m50 vacum air leak from brake booster hose

[shiremux]

I think i've found the source of problems in my engine, the rough idle etc, today i accidently heard a air hiss from hose connected to the air intake manifold, when i covered the hose with my finder suddenly the engine went into its normal rpm without shaking like before.
So, my question, can i seal this little hole with silicone or there is some hose missing in there?
IMG_20181116_145151.jpg

[CallMePuff]

I believe that should be capped off. Pretty sure it was a port that BMW used on a previous car then kept the part. I read that people have them capped off per my Google Fu, but I can also check when I get home

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[shiremux]

Yeah got to a quick conclusion near the car, if its leaking and engine is acting bad, and its good when its sealed - take silicone. So i did. Ill see tomorrow, anyway would like to make sure from you guys.
Also, could this cause worse miles per galon?

[CallMePuff]

Yeah got to a quick conclusion near the car, if its leaking and engine is acting bad, and its good when its sealed - take silicone. So i did. Ill see tomorrow, anyway would like to make sure from you guys.

http://forum.bmw5.co.uk/topic/73223-...uum-leak-help/

Here's a helpful link with some more info on it. Apparently it was used to pull vacuum over in-car air temp sensors. Not sure which car you have, but my E34's AC/Heater controls have a fan that does that for it. I don't recall a hose coming from my brake booster valve. Either way, I don't think it's a do or die situation.

Edit: if you want to be sure, check to see if that nipple is capped already near the 3 heater hoses on the firewall.

[cirrusblau]

That's supposed to have a nipple on it with a plastic cap. It quite common for these to have broken off. I just plug them off with epoxy.

[shiremux]

Ok my silicone fix didnt change anything, strange coz the day before when i sealed the leak with my finger everything seemed fine... Now its the same, maybe its still leaking or maybe its not the cause. But i think my engine harsh idle has something to do with the brake booster, it starts right when i hit the brake pedal, i can feel the engine going crazy and shaking hard untill i stop, then it still shakes but not that much. What else can i check?

[CallMePuff]

Ok my silicone fix didnt change anything, strange coz the day before when i sealed the leak with my finger everything seemed fine... Now its the same, maybe its still leaking or maybe its not the cause. But i think my engine harsh idle has something to do with the brake booster, it starts right when i hit the brake pedal, i can feel the engine going crazy and shaking hard untill i stop, then it still shakes but not that much. What else can i check?

Did you let the epoxy dry completely or get some into the check valve? Just a thought.

[shiremux]

I didnt use epoxy, i used a red RTV maker, im not sure if it was good idea I let it dry for 16hrs tho

[CallMePuff]

I didnt use epoxy, i used a red RTV maker, im not sure if it was good idea I let it dry for 16hrs tho

Hmm...if you put your finger over that hole again does it make a difference?

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[whiskychaser]

Stick your finger over the end again and see if it settles. If it does, put a strip of insulation tape over the end and then wind some round the stub to keep it in place.

If the idle doesn't change a little when you remove the oil filler cap, you have a vacuum leak somewhere. That does assume that the seal on your oil filler cap is ok though

[shiremux]

Well, triple checked, it doesnt leak anymore from this spot but the hard idle is still there, maybe a bit better coz the engine doesnt suddenly die after reving. I still can hear some hiss noise but im not sure what causes this, it appears somewhere near the belt or under the intake manifold... What else can i check that may cause this harsh idle?
Ill say what i've done:
- new sparks
- new head cover gasket
- new crankcase ventilation lines and connector
- new Mass air flow sensor
- cleaned and relubed the idle regulation valve.

The car has been to mechanic before with this sympthome, 02 sensor has been changed and the throttle has been calibrated again, its been a lot better since then but still far from perfect. From what they said they had to dissasemble the intake manifold and they didnt use new seals, maybe this is the clue?

[CallMePuff]

Well, triple checked, it doesnt leak anymore from this spot but the hard idle is still there, maybe a bit better coz the engine doesnt suddenly die after reving. I still can hear some hiss noise but im not sure what causes this, it appears somewhere near the belt or under the intake manifold... What else can i check that may cause this harsh idle?
Ill say what i've done:
- new sparks
- new head cover gasket
- new crankcase ventilation lines and connector
- new Mass air flow sensor
- cleaned and relubed the idle regulation valve.

The car has been to mechanic before with this sympthome, 02 sensor has been changed and the throttle has been calibrated again, its been a lot better since then but still far from perfect. From what they said they had to dissasemble the intake manifold and they didnt use new seals, maybe this is the clue?

Time to take some carb cleaner and spray around. It could be the intake manifold gaskets, the manifold not being torqued properly or seated properly, the idle control valve hoses. The ICV connector to the intake manifold is prone to breaking/leaking, so spray under there and see if it makes a difference.

If you the idle moves up when you spray in an area, you've got a vacuum leak there.

[shiremux]

Will get a carb cleaner soon and test it out. What if the engine rattle gets worse after a quick accelerate and brake? When i cruise with RPM under 3k its better but when i hit the kick down and and get over 5k RPM and then brake suddenly i can see the car wobling arround like a muscle car and it does a couple of frog leaps right before stoping to 0km/h. Can this round the circle to something else than vacuum leaks? maybe fuel pump, fuel filter? dying coils?