pull dipstick = sucking noise

[Blackened302]

so i was warming up the car this morning and decided to check the oil level ("low oil" light is on since we did the engine swap, even right after an oil change--seems bad, but i'm paranoid) and as soon as i pull the dipstick (the car is on, warming up) i hear a sucking noise--exactly like when you open a new bottle of coke.

the car proceeded to almost die out, but idled fine once i put the dipstick back in.

pulled it to check the level again, and same thing--i heard the noise as if i were opening a bottle of coke, car stumbled, but idled fine once i put the dipstick back in.

this is the first time it's done this since the engine swap. pcv valve is about 4-6 months old, new head/intake gaskets at the same time, too.

should i be worried?

 

[BlownFiveLiter]

You know you need to check oil with the car off, right?

I wouldn't be too concerned since the crankcase is under vacuum, hence the PCV, but it does sound like you're really getting some vacuum there. Do you have the line from the oil fill tube to the intake tube?

 

[Blackened302]

hehe, didn't realize the car had to be *off*. thing is, i've checked the level w/ the car on before and it never made that sucking sound (or, at least i've never noticed it, heh).

yes, i have a vacuum line from the oil fill tube to one of the lines on the upper intake.

 

[Stanger007]

Good problem to have, you have great vacuum and little blowby.

The stumble was from a temporary vacuum leak you created - the PCV was sucking air through the dipstick hole but the MAF didn't know about the air coming in there so it did not account for it in the fuel/spark tables.

This is why adding a valve cover breather but keeping the PCV system in place will cause idle problems if your idle is at the factory spec. Higher idle speeds tend to cover up the problem, but it is there nonetheless.

Wes

 

[Blackened302]

hehe, thanks Wes and Matt--if it's a good thing, i'm happy.

w/ all the stuff that's gone wrong w/in the last few months, i wanted to ask and be sure it wasn't another blacklist item--glad i did.

i like that old Chinese saying: "He who asks is a fool for five minutes, but he who does not ask remains a fool forever."

 

[mojopony]

Is it recommended to have manifold vacuum at the oil fill tube? Mine just vents into the CAI.

 

[Stanger007]

Your setup is correct, the vacuum of the CAI helps pull out the crankcase pressure.

Wes

 

[Yobi1Kanobi]

+1 what you dont want is Air pushing out of the Dipstick thats blowby and thats indicating ring

 

[Blackened302]

Your setup is correct, the vacuum of the CAI helps pull out the crankcase pressure.

Wes

what if the line is connected to one of the vacuum lines coming out of the upper plenum? same thing as if it were connected to the cai, right?


Yobi1--thanks, guess that's the thing i should worry about instead, heh

 

[cjones]

the tube connecting to the valve cover needs to go to a NON vacuum source, such as between the MAF and Throttle Body. that provides fresh metered air so the PCV valve will work properly. that hose and the PCV valve make up the PCV system.

 

[Blackened302]

ahh, thanks CJones. now that I rethink it, it's kinda like the way i have it now is negating it out (since both are pulling vacuum?).

i'll work on that this weekend, then. thanks!