Noise inside engine

Author
Discussion

Ricky2020

Original Poster:

1 posts

25 months

Monday 19th June 2023
quotequote all
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

anonymous-user

69 months

Monday 19th June 2023
quotequote all
Because you aren't supposed to remove the oil cap whilst the engine is running. Stop doing it. Problem solved.

SturdyHSV

10,285 posts

182 months

Monday 19th June 2023
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Have you considered similar circumstances, such as when there is music playing in another room, when you open the door it gets louder...?

jj.

562 posts

285 months

Monday 19th June 2023
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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... loser
jj

hulksta

87 posts

52 months

Monday 19th June 2023
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Saw thread title.
Opened thread praying for the appropriate responses to the question.

As expected, PH didn’t disappoint.

Thank you

Equus

16,980 posts

116 months

Monday 19th June 2023
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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

12,630 posts

224 months

Monday 19th June 2023
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If you put your ear against it does it sound tinny or tappy?

cobra kid

5,358 posts

255 months

Monday 19th June 2023
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I find that 5 ltr of cold water in there helps to quieten it down. Fills the gaps in.

J4CKO

44,309 posts

215 months

Monday 19th June 2023
quotequote all
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

10,285 posts

182 months

Monday 19th June 2023
quotequote all
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 smilebeer

Grumps.

11,652 posts

51 months

Monday 19th June 2023
quotequote all
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

2,028 posts

202 months

Monday 19th June 2023
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If you do this on a petrol, you will probably get an EML as you now have a big filler cap shaped vacuum leak....