MC Leaking?

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Vali68

Vali68

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I have a 68 Valiant with power brakes and I am wondering what common cause of fluid leaks? I see fluid is on the bottom of the MC when I look at it, But i can't see where the fluid is coming from.
If I have to, how hard is it to replace the MC on the car? I have included a picture. My son had the MC replaced by a shop about 7 years ago. The first one they got in the shop was the wrong part. So they had to send it back for a replacement. How hard are the MC's for these cars to find?
Can I get it from a place called rock auto?
 

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They're dirt cheap wherever you get them. Rockauto should have them. So should Autozone, Oreilly, Advance or whatever you have local to you. I'd say they're less than twenty five bucks but Rockauto should be the cheapest. They're simple to replace too.
 
Still available and easy to get. Just about any auto store can get them but might take a day or so to order. Rockauto is good too.

Easy to replace but make sure to bench bleed before the install or do it on the car with two temporary lines routed into the fluid chambers. You have to do a complete system bleed after install.
 
What causes them to leak at just over 7 years? I'm not sure if it matters, but it has disc brakes on the front and drums on the rear.
 
What causes them to leak at just over 7 years?
Click to expand...

Any number of reasons. They should last longer but it's hard to say not knowing where the MC the shop installed came from. Or where the leak is coming from. They should last longer but they're so cheap and easy to replace that it isn't worth quibbling about.
 
I would take the vacuum line off the power booster and look for fluid before you get a master. It could be sucking the fluid out of the back of the master.
 
New power brake booster. Easy check just pull the PB vacuum line and se if there is fluid in it. If so need a new booster.
 
You're referring to the Power booster side of the vacuum line which is the hose that goes from the booster to the manifold correct?
 

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Yes it is, take of one side whichever is easier and check for brake fluid. I f there is change the booster.
 
Pretty common but somewhat difficult to pinpoint leak is the rear seal on the piston.

Leak will be between M/C and firewall, or in your case M/C and booster.

I put a somewhat name brand M/C on my 73 Satellite the week I got it (because of the leak I just described), ant in less than two years, the new M/C is leaking in the same place.

IIRC that M/C was $30 at Advance.

Rebuild kits are available (and it's not that hard), for about $5...and you might do a better job than that 12 year old Chinese girl that did it the first time.
 
YY1, That's where it looks like most of the fluid is accumulating. But I still want to check the vacuum like halifaxhops suggests. Thanks for replying.

The pedal seems kind of stiff still. It was parked for a while and when we first started working on it, the pedal would stick. So we would pull it up with our feet. When we checked the reservoir at that time, they were both really low on fluid. so we filled them up a bit and bled the lines. Then the pedal wouldn't stick anymore, but I notice that the bottom of the MC is wet with brake fluid.
 
Just check it don't waste time analyzing it. Yes or no? Could be be both. Sorry about being rude.
 
Halifaxhop, Those with thin skin shouldn't be working on old cars anyways!!!!
No worries.
 
Any luck with it? I just noticed you are loosing fluid, is it a lot with no visible leaks?
 
halifaxhops said:
I would take the vacuum line off the power booster and look for fluid before you get a master. It could be sucking the fluid out of the back of the master.
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Unlikely in our cars. The gap between the MC and booster is open to the air, w/ just a dust filter. You are thinking of newer cars w/ flat pancake boosters. They don't have the inner belllows of ours and must seal vacuum between the MC & booster. My 85 M-B is like that, and I think my minivans.

I would first suspect fluid is slopping out the reservoir cover. A little detective work will resolve. Wipe it clean and see if you get any drops while sitting, or only when driving. Tape paper towels above the ports and see if they get wet. If so, the leak is from the cover.

You don't have to bleed the whole system when changing the MC. If you get all air bubbles out of the MC and can still see fluid in the tubes, you can just connect them and have solid fluid. Perhaps have a helper just barely press on the brake pedal as you tighten the fittings, flowing a little fluid out (catch w/ newspapers, it will remove paint). Still, you should refresh the fluid every 3 yrs or so to avoid internal rust, unless using silicone fluid (like me).
 
Bill,
If the reservior is leaking from the cover, should I replace the cover or just buy the whole MC and replace it?
 
If you don't want to keep fooling with it, and don't care about original look, I would buy a 4-to-2 bolt adapter plate ($30 ebay) and a newer aluminum 2-bolt MC. Many here use an MC from an 80's Dodge truck. I put a 95-99 Breeze ABS MC ($25 new ebay) on the same Bendix booster as yours on my 65 Newport & works great. I forgot if that booster has an adjustable rod into the MC. If so, I adjusted it to minimize "lost motion".
 
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