Rear brakes binding and brake lights on

[EuropaTC]

Hi,
Well, I didn't see that one coming, good detective work !

One thing I found with my experimenting was that a small movement of the foot made a big impact on my mind. As little as 1cm - 1/2" made me think that the brakes were awful and the car was never going to stop.  So my first thing would be "is it just in my mind ?"  You've gone from a system where the rears were binding and so you've only been supplying fluid to the fronts when you braked,  hence you'd have less pedal travel and what you've got now might be perfectly ok.

As I've mentioned before, I'm a big fan of measuring things for before/after comparisons and for brake travel I've used a length of bar which I mark the rest position and the fully depressed position. It's only hand pressure and not foot pressure (so I can mark the position whilst grovelling down the footwell) and won't be 100% accurate on travel but it's going to be good enough for comparison purposes.

I no longer have drum brakes so my figures won't be applicable but as a wild guess if you're getting 5cm travel with the Nissan m/cyl then I'd be looking for an explanation. Again a pure guess but I'd be expecting 4cm-ish ?   It's a personal feeling but once my pedal is travelling around 3cm the brakes feel "instant" 

Assuming it's a long travel problem and not your mind telling you they've got worse, I guess the next question is does the pedal travel improve with pumping or is it always the same position ?  Like yourself I'm a bit surprised you didn't get any air out of the front calipers so if it has an initial spongy feel that improves with pumping, that's where I'd start. If you're using boosters then there's a lot of travel for the front brake fluid and something might just be hanging up along the way.

Brian

[Europa73]

Hi Brian,

Thanks for the note.

I will confirm measurement.

I just tested the brake and it does firm up when pumping.

But - if I take my foot of the brake for 5 secs then press again the travel is back again.

I will give bleeding another shot.

Another thing - When bleeding the brakes I also noticed more pressure in the fluid on the rear brakes than the front brakes.

Could the issue be a worn seal in the M/C?

Cheers,

[cwtech]

I'm not sure if this info is applicable or just adds confusion.

Most drum brake circuits have a residual pressure valve in the master cylinder.  ....Some modified brake systems use an external RPV.

The RPV maintains slight pressure in the drum brake circuit to prevent air from being ingested when the wheel cylinder retracts.

By any chance, was the restriction you removed from the master cylinder, a RPV ?

Not having a RPV, or having a faulty one, can create the symptom you describe.

Can anyone say if a RPV was incorporated in the Europa's original master cylinder?

[jbcollier]

Not there originally.

[EuropaTC]

I just tested the brake and it does firm up when pumping.
But - if I take my foot of the brake for 5 secs then press again the travel is back again.

I will give bleeding another shot.

Another thing - When bleeding the brakes I also noticed more pressure in the fluid on the rear brakes than the front brakes.

Could the issue be a worn seal in the M/C?

On the worn seal, I'm not going to be any help as my only "worn" experience is with single circuit m/cyls. As a pure guess I would have expected all seals to wear at the same rate but as I say, I've never had to rebuild a worn tandem unit.

The fluid pressure might be a function of travel; with servos in the rear the front fluid is travelling to the engine bay and then back to the front of the car before splitting to the calipers. The Rear fluid is only making that trip once and then going to the drums, so at least 5' or so less pipe to travel.   

On bleed speeds, I don't have servos so my layout is the front circuit is very small and the rear circuit about the same as yours; I get slightly faster bleeding at the front than rear if using gravity alone to let fluid bleed out, which sort of ties up with your findings (only in reverse    )

Finally, the symptoms you've described would make me go back to bleeding again.  If you can pressurise the reservoir then it allows you to continuously bleed far more fluid than pressing the pedal does and that's my preferred option these days as I think it means less chance of air bubbles floating back to the high points between flushes. 

There is also a theory that holding the pedal depressed overnight causes any air to dissolve into the fluid due to the pressure. If you try that and the pedal feels ok on first and subsequent presses (after your 5sec delay) then I'd just flush everything out with new fluid and hopefully you'll be good to go.

Brian

[jbcollier]

Two good suggestions from Dr E. TC.  Pressure bleeding preferred in a convoluted plumbing system like the dual circuit, twin booster equipped Europa.  Pressurizing the pedal overnight is a good choice if pressure bleeding is not in the cards.  Don't forget the last step of flushing out the "air-charged" fluid.

[Europa73]

Many thanks all,

I will let you know how it goes.


Cheers,

[Europa73]

HI all,

I gave the pressure bleed and the compressing the brake pedal over night then flush options a good go and still I have the issue with the excess travel in the M/C.

I measured the travel and it travels over half its entire range of movement before it gets firm.

Thinking it must be the seals in the M/C I ordered a rebuild kit.

Just received it today.

it came with the replacement pistons and seals in place on the pistons.

it also came with an extra bag - see the pics - sorry for the noob question - but what are the 2 black cone shape and 2 small springs for?

Unfortunately the kit did not come with instructions - and - I have had the M/C appart twice - and did not see these items.

Any advice would be greatly appreciated.


Cheers,

Rod

[jbcollier]

That looks like a Girling kit?!  The master cylinder you have is not a Girling one.

[EuropaTC]

Gee, that's disappointing news.  John's right about the wrong repair kit, you look to have a Nissan m/cyl, as detailed on this page;

http://lotus-europa.com/manuals/misc/brakes/nissan_f10_mc.htm

It's a 0.75" unit according to the second article on that page, I'll run my spreadsheet and see what sort of travel you should be getting and edit this post later on. It will be very rough but should be thereabouts and we can go from there. My initial reaction is that half pedal travel sounds too much though.