Yesterday i bought a secondhand AU1 brake booster. I want twin-diaghram boosting, mainly because i have fitted bigger wheels. The AU1 booster is mostly made of plastic, and is a noticeable amount lighter than the EBII's, which has a steel casing.

Although the AU1 booster has only two bolts to the body rather than the EBII's four, they are a direct fit with no modification, and everything else inside the car is also a direct fit.

The only problem is the bolts for the master cylinder are wider. I could either grind off the ends of the EBII's master cylinder's bolt holes and fit thick washers to ensure strength, or maybe i could fit an EF-AU1 master cylinder?

Comments?

Last edited by relaxed_diplomacy on Fri Nov 14, 2008 9:17 pm, edited 1 time in total.

personally i would keep the eb steel one!!
if you have extractors or alot of engine bay heat the plastic ones have been known to crack and fail...

if you want the better booster get a eb/ed v8 booster.. as afaik they are the duel diaphram type

I'm keen on the dual diaghram because the wheels have brought a 15% increase in pedal effort, coupled with an increase in tyre grip.

The wreckers did say they are failing, but this one looks good, and i don't have extractors, plus i just fitted an 82deg thermostat (i was looking for say an 86deg because i live in cold country, but they only had 82 or 88).


Yes, but they are old now, and remanufactured ones are much more expensive, especially as i don't have a V8 one to send back to them for exchange.

I paid $75 for the AU1 one, i reckon many people could get a better price than this, whereas i was looking at something like $400 for a remanufactured one from repco.

Last edited by relaxed_diplomacy on Fri Nov 14, 2008 9:19 pm, edited 1 time in total.

Maybe they are also more prone to this failure due to having two bolts to the body versus the earlier models four?

i have a q on this topic, iv recently put everything from an ELv8 into my ebv8 including k frame, abs even booster and master. should i keep my original ebv8 master or put the later EL one in? The eb one is like twice the size but youd think the EL one would have more experience and technoligy put into it?>
What one should i use??

they don't fail near the bolt holes. they fail on the edge that faces the exhuast system. best bet to keep the alive is shield it from the heat and fabricate a brace that bolts onto the top of the shock tower and butts against the end of the master cylinder.

I fitted the AU1 booster to my EBII and the difference is massive, it's perfect now, just the way i want it.

In terms of fitting it, everything is a direct match-up, except the following:

- The two bolts that go through the firewall go straight through existing bolt holes, however this means the master cylinder sits at an angle (maybe about 8 degrees). I don't see this being a problem, and when you check the fluid level you can easily compensate. It would mean you can't fill the reservoir quite as much when bleeding the system, but it's not significant. If you are fussy you can drill some new holes. I fitted large washers behind the nuts to ensure adequate rigidity.

- The two bolts on the booster for the master cylinder are wider apart. The solution is to elongate the bolt holes in the master cylinder's aluminium bracket. Not having a dremel or die grinder, i used a file. This was a bastard of a job, even though i cut the back out of one of them with an angle grinder. I suggest you get a dremel or equivalent, unless you want to just cut the ends out altogether. I recommend keeping the ends as there is still 2mm there when you have finished, which retains strength and ensures the master cylinder lines up to the booster correctly. I used nuts with an inbuilt washer to distribute the load on the modified aluminium. If this job fails you will lose all braking, which is very dangerous. If you aren't competent, don't do this conversion.

- you need to trim off a small amount of the firewall sound deadening so the booster fits flush with the firewall.

After fitment i noticed the master cylinder can be flexed around by your hand, but figure this is simply the way the plastic boosters are. The brake pedal feels great.

From what i have been told both of your boosters are twin diaghram, whether they offer the same boosting i don't know. Other than that, i don't really know anything more than what i have said in this thread so far. It sounds like the other guys would recommend you use the EB one.

but the eb one is twice as big, now im thinkin of using the eb one?

I don't imagine the EB one produces more assistance, given how much assistance my AU1 plastic one provides. More assistance could be a problem if for example a fly lands on the pedal (just kidding). I guess the other posters might recommend the EB one for the cracking reason they mentioned earlier.