Loose oil cap
 

Had my oil changed 2 weeks ago at a local generic car repair shop. First time I’ve used them. Have noticed the idle running rough recently and have had a few coolant issues as well. Belching coolant despite no sign of overheating.

I believe I just found the source for the rough idle. The oil cap was loose. The shop didn’t seat it. I tightened it while the engine was running. The idle immediately smoothed out. Didn’t realize how bad it had become. Does this sound right? Does The oil system need to be air tight? Since I hear some air passing thru the oil filler with the car running, does this indicate compression leakage? Anyway the loose cap could cause coolant issues?

Everything points to that cap. Is the cap the current version? I believe it ends in the number "4". Run with that.

You could do your own oil changes... no? :cheers:

Haha Yeah, I should. Feel kinda guilty. But I have been doing my own oil changes for ~50 years. I stopped when I retired a few years ago. Mostly because i was tired of taking old oil to a recycling center. And truthfully, getting under the car was not getting Any easier.

Were you referring to the coolant cap (which I ordered this morning) or the oil cap? I am still concerned about why the seal on the oil system makes such a difference in the way the car runs. I know coolant systems Are closed systems, but I’ve never heard oil systems were as well. Thanks for your help Starter986.

I am surprised you haven't had a CEL come on by now.

Yes, the crankcase is under 5 inches of water level vacuum from the AOS while the engine is running. The vacuum is necessary to help the low tension piston rings seat properly.

Sorry, I asked too many questions. Are you saying the oil cap leaking can effect the idle or cooling issues or both?

It can effect the idle, the coolant issue is more questionable.

I stand corrected. That "4" IS for the coolant cap. You are correct.

Me thinks that if your idle problem resolved... your oil cap is fine... you're good to go. Jeff is one of the members to whom you'll want to pay careful attention and... as he mentioned about the cooling problem... keep an eye on that and report back.

Cheers! :cheers:

Question????
Is the vacuum measurement 5 inches of water?
Or 5 inches of mercury?

It is probably time to replace the O-ring seal on your oil cap.

Water, it won't even register on a mercury scale instrument.

Thank you.

Is there any correction for elevation????
Lets say a car tested in Denver Co. -vrs- Vancouver Wa.
A little over 5000 feet elevation difference.

No............................

One thing to consider if you use an oil change place, is they tend to over tighten things like drain plugs and oil filters.

They also probably don't take enough time to fully drain the motor

:matchup: Thanks again.