Non Merc specific question on old fashioned brakes!

[ChrisHGTV]

Hello all. Not a Merc specific question but may also be relevant to older Mercs.

I’m helping my Dad sort out the brakes on his pre-litigation Westfield and the trouble is we can’t remember how bad they were when they were working properly! It’s basically Escort Mk1 front disks and Escort Mk1 RS2000 rear drums with no brake booster on the master cylinder. I’ve changed the rear cylinders as these were both seized and adjusted the shoes.

Even after bleeding all corners using my pressure eezibleed the pedal would go to the floor. So I suspected a duff master, especially as it did have a small amount of black crud in the reservoir.

So, new master fitted and all bled through. Slightly better but pedal still goes to floor, albeit the car does actually stop ok. But I can’t help thinking the pedal should be firm from the start of the press.

I should add that the pedal doesn’t firm up with pumping, it stays just the same.

So could it be there is still some air in the system? In the master or lines? I did bleed through more than a litre in all. Might it need a bigger bore master to move more fluid?

The trouble is we can’t remember what it should be like, but I’m thinking the pedal should be firm from the off.

Any ideas greatly appreciated!

 

[ToeKnee]

Check the orientation of the calipers. I know some kit cars that use calipers off a production car don't always use them in the same position as in the production car so double check the bleed nipple is definitely at the highest point. If not you may have to remove the caliper, position upright and block where the disc goes (to stop the piston coming out) before trying to bleed again.

 

[Deadly Dave]

How old are the brake hoses ? They can balloon up when they get old.

 

[ChrisHGTV]

Check the orientation of the calipers. I know some kit cars that use calipers off a production car don't always use them in the same position as in the production car so double check the bleed nipple is definitely at the highest point. If not you may have to remove the caliper, position upright and block where the disc goes (to stop the piston coming out) before trying to bleed again.

Thanks, yes the nipples are at the top so should be ok. My suspicion is that there might still be air in the master but then seems strange that the symptoms of long pedal travel remain after changing the master. I’ll try bleeding the master again.

 

[ChrisHGTV]

How old are the brake hoses ? They can balloon up when they get old.

They’re braded and not that old, maybe 5 years. So I would think they are ok. All the other lines were changed to cupro nickel at the same time around 5 years ago.

 

[ChrisHGTV]

I should add there’s no obvious leaking anywhere either. Bit of a mystery!

 

[ioweddie]

master cylinder might need an overhaul

 

[Bellow]

Pedal with that set-up should be rock solid.
It seems that master cylinders require 'bench' bleeding prior to fitting.
I'd revisit the shoe adjustment lest the shoes have 'centralised' since first adjustment and, check for failed adjustor (I've had this happen on a Ford before - pedal to the floor ensued).

 

[ChrisHGTV]

master cylinder might need an overhaul

It’s a new one as this was my first thought!

 

[ChrisHGTV]

Pedal with that set-up should be rock solid.
It seems that master cylinders require 'bench' bleeding prior to fitting.
I'd revisit the shoe adjustment lest the shoes have 'centralised' since first adjustment and, check for failed adjustor (I've had this happen on a Ford before - pedal to the floor ensued).

This is my thought - should be solid. I did a kind of bench bleed of the master on the car following some you tube vids but this may be where the problem lies. Good point on the rears I’ll check again. You can hear them moving when applying the brakes when stationary.

 

[Bellow]

This is my thought - should be solid. I did a kind of bench bleed of the master on the car following some you tube vids but this may be where the problem lies. Good point on the rears I’ll check again. You can hear them moving when applying the brakes when stationary.

In GMT400 land, almost all 'long pedal' issues are resolved at the rear drums.
Out of interest, the long pedal - does it feel like lost motion or, springy like trapped air? (In GMT400 land when the problem isn't in the rear drums it's a bleeding issue!).

 

[ChrisHGTV]

In GMT400 land, almost all 'long pedal' issues are resolved at the rear drums.
Out of interest, the long pedal - does it feel like lost motion or, springy like trapped air? (In GMT400 land when the problem isn't in the rear drums it's a bleeding issue!).

Well it definitely doesn’t feel springy like trapped air, more like the leverage ratio is off. I adjusted the rears so they just rubbed slightly with the brakes off. I’ll try tightening them up to see if that makes any difference.

Thanks!

 

[ToeKnee]

Could you "pinch off" the rear flexible hoses too see if that stiffens the pedal?

 

[ChrisHGTV]

Could you "pinch off" the rear flexible hoses too see if that stiffens the pedal?

I could try, though they’re braided. I thought of trying to blank off the front or rear circuit at the master to see if I can pinpoint if it’s one or the other. Might have a play after work tomorrow. Many thanks for your pointers!

 

[Bellow]

Well it definitely doesn’t feel springy like trapped air, more like the leverage ratio is off. I adjusted the rears so they just rubbed slightly with the brakes off. I’ll try tightening them up to see if that makes any difference.

Thanks!

If it has the type of adjuster I think it has, when rotating the adjustment screw it should feel lumpy. It is a square pyramid affair and needs to seat on a flat - or it will slip back and lose adjustment if it settles on an edge. Also, its housing is alloy and corrosion prone which can disintegrate the female thread causing the adjustment screw to pop out.
The lack of springiness does imply this is more a mechanical issue than hydraulic. A basic system such as this devoid of ABS should bleed easily - and probably has.

 

[ChrisHGTV]

If it has the type of adjuster I think it has, when rotating the adjustment screw it should feel lumpy. It is a square pyramid affair and needs to seat on a flat - or it will slip back and lose adjustment if it settles on an edge. Also, its housing is alloy and corrosion prone which can disintegrate the female thread causing the adjustment screw to pop out.
The lack of springiness does imply this is more a mechanical issue than hydraulic. A basic system such as this devoid of ABS should bleed easily - and probably has.

Yes that’s the type of adjuster it has. Everything seems in good condition when I changed the cylinders. I’ll investigate and report back!

 

[jotter22]

Well? Update.

Thanks Tony.

 

[ChrisHGTV]

Well? Update.

Thanks Tony.

Aha yes success! I had another go yesterday as I was away last weekend. I bought a bench bleed kit and bled the master cylinder again in situ. I also changed the front pads for Mintex 1144 and at the same time checked all the pistons were working ok. Put everything back together, bled each corner again with the pressure bleeder and all seems good. I also tightened up the rears a tad. There’s still a bit of pedal travel but then you can brake hard with good resistance. Apparently a bit of travel is normal with this set up.

I was also going to swap out the welded master cylinder pushrod for an adjustable one but annoyingly it arrived in the afternoon when I was already at my folks. But I checked the length and it actually seems fine, with no pre-loading of the master cylinder. I will change it at some point anyway.

So I think the issue was just air still in the master cylinder - it was confusing because it was showing the same symptoms as the older one. That may have had air in it as the seals were kaput.

So all seems good -it’s going for it’s mot in the week and i just ordered 4 Yokohama A008 tyres for it.

Thanks for your help, it’s nice to get it finally sorted!

 

[ChrisHGTV]

This is the wee beastie, now with brakes!

 

[ChrisHGTV]

This is the wee beastie, now with brakes!
View attachment 173941

And now with an mot! The garage said I’d done a good job sorting the brakes and emissions (new carb, and jetted by guesswork to account for the cam and headwork etc).