Driving without Oil cap on. Possible Damage?

[uclabruins1996]

Already... I made a dumb mistake today.

I went to check the oil and to add oil to the crank case at 6am in the morning.
Forgot to put the oil cap back on.please wait 2 seconds for an uncompressed image, or press Ctrl+F5 for original quality page

Drove 125 from Los Angeles to bakersfield for my job.

While driving I felt the car like "coughing"....but didnt think much of it.

When I went to check the engine bay, I realize I didnt put the oil cap back on.
I check the oil. I didnt see any oil splash out the engine through the engine fill hole. I put in 1/3 quart of oil and check the dip stick...It's well beyond the "1/2 mark on the dipstick".....It's in the high zone now. So I know the engine wasnt deprive of oil.

I'm surprise the oil didnt splash out the oil fill hole in the engine bay...

I know dust and debris probably got in during my drive. I'm hoping the oil filter will filter that out... That's the whole purpose of the oil filter....I guess.

Before driving back, I stop by autozone and purchase a stainless steel oil cap. Yes, they dont have black ones.

My question,

Why did the engine "cough/jolted back and forth/rattle/etc ( happen only a couple of times)" while driving without the cap?....

Did I do any damage to the engine?

Does the engine require a oil cap to maintain pressure inside the engine? Like the radiator.... Without the oil cap on, it would be able to disapate heat better, right?



At no time did the low oil pressure light come on.
I had at least 5.9-6.4 quarts of oil in the engine the whole time.
Prior to adding oil, the level was at the bottom of "middle safe mark" on the dipstick.


Thanks
I will change the oil this sunday........though.


But I did get the e3 and e4 codes "O2 sensor adaption limit Cyl 1-3 and 4-6" after driving 1 mile with the Autozone cap. I reset the light. Hasnt come back on.

[Toby B]

You're just fine. If an oil change makes you feel better, do it.
Yes, a bit of dust probably got in- but unless you drove through
a dust storm the whole way, not enough to hurt anything.

THe rough running was due to extra air being sucked in through
the crankcase evacuation system. It can set a code in newer cars,
but replacing the cap will fix the problem. Won't clear the code, but the
car's computer will adapt to it, and it should run fine. Might take a few
miles, though- kind of like when you unhook your battery.

No real harm done- I'm surprised it didn't make a mess of the engine bay.

t

[jmo69]

Yeah, the crankcase operates under a slight vacuum, pull the dip stick or the oil cap while the engine is running and you've got an instant vacuum leak.

[uclabruins1996]

You're just fine. If an oil change makes you feel better, do it.
Yes, a bit of dust probably got in- but unless you drove through
a dust storm the whole way, not enough to hurt anything.

THe rough running was due to extra air being sucked in through
the crankcase evacuation system. It can set a code in newer cars,
but replacing the cap will fix the problem. Won't clear the code, but the
car's computer will adapt to it, and it should run fine. Might take a few
miles, though- kind of like when you unhook your battery.

No real harm done- I'm surprised it didn't make a mess of the engine bay.

t

Thanks for the info.!

[xlDooM]

A porsche owner I know has to take off the oil cap to pass smog... Luckily the engine's in the back and they only ever open the front bonnet to check the VIN number.

[touring intl]

I did the same thing before on a mitsubishi on our way back from Vagas, found out when we stopped for gas in Barstow bought a chrome oil cap and added oil, no harm done except some oil on the engine bay.

[advertisehere]

One thing I would do is top up the oil to the full mark.
If you're running the oil low there's a good chance you'll burn oil quicker.
I'm not sure of this but I would top it off just to be safe.

[reaganmike]

I have 645Ci and forgot to put the cap on after putting in a quart of oil.
Got in the car later and the engine started coughing halfway down the driveway, and gave me warning lights.
I hooked up my diagnostics and got error codes P0300-P0308 multiple compression errors... cylinders 1-8!
This morning I checked under the hood and saw the oil cap. I replaced it and cleaned up the oil that had spattered out.
I then restarted the car and all the problems went away!
So... it was all related to the vacuum leak due to the cap not being on.