67 Brake Fluid Flush

[Thomas S.]

This tool makes bleeding effortless and its inexpensive. Bleeding should be on your service schedule every 5 years. Buy the various adapters for your daily drivers and bleed them every 20-25K.

Always keep brake fluid sealed and stored in a controlled environment(basement). Date the bottle and dispose in a year or two. DOT 3 & 4 are very hydrophilic(absorbs water like a sponge). Don't store fluid in the power bleeder.

Once you figure out what you are doing with the master put a gallon through the system. Inspect for leaks while the system is pressurized.

Yes the fluid could have been frothed from trapped air causing the white discoloration. System contamination floating on top of fresh fluid will give off the iridescent rainbow sheen. The system simply needs more flushing.

https://www.motiveproducts.com/collections/brake-bleeder-kits

I have both the Mityvac and Motive setups and both the adapters. If you don't have a perfectly flat master cylinder top edge, it can be a very messy endeavor. There's actually another adapter that has rubber tips that fit over the hole at the bottom of the fluid wells. Hard to find but I'll report back once mine arrives.

[Thomas S.]

Some images of the master cylinder wells and "mystery" fluid. Needless to say, the master cylinder will be removed for possible rebuild.

Some additional images showing the bore, pistons, seals and other close-ups for future reference. The small piston retention bolt was also missing so my guess is that this was definitely touched as some point.

Some more questions about original vs. Lonestar to follow.

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[Thomas S.]

Received the rebuilt "original" from Lonestar. Compared to my original, which I believe to be original. The Lonestar was bit too "pretty". Not looking to knock them at all and I will be in touch with them, but casting features are way different than my original. I realize the machined surfaces should not be painted which is an easy fix.
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IMG_5543.jpg IMG_5542.jpg

[Joe L.]

Received the rebuilt "original" from Lonestar. Compared to my original, which I believe to be original. The Lonestar was bit too "pretty". Not looking to knock them at all and I will be in touch with them, but casting features are way different than my original. I realize the machined surfaces should not be painted which is an easy fix.
IMG_5546.jpg IMG_5545.jpg
IMG_5543.jpg IMG_5542.jpg

Thomas------


What is the date code on the master cylinder? You should find it stamped on one of the brake line fitting machined surfaces.

Also, keep in mind that this master cylinder was manufactured for quite a few years and there may be casting differences over the period.

[Thomas S.]

Thomas------


What is the date code on the master cylinder? You should find it stamped on one of the brake line fitting machined surfaces.

Also, keep in mind that this master cylinder was manufactured for quite a few years and there may be casting differences over the period.

So, it looks like 2 3 and maybe 9. Zoom in
The car is a mid-December build.


No marking on the Lonestar and they told me specifically that 67's, standard MC were not dated and that the dating started later. I did press them on that.




.

[Joe L.]

So, it looks like 2 3 and maybe 9. Zoom in
The car is a mid-December build.


No marking on the Lonestar and they told me specifically that 67's, standard MC were not dated and that the dating started later. I did press them on that.




.

Thomas------

Yes, they are correct; 1967 master cylinders usually have no date. The reason for my question was to determine if the master cylinder you received DID HAVE a date.

I do not understand what you mean by "zoom in". I don't see the machined brake fitting boss in any of your photos.

[Duke W.]

I see what appears to be rust stains and possible pitting. A simple rebuilt kit may not do the job, but it is a candidate for sleeving.

What is the silver color at the bottom? Paint? That may be the source of contamination.

Duke

[Thomas S.]

Thomas------

Yes, they are correct; 1967 master cylinders usually have no date. The reason for my question was to determine if the master cylinder you received DID HAVE a date.

I do not understand what you mean by "zoom in". I don't see the machined brake fitting boss in any of your photos.

Use an iPad for the reply and left out some images. The zoom in comment was before I had taken the closeup showing the numbers. What I thought to be original is apparently not becasue it does have markings by the output port. Must be for later year. That would tell me that the Lonestar is actually correct, or more correct.

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[Thomas S.]

I see what appears to be rust stains and possible pitting. A simple rebuilt kit may not do the job, but it is a candidate for sleeving.

What is the silver color at the bottom? Paint? That may be the source of contamination.

Duke

If you are referring to this image - not sure. Looks like a small bubble refracting the light from the flash on the phone.
IMG_5513.jpg


I agree, this MC is toast as is, needs some serious work. Since it has partial Julian date numbers on the out port, it's not for a 67. Not sure why I would want to put any money into it at this point if the goal was originality.

However, as is the case many times, lots learned during the back and forth and maybe some of the comments will be helpful to others.

One other question was related to replacing the fluid throughout. I will bench bleed the new MC before installing it. You had mentioned a procedure starting with the left front and so on. It was my understanding that a normal brake bleed process begins with the wheel located furthest from the cylinder and so on.

Is there a reason for the reversed sequence when you are replacing the fluid throughout?

[Mark E.]

You had mentioned a procedure starting with the left front and so on. It was my understanding that a normal brake bleed process begins with the wheel located furthest from the cylinder and so on.

Is there a reason for the reversed sequence when you are replacing the fluid throughout?

Regarding bleed sequence:

https://www.forums.ncrs.org/forum/technical-discussion/120663-proper-wheel-sequence-while-bleeding-brakes-old-wives-tale

[Thomas S.]

Regarding bleed sequence:

https://www.forums.ncrs.org/forum/technical-discussion/120663-proper-wheel-sequence-while-bleeding-brakes-old-wives-tale

Perfect. Thanks

[Duke W.]

Actually it was this photo I was referring to, but maybe it's just a sunlight-shadow effect.

Even though the old m/c may not be NCRS correct, if it's functionally correct I would thoroughly clean it with denatured alcohol. Dry and then place in a ziplock bag. Buy a rebuild kit, and if it's ever needed you should be able to get it sleeved and you have a new rebuld kit. If the latter is not in a sealed bag, put it in a ziplock bag, too.

Duke

[Thomas S.]

That area represents what was left after removing the hardened gray material that I though might have been aluminum. There is also a shadow in play.

The point I'm at now is to confirm that the MC I got from Lonestar is indeed a rebuilt 67 Delco MC and not a GM Licensed Restoration product. I was specific when I ordered and just want to be sure. Assuming it is correct, that is what will be installed.

I will have the one that was in the car sleeved and either I'll rebuild it or I'll have it rebuilt.

IMG_5521.jpg

[Joe L.]

Actually it was this photo I was referring to, but maybe it's just a sunlight-shadow effect.

Even though the old m/c may not be NCRS correct, if it's functionally correct I would thoroughly clean it with denatured alcohol. Dry and then place in a ziplock bag. Buy a rebuild kit, and if it's ever needed you should be able to get it sleeved and you have a new rebuld kit. If the latter is not in a sealed bag, put it in a ziplock bag, too.

Duke

Thomas and Duke------

One more thing: this master cylinder has, at some point, been through a commercial rebuilding operation. Note that the piston stop screw is missing from the bottom of the reservoir. Commercial rebuilders often delete this screw as they say it's "unnecessary". The way I've always figured it, if it was unecessary GM wouldn't have put it there in the first place.

My guess is this is the actual reason that rebuilders eliminate the screw: if the master cylinder is sleeved, some/all of the threads for the screw are removed when the master cylinder is bored for the sleeve. Rebuilders don't want to drill and re-thread for the screw.

[Thomas S.]

Exactly. I'm not sure of the wall thickness of a sleeve, but if it's anything like a caliper, the same bolt would likely be long enough assuming of course one decides to do it the right way.