Hey Guys,
I just got finished installing my bearings, brake discs, pads and hubs and when I started the car up (thank god it was still on jack stands), I noticed I had no brake pressure! I'm pretty sure it's the master cylinder because I can see some fluid and some bubbling coming from the seal where the brake fluid tank meets the cylinder. In fact, I'm almost positive the air leak is there. Can I just change out that one seal and see what happens? Or do I need to replace the whole damn thing which I'm sure is expensive? Thanks so much for the help with everything. You guys really made the other jobs so easy for me. I need to get this brake thing solved because this car is a daily driver for my family. Thanks again. I can't believe this car chose to do this to me........


Alex

__________________
1983 300D (parked for four years)
2012 VW Sportwagen TDI Manual
2001 Miata SE
1962 Chevrolet Corvair Rampside

Did you open the brake hydraulic system? If so, how did you bleed the brakes? If you used the "pump the pedal" method there is a good chance that the master cylinder is shot. Even if you didn't open the system moving the master cylinder piston though an area in the bore that hasn't been used in almost 20 years can rip the seals. You might get buy with a seal kit(for the whole thing, not a single seal)but if it had enough corrosion or build-up to tear a seal...just replace it.
Regards,
Randy D.

Dieselhead,

When you put in the pads, you obviously managed to push the pistons back into the calipers to make room for the new pads. Did you do anything else like replacing a hose, the entire caliper, open a bleed screw?

Assuming that you just pushed the pistons back and put in the pads, the pistons are a little too far back, and may take a stroke or two of the pedal to tighten the pads to a point where you will again "have a pedal".

As long as you didn't open any of the hydraulics, you should not have lost any seals or the like.

If stroking the pedal does not bring back pressure, try bleeding the brakes before replacing anything. The likelihood of the master cylinder coincidentally failing at the same time that you took everything apart is unlikely.

I hope this doesn't sound insulting, but we have no way of knowing what your skill or experience level is, but do you know how to bleed the brakes if necessary.

If the brake fluid is not clean and clear looking, it would be a good thing to flush the old fluid anyway. But remember, you are working on brakes, there's a safety situation involved here. We can help you, but make sure you fully understand these procedures so that you keep the car safe.

Hang in there and keep answering everyones questions as well as continuing to post more questions and we'll get you through this, just hang in there.

Good luck,

Larry,
Here's what I've done to various cars if it'll help you assess my experience:
Timing belt: Volvo 850
Brake pads and rotors: VOlvo 850
Strut mount replacement: Volvo 850
Stereo installation: Volvo 850
Hub assembly: Volvo 850
Brakes pads and rotors: Toyota Landcruiser
Strut replacements: 300D
Alternator replacement: MGB
Stereo installation: MGB
Exhaust replacement: MGB
Valve adjustment: MGB
Compression test: MGB
Thermostat replacements: MGB, Volvo 850

I guess that's all I can think of off the top of my head. I did some stuff for friends' cars but nothing was too substantial, brake stuff, A/C stuff.

Anyway, I turned the car on, and pumped the brakes a few times and nothing got better. The major mistake I made was to try and bleed the brakes with the reservoir cap still on. When I realized it, I opened it but I think it was too late. The grommet where the tank meets the cylinder was significantly wet (although there was no heavy leaking) and it was bubbling in that area. This is what makes me believe that it's not the cylinder, just that little grommet (which fastlane sells). Also, there is something white at the bottom of the tank. When I tried to bleed the brakes (front driver's side) after I realized what I was doing wrong and opened the cap, all I got was air. Actually, I wouldn't even call it air. According to my pump, there was actually a vaccum being created when I pumped the mityvac. BUT, it's interesting to note that while no fluid was being drawn, the tank was filled to the MAX line. COuld the tank have gotten disconnected from the cylinder? Please let me know what you think.

Oh, I bleed my brakes using a mityvac vaccuum pump, not the brake pumping method.

Also, someone mentioned something about the car sitting for 20 years. We've been using this car almost everyday since it was purchased.

Thank you so much

Alex

__________________
1983 300D (parked for four years)
2012 VW Sportwagen TDI Manual
2001 Miata SE
1962 Chevrolet Corvair Rampside

Dieselhead,

Here are a couple of thoughts I have.

The vacuum system at the wheel works marginally well for flushing the brakes, but if you have a serious amount of air in them, it may not work out very well. You may have to get someone to run the pedal for you, while you get under and get dirty. You probably need pressure on the system to get the air out of the system.

I don't think leaving the cap off while bleeding hurt anything, it just caused it to make a mess.

Additionally, if a great amount of air made it into the system, you may need to "bench bleed" the master cylinder. Typically when you receive a master cylinder, you put it in a vise, use some lines from the outlets back to the reservoir, and cycle it several times to bleed the air out of the cylinder itself. You could do this on the car by removing the lines and then fashioning some lines from the outlets to the reservoir, then pumping the pedal, then reconnect the lines and bleed the entire system.

I hope this helps.

Good luck,

Alex, after reading all the posts on this one, I have to consider myself lucky. The tank grommets began to leak on my car, and before I got around to replacing them, the master cylinder inhaled a bunch of air. The brake pedal traveled all of the way to the floor a few times as well. So I replaced the grommets and flushed out the air using the pump(helper) method. This worked fine and I have no noticeable problems with the brake system. I think we went through a couple of bottles of fluid to get all of the bubbles out.

Gary

Are those tank grommets hard to change out? I'm pretty much sure it's those grommets and they're not expensive so I figure I should try it and see what happens before I start to buy more expensive replacement parts.

I hate doing the brake pumping (helper) method to bleed brakes but oh well, if that's the recommended procedure, I have no choice.

Do any of you guys think it could be the master cylinder? Or something more trivial?

Thanks so much for the help

Alex

__________________
1983 300D (parked for four years)
2012 VW Sportwagen TDI Manual
2001 Miata SE
1962 Chevrolet Corvair Rampside

when I rebuilt the front calipers on my '79 300SD, I bled the empty calipers and lines by just opening the bleedscrew and letting the air come out. Eventually the brake fluid appeared so I closed the bleed screw and did the other side the same way. I made sure the brake fluid reservoir stayed full while doing the "gravity" bleeding operating.

The brakes have worked perfectly ever since, over 6000 miles.
P E H

Actually, by following P.E.'s procedure you possibly could get a pedal. What happens, even sometimes after using the old fashioned two person method, air bubles will work their way up and out. I have bled brakes before that were marginal, and the next morning, they were rock solid.

If your problem IS the grommets below the reservoir, I don't think this would be your only problem. I assume you added fluid, and any leak above the cylinder itself would not introduce air below that point and would not in itself cause a soft or no pedal.

To replace the grommets you will simply pry the reservoir out of the grommets and then pry the grommets out of the cylinder, then push the new grommets in place with your fingers.

Good luck,

From what I read, if this was my project I'd do some more bleeding, whether gravity or helper and pedal first. I'll guess that if the grommets are leaking air, it's likely to be a small amount. With a little air in the brakes you should still get some pedal feel, even though soft and springy, and they should respond to 'pumping' a few times with more feel.

I'm also guessing that if the grommets are leaking, more fluid will come out than air get in as they're submerged in fluid.

My $0.02 bet? Flush and bleed some more first. It's basic, low technology work, only takes time and doesn't involve messing with the master cylinder! Try the simple things first, as you've no doubt discovered given your experience.

Best of Luck!

BCingU, Jim

Jim, I guess my reply was a bit ambiguous. I got the air into the system because the reservoir fluid level dropped too low after leaking past the old grommet seals. I don't think any air got in through the old seals themselves.

Alex, the grommets should be completely dry. They only cost a few bucks and are well worth replacing after 20 years of drying out.

Gary

I agree with these posts and 123'. If the grommets are indeed leaking, replace them, enlist a pedal pusher, get a quart of fluid and give it fits! You'll get there.

Don't forget that if the m/c managed to get completely dry, you may have to put bench bleed lines on and push the pedal until fluid is flowing through the bench bleed lines, then hook up the brake lines.

Hang in there,

And of course, you know not to push the pedal all the way to the floor when the bleed screw is open. It's an easy way to kill a master cylinder. You don't want that piston travelling too far! Just go 3/4 of the way down and close the screw. Pump the pedal up a few times and have your helper open the bleed screw again and make sure it's closed before you hit the floor. By the way, master cylinders aren't expensive. And it might be good precaution to put one on--as well as grommets! And remember to use a good quality DOT 4 fluid, such as Ate SL type.

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Regards,
Aaron

You may be running the rear reservoir dry. I do not know which model you are working on. Sometimes the fluid level of the rear reservoir is very hard to see and there is a pin hole near the top connecting the front and the rear reservoirs, no other connections. Try to fill up the front reservoir all the way to the top. Wait for the brake fluid get into the rear reservoir and then refill again until the rear is full before bleeding. Use a flash light if necessary to check brake fluid in the rear reservoir. Be sure the pin hole to the rear reservoir is not clogged.

I hope that helps. Good Luck.

David

I replaced the tank grommets and brake fluid tank, filled everything up with fresh brake fluid, bled the front brakes using the helper method and figured that everything would be ok. I get good pedal pressure, the grommets aren't leaking, and while bleeding the brakes, got them to the point where opening the bleeder screw and pressing the brake pedal gave a good hard squirt of air free brake fluid. The problem I see now is that I can't turn the front hubs by hand. Will the calipers release themselves after I put the car back on the ground and get it rolling? Will turning the car on and pressing the brakes with the aid of the brake booster clear up my problem? Both front hubs seem to be slightly frozen. The pads and rotors are new. This car is driving me up the wall!

Alex

__________________
1983 300D (parked for four years)
2012 VW Sportwagen TDI Manual
2001 Miata SE
1962 Chevrolet Corvair Rampside