The Stovebolt Site Forums The Shop Area General Truck Talk 1950 Chevy 3600 - brakes, MC issues - What am I doing wrong??!!

O.K., I mount my booster, master cylinder & proportioning valve, run all the lines and when I try to bleed the brakes.... NOTHING. I checked all the lines again, pump the brakes, NOTHING. I loosen one of the lines from the valve, no fluid is comming through. I disconnect the lines from the master cylinder and again nothing. What am I doing wrong??

I know this is stupid but I just can't help myself: Did you fill up the reservoir? If you did, which I'm sure you did, maybe there's just too much air for the fluid to come out yet. I'd just leave one of the bleeder screws open to see if the air will come out. I know that when a pipe breaks to a faucet sometimes you have to turn it on and let the air be forced out, and sometimes that can take up to a day, so maybe you should try that? Just my opinion.

Try a vacuum type bleeder to pull the fluid to the wheel cylinders, then it may work the old way once you get started.
Sounds like you know what you are doing, but sometimes it can be difficult to bleed a new system.

Grigg

Did you bench bleed the master? The reason for doing so, as I understand it, is to avoid this problem.

I wondered about that too, but I don't think I have ever "bench bled" one, and I have yet to have a problem bleeding brakes after installing the new MC.
If I have a problem like this I think I'll give it a try though.

Grigg

When I bleed brakes I leave the cover off the master cylinder so I don't create a vacuum that sucks the fluid back up into the master cylinder.
You have to push in and release the brake pedal slowly so you don't splash brake fluid out of the top of the master cylinder.

If the linkage isn't adjusted correctly, the stroke bore will not fill up with fluid because the piston does not move back behind the inlet hole.

Sounds like a prime problem to me. When you pump the MC with the lines off does anything come out of the MC, even air?

JDL-You're one funny guy! Yep, I did put in fluid.

Old Sub - I didn't bench bleed the mc, I've installed them on other vehicles & never had to. Might have to try that.

Jim - I tried it with the cover off....nothing.

Truckernix - Linkage is adjusted properly.

Big Chevy - Tried that....nothing.

You've been very thorough. Maybe you're not doing anything wrong. The master cylinder may be bad. You said that you took the lines off the MC and still got nothing.

I thought about that too. It's a new MC, but just to be on the safe side, I had another one laying around and it did the same thing. I'm going to see if I can find some sort of vacuum to see if I can pull the fluids through.

I found that after converting my 55 to a dual power master cyl,that I had to have the engine running to bleed the brakes.

Dale,
Is that because of the vacuum booster?

Always bench bleed a dual master cyl. That gets it started. The little kits that come with them are nice but after putting it in a vice hold your fingers over the holes & pump the piston a short distance letting it come all the way back. Re lease your fingers as you pump down & put them back on return. When fluid starts squirting out both holes you are ready to mount it & bleed the rest of the system. If you can't get any pressure then something is wrong with the cyl. but that's very doubtful.

Yeah but you should at least get air blowing through.

Success, I've got brakes!!

Good for you! Wish I had some. , Although I don't need any if my truck isn't running yet!

Good job on the brakes!

well what was the problem and what did you do to fix them..Peter

Although it's a tiny pain to build one, a reverse bleed or pressure bleeder is worth the time and effort. You can assemble the system totally dry without the risk of splashing brake fluid about (although if you are not using synthetic brake fluid by now, you're a luddite). For those of you not familiar with the device, it uses a pressure pot to install the brake fluid from the bleeder nipple forward to the master cylinder. I had to build one years ago to bleed Saab clutch systems. Without it, it was possible to bleed the system, but I counted one time and it took 1200! strokes of the pedal to make it operational. I've made simple reverse bleeders from large medical irrigation syringes and a length of plastic tubing. Works just about as well as the expensive version. My current favourite is made from a Wurth *tm pressure sprayer that cost about thirty dollars and a length of silicon tubing. These spray-bottles are the best ones I've ever come across with a leak free trigger assembly and a durable pump. You can even buy an overhaul kit. Be careful that you don't pump the resevoir full to overflowing. You may need the tiniest bit of post-install bleeding as there may be a little air left in the wheel cylinders due to the relation between the location of the bleeder nipple and the brake line but this will be minimal at best. You will waste virtually no brake fluid as well.
Go for it.
Regards,
Ken Beckman

I rented a vaccuum pump from Autozone, disconnected the lines from the proportioning valve and pumped away intil I got fluid from the MC, then attached it to the lines at each wheel and pulled the fluid through. I could have bought a pump for $30 but didn't see the need. I wouldn't be using it that regularly. The rental was $50 but I returned it when I was finished. Well now that I have the stopping part down, I'll work on the "going" part. I hope to have it going soon. It would be nice to have it ready by May 10th in time for a welcome home celebration the VA is planning for the troops returning home from Iraq. My department will have a booth setup to let them know the benefits they are entitled to. It sure would be cool to have a bolt there to get their attention!