Switching to DOT 5 Brake Fluid

[Joel T.]

Guys;

I'm planning on re-doing the brake system on my 1963 this winter. It is a non PB system. I'm not sure what fluid is in there now but I was planning on going with the silicone DOT 5 fluid. I have 2 quarts in hand.

My plan was to:
Replace all 4 wheel cylinders
Rebuild the master cylinder
Replace all 4 rubber hoses with new
Blow out all the brake lines with compressed air once all is disconnected
Reassemble fill with the DOT 5 and bleed as per normal.

Will this be sufficient??

Appreciate any thoughts.

Joel

[Erich C.]

Re: Switching to DOT 5 Brake Fluid

After you blow the lines out with air I would also use a brake cleaning solvent
to remove any remaining fluid ( probably DOT 3 ) and/or deposits in the lines.
Follow that with some more compressed air. Put a white rag over the end of the line when you blow it out. Repeat the above steps until the rag stays clean when you blow out the lines.

[Erich C.]

Re: Switching to DOT 5 Brake Fluid

After you blow the lines out with air I would also use a brake cleaning solvent
to remove any remaining fluid ( probably DOT 3 ) and/or deposits in the lines.
Follow that with some more compressed air. Put a white rag over the end of the line when you blow it out. Repeat the above steps until the rag stays clean when you blow out the lines.

[Joel T.]

Re: Switching to DOT 5 Brake Fluid

Super, Thanks!! Joel

[Joel T.]

Re: Switching to DOT 5 Brake Fluid

Super, Thanks!! Joel

[Duke W.]

Re: Switching to DOT 5 Brake Fluid

You can use denatured alcohol to flush all the pipes. Then thoroughly dry them with compressed air.

If you buy new wheel cylinders, disassemble them and clean everything with alcohol, then reassemble them with DOT 5. Clean the master cylinder and rebuilt kit with alcohol, dry, and reassemble with DOT 5.

Also flush out the new hoses as they are usually assembled with DOT 3.

You want to make every effort to remove every last molecule of conventional fluid.

Duke

[Duke W.]

Re: Switching to DOT 5 Brake Fluid

You can use denatured alcohol to flush all the pipes. Then thoroughly dry them with compressed air.

If you buy new wheel cylinders, disassemble them and clean everything with alcohol, then reassemble them with DOT 5. Clean the master cylinder and rebuilt kit with alcohol, dry, and reassemble with DOT 5.

Also flush out the new hoses as they are usually assembled with DOT 3.

You want to make every effort to remove every last molecule of conventional fluid.

Duke

[Terry M.]

Re: Switching to DOT 5 Brake Fluid

When I put DOT 5 in my 1970 over 20 years ago, I used alcohol to flush out the brake lines. I would think there is nothing wrong with the commensally available brake cleaning products either. Just be sure all the residue of the cleaner and anything else is out of the lines.
Be sure to clean the new wheel cylinders internally and use DOT5 as assembly lube when reassembling them. They were likely assembled using an assembly lube compatible with DOT3/4, which is not compatible with DOT5. You want to get all residue of DOT3/4 out of the system before introducing DOT5.
I used the gravity method to bleed the new fluid. If you have a pressure bleeder that may be preferable. John Hinckley has posted links in the past to a reasonably priced pressure bleeder, and the methods to use it.

[Terry M.]

Re: Switching to DOT 5 Brake Fluid

When I put DOT 5 in my 1970 over 20 years ago, I used alcohol to flush out the brake lines. I would think there is nothing wrong with the commensally available brake cleaning products either. Just be sure all the residue of the cleaner and anything else is out of the lines.
Be sure to clean the new wheel cylinders internally and use DOT5 as assembly lube when reassembling them. They were likely assembled using an assembly lube compatible with DOT3/4, which is not compatible with DOT5. You want to get all residue of DOT3/4 out of the system before introducing DOT5.
I used the gravity method to bleed the new fluid. If you have a pressure bleeder that may be preferable. John Hinckley has posted links in the past to a reasonably priced pressure bleeder, and the methods to use it.

[Norris W.]

Re: Switching to DOT 5 Brake Fluid

Just curious, why the meticulous cleaning of system components? I've done tons of upgrades to stainless on disc brake cars (probably 40 cars or more counting my own) when I had a shop open in the '80's/early 90's, never went to that extreme and never had a problem. I don't think we ever had a comeback on a car we did.

[Norris W.]

Re: Switching to DOT 5 Brake Fluid

Just curious, why the meticulous cleaning of system components? I've done tons of upgrades to stainless on disc brake cars (probably 40 cars or more counting my own) when I had a shop open in the '80's/early 90's, never went to that extreme and never had a problem. I don't think we ever had a comeback on a car we did.

[Terry M.]

Re: Switching to DOT 5 Brake Fluid

There is an SAE paper that shows the results of mixing DOT5 with residual DOT3/4 in a brake system. It is ugly -- a black sludge that can't do any good for anything. I believe there were some brake system performance issues as a result of the sludge also, but it has been a few years since I looked at the paper. If you really want to read about it SAE has a list of available papers on their web site.

[Terry M.]

Re: Switching to DOT 5 Brake Fluid

There is an SAE paper that shows the results of mixing DOT5 with residual DOT3/4 in a brake system. It is ugly -- a black sludge that can't do any good for anything. I believe there were some brake system performance issues as a result of the sludge also, but it has been a few years since I looked at the paper. If you really want to read about it SAE has a list of available papers on their web site.

[Mike McKown]

I have to agree, Norris

I've changed four cars over. I used new cylinders or rebuilt the ones I had including one with a hydraulic clutch. I just blew the lines out. Didn't worry about the cylinders being assembled with Dot 3. I just didn't leave any standing Dot 3 in the system or ANY water. There is no sludge in the systems of these cars that I can see. A couple have been converted for ten years or more. I've never bled them so I don't really know if there any contamination in there are not. I know the brakes/clutch systems work fine. I also know what the system would look like if I still had Dot 3 in it. Sludge!

I would agree if you leave old cylinders in place, with old fluid in them and rust/corrosion on the bores and the boots full of sludge, you'll have big problems, sooner than later. A simple flush will not clean that stuff out.

[Mike McKown]

I have to agree, Norris

I've changed four cars over. I used new cylinders or rebuilt the ones I had including one with a hydraulic clutch. I just blew the lines out. Didn't worry about the cylinders being assembled with Dot 3. I just didn't leave any standing Dot 3 in the system or ANY water. There is no sludge in the systems of these cars that I can see. A couple have been converted for ten years or more. I've never bled them so I don't really know if there any contamination in there are not. I know the brakes/clutch systems work fine. I also know what the system would look like if I still had Dot 3 in it. Sludge!

I would agree if you leave old cylinders in place, with old fluid in them and rust/corrosion on the bores and the boots full of sludge, you'll have big problems, sooner than later. A simple flush will not clean that stuff out.