Brake booster & master cyl retrofit

gazman

We've known since the beginning that the brakes were shot on this bus, but after stepping hard on the pedal and having it go to the floor and stay there we knew it was time to fix them. Having recovered from the mild heart attack brought on by seeing the price for new parts (very pricey on this side of the globe), and knowing that we'll probably go for a bigger caliper / disk setup at some stage, we looked at the possibility of fitting a larger Holden Commodore booster & master cylinder.
FYI - Holden Commodores are an Aussie made family-sized car originally designed loosely on the Opel Monza, and the latest models are exported to Europe and rebadged the Vauxhall VXR8.
Here are the stuffed original parts-

And removed from the bus, the booster, master cylinder and reservoir, hoses and brake lines.

A rummage through the shed-full of left over Commodore parts from the V6 conversion found a good secondhand VN Commodore booster & master cyl. These were held roughly in place to see if they would physically fit in the original space on the bus.

Because the position of the booster on the bus is more exposed it will need a dust boot to keep the crud out. A spare vw gear selector rod boot fits perfect. The square flange on the rubber bushing on the new booster is also cut off so it will fit in the vw booster bracket.

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gazman · Posted: Tue Mar 30, 2010 5:18 am Post subject:

Obviously the Commodore booster doesn't bolt straight on. Here is the VW booster bracket, the white paint marks show where the Commodore booster bolts need to fit.

A little grinding and the new booster fits in place. If the beam comes out in the future (for adjusters maybe) I'd like to weld in a new booster plate that's been drilled to suit the Commo booster. Meanwhile if we had any probs with our retrofit the original parts can still go back in!

A couple of pieces of flat-bar with holes drilled are fitted, and the booster bolts on nice and solid.

This threaded insert holds one of the beam bolts, but touches the new booster. Since the bolt stops before exiting the other side we could safely grind a few mm's off to clear the booster.

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gazman · Posted: Tue Mar 30, 2010 5:22 am Post subject:

Well its close, but at full steering lock the steering bits just clear.

Next a new linkage rod needs to be made to go from the brake pedal lever to the booster.

An extra bolt hole is drilled in the end of the booster rod to give the new linkage rod some stability.

Two pieces of flat bar drilled to fit the booster are welded to a length of rod.

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The V6 Lowlight. See the full build here - http://osp.metrohosting.info/kombiv6.html

gazman · Posted: Tue Mar 30, 2010 5:24 am Post subject:

Kombi's have the brake switch mounted on the master cylinder, but Commodores have one mounted above the brake pedal. Since we kinda need brake lights we had another rummage through our shed of endless Commodore parts until we found a brake light switch. We then fitted it into the chassis, next to the hole that the linkage rod passes through.

The linkage rod is finished and includes a lever to operate the brake light switch.

Here is the rod fitted, you can see how it operates the brake light switch.

Next the master cylinder is fitted. Commodore master cyl's are dual circuit with a built-in proportioning valve. Part of the original proportioning valve can be seen on the far right of this pic, and it can be removed from the vehicle.

_________________
The V6 Lowlight. See the full build here - http://osp.metrohosting.info/kombiv6.html

gazman · Posted: Tue Mar 30, 2010 5:27 am Post subject:

Now we need to make some new brake lines. You must use an 'internal/external' flaring kit to avoid leaks.

The flare on the left is the kombi one, a 90d external flare. The commodore one on the right is a 45d internal/external flare. We'll need the lines to fit the commodore master cyl on one end, and the kombi flexible brake hose on the other end.

The lines are finished and fitted. The threaded end fittings can be bought new, but there was nothing wrong with the vw ones, and of course we had some good s/hand commodore ones, so we just reused these.

The last problem we had was the handbrake cable rubbing on the booster.

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The V6 Lowlight. See the full build here - http://osp.metrohosting.info/kombiv6.html

gazman · Posted: Tue Mar 30, 2010 5:30 am Post subject:

Here's how the handbrake assembly looks-

We took off the handbrake link rod and made another one slightly longer (hard to tell in the pic)

Then when we refitted the new rod we had enough length to cross over the cables to gain the clearance we need.

The handbrake works great, doesn't rub or bind anywhere and it misses the booster by heaps.

_________________
The V6 Lowlight. See the full build here - http://osp.metrohosting.info/kombiv6.html

gazman · Posted: Tue Mar 30, 2010 5:32 am Post subject:

You might have noticed that the Commodore master cyl doesn't have a remote fill reservoir so it's a little tricky to fill and bleed from under the kombi. We used an old fluid bottle with a long hose attached to the lid to squeeze the fluid in, taking care not to get any dirt etc in there. Fortunately we don't need to do this too often.

The brakes are bled, vacuum hose connected to the booster and jobs done. The bus stops really good now, considering its got stock discs & drums, plus the extra V6 engine weight. Very happy with the results and I'm looking forward to doing more soon

_________________
The V6 Lowlight. See the full build here - http://osp.metrohosting.info/kombiv6.html

13 window deluxe · Posted: Tue Mar 30, 2010 7:19 am Post subject:

hi great write up there dude

did exactly same on my split but used vw golf mk2 parts because i had them and they were free Grin

the mk2 golf servo even had the correct hole centres, i also fitted a tee piece in one of the brake lines and screwed in the stock brake light pressure switch rather than fit a mechanical switch,the late bug remote reservoir fluid line fitting push straight into the golf master cylinder as well so i could have the brake fluid reservoir under the seat Grin

one thing to watch, is the gearlever boot tight round the new brake pushrod? air is sucked in here as the servo is opperated and if the boot is too tighter seal then you might have problems
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1964 rat 13 window deluxe 1Z tdi,
1975 rhd twin slider tintop (TBA)
1991 golf 2 gti with tweaked AHU tdi,

previous tdi swaps: gone but not forgotten
1979 rhd twin slider tintop bay ahu 1.9tdi
1990 T25 1Z 1.9tdi
1993 suzuki samurai with 1Z 1.9tdi

1303Steve · Posted: Tue Mar 30, 2010 7:21 am Post subject:

Hi

Nice work there.

You have the brake light switch sorted already but you can use one of the brass 3 way connectors that VW used for joining brake lines, the VW brake light switch screws straight in.

Steve
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STI powered 1303 now running
G50 box, Boxster/944 brakes, Adaptronic 1280E ecu, PWR intercooler etc

ElusiveStranger · Posted: Tue Mar 30, 2010 12:04 pm Post subject:

Nice write-up Gazman, thanks
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The advice you receive on here is worth the paper it's written on.
Your experiences are worth shed loads to others, including the f'ups - live and learn.
Wouldn't YOU rather learn by someone else's mistakes? So would they.

'78 Bay, 2 litre 091 box, EJ20 NA & the ashtray's on the 'right' side.
I don't lean forward for hills any more Grin

Bugger, missed out on "Live fast, die young"

gazman · Posted: Wed Mar 31, 2010 3:13 am Post subject:

Thanks for the comments guys Grin

The VW Golf wasn't a very big seller over here and parts are harder to come by, otherwise I might've used Golf parts just because they bolt straight on.
I used to do heaps of Commodore engine conversions (hence the 3.8lt Commo V6 in this bus!) and I quite literally have a shed full of parts, so using these seemed the most obvious and cheapest option for me. Plus they come standard with a 15/16" (23.8mm) master cylinder, and V8 models with a 1" (25.4mm) one.
I have had to change the brake light switch on VW's a few times and thought it was a bit of a pain to have to bleed the brakes afterward, so I was happy to change to the Commodore external switch.
_________________
The V6 Lowlight. See the full build here - http://osp.metrohosting.info/kombiv6.html

13 window deluxe · Posted: Wed Mar 31, 2010 9:09 pm Post subject:

i see what your saying with the holden bits they were free and plentyful Grin

_________________
1964 rat 13 window deluxe 1Z tdi,
1975 rhd twin slider tintop (TBA)
1991 golf 2 gti with tweaked AHU tdi,

previous tdi swaps: gone but not forgotten
1979 rhd twin slider tintop bay ahu 1.9tdi
1990 T25 1Z 1.9tdi
1993 suzuki samurai with 1Z 1.9tdi