I just replaced the front calipers on my 67 cutlass. I tried to bleed all four corners afterwards but got no fluid out of either rear drum. The front calipers bled fine. I decided to lift the back off the ground to test the rear brakes and sure enough they are completely inoperative. (The parking brake still works) The rear brake shoes and drums were replaced about 2 years ago. I'm thinking its a bad master cylinder, but do you think it might be a bad distribution block? What would cause no pressure to either back brake? I was hoping to get some advice before I rip apart the brake system.

I'm guessing the rear brakes haven't worked in some time.

Thanks.

 

I've never had a distribution block go bad, but that doesn't mean it can't happen. First I think you should try to pinpoint where the fluid stops. Since you said there's nothing getting to the rear wheels, try loosening the fitting from the master to the distribution block, then pump the pedal to see if you have fluid pressure there. If so, loosen the fitting on the back of the block that leads to the rear brakes to see if you have fluid there. Continue until you stop seeing fluid and look for the problem between those two points.

John

 

I agree with the above, starting at the master cyl. loosen each major junction to locate where your blockage is. You will need someone to pump the brake pedal and apply minor pressure while you loosen each connection.

 

I'd start at the other end. The rubber hose at the axle (does it have one?) would be my starting point.

 

Ok, I followed 2blu442's advice. I'm getting good fluid flow downstream from the master cylinder and the distribution block. Unfortunately the remainder of the fittings past the distribution block are seized (and now rounded off) so I wasn't able to check the rest of the line. The fittings that connect directly to the drum came out easily, but as expected...no fluid. So, the MC is good, but I have a blockage somewhere between the distribution block and the drums. I am going to replace everything aft of the distribution block. I found all the parts online though various retailers and plan to get them ordered tomorrow.

Once I get it back together I'll update this thread. Thanks for the help guys!

 

It's probably the flex line at the differential.

 

Two possibilities here. First (and this happened on my friend's 72 Supreme) is that rust can block the bleeder port in the wheel cylinders. We completely unscrewed the bleeders in his back brakes and still nothing came out until I poked in the hole with some copper wire. Of course, if there's that much crap in the wheel cylinders, they probably want to be replaced. The other option is that the piston inside the distribution block has moved all the way to one side. This can happen when you bleed the brakes. If the dist block has any crud or rust in it, the piston can stick. Sometimes you can move the piston by opening a FRONT bleeder and pressing hard on the pedal to build pressure in the back circuit. Of course, you might push it too far the other way. Failing this, you need to disassemble the dist block, clean it, and recenter the piston.

 

Sounds like the proportional valve has set isolating the rears. This can happen when there is pressure up front but none in the rear. Easiest way to fix it is to watch the brake light or put a continuity meter (ohmmeter) across it to ground. If there is continuity to ground or the brake light is on its more than likely set. To reset the valve open a front bleeder to depressurize and step on the pedal hard to center it. The ohmmeter will open circuit indicating the valve is in center position. From there, gravity bleed. Then start the rears first and then the fronts. Had this on my 73 when I replaced all the lines.

 

Hey guys. I think I did a poor job of explaining the situation before. My distribution block seems to be working fine. I disconnected the front-to-back line at the downstream side of the distribution block, pressed the brake pedal and fluid squirted out of the distribution block. So it appears that the system is working properly up to that point. As I go further back, I can't get any of the remaining fittings loose (end of front-to-rear, flex hose, and axle lines). However, I can remove the fittings where the axle lines connect to the drums. I disconnected those and pressed the pedal, but got no fluid out of those lines. So to the best of my knowledge there appears to be a blockage somewhere between the distribution block and the drums. The wheel cylinders may be bad, but I wouldn't know because they're not getting any fluid to them. I plan to replace them just in case. In addition, I'm going to replace the front-to-rear line, flex line, and the two axle lines.

BTW, I don't have a proportioning valve as far as I can tell. My car was originally equipped with 4 wheel drum brakes. The PO converted it to front disks. Not sure if that's why I don't have one??

 

Ok, here are the parts I bought. I can't wait to get them as "convertible weather" is in full swing here in Virginia Beach. I'll repost my results. Thanks for the help!

Front to Rear Line:
http://www.jegs.com/i/Right+Stuff/96...FcWTfgodGIAAew

Flex Hose:
http://www.stockwiseauto.com/product_info.php/products_id/735381/fit_id/1051/Year/1967/Make/Oldsmobile/Model/Cutlass/source/googleps?gclid=CNHA0YzFhL4CFcdefgodkDwALQ

Axle Lines:
http://www.jegs.com/i/Right+Stuff/965/ARA6702/10002/-1

 

Well the parts did the trick. The fluid is flowing normally and the rear brakes are working as advertised. Thanks for the help guys.

 

Glad it's working! Did you narrow down where the blockage was?

 

I wasn't able to isolate the blockage due to all the rounded off fittings. I know where the blockage is now...the city landfill!

 

True dat.