Lotus Europa Community
Lotus Europa Forums => Garage => Topic started by: Europa73 on Sunday,June 25, 2017, 05:26:50 PM
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hi all,
I had my 2 brake boosters rebuilt.
bled the system - front and back.
Adjusted the drums so the rear wheels are rotating freely.
the brakes work well and are firm.
The issue I have is.
when I brake hard the brake lights remain on and the rear brakes start to bind.
This issue remains until everything cools down.
Any thoughts?
Cheers,
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First check that there is free play at the pedal of the main master cylinder. There is a small compensating port that is exposed only when the piston is all the way back. This port is what releases any pressure changes due to fluid temperature change. If that is not it, then there is a similar issue in the rear circuit's booster with probably the booster's diaphragm sticking.
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Thanks for the information,
The prior owner fitted a tandem master cylinder running off separate reservoirs. The car still has the dual braking system.
The issue is - there is a slight brake engagement on the rear drums (brake light is also on), just enough for them to get hot and start binding.
The brake light stays on even when I disconnect the booster. When I release the brake the brake light goes out for bout 1 second them comes back on.
The brake light even comes on when the engine is off and I pressed the brake several timed to remove the vacuum from the booster.
I have striped and checked the boosters diaphragm and thats working.
Is there a way yo test if its the compensation port?
Any advise would be greatly appreciated.
I am out of ideas and desperate to hit the road - we finally have good weather in Toronto :-(
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Pump the system so that the brake light is on with the pedal released. Crack one of the rear wheel bleeders to relieve any pressure.
Brake lights now off? Somewhere in the hydraulic system it is not releasing the pressure as it should.
Pump it up again so that the brake light stays on. Crack the line to the rear at the master cylinder. If this solves the problem, then double check for free play at the pedal. Enough free play? Pull the master and see what's up.
If cracking the line to the rear at the master does not solve the problem, then it is in the boosters.
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Here is a pic of the master cylinder
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Many thanks!
I will give it a go!
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Hi jbcollier,
Thanks for the recommendation.
I did follow your instructions, please see the below.
Pump the system so that the brake light is on with the pedal released. Crack one of the rear wheel bleeders to relieve any pressure.
Brake lights now off? [RD - yes the lights went off - but - while the car was idling the lights came back on after a few mins] Somewhere in the hydraulic system it is not releasing the pressure as it should.
Pump it up again so that the brake light stays on. Crack the line to the rear at the master cylinder. If this solves the problem [RD - yes the lights went off again- but - while the car was idling the lights came back on after a few mins] , then double check for free play at the pedal [RD - I have about 5 mm of play. is this enough?] . Enough free play? Pull the master and see what's up.
Hoping you may have any ideas before I pull the master C.
Many thanks,
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Do you still have the boosters?
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yep they were both re-built and I have striped and checked the boosters diaphragm and thats working.
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Temporarily bypass the boosters by connecting the in and out brake lines together. Bleed the system and try it again. If the problem goes away then the problem is in the booster fir the rear brakes.
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Brake lights now off? [RD - yes the lights went off - but - while the car was idling the lights came back on after a few mins] Somewhere in the hydraulic system it is not releasing the pressure as it should.
Pump it up again so that the brake light stays on. Crack the line to the rear at the master cylinder. If this solves the problem [RD - yes the lights went off again- but - while the car was idling the lights came back on after a few mins] , then double check for free play at the pedal [RD - I have about 5 mm of play. is this enough?] . Enough free play? Pull the master and see what's up.
I think John has it right and the problem lies with the servo/booster for the rear brake system.
If you can relieve pressure and the hydraulic switch goes off but later comes on with the engine idling but without pressing the pedal, then I would expect it's the engine vacuum causing the rear servo to move. I wonder if simply clamping the air hose feed to the rear booster would be enough to take it out of the circuit and prevent the lights coming on at idle ?
If you're not pressing the brake pedal then I'm struggling to see how the m/cylinder could apply enough pressure to the system to lock the rear brakes on it's own.
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Looking at you picture, you seem to have the Nissan F10 master cylinder installed on a car with boosters. That probably makes braking a bit touchy with the boosters. Before pulling the master cylinder, try hydraulically bypassing the booster as JBC suggests. The 3/4" bore Nissan master cylinder by itself should give you excellent braking force and feel. I had the Nissan master cylinder on my TCS and the brakes felt great.
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Just when you think you have the brake system finally sorted out.
I have been plagued for months with an intermittent issue with the brake light coming on and the rear drums binding.
Thanks to all your advice, I finally chased the issue to the master cylinder.
On removing and inspecting there was a tiny foreign object that was stick in the fluid return hole.
I re-assembled the master cylinder, bench bled it and EUREKA – the issue was solved – no more constant brake lights on and the rear brake cylinders retracting nicely.
BUT –
Now I have excess travel in the brake pedal, it feels like it travels half way before engaging
I have a duel brake system – and – bled the brakes per the workshop manual sequence. No improvement. I re-bled the system using the sequence furthest from the master cylinder approach and still no improvement in the pedal travel.
What was interesting – in bleeding the brakes after re-fitting the master cylinder – I had air in the rear system but no air in the front system.
I thought as this is a duel system car I would have at least a bubble or 2 in both the front and rear systems.
I confirmed that the rear drums are adjusted correctly and now out of ideas.
Had anyone out there been through the same and have a resolution to this?
Many thanks,
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Did you bench bleed the M/C? That might be something to try...
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yep - did that twice and no improvement.
Had no travel in the pedal before I removed it.
Cheers,
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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
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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,
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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?
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Not there originally.
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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
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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.
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Many thanks all,
I will let you know how it goes.
Cheers,
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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
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That looks like a Girling kit?! The master cylinder you have is not a Girling one.
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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 (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.