Pipe sizes

[troy_fb]

Can anyone tell me what the brake/clutch pipes size is? While I'm at it, what about the thinner vacuum pipe to the dizzy? Are they measured in internal or external diameter.
I can't seem to find anything in the manual.
Troy

[Thommo]

Gday Troy
I'm guessing 3/16" internal diameter.
I know any pipe/tube designed to transfer air/liquids is measured internally.
Any structual pipe for fabrication is measured externally.
Sorry I dont have any around to measure.
Cheers
Jeff

[Sammy]

the pipe i used to make my new brake lines is 3/16's so i'll be going with that

[Dr Terry]

Hi Guys.

All steel bundy tubing used in cars (brake, clutch & fuel etc) is measured OD (outsde diameter). Most flexible hoses however are measured ID (inside diameter).

The 4 common tubing sizes are 3/16", 1/4", 5/16 & 3/8" (All OD).

Holden used 1/4" for all brake & clutch lines for FX, FJ, FE & FC. Fuel line was 5/16".

For FB onwards the brake tubing reduced to 3/16" & this is still used in the current VE Commodore. The clutch tubing remained at 1/4", as a higher flow rate is required.

Fuel & auto trans lines for nearly all models are 5/16", although some high performance models (GTS350 & L34 etc) when up to 3/8" for the fuel.

Power steering return is also usually 3/8".

It's a bit like wheel rim sizes, even though just about the entire world is metric, most automotive tubing is still measured in nominal inch sizes.

Dr Terry.

[mrs ratbox]

there just happens to be a little thing along these lines in the latest SM a guy couldn't get his clutch to work properly (slow return) and that's what the prob was the pipe diameter was too small

[troy_fb]

Thanks heaps Dr Terry,
I had to get a new pipe made up for my brake booster. ABS were lasy and had made me up one which was a smaller diameter (3/16") to the sample I took in. Problem was it just wouldn't seal properly on the double flare fitting and I suspect was also slowing the return and causing a pressure buildup. Anyway took it back and got it done properly.
Found I also had restrictions in all my flexible brake lines(3) which I could hardly blow through. And my clutch line, its sooo light now! Don't know how I have put up with it for so many years.
All the flexible lines must degrade inside and block up? Or maybe a buildup of brake fluid sludge in them?

Troy

[oldnek]

Flexible brake hoses do actually swell from inside, thus reducing hose size considerbly, and even to the point where you apply the pedal and the brakes will stay locked on, due to no fluid return. A common mistake that is often overlooked for binding brakes or clutch problems.

Regards John

[FB MAD]

Yep, like John said, they can deteriorate from the inside out.Bits of rubber can flake off and get caught and and create a restriction/part blockage, as well as sludge build up due to brake fluid being Hydroscopic ( moisture absorbing ) which can also create problems in the system.

Pays to bleed the system regularly to minimise problems with old brake fluid.

A slow returning clutch pedal can be one indication of a partly blocked flexible line that is often blamed on weak pressure plate springs and/or pedal return springs as has been mentioned above.

Terry.

[Dr Terry]

due to brake fluid being Hydroscopic ( moisture absorbing ) which can also create problems in the system.

Terry.

I know people think I'm often too pedantic, but the word is 'hygroscopic', not hydroscopic.

I had this pointed out to me recently by someone with about a dozen letters after his name, so I assumed he knew what he was on about. Apparently a hydroscope is an optical device for making observations under deep water.

On the same topic, I use Dot 3 brake fluid in my older cars. The main difference between the old Dot 3 & the current Dot 4 brake fluid, is that the newer fluid has a higher boiling point (for use in high performance disc brake systems). The downside is that the newer fluid is thinner (less viscous) so small fluid leaks in old cars' wheel cylinders etc. will leak at a quicker rate. The other problem with Dot 4 fluid is that it is even more 'hygroscopic' than Dot 3 & needs changing every 2 or 3 years, whereas the old Dot 3 fluid will last longer than that.

Dr Terry

[FB MAD]

Nah, I don't reckon your pedantic Dr Terry.

I'm always happy to be corrected

It's a bit like Hydramatic and Hydromatic

Been a long time since I went to Tech college.

Cheers,

Terry.

[troy_fb]

I have been wondering about the dot 3/4. Does it matter if you mix the two? Will it just end up somewhere in between for viscosity? I had trouble getting dot 3 on the weekend at the servo and had to use dot 4 which said it was suitable for dot 3 vehicles. Good to know the difference now though, thanks Dr

Troy

[FbSTDwagon]

Great post for me to get some sizes of the pipes.

Went out side and double checked all the samples that I have and it’s all correct to the above sizes mentioned.

Now just got to get on with buying some bundy tube and fittings!