Knocking noise from engine when started in cold weather

[irish lad]

Hi folks,

I bought a BMW 320D about two months ago. Best money i ever spent, However in the last few weeks, with the v cold weather, i have noticed a pronounced knocking sound coming from the engine when 1st started. This goes away after she heats up. Anyone got any idea what this could be? This only happens when it is cold weather. Im really concerned that im doing damage by driving her but my mechanic cant see me till next weekend...

Any help you can give is greatly appreciated

Thanks guys

[johnnyBgood]

Originally Posted by irish lad

Hi folks,

I bought a BMW 320D about two months ago. Best money i ever spent, However in the last few weeks, with the v cold weather, i have noticed a pronounced knocking sound coming from the engine when 1st started. This goes away after she heats up. Anyone got any idea what this could be? This only happens when it is cold weather. Im really concerned that im doing damage by driving her but my mechanic cant see me till next weekend...

Any help you can give is greatly appreciated

Thanks guys

Welcome to the Werkz.......Are you sure its knocking sound, because I know the secondary pump (smog pump) makes a sound that sounds a little like a knock, but more like a muffled tapping sound until the engine warms up......this is normal. You can look & listen for it, it should be mounted up in the right inner corner of the engine bay against the firewall.....any how it looks like this: #1




johnny,

[irish lad]

Hi Johnny, thanks for the welcome!

I will check this out tonight for sure. However if it was the smog pump would the knocking get worse in cold weather? We are experiencing below freezing temperatures here at night for the past week. It is only on the morning after a cold spell that the sound is so clear (it is quite distinctive and pronounced. You can hear it inside the cabin or even from a 15 - 20 feet away from the car)

p.s you car is awesome looking. i must get a pic of mine on as a profile pic so you can have a look.

thanks again

lee

[johnnyBgood]

Originally Posted by irish lad

Hi Johnny, thanks for the welcome!

I will check this out tonight for sure. However if it was the smog pump would the knocking get worse in cold weather? We are experiencing below freezing temperatures here at night for the past week. It is only on the morning after a cold spell that the sound is so clear (it is quite distinctive and pronounced. You can hear it inside the cabin or even from a 15 - 20 feet away from the car)

p.s you car is awesome looking. i must get a pic of mine on as a profile pic so you can have a look.

thanks again

lee

Oh.....below freezing.....another common thing that happens in very cold weather is moisture feezes up the Pressure Regulating Valve/Oil Separator
causing high crankcase pressure.....this is very common in sub-freezing weather....there is a flap in this valve that freezes shut because of moisture,
the only thing you can do is try get the car into a garage to kind of thaw out!

johnny,

p.s. thanks for the compliment..... & post some pics when it gets warmer...

[irish lad]

Hey Johnny, So you the pressure relief valve could be my problem in the cold? I wonder if it causes any damage??
thanks again - you've been a great help with this mate.

p.s check out my profile pic and tell me what u think of my baby! Shes not quite as "blinged" out as yours yet...but im working on it!!

[johnnyBgood]

Originally Posted by irish lad

Hey Johnny, So you the pressure relief valve could be my problem in the cold? I wonder if it causes any damage??
thanks again - you've been a great help with this mate.

p.s check out my profile pic and tell me what u think of my baby! Shes not quite as "blinged" out as yours yet...but im working on it!!

I checked out your ride in your picture profile, looks real nice. The picture is real small though. Post some pics through the manage attachments button below in the advance post section!

johnny,