How to mod a late booster for MK1.

[Peter Jones]

Holiday workshop time again.

Today I'm modifying a Cordoba booster to fit in a MK I.

I purchased a MKIII booster and 22mm master cylinder from Valver to do this mod with but I also had a complete Seat setup here as well. I didn't realise how similar they are.

No problems - I need two boosters/cylinders anyway

I started on the Cordoba booster because I thought some practice would be a good idea, I'm not so fussed if I bugger up the Cordy booster.

As some of you are aware the boosters out of the later cars bolt up but they have a ball linkage rather than a yoke and clevis pin setup.

I pulled a MKI booster setup out of a wreck to take measurements from.

By my reckoning its 129mm from the mounting surface to the centre of the clevis pin.



Here's the before shots - before I get too carried away.



MK III booster on the left, Cordoba booster and cylinder on the right.

[Peter Jones]

There's a limit of 4 pics per post - so bear with me here.

Measurement shots of new boosters.
Seat



MKIII



MK I



Hmm lunch has just arrived - stand by for more later.

[Jarred]

haha pausing for lunch. THis will be interesting to see. I await part 2 with much anticpation! I'm surprised how similar in size the mk3/cordy booster is with the mk 1 unit. should make for easier modification I geuss?

[Peter Jones]

Now to work.

I wanted to thread this conversion to allow for adjustment if I got it wrong. The yoke came off the old cylinder assisted with a bit of heat.

Interestingly the yoke that is on the rod across the engine bay is identical except that it has an M8 x 1.25 thread inside of it rather then the M10x1.5 of the booster yoke. I'll drill that out and tap a M10 thread into it to do the other booster with.



There's not much to hold on to in order to turn a die down the Cordoba booster shaft which is conveniently 10mm diameter. So the plan here is to grind the ball on top down to a square that the die will pass over but still be enough to clamp in a vice.

I used a bench grinder for this but I'm a little worried about whatever's inside the booster melting from the heat so every now and then I dip the ground end of the booster rod into a bucket of water to cool it down.



Yes that shaft is a little bent at the tip, I wasn't too gentle with it when I wrecked the Cordoba. Never mind I'm going to cut that bit off anyway.

This should make it a little clearer. The thread size is M10x1.5



Good idea, but the shaft is too thin below the ball for the torque of the die and it snapped off. There's still plenty of length to get rid of so I ground some new flats on the shaft.

[Peter Jones]

Here's what it looks like.



A couple of careful measurements later, I simply cut off the excess with a hacksaw, holding it in the vice as before.

I really wanted to put a jam nut onto the shaft to lock the yoke against but normal nuts were too thick. So I made a thin one!

You could do this with a hacksaw and file if you don't have a lathe handy. You only need one square face on the nut .

I'm afraid the last bit is a bit of an anti - climax, you just screw it all together!



I left the shaft a couple of threads longer for adjustment if I needed it later on. There's nothing that will foul on them in the mechanism.

And a quick measurement before adjusting, pretty close I'd say! (Actually spot on, but its hard to hold the ruler and take photos at the same time!)



I'll triple check the length and add some loctite for luck before I tighten the thing together. Now I'll pull it all apart and clean it all up for a coat of paint.

I'll add some more photos of it all installed in a few days. If anyone wants more detail, measurements or pics sing out and I'll add them to the thread.

I guess I'd better go and do the MKIII booster now while it's all still fresh in my head and the tools are out.

Pete

[Peter Jones]

A left over photo of the 22mm 16v Master cylinder to go on the MKIII booster. There's not as many ports on these so I'm going to ditch the brake switches off the master cylinder and install a mechanical one off the pedal directly.

[gldgti]

this has been said before, to me, by our founding father brackie - now pete I say it to you -

"you are a man after my own heart!"

brilliant! fantastic writeup, great discriptions, good clear easy to follow instructions. If a monkey could read, i reckon he'd have his golf as good as yours!

well done!.... now, to find a cordoba booster for myself...

[Peter Jones]

Just remember you'll need the master cylinder too. The rod length inside the booster is different. I'll try and get some pics later on. The late cylinders only have 4 ports while the MKI ones have 6. You could get around this with T pieces or do as I'm intending to do - loose the brake light switches in favour of a mechanical pedal based swith.

Maybe I should hit Matt (Golf Loon) up for a commission for the surge in Cordoba booster/cylinder sales!

Pete

[alex g]

nice work pete

has been a productive few eeks for you

great to see some quality engineering / fab going on

[Peter Jones]

Here's why you can't run the later booster with the early master cylinder.

The MK I booster's internal rod protrudes slightly from the booster, by a few mm.



Whereas with the Late boosters the rod is about 25mm down inside the booster.

[Peter Jones]

The more I look at the Cordoba and MK III booster the more alike they look. I suspect they're interchangeable parts. That would make sense as they're practically the same car.

The only obvious difference is that the Cordoba has 4 studs to mount it to the firewall and the MKIII one has only 2. I guess you could always cut two off the Cordoba one to Make it fit in a MKIII if you had to. Otherwise they measure up the same in all dimensions.

Here's comparison shots front and rear.
From left to right - Seat - MKIII - MK1

(I'd started to paint the Cordy booster at this point)

[Peter Jones]

Here's some shots for anyone that wants to know the Diameter of the boosters.

Cordoba



MKIII



MK I

[Peter Jones]

Seat Master Cylinder FYI

[Peter Jones]

I only had one reservoir bottle and needed another. Valver suggested that the Golf / Seat ones weren't terribly attractive and suggested a reservoir off a N13 Nissan Pulsar would do the trick.

I have no idea what an N31 Nissan Pulsar looks like but I found the Nissan isle at the wreckers, popped a lot of hoods and came up trumps with a couple of these.

Cleaning up nicely here in the parts washer.

[Peter Jones]

A detailed shot of the end of the MKI booster FYI.