No Escape from NADA Dual Line Brake Hell

amcdonald

amcdonald

Active Member
Hello

After a decade long restoration, Saturday was supposed to be the big reveal with the car going out for the first time not sitting on the back of a flatbed. Unfortunately, a seized caliper on the attempted reversal out of the garage sent that plan down the toilet. Caliper was fixed up; I capped the brake line at the hose hoping no further bleeding issues would arise after spending hours and hours over multiple times trying to bleed these brakes before.

But no. In the past I worked out that you MUST bleed the rear brakes completely first before doing the fronts. Also on the fronts you get a half pedal range of motion because of the BS arrangement of things. Previously after boning up on some forum commentary I have pressed the pedal slowly and eventually got a functioning pedal. This time, after doing the rears again for the fun of it, on the fronts the pedal will do one long push when quickly the range of motion during bleeding decreases to about 1" and of course next to no fluid emerges. There is no front braking at all. I cracked a few lines and bled around the servo half-heartedly to avoid removing all my engine bay paint (again).

Any suggestions about what to do next? To say I have had enough of these brakes would be an understatement.
 
Is this on a four or 8 cylinder car? On my 2000TC I replaced the bleed nipples with the ‘one man’ bleeders (basically a bleed nipple with a spring loaded tip that acts as a non return valve when opened). Following normal bleeding order; rear, front passenger and front driver. I’ve had very good success with the manual approach of a full depression of the pedal, followed by three rapid pumps to half way up the pedal travel then release. I’ll do a few cycles of these, check reservoir level then do again.
If you have the twin remote servos fitted to a four cyl car you can crack open the pipe unions on the servos with a rag wrapped around them to ‘burp’ them before bleeding. They are a high point on the system and it really helps. I can’t say what the 3500S equivalent would be for that.
 
I have a NADA 3500S with dual circuit brakes and I bleed them in accordance with the Rover manual. I have never had any issues with them.
 
How old is the original fluid in the lines? It turns to jelly after a while and requires some very hefty pressure to get it through the lines. Only proper fix is to completely dismantle and clean everything though I've had some luck with disconnecting the rubber lines at their end and forcing fresh fluid through to push the gunk out. it works but isn't a long term solution. I'd also be more inclined to follow the manuals instruction on bleeding them. From memory that means front brakes first and there is a trick at that point which i forget but it's in the writing.
 
Oh, and the dual circuit system has a check valve in it between the two circuits so if one circuit loses pressure when compared to the other one, it is shut off by the good circuit's pressure. It's just the thing to make bleeding a pain....
 
The 3500S dual circuit brakes are basically identical to the E-type series 3 and the circuit is as follows:

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The Rover manual says to bleed the rear first followed by the front furthest from the master cylinder, then the last front. I seem to remember if you start with no fluid in the system, the sliding piston in the tandem slave cylinder can slide across when bleeding the rear brakes, to cut off the front brakes. Then you can't bleed the front. When I did mine I loosened off all the bleed nipples and let the system feed by gravity initially before doing a proper bleed.
 
Hi

Thanks. yes it’s the V8 with the shuttle valve. The entire system is new and reconditioned. Before I rebuilt one caliper it was bled and working. It’s almost certainly related to the valve but in previous attempts I could always get the fronts to bleed, after a bunch of faffing, but not now.

I did consider opening the rear up to equalize the pressure but did not yet try it open at the same time as the fronts. It makes sense this would stop the valve causing a problem on the fronts. If you bleed the rear, it always resets the fronts so you can get a couple of pumps in before it locks up again. And repeat the cycle…..

what is most odd is the sudden change in behavior.
 
amcdonald said:
Hi

Thanks. yes it’s the V8 with the shuttle valve. The entire system is new and reconditioned. Before I rebuilt one caliper it was bled and working. It’s almost certainly related to the valve but in previous attempts I could always get the fronts to bleed, after a bunch of faffing, but not now.

I did consider opening the rear up to equalize the pressure but did not yet try it open at the same time as the fronts. It makes sense this would stop the valve causing a problem on the fronts. If you bleed the rear, it always resets the fronts so you can get a couple of pumps in before it locks up again. And repeat the cycle…..

what is most odd is the sudden change in behavior.
Click to expand...

One thought: Is the master cylinder push rod adjusted correctly? I've seen those create problems when the pushrod doesn't allow the piston to return to the correct position not allowing fluid into the system properly when bleeding.
 
Yes, bleeding the rears has the pedal go through full range of motion down to the floor and fluid splurging out as it should. Switch to the fronts it's a 1" pedal travel after the initial pump or two. Even after pressing the pedal down ridiculously slowly each time.
 
Well I did not expect do descent further into the final circles of NADA 3500 dual line brake hell but I made it this weekend. If this wasn't the final insurmountable hurdle of a decade long ordeal it would not be so bad. A couple of weeks ago I thought all that was left on my resto was screwing down the shifter gear indicator plate. Wrong!

First issue - front brakes would not bleed. As I mentioned before, when bleeding the rears things are fine. When doing the fronts the pedal soon reduces to a 1" range of motion. I ran fluid through using gravity and a few crappy pumps and then called it done, even though it wasn't. But they were doing something at least.

The caliper rebuild I did in the midst of this turned out to be a sneaky red herring and not strictly necessary. It was something else entirely all along. The brakes were actually ALL locking up with the motor running, seemingly as a result of a brake vacuum side issue. It was just that the first wheel I tried was locked up (hence I immediately thought it was the problem and fingered the caliper as the cause) and by the time I got round to trying to rotate the other wheels they had unlocked enough for me to ignore them as potential problems (coincidentally the "suspect" wheel had a somewhat crud-covered caliper too).

So, in addition to the inability to properly bleed this system, it locks up badly as soon as the pedal is pressed. Without the manifold to servo hose connected, things work normally as far as I can tell, brakes don't bind.

A few hours going through the Jaguar forum and I inspected the master cylinder which sounded like the most viable culprit. Especially as I had to rebuild it after it failed (leaking to footwell) after never being actually used except during bleeding after its previous, professional, rebuild. The MC action is good, I greased up the small actuating pin to the reaction valve and it looks like it's working fine. I can't see any obvious fault with the reaction valve. The external rubber seal is tight and holds the vacuum and the parts are all new. I poked a long allen key into the hole where the actuating pin goes and pressed the lever/flapper and it clicks back and forth with no sticking. So I can't see any issues.

So now I am fingering the servo as the cause. They can be sticky according to the jagsters and it is a known thing. I am thinking this could account for the inability to bleed as well as the brakes sticking. The servo was also professionally rebuilt and has seen zero miles. But in the mix I also have the BS five port switch/manifold downstream of the servo and god knows what that is doing.

I did not want to disassemble the system AGAIN (third or fourth time) and get brake fluid everywhere until I got a decent idea of the problem.
BUT now that is irrelevant as the final (probably not) punishment surfaced. Now the rear caliper is leaking fluid. I thought I could get away with not touching the rears. Wrong.

Anyone want a California NADA 1970, rebuilt engine new paint job perfect interior, no brakes?
 
One question to your servo; are you certain that the slave cylinder rod is attached correctly inside the servo? It is well described in the WSM, nevertheless I managed to not attach it correctly, with the result if I remember correctly that the front brakes locked on as soon as I started the engine. My 3500s LHD has the same dual brake system as your Nada. So I had to dismantle the servo and slave cylinder and found out what I had done wrong, and It was Ok, except for problems to get the brake fluid all the way to the aft calipers. That was caused by an airlock in the 5 way valve. Had to crack open each connection from that and to the aft calipers, then I finally got some action there. Don’t give up, your brakes will eventually work, however not great, but working.
Regards, Barten
 
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Sorry to hear about your tribulations. A friend of mine recently had his tandem circuit brakes binding on. I pointed him towards the one-way plastic valve on the booster bell and by chance it turned out to be stuck open or otherwise failed. Replaced, working.

The other point is that I learned the hard way that the shuttle valve must be arrested in its centre position when bleeding the dual system, or it’ll slide over and block one circuit for you giving you little joy with your fluid pumping efforts. Simple enough, with a pointy thingy that can be sat in the bore and secured with an elastic band. I had no idea of this the first time I successfully bled my former car, but it came to pass on my current.
 
Just another point. Don't use silicon brake fluid. It really screws them up! I tried it and had the most strange things going on. The seals are certainly not compatible. Odd though as I used it in an MG Midget for years with no issues at all. Probably a topic for another thread though!!
 
Hello

I got the servo back from the rebuilders, and it worked okay for the first two times I managed to bleed the system and got it running okay on short test drives around my development. So up to now I don't have evidence there is a problem with it. The coincidence is now the brakes are locking up after I removed and rebuilt the MC (after the professional job leaked!). So all fingers point to the MC logically. But upon inspecting the reaction valve and piston I can see absolutely nothing wrong. The parts are all new, the outer seal to atmosphere is super tight. If you just pull the seal of the reaction value up a bit to let air in the brakes instantly apply. Now I can't recall whether they release when you let the valve reseal to stop air pressure getting in and reverting the system to manifold pressure. I think they stay on.

And I am 100% sure the 5-way valve is a troublemaker for bleeding. I never took the switch part out to look at the center connection hole but next time I will investigate that to lock the shuttle in position, as previous commentators have suggested. If I ever get that far.....
 
I recently had trouble with a Lockheed branded master cylinder. The pedal action was like trying to push through heavy treacle, and the pedal would only return slowly.
Turned out one of the seals was totally different in profile and had been attacked by the brake fluid and swollen and gone 'mushy'.
As the cylinder assy was not very old a new seal kit cured the problem. Both the seals in the new kit were of the same profile, so a new Lockheed product had been assembled using suspect parts.

I am afraid these days you cannot assume any part is good just because it is, new, branded, or rebuilt by others.
 
See if you can track down a 1968 first edition manual. Its very very detailed compared to the later ones with a much more detailed brake section from memory. I recall there was a specific note about setting up the valve in the end of the master cylinder correctly and dealing with the shuttle valve.
 
Unfortunately my copy is in a box along with 250 other, similar boxes. i've just finished moving all my stuff into my new shed but I've yet to build the library for the books in the boxes....I got my copy off the net, the cover is blue and red (on white) I think where the later ones are something (red?) and black. obviously it doesn't cover any mods post the NADA cars.
 
So I removed the MC again to get a better idea of the little piston that actuates the reaction valve. I had gooped it up with brake lube last time, but when pressing the main piston by hand and blocking the brake fluid exit port with a finger the little piston only pops out when the plunger is fully depressed and it pops out like a champagne cork. Sometimes it does not even budge. So I am thinking this piston should be a lot easier to move in the bore than that.

This was a professionally rebuilt part and I think it was just not completed properly, or the seals are over size. Looking into the bore, it's definitely not a smooth mirror so maybe it was rebuilt in a dodgy state to start with.

So I am buying a new MC ($ ouch) along with my rear caliper rebuild kit (fun times) and crossing my fingers for the umpteenth time.
 
I'll try to walk you through the mechanism as the pictures aren't very clear. Referring to the jag picture above of the master cylinder it contains several valves. Starting at the end with "reaction Valve" next to it. the first thing is a little filter with a cap that lets in atmospheric air when the valve under it (to the right) is open. Then there is a little rod which goes to the centre of the diaphragm which separates the two air chambers. There is also a second air valve here which lets vacuum back into the left hand chamber when the pedal is lifted. This is the squiggly bit on the drawing. The right hand chamber is permanently in vacuum as is the left had end of the booster. Both these valves are relatively straight forward and look like what they do. Next on the right is the pushrod which opens and closes the air valve. It has a seal a little way along which separates the air side from the brake fluid side. At the brake fluid end of the rod comes the tricky bit. The rod isn't a piston; the piston is the obvious thing to the right. Looking carefully at the diagram you will notice they've drawn a little angled piece at the bottom of the pipe connection which doesn't appear to have any function or think it's the end of the return spring. Its actual purpose is to push the rod forward immediately the brake is applied. It can sit is several different positions in the chamber but unless its positioned as drawn nothing works properly. It can also fall into the wrong position by just sitting around in an empty chamber so it needs to be checked before installation. so do check it before you head off to the shops...

Note that the internals are never mirror polished but are both smooth and straight (flat - no ridges or hills).

I hope this is helpful

Mike
 
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