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MG MGA - Brakes AND clutch fluid, right?

I think I screwed up. I'm switching to silicone brake fluid and replacing the wheel cylinders. So I drained the brake bleeders, flushed out the system with alcohol, put in the new stuff and bled the brakes. Not once did I even think about the clutch. I'm guessing that I should have flushed that line as well? Can I still do that without contaminating the new stuff in the MC? Separately (or maybe it's not separate), I cannot get a hard pedal without pumping the brakes 4-5 times despite not seeing any air bubbles and having bled the brakes twice with an Ezibleed.

Like so many of these projects, I know just enough to get myself into big trouble. Any advice, Doctors?

58 MGA
J Plegue

The master cylinder has a center divider, so about 25% of the total volume of fluid will remain in the clutch side of the reservoir when you blow out the brake circuit. You should suck as much fluid as possible out of the reservoir first, then flush all brakes and clutch with alcohol, and blow out with air before filing with fresh fluid. If you only bleed the brakes, then the clutch circuit and part of the reservoir still contain old fluid which would be mixing with the new fluid.

To do it right you should replace all of the rubber parts in the whole system, including replacing or repacking the master cylinder, all slave cylinders and replacing the four flex hoses.

I know it's a pain, but seems like you should start over, blow it all out and flush with alcohol again, blow out with air, replace any rubber parts you didn't do the first time, reassemble, and then fill with new fluid.

Bleeding the system after reassembly with air inside can be tricky. EeziBleed usually works when you pay attention to getting air out of the slave cylinders. The clutch circuit may be trickier than the brakes. If all else fails, install fluid at the bleed nipples and push it upstream into the reservoir. A trigger pump oil can or MityVac works well for reverse bleeding.
Barney Gaylord

Thanks for the quick response. Well, that's depressing news. This has become the project from hell.

I've replaced everything but the master cylinder. I assume a rebuild kit is what I need? What's the trick to getting the air out of the slave cylinders?

J Plegue

Barney and others,

What''s your take on DOT 5.1 brake fluid? It appears to have all the qualities of silicone and is compatible with DOT 3 & 4. I put it in my 1600, without changing anything out, when I replaced a caliper about five months ago--so far so good.
David Werblow

Non of the advantages of silicon, still absorbs water and dissolves paint. Just a higher boiling point, which makes it more suitable for competition use. Needs changing most often of all types to maintain its' performance.
N McGurk

The DOT standards are performance spec's, not material spec's. By coincidence, the DOT-5 standard was written with silicone fluid in mind, so all DOT-5 fluid is silicone. However, DOT-5.1 is a Glycol fluid more similar to DOT-4, with all the same drawbacks. In particular, it will eat paint.
Barney Gaylord

This thread was discussed on 29/09/2012

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