oatmilk Posted April 13, 2014 Share Posted April 13, 2014 Hello All, I have a basically stock 1973 240z thats been lowered by the previous owner. Probably cut springs. I drive the car about 3-4 times a year so obviously it sits for long periods of time. I knew from a while back the brakes seemed to be dragging. Well I went to drive it yesterday and the rears are really dragging. The car will not roll even on a slight incline. If you jacked up the rear you cannot turn the wheel. The car will move forwards and back by the power of the engine in first gear but it will not roll. Let off the the power and it will not roll. I changed the master vac a while ago using a Cardone A1 reman unit. I recently verified that the reaction disc is in place. A new master cylinder was installed at the same time. So I need to know the proper steps to diagnosing this. If I unbolt the master cylinder from the master vac there is no change, the rear drums stay locked. The emergency brake is in the down (not engaged) position. I'm wondering if its the master cylinder but I have no idea how to test it on the car or off. The stock front brakes also seem to be dragging but nothing like the rears. Not even close. Still leads me to the master cylinder. In regards to adjustment of the rod from the master vac...not possible Maybe some are adjustable but mine would not budge a mm. Yes I can see it has threads behind the acorn shaped end piece but they appear to be simply decoration as that thing doesn't budge. I havent tried any PB Blaster on it though. If I open the rear hydraulic lines for each rear drum brake will that release the brakes? All brakes lines appear to be in working condition. I'm not sure if I had the emergency brake on when it was sitting for the last long period or not. Just want to drive this thing and now I can't. Thanks for all the help in advance. Quote Link to comment Share on other sites More sharing options...
oatmilk Posted April 13, 2014 Author Share Posted April 13, 2014 Also tried banging on them with a mallet. No change. I don't have a propane burner to try that method. Quote Link to comment Share on other sites More sharing options...
Miles Posted April 13, 2014 Share Posted April 13, 2014 Try opening the bleed screws on the MC. If fluid pushes out and the car rolls without resistance then most likely the push rod is adjusted too long. A push rod adjusted too long will not allow fluid to return to the MC after braking. Google how a MC works to see why. Suggest that you spend several hours searching and reading in th brake forum as this has been covered many times. Quote Link to comment Share on other sites More sharing options...
oatmilk Posted April 13, 2014 Author Share Posted April 13, 2014 Thanks. Went through many searches on here and the web. Just wanted an answer likes yours that kind of tells me what to expect or look for. Thank you. Quote Link to comment Share on other sites More sharing options...
Six_Shooter Posted April 13, 2014 Share Posted April 13, 2014 I assume this problem only occurred after the car has been sitting for a while. The car would roll fine when it was parked? If that's the case, you're looking at the wrong end of the braking system. The problem will be within the rear drums themselves. This can especially happen when parking brake is left on. Usually the parking brake portion get stuck on, due to lack of lubricated joints, and won't release right away. It would be best to pull the drums. You can back off the adjustment to loosen the drums, get everything in the brake system moving freely, reassemble and re-adjust. Quote Link to comment Share on other sites More sharing options...
Miles Posted April 14, 2014 Share Posted April 14, 2014 The attached file should answer most of your questions. If you haven't done so, download a copy of the Factory Service Manual (FSM) for your Z. Buy a Haynes Manual for your Z. Buy a copy of How to Restore Datsun Z Car by Wick Humble. Available at MSA, Amazon, Black Dragon etc. If you haven't already done so, completely rebuild your brakes including new hoses. It will solve most problems associated with an old car that may not have had the brakes serviced in years and will improve the safe operation of the car. The books above will guide you. BR Brake System.pdf Quote Link to comment Share on other sites More sharing options...
RebekahsZ Posted April 14, 2014 Share Posted April 14, 2014 Buy a huge rubber dead-blow hammer. Make sure parking brake handle is down. Smack the ever-living snot out of the drum at the curved edge between the flat face of the drum and the fins. If you hit on that curve, you are unlikely to hurt anything. But if by chance you shatter a drum, you are half way there. Wear eye protection. Hit it HARDER! Stand up and smack it some more. Use both hands. Quote Link to comment Share on other sites More sharing options...
oatmilk Posted April 15, 2014 Author Share Posted April 15, 2014 Okay here is the latest. Put the rear of the car on jack stands. Then i used my flare wrench and some tubing and loosened the rear bleeder on the master cylinder. The brake fluid only dribbled out. No gusher at all. Went to spin the rear tires. Passenger side rear spun a little but still dragging. Driver side rear, no bueno. It wouldn't budge at all. I then removed the master cylinder from them the brake booster to see if the master cylinder was moving at all inside the cylinder. I pushed the tip of a screwdriver in to force it compress. It only moved a 1/4" at best with as much pressure as I could muster up. Being a newbie to M/C movement I wasn't exactly sure what the correct stroke of the 240z should be. But taking one of the post above into consideration, when putting the M/C back together with the booster I put some washers on the two bolts before putting on the nut. The net effect being like I adjusted the rod coming from the brake booster back a tad so as to not make the master cylinder force the brakes into a dragging posture. So i moved on to the emergency brake. Looked it over on the outside and didn't see anything unusual. Pulled the clevis on the driver side rear and wiggle that around a bit and no change. I then took out the big sledge hammer and gave a few whacks on the curved portion as recommended in a post above. You could see the drum moving a bit front to back. That was at least good news because I now know the the drums are not frozen from motion front to back but just from rolling motion. I then went for a non-no. I sprayed PB Blaster inside the drums via the one small hole on the drum face. I didn't care about ruining the shoes since I will redoing them anyway. I just wanted to see if a combination of PB and inertia from the engine turning and weight of the car forcing the wheels to rotate would loosen things up enough for the car to freely roll. Knowing the amount of reduced braking this could result in, I just slowly began to drive the car back and forth in the driveway only. Sure enough the car started to move more easily. The engine wasn't having such a hard time. Picture a big smile on my face. After having did a valve adjustment, SU carb adjustment and install of a new electric carb friendly fuel pump which go the engine running much better the two days before I was on Cloud 9! Decided by a few good runs up and back on the driveway that the car was braking well and rolling backwards via its own weight down the inclined part of the driveway to drive for a spin slowly up and down the block. Again it was working perfectly. Happy, Happy Joy Joy. Figured the God's must be looking down favorably on me today. Company came over to the house so I put the tools away and went in for a bit. Went back out a hour later to move the car farther up in the driveway. Uh-oh! Not good! No rollie via its own weight anymore. Can hear the rear drums dragging again and catching and releasing a bit. This was far from Miller Time, it was Bummer Time. Ok at this point I'm figuring the PB blaster must have worn off or something. Next up take up further advice from posts above and remove the rear drums tomorrow and take a look. Unfortunately I still haven't been able to completely rule out anything from either end of the car being the problem. As they used to say on TV "To be Continued". Thanks for the help and ideas. Quote Link to comment Share on other sites More sharing options...
Six_Shooter Posted April 15, 2014 Share Posted April 15, 2014 The fact that you opened the bleeder and that did not release the brakes rules out the hydraulic portion completely. It's the linkage in the drums causing this, it's a common issue with drum brakes, and mechanical parking brakes. Drum brakes are especially bad because the brake dust is contained in the drum and will get into the pivot points in the brake linkage, gumming up the works. Quote Link to comment Share on other sites More sharing options...
oatmilk Posted April 15, 2014 Author Share Posted April 15, 2014 Thanks Six Shooter. Onto the drums tomorrow. Will update hopefully with good news. Thanks again, Quote Link to comment Share on other sites More sharing options...
johnc Posted April 15, 2014 Share Posted April 15, 2014 Take a step drill bit and enlarge the hole in the outer face of the drum to about 3/4" Drill it with the hole at about 2 o'clock. Disconnect the e-brake cable from the clevis. Turn the brake drum so the hole is at 6 o'clock. Using a screw driver, push the e-brake lever down and away from the wheel cylinder. If it keeps popping back up stuff some toothpicks in there to keep the lever down, away from the wheel cylinder. Turn the brake drum to about 5 o'cock so you can get to the adjuster teeth. Turn the teeth down (IIRC) to move the shoes away from the drum. Quote Link to comment Share on other sites More sharing options...
oatmilk Posted April 15, 2014 Author Share Posted April 15, 2014 Thanks John. Headed to Lowes now for the stepped 3/4 drill. Quote Link to comment Share on other sites More sharing options...
oatmilk Posted April 16, 2014 Author Share Posted April 16, 2014 (edited) Latest update. Well Lowes didn't have any reasonably priced Step drill bits just the $40 + dollar Irwin Uni-bit. Not sure that it was HSS steel and would drill well on cast iron I went back home with the idea to just try and remove the drums and have a look inside. As mentioned in my first post I had an idea that removing the drums wasn't going to be difficult and sure enough it wasn't. Reviewed the FSM and moved forward. Since the car is not driven much and I had the brakes done years ago, the shoes looked brand new. The only differences between the rear passenger and driver side were that the driver side had the wheel cylinder replaced way back when and you can tell its still pretty much brand new. After adjusting the wheel cylinder with a flat head screwdriver ( sitting facing the drum in a downward motion) to loosen the brakes I put the drum back on and it spun relatively easily. I re-hooked up the emergency brakes by reinserting the clevis pin and had my daughter pull the handle to see the motion of what it was doing. Looking at the emer. brake operation it seems every time its applied the drums move out more and more and don't return making the brakes tighter and tighter. I can't see that not happening. I looked at how the adjustment is done in the FSM and man I wish I could see a video of proper operation. For now I have the emergency brakes disconnected. I can still hear the drums rubbing in a specific location during rotation of the drivers side rear wheel. Me thinks that perhaps the return springs are not strong enough of the wheel cylinders are not moving properly. This is where I'm at a disadvantage due to me not working on brakes a whole lot especially drum brakes. So next up is the either doing the brake adjustment the FSM way ( which based on visuals of my Emer.brake operation may re-lock up the drums) or take it to someone that knows correct brake drum operation to get another viewpoint. Thanks all, Edited April 16, 2014 by oatmilk Quote Link to comment Share on other sites More sharing options...
RebekahsZ Posted April 16, 2014 Share Posted April 16, 2014 Drill that hole like johnc said while the drum is off. A regular bit works fine and the drum is usually aluminum, not iron, so it drills fast and easy. Get step bits from Harbor Freight for $9-ish. Go ahead and get one-I can't live without mine. If you don't find anything else, try disassembling the parking brake cable to clean and grease it. That is a good place to have a bind. Quote Link to comment Share on other sites More sharing options...
RebekahsZ Posted April 16, 2014 Share Posted April 16, 2014 The parking brake return spring is on the wheel end of the cable near the spindle pin. That could rust and break, or it is often removed for a disc brake conversion. Quote Link to comment Share on other sites More sharing options...
Miles Posted April 16, 2014 Share Posted April 16, 2014 Clean and rebuild the rear brakes with new parts, adjust the shoes properly, and you will be done with it. Quote Link to comment Share on other sites More sharing options...
oatmilk Posted April 16, 2014 Author Share Posted April 16, 2014 Thanks Miles. That is the plan. Thanks to all for contributing. Quote Link to comment Share on other sites More sharing options...
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