Noise inside engine

[Ricky2020]

Does anyone gave any idea why that when my car is running the sound is quite normal for a diesel but when I open the oil cap the noise gets louder.

Sounds like something is running unbalanced but not a clue what it could be
Many thanks

[yellowbentines]

Because you aren't supposed to remove the oil cap whilst the engine is running. Stop doing it. Problem solved.

[SturdyHSV]

Have you considered similar circumstances, such as when there is music playing in another room, when you open the door it gets louder...?

[jj.]

Sounds to me like it might be your Double Over Head, Flyback Lifter is starting to ride up on it’s knurled adjustment nut. Damn expensive last time I got that fixed.! I’d shift that PDQ if I were you...
jj

[hulksta]

Saw thread title.
Opened thread praying for the appropriate responses to the question.

As expected, PH didn’t disappoint.

Thank you

[Equus]

Try sticking your finger in the hole and revving the engine to the limiter whilst poking around - you might be able to dislodge whatever is making the noise.

[TheAngryDog]

If you put your ear against it does it sound tinny or tappy?

[cobra kid]

I find that 5 ltr of cold water in there helps to quieten it down. Fills the gaps in.

[J4CKO]

The answer is, that by taking the oil filler off it will allow more noise out of the engine from the internals, also the engine has certain levels of pressure from the combustion process which varies from one engine to the next and can become more pronounced as the engine wears as some combustion gas can leak past the piston rings, called Blowby. Which can then show as air pulsing from the oil filler, a little is normal but if its pronounced there may be issues, there will always be a little haze as there is a lot going on in there, oil and air and the two mixing.

It is, generally ok to remove the oil cap whilst it is running but probably best not to unless trying to diagnose an issue as the chances are it will, on some engines flick oil out (depends on the design and whether it has any kind of baffle, between the moving parts and you)

Removing the cap will allow any pressure to escape and can show as a change in engine sound alongside the extra volume, perfectly normal, and if it runs ok, dont worry.

[SturdyHSV]

J4CKO said:

The answer is, that by taking the oil filler off it will allow more noise out of the engine from the internals, also the engine has certain levels of pressure from the combustion process which varies from one engine to the next and can become more pronounced as the engine wears as some combustion gas can leak past the piston rings, called Blowby. Which can then show as air pulsing from the oil filler, a little is normal but if its pronounced there may be issues, there will always be a little haze as there is a lot going on in there, oil and air and the two mixing.

It is, generally ok to remove the oil cap whilst it is running but probably best not to unless trying to diagnose an issue as the chances are it will, on some engines flick oil out (depends on the design and whether it has any kind of baffle, between the moving parts and you)

Removing the cap will allow any pressure to escape and can show as a change in engine sound alongside the extra volume, perfectly normal, and if it runs ok, dont worry.

190 months and still helping people, you must have a big heart

[Grumps.]

Ricky2020 said:

Does anyone gave any idea why that when my car is running the sound is quite normal for a diesel but when I open the oil cap the noise gets louder.

Sounds like something is running unbalanced but not a clue what it could be
Many thanks

Sounds dodgy to me.

[gamefreaks]

If you do this on a petrol, you will probably get an EML as you now have a big filler cap shaped vacuum leak....