Help please! Only 36 hours to fix brake line problem!

[craig-ultima]

I only have 36 hours to fix this problem since I have a road event that I realy want to go to. Spent all night working on it to no avail.

Here is the problem:

When I originally put my brake light pressure switch in, I had a lot of trouble getting it to mate to the threads on the 4-way unit that is in the rear brake line. I eventually got it to work, but only after using 3 copper washers to space the pressure switch back from the 4-way coupler.

I know this is not ideal, but it worked. The switch recently failed, and when I put the replacement unit in tonight, I couldn't get it to seal properly, and it is leaking brake fluid.

What is the right answer here? Do I re-thread the 4-way coupler? Use a sealant? Get a replacement 4-way coupler?

I'm desperate since I want to attend the event on Saturday morning, but I can't do it if my rear brakes are going to fail!!

[ezakimak]

If your pushed for time and cant get replacement parts, you might be able to find a matching threaded bolt to the brake light switch and just thread that into the 4-way connector and remove the switch for the short term interim, don’t know weather that will be acceptable from a scrutineering point of view, but at least you will have brakes

I would try a matching bolt before trying to re-thread the hole as re-threading will remove more material from the connector, which is ultimately not the best solution in the area of brakes. Have any of your local guys from your car club got any spares that you could get at short notice

[bluesatin]

Try thread sealant such as 592 PST Thread Sealant. Should be able to get it from any decent auto supply store.

[steve_D]

Is the new switch also too long requiring extra washers?
If so then my main concern is that the end of the switch is too far into the four-way and may be resticting flow to the brakes.

I would cut the switch down so that only one washer is required. If it still won't seal then refit the old switch until you can source another switch and mating four-way.

Steve

[tuxman]

can you P.T.F.E. it white sealing material that is used in gas ind you wrap it around threads and then tighten in ?

[YIIHAA]

My four way adaptor also leaked. I found the problem was that two of the mating surfaces had casting flash lines that were so irregular that a copper washer wouldn't seal. I stuck some wet and dry abrasive paper to a flat surface then rubbed the adaptor on that to flatten the mating surface. Worked fine after that.

[GreenV8S]

Lateral thinking, can you fit a mechanical switch on the pedal? Keeps the safety-critical hydraulics as simple as possible, also means the brake lights will probably come on sooner, better all round I would say.

[NDS]

IMHO
Its not worth using PTFE tape on a brake system. The orifices are so small in the brake callipers etc it may cause a problem this also applies to thread sealants etc.
Hard braking creates very high hydraulic pressure please do not re-thread the fitting.

In a critical application I would strongly recommend using a new (correct) part.

I have used the Pressure sender manufactured by Areoquip It fits into the out put thread on the front circuit master cylinder. And utilises two Banjo bolts for the front RH and LH circuits. But perhaps not a 36 hour solution!

[CanAm Dave]

I have fitted a switch to my brake pedal as I was getting complaints from people following behind me. The hydraulic switch should be in the front circuit due to brake bias. My lights were coming on but only under hard braking. I'd leave the old one where it is and fit a switch on the pedal.

Regards Dave

[craig-ultima]

Thanks everyone - here is where I ended up:

I replaced the factory 4-way unit with a series of T fittings. My local race shop was very helpful in identifying the problem - their view was that the original brake switch is a straight 3/8 thread whereas the 4-way connector is expecting a pipe (i.e. tapered) thread.

I also now have a true pipe thread pressure switch to match the T fittings. It all went together quite well, and there are no leaks, and the brake lights work, so I will be off to the races tomorrow! (I will be taking all the spare parts and tools though!)

I did notice that the new pressure switch requires more load to make the brake lights go on, so I might end up going with the mechanical switch on the brake pedal as an additional switch. Either that, or getting a replacement 4-way unit from the factory and maybe ask them to install the pressure switch.

[steve_D]

I replaced my switch with an adjustable unit after a number of people had complained that they didn't know I was braking when travelling in convoy.

Steve