The International Cessna^® 170 Association

I’ve searched this topic but still have a question.

Any reason not use vented cap on the left tank as well the right? I ask for two reasons.

1. When I had my 58 172 I did this because it apparently had a blockage in the cross vent causing a vacuum in the left tank. The only symptom was oil canning. On the advice of the mechanic I put a vented cap on that tank. No more problem and no I’ll effects.

2. After a three hour flight the other day in my “new” 170B the right tank drained about a quarter tank ahead of the right. However, it was very turbulent and that may have caused it, or maybe it’s normal.

If the venting system is ok, will having two vented caps cause any issues?

Thanks
Rich

Rich, I've been using vented caps on both tanks since I bought my '52 170B about 6 years ago. No issues, problems, etc.

But that won't stop the uneven draining of the tanks. Mine still does it. My right tank almost always drains faster than the left when the valve is in the "both" position. Uneven draining is a common quirk of 170's that you get used to. The reason for it is still a mystery to me.

Rich, there is nothing wrong with both caps being vented... IN FACT if you order new fuel caps from Cessna FOR EITHER SIDE you will get ONLY a VENTED fuel cap.

As for the uneven fuel burn on “Both”... it’s been discussed many times, Here is the basic explanation: http://www.cessna170.org/forums/viewtop ... uel#p24083

And, if you’re bored sitting at home with the pandemic and need an hour’s entertainment, here’s an extensive discussion of fuel caps, fuel burn, and dipsticks for the tanks: http://www.cessna170.org/forums/viewtop ... fuel#p9094

Thank you both for those comments

Rich