Intermittent front locked brakes :(

[min]

Hello everyone,
I‘m writing here about my latest problem on my 2001 2.2HDi 406 – intermittent front brakes lock (no errors in Lexia).
But first a short description of the events: I tried to change myself the front discs and pads but, of course, I couldn’t release the T55 screws which hold the caliper bracket. I went to a mechanic who was able to release them (after a strong hit with a hammer in each of them), replaced the discs and pads and also cleaned one caliper slider which was a little locked by rust. I also asked him for a bleeding since it seemed that the second consecutive brake pedal has a higher pressure point and therefore I suspected some air in the brake circuit; the bleeding took place only for the front wheels since the rear bleeding screws were very rusted and we thought it’s too risky to try to open them.
So after the replacement the improvement was obvious: the brake pedal free travel was smaller, no free travel change in case of two consecutive pedal pushes. After a break-in of less than 100miles the brake efficiency was much better than with the olds discs and brakes.
And then the troubles started: after 400miles I noticed a slight brake lock (when stopping at traffic light and releasing the brake pedal the car remained stopped even if there was a slight slope). When I parked the car I tried to push it by hand and it was obvious that the brakes where locked. On my way to the garage there are also some miles on highway on which the brake lock was obvious: reduced dynamic performance and finally at around 70 mph noises from front wheels (like blocked roll bearing) could be heard. I stopped, noticed very heated front wheels and after less than 1 minute I decided to continue the trip with moderate speed but surprise: when moving the car after less than 1 minute stop the brake were not locked anymore?! When I arrived at my garage I decided to put back the old discs (the new ones turned blue due to overheat and also started causing pedal trembling while braking at high speeds): when I removed them I also found that the pads were fitted to tight in the caliper bracket (one of them could not be removed by hand), I filed them and I was relieved that, although the new discs were damaged, at least I found the root cause of the problem. I also checked all the caliper sliders and made sure all of them slide smooth; I also made some trips of the brake pistons and pushed them back with a spanner. As a conclusion the only issue identified was related to the tight pads which I solved. The brake pedal trip increased again (I assumed that was normal since the new pads were touching the old disks only on the external circle where a significant wear shoulder was created on the old discs). Gradually the brakes were efficient again and I was sure that I solved the problem.
After another 500 miles I felt again the car was losing power and instant mpg decreased on the computer; after a few miles the free travel of the brake pedal was almost zero and if I pushed the pedal the brakes worked ok (so I didn’t suspect any vapor lock). I pulled over, noticed front over heated brakes and went further after a 2 minutes pause. Of course the brakes were not locked anymore?!?!?!?
The same behavior was faced also last weekend when I drove 800miles: the first part of the trip was on highway (~500 miles) with no problems (also moderate usage of the brakes on the highway). After 100 miles of secondary roads the ‘twilight zone’ was back: tough brake pedal, almost zero free play of the pedal, reduced power and affected mpg. After 5 miles of driving without using the brakes I pulled over, of course the front brakes were overheated (on the rear ones I could not put my finger close to the brake disc but the wheels were much colder than the front ones); while the car was standing with running engine I pushed the brake pedal and the free play came back to normal and, of course, I started again and it was obvious that the brakes were not locked anymore ((((((((((((

So any solution?  It’s a pity that although the 406 is a great car and design it has some sort of a magnet for atypical issues which are hard to track and solve  . I own it for only 6 months, I drove it 10.000 miles but it cost me much more money and headaches than my previous cars 
Going back to the issue, the fact that after a very short stop everything comes back to normal I think eliminates the possibility of stuck brake piston, clogged brake hose, stuck caliper slider or pad. Could it be something related to ABS pump or sensors and when it senses all wheels stopped releases the pressure?!

Any suggestion is welcome.
Thanks.

[lozz]

Sorry icouidnt read it all,
but after reading youve already had the calipers etc freed off,
have you had the Wheel bearings checked -it might not be that but obviously somethings getting hot for the brakes +disks to lock on,

Are you 100% sure the calipers arnt sticking thats what id be looking at anyway,

[lozz]

Whats with the 

[V6Exec]

Whats with the 

Might be this -> http://www.htmlescape.net/f0/unicode_char_f04c.html

[lozz]

Whats with the 

Might be this -> http://www.htmlescape.net/f0/unicode_char_f04c.html

Seen it before,on another forum,

Ithink its Chinese

[steve_earwig]

It's some character he's tried to use but the board couldn't cope with it.

I don't think it'll be a caliper if all 4 wheels are affected, it's gotta be a master cylinder or abs fault. Interesting that it recovers after a while being stationary, almost like there's only a tiny amount being returned - can the fault be reproduced while the car is still stationary? Try pulling the abs fuse...

[V6Exec]

http://www.htmlescape.net/f0/unicode_char_f04c.html gives but it might have been better if was used

[min]

It's some character he's tried to use but the board couldn't cope with it.

I don't think it'll be a caliper if all 4 wheels are affected, it's gotta be a master cylinder or abs fault. Interesting that it recovers after a while being stationary, almost like there's only a tiny amount being returned - can the fault be reproduced while the car is still stationary? Try pulling the abs fuse...

Judging by the heat from the wheels, only the front wheels are affected. It occurred 3 times till now since I changed the discs and pads and only while driving; it's also strange that it occurs only after 3-400 miles, so after any change I have to drive a lot in order to test and guess if it's solved or not. I'll try driving without ABS (removed fuse) for some time although tomorrow it's going to snow here .

[madmadmax]

did you put copper slip on the places where the pad contacts the carrier?

[min]

did you put copper slip on the places where the pad contacts the carrier?

No, I didn't but I filed a little the pads in order to have enough space for a free sliding, so I'm quite sure this is not the cause

[DaiRees]

How does the 406 do brake balancing lads? Has it got a balancer of some kind?

[madmadmax]

depending one year electronically(abs) or a brake balancing valve on there rear suspension

rust can take up a lot of space and will cause the pad to drag and catch