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Servo / Pedal Travel on Vitesse


Froc
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Hi all.

I've just replaced the servo on the Vitesse (sticking air valve on the old unit). The servo is a 1.9 Powertune (Lockheed type).

All is well, except I seem to have more pedal travel before the brakes bite than I did before. Brakes work fine, no air in the lines or the servo. More of a curiosity than a problem. Has anyone else fitted a powertune servo to a Vitesse and noticed a change in pedal travel?

Thanks

Froc

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I replaced a knackered Girling with a Lockheed and the pedal was lower. There didn't appear to be air in the system everything was working OK.  But I was advised to disconnect the feed between the servo and the brakes at the servo. Then re-bleed to ensure there was no air in the servo slave cylinder. Did that and the pedal came right back up. I guess the nature of the servo covers up the fact that there's air in the system.

 

Alternatively, was your previous servo a Girling? If so there may well be a difference between the two.

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Thanks Doug.

The servo I took off was an original Lockheed. The replacement was Powertune's Lockheed repro, so basically like-for-like.

I did bleed the servo at the outlet as you have described. In fact, I did the whole system twice (second time with the engine running!), so I am confident that the system is air-free.

I have a loose theory that there are differences in the air valve assembly between the old and new units, possibly amounting to a little extra lost motion on the new unit. However, that's just a theory. Not planning to take my new servo to bits to check! ????

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I think you're right about the air valve. I had some problems with my new servo (I couldn't return it having shortened the mounting bolts to get it in :angry:)​ I stripped it down and sorted it out but was left with one problem. When I took my foot off the pedal the servo remained locked on for several seconds. Having become familiar with how it worked I thought there was something wrong with the air valve so bought another off ebay. I couldn't see any difference between the two air valves but once fitted the new one worked perfectly. I think the whole design is a bit Micky Mouse, there's no measuring, setting up or adjustment, it works or it doesn't. However, having got it going it's not been any further problem.

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Ive got a brake hang on servo on the shed, have stripped all makes over the years mostly truck but

principles are all same there is a plate inside the pushrod passes, if out of line it restricts free return.

 

but the air valve is the main culprit, its a bit crude, tried a bigger spring , made no help, nothing appeareds wrong but like you all bought another and totally different operation, still bugs me I should solve the problem but ,,, Noooo.

 

the diaphragm if it baulks will slow the return but with atmosphere attacking the manofold vacuum theres a hole lot of energy which should easily over power the rubber

 

to get the air out the servo it must be fixed tilted as per the instruction or air stays in the end of the cyl.

 

make sure you have not got excess hub end float, the extra effort the servo gives can make this evident

where as a dull pedal will mask it

 

pete

 

pete

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