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View Full Version : Does An vacuum Easy Power Brake booster conversion exist for E24s?



BMWtyro
08-25-2018, 02:17 PM
I have just had the hydraulic brake booster on our 8-84-built 633 fail for the third time in 5 years. :mad The problem is as it has been before: massive amounts of red hydraulic fluid leaking from between the master and the booster.

This has prompted me to wonder whether a relatively simple vacuum booster conversion exists --- one that does not require re-engineering of the entire engine compartment. Your thoughts?

Jeff

DesktopDave
08-26-2018, 08:41 AM
The earlier model E24 has a dual-servo vac booster that would be my first choice. I'm not sure if it would fit due to the accumulator bracket and other stuff but it's worth a look. I'd also check the E34 535i setup, since that braking system is near-identical to the E24. The E24 hydro boosters fit the E30; I'd bet the smaller E21 or E30 vac booster would fit in the E24 but might not provide enough assistance at low vacuum situations.

BMWtyro
08-26-2018, 09:01 AM
Thanks, Dave. Wow, I just reviewed my title for this post and it turns out to be a real tour de force in "backwards do I talk"!

Question: are you saying that the E34 set-up is vacuum-boosted or hydro-boosted? I am largely unfamiliar with those cars. Either way, I might be interested.

Jeff

DesktopDave
08-29-2018, 02:36 PM
There are a lot of boosters that can be made to fit. BMW, Porsche, VW and Volvo all use the same bolt pattern during the 70s & 80s AFAIK. The variations I've seen include a firewall extension on the back of the booster, and some have longer actuator rods to fit the brake pedal. You can't get anything much newer than about 1993 unless you also upgrade the master cyl. BMW or ATE swapped the brake master bolt pattern to an offset version.

After all that it's basically just a clearance issue with the cyl. head or intake manifold. You'd also need a large vac source off the manifold (the E34 535i intake manifold for instance), assorted vac hoses, one-way valve, and possibly a vac reservoir. You can get a lot of good info by checking what the E30 M50 swaps are doing. They always have to source a compatible unit since the M50 manifold is so much larger. The E21 320i is a popular choice.

The E34 and E32 used a lot of different variations. My '89 525i (M20B25) definitely used a single-stage vac booster. The V8 models I've seen use a huge double-stage remote vac booster set-up. It's in the front fender well just behind the headlights, triggered by a long linkage to get around the left cylinder head.

BMWtyro
08-29-2018, 05:43 PM
Thanks, Dave!