[TR] DOT 5 Brake Fluif

[Brian.L.Jones at gsk.com]

Once again this august list, and resulting archive, proves a wealth of 
information.

Late last year, my brake master cylinder seals failed and distributed DOT 
4 around the mounting bracket and driver's side engine bay and firewall. 
The paint turned to a putty-like consistency and could be easily scraped 
to bare metal.

I decided to take the winter 'off' regards the TR4, and have only now 
attended to this issue. With the paint replaced, I rebuilt my master 
cylinders and read up the DOT 5 switchover posts from the archive. Why 
switch to DOT 5? It is benign to paint, its now readily available. It 
costs slightly more initially, but as it doesn't soak up water, it need 
not be replaced every three years or so (so is actually cheaper than DOT 
4, I think).

On switching to DOT 5, we have two schools of thought: 

One advises to replaces everything rubber, clean all lines with a 
particular solvent, blow out solvent with dry air, then introduce DOT 5 
after this thorough rebuild. The solvent is available from pharmacies 
(Methyl alcohol, as I recall).

The other suggests removing and DOT 4 from the master cylinder by syringe 
(if this is not a master cylinder rebuild, and just a switch over), and 
pour in DOT 5, then bleed until clean, clear DOT 5 appears at the bleed 
nipple at each wheel.

I opted for the latter of these, so I hope to have as much success as many 
of you have enjoyed.

There was some conflicting information about bleeding wheel sequence. Many 
start at the left rear, then right rear, left front, right front. There 
was, in the archive, a Triumph service note that stated this was the 
correct sequence for cars with drum brakes on the front. It also stated 
that cars with discs on the front should be bled starting with the front 
left wheel, but made no mention of the subsequent sequence. I cannot work 
out why there would be a change in sequence with discs.

Many cautioned about DOT 5 bubbles when pouring. I half expected this to 
behave like a shaken can of coke, but if you pour slowly there is no 
problem. If you pour in a way that creates bubbles, they can apparently 
take some time to disappear.

Thanks to all those whose experiences populate the archive.

Brian
TR4, CT 14455-L 1962
Valley Forge, PA