Hi all, I have an odd problem with a build I’ve been working on. I have a car on four drums with a proportioning valve between to account for the fact that the rear drums are substantially larger than the front as the cars engine, transmission and rear axle are all swapped in from another later vehicle including a brake servo. The front brake hardware is original aside from replica brand new cylinders to replace the shockingly crusty, leaking old ones. To account for the size difference I have a Wilwood proportioning valve installed above the gearbox that distributes the braking force in favour of the front as the rears steal the show without. This replaced a dodgy Amazon unit installed by previous owner with incorrect flares that popped after I slammed my foot on the brakes in testing. My bleeding procedure goes: 1. Run engine, pump foot on the brake until hard. 2. Turn off engine, navigate to furthest bleed ****** from reservoir, undo, redo. 3. Without restarting the engine, pump foot on the brake, then repeat process until no bubbles or old fluid is present. 4. When this is done, begin next brake. *all done monitoring reservoir level I today installed new brake cylinders to both sides at the front including new copper pipes connecting the top and bottom pistons. After doing so I followed this brake bleeding procedure, attempted to drive back and forth for testing and found my brakes had applied themselves after pressing the pedal a few times at standstill (engine running)- pedal became rock solid, car was immovable. I then proceeded to bleed the farthest brake which resulted in a huge pressurised spurt of fluid and the car rolling back. I searched and identified a small leak from the braided hose connecting to the left set of pistons which I rectified by tightening (had not been tightened with any substantial force after replacing the new cylinder- which is my bad), tested by whaling on the pedal with the car off and saw no further fluid. Running the car and testing the pedal again I found the brakes again applied themselves to a full lock, relieved by switching off the car and standing as hard as I could against the brake pedal and releasing. I am ***uming the lack of pressurisation in the loose line means the car has inducted air from the atmosphere into the brake system hence the lockup and huge jut of fluid out the back. I won’t pretend I’m an expert- I am 22 and three years young to rodding but want to see if I need to be looking somewhere else tomorrow. Any advice appreciated!
The rod between the brake pedal to the booster or the from the booster to the master is too long. Not allowing g the master piston to release back all the way. Check for free play between the pedal and the booster. If that's OK, add some washers between the booster and master and see if that helps. If it does shorten the link from the booster to the master.
How were the brakes working before you did any work on them? Since you said there was already a proportioning valve on the system was that done by the previous owner because the rear brake drums were larger?
It's not air. Either the booster isn't returning or the rod between the booster and master is too long. This will prevent the master cylinder from returning far enough to uncover the compensating port thereby not releasing the pressure in the system.
The brakes did not work at all. There was very little and very old fluid in the system, they were completely ineffective. One cylinder was weeping heavily.
I think you do not have enoughfree play in the pedal to master cyl . Not allowing it ( master cyl ) to retract completely
Copper? I hope you mean Nicop, or Cunfer lines, and not actually Copper. Copper has no place in a brake system!
You do not describe the MC or servo. You bleed with the servo powered at first, then shut off the engine and do the remaining steps. You mention left pistons, but not F or R. You tell us some other stuff that is no longer a part of the system. I'd guess you are being a bit cagey about exactly what the OE front brakes are and what the later model rear brakes are and what kind of servo is in this. All of that may have a profound effect on diagnosing this, or it may not be an issue. I'd agree that the basics as outlined by others is the best guess with incomplete info. It's messy and hard, but the next step is to remove a part of the system that is questionable and retest. In this case, block off the rear brake portion of the system and check to make sure the MC and front work properly.
I have no idea if they’re called something else in the states but copper brake pipes are standard here. Brake hoses are braided stainless in case there’s some confusion.
You’d ***ume correctly as I am in ownership of what was quite a widely followed build here in the UK about ten years back. I suppose I have nothing to lose- The rear axle is a Ford Capri, the brake servo is from a Ford Sierra, the car itself is a Hillman Superminx with the original front brake ***embly being tied to an Austin Ten beam axle. I believe that the master cylinder is an original Hillman one. I purchased this vehicle with little do***entation and as the car has p***ed through around 8 owners, each adding, I’ve refreshed almost the entire brake system in terms of piping and fluid. All front brake cylinders are new, the Ford Capri brake cylinders are original as they’re in perfect nick. The servo huffs and behaves exactly as I would expect. The problem has been intermittent and there was a period where the brakes worked as expected and I could drive with no problems- I then discovered a small leak I rectified, and the problem resumed. So to me it would be something pressure related.
Have you tried asking about this on Rods and Sods? It seems a much better place to find experience with the specific components you have . Plus more likely to inadvertently run across a previous owner, seeing as you mention it being a 'known car' over here. (I've personally never heard of a well known Super Minx)
The problem you're experiencing sounds very much like that mentioned in the first sentence of the first response that appears to have p***ed you by. To explain further, there needs to be a smidge of play between the pedal piston and the booster / servo and also between the servo and the master ( this is internal between these components and can't be seen or felt. Dismantling and judicious measurement required). Absence of free play in these areas will cause pressure retention and binding. Where in the UK are you? Lots of help on UK nsra forum and rods n sods forum, and might illicit some local help too. Chris
Re reading what you've said, I surmise you've never known the brakes to have worked on this car, correct? The ***ortment of parts from different sources could well mean that the clearances previously mentioned could well require attention indeed the builders may have never appreciated that? At least the brakes seem to work which is a useful start, you just don't want them to continue to work when you don't want them to! Your brake bleeding procedure sounds unusual, but no reason why it shouldn't work. Slowly cycling the pedal whilst watching the fluid and air come out is the more usual method. May or may not require ***istant though in which case you can close the bleeder on the pedal release stroke, speeds up the process. Chris
Thanks @fredifink . While it's not fully HAMB vintage, it can help us visualize what these parts are. I'll also say intermittent problems are a ****** to diagnose and solve. I hope you are able to check the pedal freeplay and linkage for stickiness to make sure that's not it, and ensure all the lines and hoses are not causing issues. Make sure the servo is fully returning when released too.
The brakes were most likely working for a while because of the leak. That was letting the brakes release and once you fixed it, they went back to locking up.
Thank you everybody for the replies. I will investigate the specified linkages- I feel like it’s not stick-age but could certainly be misadjusted as the car was sold with an unspecified ‘braking problem’. Not that I am an expert, as I’ve demonstrated, but it seems su****ious the car braked quite nicely for a time and I had no issue with the pedals movement until swapping to new components- I’ll still give a better go at a bleed though I know this usually presents reverse symptoms of a pedal too slack. I’m not sure how to tag somebody with the @ but in reply to you Clydesdale this build began in 2011 on Retrorides (search: Hillman Superminx G***er) and made its way into my ownership during Covid. I’ve had a couple of the old owners posting asking it’s whereabouts who I’ve spoken to about the project- it’s more to shield myself from intrusion or judgement though arguably I’ve put more life, labour and money into the car than it had received for a half decade prior.
Simply type in the ampersand, then whoever you want to tag. As you go, there will be a drop down menu to select, or just type the whole thing in, then click on the name. @fredifink will just list only you at @ fredi for example. This is for a desktop, not sure on a phone.
The Jalopy Journal
