pqn628

Does anyone top off their gas (adding an additional 50 cents to 1 dollars) to your tank?

I have had this knocking in the rear after the last 2 fill ups but the issue has been happening for over a year. I brought it in to Lexus awhile back but we were not able to reproduce the issue. I finally noticed that it only happens with a full tank of gas. I only get gas every 3 or 4 weeks so I was wondering if anyone else has this knocking issue. It sounds like someone is taking a metal bar and hitting the gas tank. Next time I will not top off to see if the issue occurs.

Htony

Knocking happens in the combustion chamber of the engine. Don't fill up up to the brim. In hot summer weather fuel can expand.

pqn628

Temp doesn't matter in this case. It happens year around. The knocking is def in the back. I got under the suv and can clearly hear the knocking around the gas tank.

Oldfart

I do not know where evaporator canister is located in RX but it is possible when you top off gas can be sucked into the canister. That is why topping off is not recommended.

jim256

+1 on adding beyond the cutoff, but there have been some reports, along with my experience, that when full there is a slight knock from the tank on a rough road, goes away quickly with use. In the old days it would be a float, no idea now.

TeKKieNYC

Why top off? What's the benefit? You are filling beyond capacity, gas needs the room to expand, plus you may be flooding your charcoal vapor canister.

mikemu30

Im in NJ one of the few states that still prohibits self serve. First thing I tell them when I pull up to the pump - DO NOT TOP OFF.

Soyabean

Old school people like to top off to the nearest dollar or even to the nearest 1/4,1/2,3/4 of a dollar so they dont need to get change or something. I usually dont do it anymore because i use credit card and a few times I've experienced it over flowing out when it did it on my old mazda

jim256

Flooding a canister will cost you $350-$500 just for the canister--not worth the risk for an eighth of a gallon.....

ravenuer

Topping off is a bad idea with modern cars. Going to the next nickel or dime is probably ok, but that's it.

RxNYC

Only happens when you over filled the tank. I've had that happen since December 2016.

aznkorboi

Damn... I press the lever twice before it stops. I should stop doing that..

mikemu30

Why even bother with that unless you're paying cash and have the odd change.

ravenuer

My point was if you're paying cash and don't have the odd change. But with the price of gas today, it's kind of hard to stop the pump at any particular amount.
I'd say most people pay by credit/debit today, so just let the pump stop itself.

bdspilot