Did I waste my money?

[Robbie693]

Continuing with my ongoing brake saga I fitted a new servo in the hope it would finally sort it out...

No Joy. There is exactly the same problems as with the old servo, I.e. Firm pedal with engine off, mushy pedal with creep evident with the engine running. Arrrhhhhgggg!

I've run out of ideas now and, much as it grieves me to do so, I think I'll have to call in the cavalry, otherwise known as Mr Matty.

In all my years of fixing crap cars I've never had so many problems with brakes as with this one...

[sulzeruk]

Sounds as though there may be a bit of air still in the sytem to me or you master cylinder seal is starting to fail?
AL Cowan

[Elanintheforest]

What have you done altogether on the brake hydraulics? The only other things I can think of is a sticky piston on either the master cylinder or a caliper, or a soft flexible hose. Pistons can stick on the rubber seal, not moving when applying normal pressure, but moving just a wee bit when a lot of pressure is applied i.e with the servo working when the engine is running. Flexible hoses can go soft and balloon under pressure.

All you can do is go through the system methodically...easy bits first.
Replace the flexible hoses
Overhaul the master cylinder
Overhaul the front calipers
Overhaul the rear calipers.
As you've done the servo, there's nothing left to do then.

Have you flushed the pipes through to make sure there is no compressable bits in there, like an old lump of rubber seal?
Mark

[Robbie693]

So far I've done:

New Master Cyl,

New Near side front Caliper

Copious amount of Bleeding (?50.00 worth of fluid or thereabouts... )

And the servo.

The worst place for trapped air was the new caliper - If I clamped the hose the pedal would go hard. However, with the clamp still in place the pedal was still soft with the engine running.

Pedal is pretty hard with the engine off at the moment, although I have to bleed it with the easybleeder - normal bleeding makes it spongy again.

The hoses look ok and I know that although they are probably about 10 years old, they have less than 500 miles on them...

[Elanintheforest]

Robbie...you're still dealing with too many unknowns, on a car that's 35 years old that had a designed life of 10 years..if you were lucky. The flexi hoses are past their use by date, you have one 'new' caliper and 3 old ones, which may not have been touched for 10s of years...anything could be going on in there...rusty pistons, gummed up oilways, seal breakdown, non-sealing bleed nipples.

If you took it to Paul Matty, he would recondition BOTH front calipers and BOTH rear calipers and replace the flexible hoses. He would also inspect all the brake pipes to ensure that you don't have rusty steel ones left on there...they rust from the inside as well, as the brake fluid is hydroscopic.

I just looked at Classicar Automotive prices...?45 for a front caliper, ?125 for a rear, including all the handbrake linkage. And they come back re-plated and tested...fit and forget, for another 5 - 10 years anyway.

Once you start messing about with something like a brake system, the whole lot tends to start to play up if it's old and past it's best. And a golden rule for anything to do with brakes, steering, suspension or tyres is always fix the axle set...never just one side. If the spongy brake problem hadn't occoured, you may have found the the brakes would operate with a different effect on each side, giving you a very hard time when you have to brake hard. So get that 'new' caliper reconditioned at the same time.

Lecture over
Mark

[Robbie693]

Yes, I know what you mean.

It's a bad idea to try and do anything on the cheap with a Lotus.

In defence I'd say that everything worked fine until the Master Cyl went...

The car was restored some time ago - new copper piping and rear calipers BUT the fronts looked like they were just re-sealed and painted up. They were a bit stiff when I first tried to change the pads and the bleed screw stripped in one - hence the replacement.

You got me thinking, maybe the compressability is from the other old caliper.

I was going to do the braided hose conversion too, so it looks like Caliper and hoses is the next step.

Thanks for the lecture/reality check!

I appreciate your help

Cheers

Robbie

[iain.hamlton]

Robbie, I had a very similar symptom. I suggest you try the following very simple test. Get in and push the brake pedal very slowly until it creeps. If you can get it to do it consistently (i could), get someone to look into the master cylinder resevoir while it is creeping. If there is disturbance in the fluid, suspect your new master cylinder.

good luck and best regards, iain

[pmallinson]

Robbie

Nearly for certain its the flexible brake hoses that are giving you a spongy feel to the peddle, I replaced mine and couldn't believe the difference !
Best of Luck

[Robbie693]

Yes, thanks for that Peter.

I suppose what made me think that they are ok was that the pedal feels fine without the engine running but, as Mark points out, the boost from the servo would highlight any weaknesses.

Iain - Thanks for the tip, I'll give at a go.

[msd1107]

Robbie,

Gee, why do you not just delete the servo?

Better brake feel, more linear, fewer points of possible failure, less weight.

And if the brake pedal is too hard, do some weight training so you can push harder with less effort and so the car stops at the limit of traction.

David
Servoless 1968 36/7988

[CBUEB1771]

And if the brake pedal is too hard, do some weight training so you can push harder with less effort and so the car stops at the limit of traction.
Servoless 1968 36/7988

I have ranted about this recently. You might be able to get away without a servo on an Elan but it is pretty scary in a +2 with 220 more kg to stop. I tried it and went back in a hurry. Weight training just makes it all that easier to push the pedal box clear out of the bulkhead. The sound of cracking fiberglass is sobering when you are trying to stop.

[alaric]

Hi.

With the engine off the servo is at atmospheric pressure, so is effectively out of the loop. When the engine is not running the pedal is firm. Therefore it's not a caliper, or the master cylinder, or leaking pipes, or air in the system.

(I had a bit of a mad 5 minutes at this point - I've deleted references to the chassis reservoir).

Since the servo has now been replaced it must be the vacuum system; the engine is not sucking air out of the reservoir quickly enough; I bet that's because there's a leak in one of the interconnecting pipes.

As a final test, if you switch off the engine how long does it take for the servo assistance to dissappear? If it stays for about 4 or five firm presses on the pedal then I'm talking b******ks.

Check all the pipes carefully. Good luck.

Hope this helps.

Sean.

[Elanintheforest]

Now, Sean, poor Robbie will be sobbing into his beer at this rate

The take-off for the servo is from No.4 inlet manifold, straight to the servo...no chassis vacuum tank involved. Only the headlights use the tank, via take-off from No.1 inlet manifold.

Keep it clean now, boys
Mark

[berni29]

Hi There

I am sorry to hear about your brake agro. I had a similar problem with the mushy pedal and in my case the servo was filling up with fluid, not the case with you I know. At the same time my master cylinder was suspect and I had a lot of problems bleeding it. In the end I did it off the car using a flexible hose to pump fluid back into the reservoir until all the air was definitely out. At the moment the car is servoless, and although I have not driven it much without the servo I can tell you that it is unsafe to do so. A servo is cheap against the crash that you will definitely end up having at some point as a result of reduced braking power.

I think that changing the hoses for the braided type is the next thing for you to do. I did it to mine and it is a worthwhile upgrade regardless of any problems.

Good luck!

Berni

[alaric]

Oops. My mistake - it's got nothing to do with the chassis at all has it. How did I manage that!? Got a bit carried away. Told you I was probably talking b****ks. Sorry for any alarm. On a positive note, that means it may just be a leaky vacuum pipe. Is the engine a bit lumpy on tick over?

I've edited the post...

Sean.