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Mushy brakes  Rating:  Rating
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 Posted: 05-18-2011 04:58 pm
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mcguan.2
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Jody,

Any particular brand of DOT 5 fluid I should use?  Also, what's the capacity of the system, i.e. how much should I buy?

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 Posted: 05-25-2011 03:32 pm
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JodyKerr
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no particular brand, I've used a couple different ones. I don't remember the fluid capacity of the brakes. I buy stuff in volume because of the number of cars I work on. Accounting for bleeding, I'd hazard 2 bottles should be sufficient.

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 Posted: 05-25-2011 05:45 pm
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Greg Fletcher
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Just my 2 cents and based on my specific experience- rebuilding, reboring, resleeving (in brass, stainless, it doesn't seem to matter) or or whatever else you can do to an old master cylinder is a fool's errand. I've done them all multiple times over the years and they have ALL ended with what I can only describe as premature failure and money not well spent. This failure rate varies from less than 1 minute to less than one year of normal driving. On three completely different occasions (using different rebuilt master cylinders), this resulted in catastrophic brake failure meaning I had no brakes to stop the car. This is not a fun feeling and I would recommend you keep the brake system up to scratch and keep it safe by avoiding rebuild masters. Again, your mileage may vary, this is simply my experience with the brake system on the Jensen Healey that an owner is well ahead in installing a new master cylinder. A master cylinder on any vehicle should always be considered a consumable item.

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 Posted: 05-28-2011 01:08 am
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mcguan.2
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OK, so I installed the new master cylinder (the TR6 model) and changed over the brake fluid to DOT 5.  However, I'm still getting a little bit of leakage right behind the MC, where it meets the booster.  Did I miss some sort of O-ring or something?  It did seem a little weird how the two just seem to "go together" without any sort of seal. 

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 Posted: 05-28-2011 01:14 pm
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Brett Gibson JH5 20497
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No seal there, sounds like your new master cylinder is leaking.

Brett

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 Posted: 05-28-2011 02:00 pm
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Greg Fletcher
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These Lucas units have old school rubber based seals inside and are designed to use mineral based fluids. I don't recommend the use of synthetic brake fluid in a JH system for this reason.

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 Posted: 05-28-2011 08:09 pm
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mcguan.2
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Greg, understood, but wouldn't it be strange for a brand new MC (purchased from the club store) to start leaking within minutes of installing?  I completed this whole project yesterday, and literally as soon as I took the JH for a test drive, the MC started leaking out the back.  To me, that would seem more like a faulty piece of equipment than a seal failure due to using a synthetic fluid. 

Has anyone else had anything like this happen?

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 Posted: 05-29-2011 03:20 pm
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LambandAndy
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Are you sure that fluid from your old master cylinder didn't leak into the brake booster and that is what you are now seeing leaking out?

Andy

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 Posted: 05-29-2011 03:28 pm
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Greg Fletcher
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It shouldn't leak, some people can get it to work with DOT 5 and have no problems, but putting in the fluid recommended by the manufacturer is usually a safe bet. Take a look at the box or the instructions that came with the unit. They usually say what fluid is required, some actually say DOT 5 with void the warranty- it depends on the brand. I would try draining the system, replacing with DOT 3 or 4 and do a complete flushing and see how it works.

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 Posted: 05-30-2011 01:45 pm
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JodyKerr
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How much is "a little"?

And what colour is it?

purple = dot5, dirty/brown = old fluid.

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 Posted: 06-25-2011 11:40 pm
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mcguan.2
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It's really hard to tell what color the fluid is because it's not coming out in copious amounts, just seeping out. I've been driving it around to see if it was doing as you suggested and just coming back out from the booster side (from the previous MC failure) and it's still coming. It does not appear to be dirty fluid, though, which suggests that it is the new fluid.

I put a white napkin under the booster, but like I said, it just seems to be in such small amounts that it's "clear" if anything. I thought that if it was just residual coming out of the booster, that it would stop after a few drives, but that doesn't seem to be the case. I'm trying to strategize my next move. If I have time tomorrow, I might do as Greg suggested and just empty it all out and try again with DOT 4.

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