How much blow-by is normal?

[gregk24]

When I was out working on the Accord today, out of curiosity I popped off the oil fill cap to feel how much air was coming out. I was expecting a very small, almost imperceptible amount of air to come out, but to my surprise some very pressurized sequential gusts were shooting out. I have always thought that the more air coming out would hint that the piston rings had more wear, allowing blow by. Is it normal for a good amount of pressurized air to come flowing out of the oil fill cap at idle? The Accord only has 120K on it, and consumes very little oil over the course of an OCI, although in the 5 month OCI it only had about 3000 miles on it.

 

[actionstan]

I don't think that's a accurate way to measure blowby... If it doesn't consume much oil and idles and drives smooth and even, that's a better sign that there is little blow-by

 

[JOD]

What you're describing has nothing to do with "blow-by". There's a check valve in the pan which pressurizing the block. The engine's doing exactly what it's supposed to be doing.

 

[Finz]

Greg... When was PCV last changed?

I've never noticed or tested on my 05 but my daughter's 98 is like a hair dryer.

Never mind PCV question... I see you other post

 

[gregk24]

Originally Posted By: JOD
What you're describing has nothing to do with "blow-by". There's a check valve in the pan which pressurizing the block. The engine's doing exactly what it's supposed to be doing.


Really, this is the first time I have heard of that. Still have learning to do. So its supposed to be pressurized like that?

 

[friendly_jacek]

Check valve? News for me too. Unless he is talking about PCV.
BTW, did you check cold or warm idle?
There is some interesting discussion on this subject here: https://bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2696318

 

[Chris142]

your feeling a couple liters worth of parts moving around in there. normally blowby is accompanied by smoke.

 

[friendly_jacek]

Originally Posted By: Chris142
your feeling a couple liters worth of parts moving around in there. normally blowby is accompanied by smoke.


good point

 

[Vikas]

Honda service manual should have a specific test to measure blow-by. You will know you have excessive blow-by when your oil dipstick starts popping out on its own. After 200K miles, my 83 Prelude started doing that.

With working PCV, minimal oil consumption and no popping of the dipstick means your do not have excessive blow-by.

 

[gregk24]

Originally Posted By: friendly_jacek
Check valve? News for me too. Unless he is talking about PCV.
BTW, did you check cold or warm idle?
There is some interesting discussion on this subject here: https://bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2696318


It was at cold idle