Leaking behind master cylinder

[bmiszuk]

I've got puddles in the garage... again. It's leaking between the master cylinder and the hydraboost. I assume it's the hydraboost unit that leaking (since it's the most expensive!). Can they be repaired or do I have to buy another unit?

[DmaxMaverick]

You need to determine what fluid is leaking. Is it PS or brake fluid. While the HB can leak at the front, they generally leak at the accumulator, or at the rear seal. The master cylinders can be a problem. If yours is aluminum, that's a more likely candidate. There are a bunch of inferior aftermarket MC's, even if new, not reman. If you are getting a "puddle" of fluid, either one should show a decrease in the fluid level.

If it is your HB, there are rebuild kits available, but not advisable unless you have extensive hydraulic component experience. They can be quite demanding, and in many cases, hard parts not included in the kit have failed.

[doncannon]

Hello all,


bmiszuk: When I sold auto parts and there was a leak between the master cylinder and the booster (vacuum) with fluid running down the booster it was the master cylinder. I think it would be the master cylinder. I agree with dmax see if you can put you finger in it and smell it. Should smell like brake fluid or power steering fluid. FYI: However there was some people that used transmission fluid in their power steering.

Hope this helps,
Don

[TB1]

If it is the master cylinder buy a NEW one not a reman I just replaced my front brakes and MC bought a new Raybestos unit cost $94 Canadian. A buddy of mine went through three rebuilts before he finally bought a new one and there have been no problems. As for the leak mine was the same leaking between the M/C and H/B. Sometimes it's better off to spend the money up front than do the job 2 or 3 times.

[bmiszuk]

I'm losing both brake fluid and ps fluid. This weekend the ps hoses get replaced to solve at least part of that problem. Hopefully then I can figure out what's leaking from the master cylinder area.

Are the master cylinder rebuild kits worth trying? My master is not aluminum. It looks like cast metal and has a rebuild stamp on it showing "12-03". The rebuild kits seem to be just a few seals and a piston or something for about $15.

[DmaxMaverick]

You can rebuild a cast iron MC, but....

The bore, input shaft, and plungers have to be in relitavely good shape. If you can make it like new with a hone, it'll be OK. The kit should have a statement of min's/max's for critical components. If it takes a lot of honing, or has deep scores in it, it needs to be bored, and oversized cups and plungers are needed. At that point, there's no point in doing it yourself. If you only plan on doing one or two MC rebuilds, it really not worth rebuilding yourself. The tools and equip. will cost more than a good MC.

Some aluminum MC's have steel or CI bore sleeves, and those can be rebuilt like cast iron MC's. If you have to replace a sleeve, the cost to get just one will be more than buying a new MC.

Also.....
If you are already having ussues with leaky hoses, fix those first and leak check after. The hose leaks can weep down and make it appear to be leaking elsewhere.

[doncannon]

Hello All,

bmiszuk: when I was in the auto parts we priced a kit to rebuild and then a remanufactured master cylinder. The reman was usually cheaper than the kit. I know it does not make sense however it is cheaper. I would price a new one like the other members suggest they may not be too much more. New is always better.

hope this helps,
Don

[doncannon]

Hello All,

bmiszuk: when I was in the auto parts we priced a kit to rebuild and then a remanufactured master cylinder. The reman was usually cheaper than the kit. I know it does not make sense however it is cheaper. I would price a new one like the other members suggest they may not be too much more. New is always better.

hope this helps,
Don

[bmiszuk]

This weekend I replaced all the power steering lines which solved those problems. Then after pressure washing the engine and cleaning the MC, I found that it's actually leaking brake fluid from the CAP. As I drive, fluid is splashing out the lid and running down. I cleaned the MC body with brake cleaner then after driving to work, it's all wet again and obviously coming from the top of the MC. Sunday I replaced the MC cover gasket with one of those Help! ones from the parts store but it's still leaking this morning.

[Robyn]

Does your truck have a plastic reservoir?
If so it probably the reservoir leaking

[bmiszuk]

Cast iron reservoir with metal lid held in place by a wire over the top.