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Brake servo problem? - Suspension/Brakes/Wheels/Hubs/Steering/Geo - The Lotus Forums Jump to content
soldave

Brake servo problem?

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Now first of all, I know I've got an Eclat but I believe they share the same brake servos as the Esprit (or at least use the same rebuild kit according to http://www.mevspares.co.uk/BRAKE-SERVO-KIT-Lotus-Eclat-Elite-Esprit-and-Excel.html).  When I'm driving slowly or stood and I put my foot on the brakes, I hear a "ch-ch-ch" noise in time with the engine ticking over.  It doesn't seem happen when I'm at speed and from what I've read online it suggests the brake servo.  I've checked the hose going from brake servo to engine and that's in perfect condition.  Braking seems ok for a 35 year old car although I'm not sure it feels like it's servo assisted (need to check that though with the pedal down and engine off compared to on).

 

Have put my foot in the driver's footwell and the sound is definitely coming from the servo.  Listened from outside but even with my head stuck in the engine bay can't hear a thing.  I've seen these rebuild kits as above and a few people have mentioned that there's a seal between the pushrod and the servo itself which could be gone.  Does this problem sound familiar with you, and if so do you think a rebuild kit like this could possibly fix it?

 

Thanks for any thoughts anyone can offer on this one.

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As an additional question, what's the brake servo off? Is it a Ford Escort Mk2?

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I rebuilt the servo on my Europa, it was a right bitch to put back together & still didn't work properly because of internal fluid leaks so I'd replace rather than rebuild if I was you. :thumbup:

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I rebuilt the servo on my Europa, it was a right bitch to put back together & still didn't work properly because of internal fluid leaks so I'd replace rather than rebuild if I was you. :thumbup:

Thanks for the thoughts.  Was asking as SJS are wanting £220 for a reconditioned one.

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Lotus bits have loads of scrap loti i have given them 3 so worth a call for a s/hand one.

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Sounds like the none return valve in the servo. It makes a ticking noise that is particularly noticeable at tickover. Replace it. Cheap easy fix.

 

Pete

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Sounds like the none return valve in the servo. It makes a ticking noise that is particularly noticeable at tickover. Replace it. Cheap easy fix.

Pete

If it was that valve, wouldn't it be audible from the engine bay, sticking my ear close to the servo? That valve does have some movement in it in the servo, so it's not out of the realms of possibility.

Where would I source a replacement valve from?

Edited by soldave

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Thinking a bit more, is there any way of confirming it's the valve rather than the servo?  And I'm guessing the brake servo will need to be taken apart to replace the non-return valve, or can the grommet and valve be fitted with the servo in situ?

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It's easier to do it on the bench with the Esprit but it might be more accessable in the Eclat.

 

Pete

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It's easier to do it on the bench with the Esprit but it might be more accessable in the Eclat.

 

Pete

What's involved in replacing it; is it a take-apart-the-servo job?  Am coming up with nothing so far in sourcing the valve either :(

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I believe the servo is a Girling Supervac also fitted to the Esprit S1 and also many Triumph's such as the TR6 and Dolomite. In which case the non-return valve is available from Rimmer Bros :

 

http://www.rimmerbros.co.uk/Item--i-RTC812


Forgot to say, its an easy replacement assuming you can get to the vacuum hose. Remove the vacuum hose, lever out the old non-return valve, replace the sealing washer and press back in the new valve - its a tight fit.

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I believe the servo is a Girling Supervac also fitted to the Esprit S1 and also many Triumph's such as the TR6 and Dolomite. In which case the non-return valve is available from Rimmer Bros :

http://www.rimmerbros.co.uk/Item--i-RTC812

Forgot to say, its an easy replacement assuming you can get to the vacuum hose. Remove the vacuum hose, lever out the old non-return valve, replace the sealing washer and press back in the new valve - its a tight fit.

I can get to the current fitting and hose - it's at the top of the servo in the Eclat. Any way I could confirm it's this and not something inside the servo itself?

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I can't really think of a way Dave - without some specialist gear to test the servo on a bench. You could remove the vacuum hose from the servo and securely plug it - just to confirm that the noise goes away. If you then drove it (carefully) the lack of servo assistance would be noticeable. Proof that the servo was working (or not!)

 

Obviously, if the noise doesn't go away, its not the servo and you have a small split/hole somewhere in the hose.

 

If it's the servo internals that are at fault, like a split diaphragm, then there are no parts available to repair it anyway and the only option is an SJ replacement.

 

Any significant vacuum leak might affect the engine idle - does the idle speed change when pressing the brake pedal ?


There is a seal between the front of the servo and the master cylinder that keeps the vacuum - if that were split/perished it will leak. Those parts are available in the rebuild kit, but thats about it from what I remember.  

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Any significant vacuum leak might affect the engine idle - does the idle speed change when pressing the brake pedal ?

Interesting you say that.  My experience with other (admittedly more modern) cars is that repeatedly pumping the brake when idling will cause the idle to drop.  What I've noticed now I've fixed the fuel mixture on the Eclat is that pressing and holding the brake down will drop the idle speed noticeably (100-150rpm at least).

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I don't think it should drop the idle speed for longer than a couple of seconds while the servo pulls in, then the vacuum should be constant and the idle should return to normal I would have imagined - unless there is a leak in there of course with the pedal depressed.

 

Give these guys a call http://www.jlspares.com- they'll probably have the answer, or if not could at least test and rebuild if required.

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Yeah, that's what I was thinking.  I'll try calling that place once they're back after Christmas.

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I would replace the valve first. My Esprit made a loud ticking from the servo after starting it up after 28 years idle. It sounded like the engine had a badly adjusted tappet except the noise was coming from the front and the engine is obviously in the back.

 

It could be your valve is leaking also not sealing the vacuum in the reservior within the servo when the cylinder with the vacuum take off is not creating a vacuum.

 

Cheers Mike 

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Slight update today.  As I was playing in the engine bay I had a good listen around and did find the same ticking coming from the tube that goes to the brake booster.  Pinched the hose and the sound went away.  Pulled the hose off the non-return valve and the sound became louder (from the hose) and the revs dropped a little.  Put the hose back on the valve and tried blowing & sucking through the other end.  Valve won't allow me to blow and can't suck anything through it, although probably because it was still connected to the brake servo.

 

Can anyone confirm the check valve can just be removed and replaced from the servo without having to take it apart (is it just a pull out/push in replacement)?  Have seen a replacement 2nd hand.  Would need a hell of a clean up, but should solve the problem.

servo_zps0495f68a.jpg

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Hi Dave, yes the valve just pops out - its a very tight fit on some barbed plastic into the rubber sealing ring - at least mine was. Also it needs a good press (aka soft faced hammer) to refit it.  

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Hi Dave, yes the valve just pops out - its a very tight fit on some barbed plastic into the rubber sealing ring - at least mine was. Also it needs a good press (aka soft faced hammer) to refit it.  

Much appreciated.  Will probably go for this replacement servo and see how I get along with it.

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Well I got a used brake servo last night, and finally got around to pulling the non-return valve out of my current one.  The one that was on my car came out with a pop, but I found I could easily both blow and suck through it.  So not so much a valve as a tube!  Tried the valve on this used servo and I couldn't blow into it (a la air going from the engine to the servo), but I could suck (a la engine vacuum sucking air from the servo).  Fitted the valve but not had chance to drive it and check yet.  I started the car and the little chattering was still there but seemed quieter.

 

We'll find out more tonight...

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Well... it was a partial success I think.  Driving along I can now sometimes hear a ticking noise from the brake servo when I'm on the throttle or cruising along.  That sound seemed to go away as I drove more though.  When I braked I think the brakes seem a little sharper and on point.  I was able to get them to lock up, although that might have been more due to the road conditions tonight than anything else!

 

But there was still the ch-ch-ch noise when I brake, and idling and I press the brakes the revs drop and don't pick back up again.  Which would make you think air is entering the servo somehow, then getting sucked into the engine by vacuum, which is making it lean and dropping the idle until I let off the brakes.  So the next step is to replace the servo itself this weekend, once it's been cleaned up and painted.

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The fact that your old valve worked both ways is definitely busted. Interested to learn if it makes any difference with the new servo. I presume you know the replacement is 'good' ?

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The fact that your old valve worked both ways is definitely busted. Interested to learn if it makes any difference with the new servo. I presume you know the replacement is 'good' ?

I knew someone was going to ask that ;)  Errr,,, no I don't (I know... I know)

 

But we'll see when it gets switched out what happens.

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What an absolute pain in the rear end that was. Those 4 nuts in the pedal box holding the servo in are an absolute nightmare to remove. Was upside down in my footwell all morning trying to release them. And one typically fell behind the carpet somewhere and was eaten by the car. :-(

Got the new servo fitted, and apart from the split pin that holds the pedal-to-servo pin in place (last I heard of it was it springing off somewhere) and that nut, it's all gone together ok. Went for a very quick drive and was nearly thrown through the windscreen! Yes, the brakes do work now. Very well.

Does anyone know off-hand what size and thread pitch nut fits the servo? Got 3 on and tight but need another before I want to do much driving. The split pin I can replace easily enough.

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