Sticking rear brakes on a 411
Here is how to identify if the brake lines are blocked and what to do.
- New hardware store oil can (metal tank with pump squirting lever and 1/4″ solid tube) See amazon.co.uk/dp/B000LFTT5Q for an example
- New hardware store 6mm clear plastic hose (3 metres) and several hose clamps to fit
- New brake fluid
- Kunifer brake line (a soft alloy also known as cupro/nickel) 3/16″ SAE and male & female flare tube nuts to match the Bristol thread
- Brake flaring tool that does double flare
Remove the driver’s side (RHD) brake tube flare nut (male) from the T section. Temporarily you will be replacing this with a test brake tube flare nut. BTW, if you don’t know how to flare Kunifer brake line, it’s forgiving and easy to learn. Get the tools and watch a few YouTube videos or buy a case of beer and stop by your brake supply shop half an hour before closing time for a tutorial.
Make up the testing tool:
- Slide the clear plastic hose over the oil can tube and hose-clamp it tight
- Take a section of the Kunifer brake line (say 300-500mm) and double flare one end with a male tube nut that will go into the T section.
- Put a similar double flare on the other end and slide the clear plastic hose over. You will need to use the host clamp on top of the flare to keep it from leaking under pressure.
- Slide the other end of the clear plastic pipe over the oil can and hose clamp it.
- Fill the oil can with new brake fluid (this is why you buy a new oil can… no contamination)
- Open the bleeder valve on the opposing side of the rear axle (left/passenger side on RHD). Attach a hose into a clear glass jar on the ground that you can see from your side.
- Pump the can. If fluid comes out on the opposing side, you know the rear axle lines are clear. You might as well keep pumping until the fluid is clear, you’re doing the equivalent of a bench bleed.
- Close bleeder valve
- At the front end of the car in the battery compartment, disconnect the battery to avoid sparks and then disconnect the brake line leading into the servo that connects to the rear brakes and pump again. If you are unsure which servo, climb under the car and follow it from the back to the battery compartment.
- In theory this would reverse flow brake fluid forward until it dripped out (have a cup or big towel ready to catch pumping brake fluid (or make up and attach a female nut to metal line to plastic hose to glass jar)
- If it does nothing (no flow from the front brake line), remove the rubber flex hose that connects the body brake line to the axle brake line. This probably is the culprit (it was for me). Try blowing air through it. If no air, you know it is junk.
- Then hook the testing pump to the metal brake line in the battery compartment . If fluid flows out of the rear line where you removed the rubber hose, you can presume the metal line is OK.
- You can also mechanically test this if you have a new stainless steel bicycle brake cable wire that you slide inside the car’s metal brake lines. It should come out the other end clean and with no resistance.
When doing this job, make sure you know where to buy replacement Kunifer brake lines and matching nuts because most cars will not come apart easily. Nuts may strip, or if frozen may twist the old metal lines, requiring replacement. A brake supply house should carry both the metal lines and the rubber hose. The 1970 411-S1 hose seems almost identical to “H892 Hose for British Ford, Hillman and many other British cars” (try also GBH136). Try Powertrack for parts.