S4 Brakes

PostPost by: miked » Thu May 06, 2004 10:46 am

Can anybody advise. I have a restored S4. everything has been done on brakes. However, I never feel like I have all the air out of the system. I can always do a second dab and the pedal raises and feels better. This somewhat annoying as I like everything just so.

I have a gut feel that air traps some where and may only be released by unbolting the capliers and moving them about to try and ensure air goes to the top. What do we think. Does anybody know the secret, is it something like this. I am about to try.

Everything is new and there are no leaks of fluid. Second master cylinder fitted. Tried the Trye air business and was unimpressed, messy hard to seal and still had to operate the pedal.


thks Mike
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PostPost by: steveww » Thu May 06, 2004 11:29 am

If you have a lot of new bits in the braking system you can get very small air bubbles clinging to the walls of the pipes and cylinders. I have found the only way to get rid of these is to use the car with the slightly soft pedal, then after giving the system some time to settle down bleed through again.

Also if you have just fitted new pads they can be a bit springy until they have bedded in.

One more thing, you will never get a really firm pedal with a servo in the system, these always have some spring in them due to how they work. I have removed the servo and fitted calipers from the +2 which are bigger and maintain a good mechanical advantage. The pedal is now solid and takes a bit more effort but this makes heel/toe changes much easier.
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PostPost by: miked » Thu May 06, 2004 4:36 pm

Steve, thanks for reply. I will try the servo out of circuit. I have run about 2500 miles hoping to get a better bleed, had the same thought. I take it the plus two calipers go straight on with no mods whatsoever. I have had 2 elan plus two's but can not remember the caliper details.

thanks Mike
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PostPost by: nebogipfel » Thu May 06, 2004 5:59 pm

It might be worth doing a pressure or vacuum bleed on your brakes if you think you are not getting all the air out
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PostPost by: elansprint71 » Thu May 06, 2004 9:29 pm

I have just changed my chassis and replaced everything in the brakes except the rear calipers; I chucked out the servo and fitted +2 calipers. I have exactly the same symptoms, second push and the pedal is firm; I too have come to the conclusion that there must be "micro bubbles" clinging to the pipes etc and I have decided to drive it around for a couple of weeks and bleed the system again to see if it improves. I have already bled it 3 times and it has got much better each time.
A neighbour who has a Jensen Interceptor (well 3 actually, and an FF and a 541)has confirmed that he has had exactly the same problem each time he has rebuilt his cars but he has discovered that they have a bleed valve on the master cylinder, prior to this he bled the system evey couple of weeks until all the air had been purged, he reckons that the air collects at a high point near the M cylinder, maybe the Elan is the same?

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PostPost by: steveww » Fri May 07, 2004 3:00 pm

+2 calipers sort of bolt straight on.....

First get your calipers, I got mine from classicar, advert in Lotus Owners Club mag. Get the older imperial ones. They are the same as fitted to Triumph GT6/Vitesse

Next you need mounting brackets from a +2. Spyder engineering have loads of these or any other +2 spares breaker.

Finally you need +2 size disks as well. I got some grooved disks and EBS pads from Powerstop but plain disc and normal pads from the usual suppliers would be just fine.

You will also need a new pipe making to go from the master cylinder to the junction. My local parts shop made this up "while you wait". I took in one end of the old pipe so they could see what they should make.

The mod does not cost much and only tool me a morning to fit.

Tip: You might need to grind the back of the wheel pegs (if you have KO) to get clearance with the new caliper.

Any other questions - just ask :D
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PostPost by: types26/36 » Sat May 08, 2004 4:33 pm

Mike,
Check that your front wheel bearings do not have excessive play, if they do, the caliper pistons could be pushed back as you go round corners, you would then have to "dab" the brake pedal to bring the pistons close to the disc's.
Another check you can do is to clamp all four flexible brake hoses (there are special clamps for this) but you can use small vice grips (be careful not to damage the hose) you need to clamp the hose only enough to stop the fluid flow, the brake padal should now be rock solid, now release one clamp at a time feeling the brake pedal each time.........it will be self evident if by the pedal travel which if any of the calipers are holding air.
Regards Brian. :)
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PostPost by: miked » Mon May 10, 2004 3:51 pm

Steve, Pete, John and Brian, thanks for you help.

Will try and locate the air and am intrested in the Plus 2 (no servo) route if I dont cure it.

Brian, funny you should say about the wheel bearings as it is time I took a little play out of them.

thanks Mike
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