Hello all, I just picked up a 2014 S60 for my son who will be going for his permit. Looks like a great little car and lots of safety. Just got it registered and started driving it to see if it has any issues. One thing I have already noticed it some type of thumping sound under the floor. Sounds like a vent valve or solenoid thumping. It does it even sitting still. Anyone have any idea what it might be?

Few other odds and ends also but nothing serious.

Thanks in advance.

 

So I found out a few things. when I bought the car I did not hear the noise. I did get a dash notification saying "Gas Cap Loose" I stopped to fill the tank. Cap was completely loose??? I tried to pump gas and the nozzle kept clicking off. I couldn't pump for more than a few seconds and the nozzle would click off. Took forever to fill. I just thought I was using a bad nozzle. After I filled up is when the sound started. I found out the fuel cap was loose for a reason. The tank is not venting as it should. The seller loosened the cap so that it wouldn't make that noise. If I loosen the cap, no noise however eventually the check engine light comes on.
I'm guessing the tank is damaged or there is a bad baffle, solenoid, vent, EVAP, etc... Not happy about the dishonesty! The seller did tell me the car will need an injector, thats fine but!!!!!

 

sounds like an evap system issue. The way the evap system works is there's a vent from the tank to a charcoal cannister. Gas tank vapors are trapped in the cannister until the purge valve opens to pull the vapors into the intake for combusion. The system requires a sealed gas tank to pull the vapors in, so there's also a leak detection pump to sense if its not sealed (which is why a loose cap can set off a CEL). Normally the CELs point to small evap leaks (like a torn vacuum line bad purge valve etc) or a large evap leak (failed cannister, torn vent line or failed leak detection pump ) but since you sense the tank is not venting - I'd move the charcoal cannister to the top of the list on the theory that the charcoal has broken down and some has gone on and clogged the vent hose to the tank. You'd probably need to replace the cannister and clean or replace the vent hose as well.

Here's a write up of the evap emissions system.

https://www.nyvip.org/PublicSite/OBD...20is%20started.

 

Thank you for this information. yes, I believe the tank is not venting. The vehicle runs fine for about 10 minutes. Then the thumping begins which I know believe is the tank starting to collapse/expand itself because it is not venting. Loosening the cap cures this issue however after about 15 minutes of driving, the "Tighten gas cap" notification cones up on the dash and then a few minutes after that the CEL comes on. Its interesting that the CEL does not come on when the gas cap is tight and the tank is unable to vent?
I will start by looking at the canister and purge valve.
Thank you.