the broken screw milled/drilled out? 

Anyone have ideas on what they have done in this situation?

Rocky Mountain Region Membership Chair & Treasurer
1970 DeVille Convertible Chateau Mauve Firemist
1970 DeVille Convertible Lanai Green Metallic

chrisntam

I'd get a rebuilt caliper.  Is one available?
1970 Deville Convertible 
Dallas, Texas

Cadman-iac

Nicholas,

The end of the bleed screw is tapered to seal off the passage when seated. As for the thread pitch and size, there were at least two different sizes that I know of, depending upon the manufacturer and year.
I would have to check a few of the extra bleeder screws I have for the sizes. You could try removing the one from the other side to check the size, and but that may create double the problem if it is also stuck.
If you do try drilling it out to remove it, if you hit the seat it will render the caliper useless. I don't believe that the seat is replaceable like the ones in a steering gear box.

  Rick

 
CLC# 32373
1956 Coupe Deville A/C car "Norma Jean"

Cadman-iac

Nicholas,
  I found the extra bleeder screws I have, and here's a picture of the various sizes. I don't know which one you have, but,  the two on the left have the same thread as a fine thread 3/8" bolt, or 3/8-24.
The smaller one next to those is a 5/16-24 thread size. The last one I can't tell. I believe it's metric, but you won't have that on a 70 anyway.
If you manage to get the rest out and have to clean up the threads in the hole, you could use a tap of the correct size, but be extremely careful that you don't go in too far and hit the seat. If that's messed up, you'll have a leak you can't stop.
Hope this helps.

Rick
CLC# 32373
1956 Coupe Deville A/C car "Norma Jean"

colorado4x4

Thanks for the replies and insights. 
Doing some research, I found an old school machine shop here in metro-Denver that is going to give my existing caliper some TLC and carefully mill out the remaining portion of the frozen bleed screw and tap it back to the 3/8-24 original thread.  He is aware of the trickiness of not disturbing the taper at the bottom.  I should have it back in a day or so. Fingers crossed.  Will report on whether "plan A" is a success (hourly rate is $110), otherwise "plan b" would be to mill/drill to a larger bleed screw size, and "plan c" would be to get a re-man caliper from USA parts supply, which are $80+$75 core, so $155 for a re-man caliper.

This problem child caliper is the passenger side, so now I am going to carefully assess how to get the driver side bleed screw out, utilizing torch heat and CRC freeze in a number of cycles to see if I can get it out without breaking it off.  Brian at the machine shop suggested using a mixture of 10% acetone and 90% ATF fluid to soak the exterior and interior of the stuck bleed screw in combination with the torch heat cycle to break the rust bond.

At any rate, unforeseen projects like this always present an opportunity to buy more tools, that I didn't know I needed, but now got to have !!
Rocky Mountain Region Membership Chair & Treasurer
1970 DeVille Convertible Chateau Mauve Firemist
1970 DeVille Convertible Lanai Green Metallic

cadillacmike68

1968-71 were essentially the same caliper. The piston went from 70mm to 75mm but the casting is the exact same size.

I'm not sure about 1972-76 or 1977-later because:

A: Cadillac went from rear steering to front steering in 1972.
B: Somewhere down the line, the inlet fitting on the caliper went from SAE to Metric.
C: Somewhere down the line, after B, ABS went from nonexistent to standard equipment.

HOWEVER: ALL full size RWD Cadillacs (and some other GM lines) from 1968 through 1996 take the EXACT SAME BRAKE PADS. I have a 1968 DVC and a 1996 Fleetwood Brougham and they take the SAME pads. Further, you can get them in Ceramic for cleaner wheels!  8).

This means that the caliper castings were the SAME size. It's is the size and location of the inlet fittings and bleeder fittings that changed over the years.

So, you should not need to go through USA PS, they should be available from other sources.
Regards,
"Cadillac" Mike

Caddylackn

Quote from: colorado4x4 on May 24, 2021, 07:02:54 PM

I am going to carefully assess how to get the driver side bleed screw out, utilizing torch heat and CRC freeze in a number of cycles to see if I can get it out without breaking it off.  Brian at the machine shop suggested using a mixture of 10% acetone and 90% ATF fluid to soak the exterior and interior of the stuck bleed screw in combination with the torch heat cycle to break the rust bond.



This is what I would try, it usually works.  Heat the bleeder and around the base to hot with a propane torch but not glowing.  Cool it fast by using just the expanding gas from a propane torch that is not lit.  The smaller metal mass of the bleeder valve will contract much faster than the larger metal mass of the caliper around it, and usually will break the death bond of the corrosion.  Then hit it with penetrating oil mix, on the inside of the bleeder valve as well.  I also tap on the bleeder tip with a hammer a bunch of light taps trying to get the penetrating oil to sink in deeper.  Give it 24 hours then try to remove it with a six point deep socket.
'61 Fleetwood 60- owned for 31 years
'61 Series 62 2-door - sold
'64 Series 62 2-door -sold
'67 Sedan De Ville - sold
'74 Eldorado Convertible - sold

colorado4x4

Once back in operation, what is best practice to keep the bleed screws from seizing in the future, interim between fluid change bleeding......anti-seize on the bleed screw threads and a rubber cap to keep out moisture for the bleed screw?
Rocky Mountain Region Membership Chair & Treasurer
1970 DeVille Convertible Chateau Mauve Firemist
1970 DeVille Convertible Lanai Green Metallic

35-709

That is what I use --- a little dab of anti-seize on the threads of the bleeder screw.
1935 Cadillac Sedan resto-mod "Big Red"
1973 Cadillac Caribou - Sold - but still in the family
1950 Jaguar Mark V Saloon resto-mod - Sold
1942 Cadillac 6269 - Sold
1968 Pontiac Bonneville Convertible - Sold
1950 Packard 2dr. Club Sedan
1935 Glenn Pray - Auburn Boattail Speedster, Gen. 2

TJ Hopland

The cap seems to make a huge difference.   I have not found anyone selling caps specifically for that but vacuum caps fit and those are easy to find.

Rattling them with a hammer or better yet an air hammer while trying to turn them also seems to work.

In this case I do wonder if it was a 'simple pad job' why you would even mess with the bleeder screw.   Bleeding anything and simple don't ever seem to go together for me. 

I also wonder why not just a new or rebuilt caliper?  I don't recall anyone saying this one is at all hard to get or expensive.  If its had enough corrosion to stick the bleeder chances are good the slides as well as the piston are not going to be moving like new either.    Currently available rotors and drums are pretty terrible but calipers are one thing I have not had any issues with even the econo store brand ones.
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

The Tassie Devil(le)

I used to find these small caps on Japanese vehicles in the wrecking yards, and picked them up when I was scrounging.   I am talking about the earlier cars, like up until the 90's.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

Caddylackn

Quote from: TJ Hopland on May 26, 2021, 08:06:49 PM

In this case I do wonder if it was a 'simple pad job' why you would even mess with the bleeder screw.   Bleeding anything and simple don't ever seem to go together for me. 


The biggest reason is to get out all of the old brake fluid out of the calipers, wheel cylinders, and master cylinder and put in fresh.  Brake fluid contaminated with water is what causes master cylinders,  calipers, and wheel cylinders to rust on the inside and fail.  After  replacing pads and shoes, suck out the old brake fluid from the master and the sediment, then add fresh, then crack one bleeder at a time and flush all the calipers and wheel cylinders until the fluid comes out clean.
'61 Fleetwood 60- owned for 31 years
'61 Series 62 2-door - sold
'64 Series 62 2-door -sold
'67 Sedan De Ville - sold
'74 Eldorado Convertible - sold

35-709

When I do "a simple pad job" I don't touch the bleeder either.  When I do an involved brake job with a fluid change, then the bleeders come into play.  Comparing apples to oranges here.
1935 Cadillac Sedan resto-mod "Big Red"
1973 Cadillac Caribou - Sold - but still in the family
1950 Jaguar Mark V Saloon resto-mod - Sold
1942 Cadillac 6269 - Sold
1968 Pontiac Bonneville Convertible - Sold
1950 Packard 2dr. Club Sedan
1935 Glenn Pray - Auburn Boattail Speedster, Gen. 2

TJ Hopland

That's why I was questioning it,  he did say it was a simple pad job,  not a full refresh sort of thing.
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

35-709

1935 Cadillac Sedan resto-mod "Big Red"
1973 Cadillac Caribou - Sold - but still in the family
1950 Jaguar Mark V Saloon resto-mod - Sold
1942 Cadillac 6269 - Sold
1968 Pontiac Bonneville Convertible - Sold
1950 Packard 2dr. Club Sedan
1935 Glenn Pray - Auburn Boattail Speedster, Gen. 2

The Tassie Devil(le)

I too have never had to touch the bleeder when doing a simple brake pad or shoe change, but any "Simple" task can turn into a major problem if one doesn't know what they are doing.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

cadillacmike68

Quote from: Caddylackn on May 27, 2021, 12:05:37 PM
The biggest reason is to get out all of the old brake fluid out of the calipers, wheel cylinders, and master cylinder and put in fresh.  Brake fluid contaminated with water is what causes master cylinders,  calipers, and wheel cylinders to rust on the inside and fail.  After  replacing pads and shoes, suck out the old brake fluid from the master and the sediment, then add fresh, then crack one bleeder at a time and flush all the calipers and wheel cylinders until the fluid comes out clean.

DOT 5 brake fluid
Regards,
"Cadillac" Mike

35-709

Agree 100%!  Have been using DOT 5 in all of my old cars for ~ 25 years now.  No problems with it whatsoever, although bleeding the system requires some extra care as 5 tends to get bubbles easily.  After bench bleeding the master, I let it sit overnight to let any tiny bubbles dissipate and carefully bleed it again the next day.  Master cylinders and wheel cylinders last much longer and I have never experienced water in any of the many brake systems I have converted.  My '35 Cadillac resto-mod has had DOT 5 fluid since I finished building the car in January of 2011, 30,000 miles ago.  Have never had a single problem with the brake system in that car and when checking the fluid it is as clean as day one.  Only caveat is that the brake system must be completely clean of any old DOT 3 or 4 fluid (preferably a new system).   
1935 Cadillac Sedan resto-mod "Big Red"
1973 Cadillac Caribou - Sold - but still in the family
1950 Jaguar Mark V Saloon resto-mod - Sold
1942 Cadillac 6269 - Sold
1968 Pontiac Bonneville Convertible - Sold
1950 Packard 2dr. Club Sedan
1935 Glenn Pray - Auburn Boattail Speedster, Gen. 2

cadillacmike68

I would love to bee able to use DOT5 in my 1996 Fleetwood. but the manuals say not to, supposedly because it does not absorb water (which I consider a GOOD thing) and that that separated water could boil faster at high temps in the system and thereby throw off the ABS under hard high speed braking.

I'm still considering it, water should NOT get into the system to mess it up in the first place...

Regards,
"Cadillac" Mike