Servo assistance for clutch

[Martin]

Hi,

The clutch on my TD5 90 is too heavy for me - I've had a knee injury that I'm having trouble recovering from and whenever I drive the 90 it just makes my knee worse. At the moment I'm using the wife's car (the clutch on her Audi is just so light), but really want to be able to use the 90 everyday (especially before Nicky gets too attached to it!).

I'm thinking about putting a remote servo in line between the master and slave cylinders. I've seen these advertised new for around £80 (Lockheed LE72696), so should be able to do the whole job for less that a hundred notes. Has anyone experience of doing this and what are the possible pitfalls? I read on an AC Cobra forum of somebody who did this and if they were repeatedly on and off the clutch then the bite point moved around (something to do with master to servo or servo to slave cylinders being different sizes?).

Cheers,
Martin

[Range Rover Blues]

Probably got more to do with the hydraulics pumping up but there is a tiny amount of lag when the servo valve is opening.  I'd say give it a try, for £80 it's a no-brainer.

[Martin]

Thanks for the reply. I'll give it a go. Have now ordered the servo, hopefully will have it by the weekend.

[LeanneNCharlie]

Have you done it yet? Has it made it any lighter?
I have a 90 and struggle with the clutch, and would love to make it lighter so I can drive it every day. Where did you get the kit from?

[Disco-Ron]

The Landcruisers have a servo on the clutch as standard, BUT it's a small servo, i suspect that a 'brake' sized servo may be too much for a clutch, i watch with interest.

[Martin]

Not finished yet, got a bit delayed over the New Year break.

I got the servo mounted last weekend - spent all of Saturday making the bracket and fitting it (then removing, modifying it and refitting...). Am just waiting now for the last of the hoses/unions/T pieces that I ordered to arrive, should be today or tomorrow. This weekend's job is plumbing it in.

Once I've finished I'll let you know how I got on and will post some pics of the installation.

[Evilgoat]

I( was gonna say, the Audis use a Power Assist system. You should be able to pull everything right of a B4a/B4b (1985 - 98)Audi 90/80/100/Avant) including the pump, cylinders etc.

They are fed from the PAS pump IIRC

[unknownmanxman]

Sounds like a nice idea.. Anyone know where to get one from?

[Martin]

I think the simplicity of the method I'm using is a big plus point (well it is for me - as its a bit experimental I didn't want to try anything too complicated). Using a remote servo means I only have to split the hydraulic pipe between the existing clutch master and slave cylinders, insert the servo and then get a vacuum connection from the vacuum hose to the brake servo.

I've read that this method has worked on an AC Cobra replica and I'm using the same servo as was used on that. The Cobra had problems with vacuum at idle - you don't get much vacuum at idle from a petrol engine, but at least on a diesel you already have a vacuum pump.

As I said before, once its installed I'll let you know how well it works and will post up pictures and details in case anyone else wants to have a go.

[LeanneNCharlie]

Look forward to hearing your report!

[Range Rover Blues]

I think the simplicity of the method I'm using is a big plus point (well it is for me - as its a bit experimental I didn't want to try anything too complicated). Using a remote servo means I only have to split the hydraulic pipe between the existing clutch master and slave cylinders, insert the servo and then get a vacuum connection from the vacuum hose to the brake servo.

I've read that this method has worked on an AC Cobra replica and I'm using the same servo as was used on that. The Cobra had problems with vacuum at idle - you don't get much vacuum at idle from a petrol engine, but at least on a diesel you already have a vacuum pump.

As I said before, once its installed I'll let you know how well it works and will post up pictures and details in case anyone else wants to have a go.

There will only be a problem with vacuum at idle if the non-return valve is goosed, or of course you operate the clutch a lot, but as you say on a TDi no such problems.

Keen to hear how you got on, I'm serioously considering the other way round the heavy clutch problem, I've a 4.6 auto in the LSE I'm cutting up to go in next summer :D

[Evilgoat]

I think the simplicity of the method I'm using is a big plus point (well it is for me - as its a bit experimental I didn't want to try anything too complicated). Using a remote servo means I only have to split the hydraulic pipe between the existing clutch master and slave cylinders, insert the servo and then get a vacuum connection from the vacuum hose to the brake servo. .

As I said before, once its installed I'll let you know how well it works and will post up pictures and details in case anyone else wants to have a go.

I beleive this is why thet use the PAS pump on the VAG cars. Also all the bigger engines hadve a vacuum booster, but there is NO WAY that you'll retrofit that on a non VAG engine. I'm sure something has a vacuum booster on the back of the alternator.

[Martin]

Almost there (having trouble bleeding the system - hence my other post titled "bleeding clutch")

The T piece for the vacuum hose I bought was the wrong size - dad is making me one up in his workshop this evening/tomorrow morning. I did bodge on the vacuum hose just to make sure it works. Had to give it some revs to get enough vacuum as it was leaking but the clutch was then so light!!!! Another effort tomorrow and should be finished.

I measured the weight needed to operate the clutch before starting using the bathroom scales - around 25 lbs! Should be half of that when I'm done.

[Martin]

OK - basically all done now. Still a little bit of air in the system so will drive the Landy around for bit and then bleed again. The clutch is now very light. I tried before and after measurements of the weight needed on the clutch pedal : around 25 lbs before and now requires around 14 lbs (this was using the bathroom scales and was a bit fiddly so I can't guarantee those numbers).

Here are a couple of pics of the servo in place:  





For those interested, the servo I used was a Powertune RLE72696. I made up the bracket to mount as shown. Then removed the hydraulic pipe from the clutch master to slave cylinders and made up 2 new pipes - master cylinder to servo and servo to slave cylinder. I had to use 3/16" tube because of the servo unions. The other unions needed are M12 male for the master cylinder and 7/16 UNF female for the slave. All that is left is to run the vacuum hose around to the brake servo and use a T piece to tap into the vacuum pipe there.

Took me just over two full days to do, the real time consuming bit being making up the braket to support the servo.

Total cost was £80 for the servo, £10 for the copper tube, £20 for some vacuum hose, £10 for a load of hydraulic unions (as I wasn't sure which ones I'd need), £8 for brake fluid and a couple of quid for some hose clips [and I now owe my dad some favours for use of his welding gear for the bracket and for making me the unequal T piece for the vacuum hose].

[LeanneNCharlie]

Glad it's worked. Where did you get the servo from as I'm going to try and persuade "him indoors" to have a bash at mine!

[Martin]

Glad it's worked. Where did you get the servo from as I'm going to try and persuade "him indoors" to have a bash at mine!

I got the servo from MG Services Heathrow via e-bay. They had a special offer over Xmas, I think they're around £20 more now. Just have a surf on e-bay as there are a few shops on there selling new ones or check out anyone who sells stuff for old cars as this servo is used by a lot of the classic car people who want to add a servo to their braking system.