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TR2/3/3A Advice needed - cleaning TR3 brake pipe union

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Bob_D

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Hi,

I'm installing new brake hydraulic pipes on our TR3 and have removed the union w/switch. My plan is to remove the switch and then soak the union in brake cleaner and then blast with compressed air to make sure any gunk is gone. Good idea? Alternatives? Thanks
 
Excellent way to clean it up. Also, you might rinse thoroughly with clear water to remove any brake cleaner residue and blow dry with compressed air!
 
Bob: Coincidentally, I'm replacing brake lines in the TR250 this weekend. I think your plan is very good. I would also suggest that you examine the fittings carefully, especially the threads. You might want to chase the threads with a tap. If you have any doubt, replace them. The're not expensive and there's no substitute for safety.

good luck

fja
 
I'll disagree with both water and thread chasing. A quality brake cleaner doesn't leave a residue, but tap water does. And if the threads need chasing, IMO you should just replace the fitting. It's too easy to damage the sealing surface with the tip of the tap.

Also, if your TR3 has front disc brakes, there will be a residual pressure valve screwed into the top of the 5-way, which IMO you should also disassemble (taking careful note of how it comes apart) and clean. Since I didn't like having the brakes drag, I left out the internals from mine when I put it back together.
 
Be careful when putting in the new lines into the 5-way union. The fine threads on the fittings make them difficult to start straight if you don't have some wiggle room on the pipes or the fitting. It would be best to leave the fitting loose in the chassis, and get all the fittings <span style="font-weight: bold">well started by hand </span>before tightening everything up. This job is best done with the body off!! :lol:
 
After you take it apart, you'll be glad I sent you this.
 

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I meant clear tap water, not water from your septic system! I clean brake parts as a course of doing this for a living... and ALL brake cleaning products leave a residue.... and the water never hurts a thing if parts are thoroughly blown dry... er, uh, didja get that part?
 
Randall:

You’re correct. A conventional tap could damage the seat in the union. Recently, I reported about receiving some bad rear wheel cylinders. The threads in the aluminum body were too shallow. I noticed this when I encountered a lot of resistance when trying to attach the end of the brake line. So I used an old brake-line end fitting as a tap to re-make the threads. It worked perfectly.
 
Thanks for all the great advice. I'm restoring this TR3 with my son, and I don't know how I managed a similar project 35 years ago (yes, another 3) with my father without ebay and this site.

One quick question related to TR3driver's comment -- I ran into the residual pressure valve screw as I disassembled the unit (thanks Don for the drawing, it was immediately helpful) and my son and I puzzled over it for a good 20 minutes. What is its purpose and what are the pros/cons of leaving it out?

Thanks again,
Bob
 
Bob_D said:
I ran into the residual pressure valve screw as I disassembled the unit (thanks Don for the drawing, it was immediately helpful) and my son and I puzzled over it for a good 20 minutes. What is its purpose and what are the pros/cons of leaving it out?
Click to expand...
The RPV is supposed to hold some pressure in the braking system all the time. In theory, this keeps the front caliper pistons from being pushed back into the calipers when the front spindles flex in hard turns (or more accurately, when one piston is pushed in, the other one extends). However, it also makes the brakes drag (when it's working properly).

Without the RPV, you can find a low brake pedal after taking a hard turn, which can be disconcerting if you are not expecting it. However, I have never found it so low that I couldn't get full braking without having to pump the pedal; and only rarely do I even notice a low pedal (ordinary driving doesn't cause enough flex to demonstrate the problem) even with wide sticky tires and various other suspension upgrades.

Even Triumph (actually British Leyland) eventually decided the RPV wasn't worth the hassle and expense, so it was deleted some time during the TR4 run even though the problem of spindle flex remained true through the end of the TR6.

If you do find spindle flex (and subsequent low pedal) to be a problem, I recommend Uncle Jack's spacer kit:
https://www.zeni.net/trf/TR6-250GC/index.php?menu=S&page=119
 
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