brake vacuum and big cams

[bmw2101]

ive got a bmw e36 with a b230 in it. the inlet is the lh2.4 style, and its got a t5 cam in it that is 300 degs. I am finding that when i brake lift off and brake again, all the vacuum has gone, and the pedal goes hard.

Is there a volvo type fix for this you all do?

thanks!

[JoBy]

These two together. There are more similar pumps and valves. These are from Volvo S60 2001-2004.
Many available from used car parts dealers. Pump usually in the €60 price range and the valve cheaper.

The first is an electric vacuum pump. Second is a three way check valve with a built in pressure switch.
One hose connection for engine vacuum.
One hose connection for the electric pump.
One hose connection to the brake booster.

From ignition, power the pump thru the pressure switch. No relay is needed.
In case engine vacuum is too low then the electric pump starts resulting in full braking power even without engine running.

https://www.volvopartswebstore.com/prod ... 17445.html

https://www.volvopartswebstore.com/prod ... 00692.html

[therealpinto]

That is a nice solution that will give consistent braking.

However, step 1 might be to make sure you have a one-way valve or a check valve fitted, either it is in the vacuum hose itself or in the actual fitting on the vacuum booster. All stock installations have this to keep some vacuum in the booster as you apply the pedal. In a standard installation this means you have 2-3 braking sessions with some assist even in there is no vacuum available.

It might not solve your issues but it is an easy thing to overlook in a custom install. And a check valve is very easy and cheap to try

Gustaf

[bmw2101]

jonas thanks! ill look into that, i have asked on a forum also here un the uk and someone suggested one of these but i dont know if that would cope.

Gustaf thanks , the valve is there, it works , just the vac is not enough as of the camshaft

[bmw2101]

These two together. There are more similar pumps and valves. These are from Volvo S60 2001-2004.
Many available from used car parts dealers. Pump usually in the €60 price range and the valve cheaper.

i have now fitted this to the car, it seems to work but not sure ive only driven it out of the garage. every time i press the brake pedal the motor runs for like 3-4 seconds. is that right, even with the engine running?

thanks

[JoBy]

On a low vacuum engine at idle that is normal. With a bit more rpm av engine braking you get more vacuum from the engine.
I had a small leak where the hose connected to the booster and with ignition on the pump would start every minute or so. After fixing that the interval is much longer as long as I don't touch the brake. With engine running I don't hear the pump so I can't really say.

[bmw2101]

ok thanks, i just wasnt sure! ill see how it goes as i have only driven the car out of the garage and back some 2 meters!!! leaving the car on its own not running it may pulse once every 3 mins.

[bmw2101]

oh oh oh!!! i put the 1 way valve on the wrong way to the engine, so there was no engine vacumm, it seems ok now, but also so do the brakes! thanks!!!

[bmw2101]

These two together. There are more similar pumps and valves. These are from Volvo S60 2001-2004.

done a rally now with this, works really well. thankyou! i used relay though inline with it ...