Is it the head gasket? 2005 V6

Hi all,

I have a 2005 V6 with 208k miles on it. A few weeks ago the CEL light came on together with the VS track and VSC. I thought it's the gas cap issue, so I did the "reset" (turned the cap until it clicked once, disconnected the battery for 5 min). Lights went off, but then a few days ago they came back again, then yesterday they went off now it's on again. I also noticed that a little coolant disappeared from the coolant tank (about 1 finger in 600 miles of driving). Today I had the codes read and it gave me P0306 Cylinder 6 misfire. Also, I have a rough idle for not more than 5 seconds, but not every time, only sometimes. Otherwise the car drives great, no overheating, no smoke, oil looks clean, coolant looks clean. Is it the head gasket or I have hopes that it's something less expensive, such as water pump and the intermittent rough idling is actually spark plugs and coils? One can only dream...

Thanks!

 

There is a chance that your gas cap is bad and not sealing properly. My Corolla had the same lights and after I replaced the cap, the lights never came back on. It read a bunch of codes but it was the cap after all. Try that first. It is the cheapest fix. If it happens again then go for the plugs and wires. From what I understand, the best sign of the head gasket going is white substance in the coolant. Good luck.

 

My guess is you have two separate issues going on.. one is the gas cap, the other is the missing coolant. Being that you have a 2005, my thoughts go to head gasket. You can try to do basic things to try and help the bad idle, but spark plugs and coils don't make coolant disappear.. if you can't find any other leaks, it's got to be going somewhere, most likely into cylinder 6 and out your tail pipe. Check your weep hole, bottom corners of the radiator, all your hose connections, overflow tank connection, etc. Definitely do the due diligence to rule out other things, since it sounds like it's a small amount going missing for now and you probably have time before it gets worse, if it is actually a head gasket.

 

A whole finger worth is not a small amount of coolant loss, you should be able to easily see if the rad or other places are leaking, if not wet it will be a pink crusty residue.

Gas cap will send a specific code for emissions evap, it wont or at least shouldn't trigger a misfire code in a cylinder. When you unplugged the battery that cleared the codes but then they came back, most likely not gas cap related.

Being a 2005 chances are it's a head gasket, there are testers that can determine if there is combustion gas in the coolant, it wont always cause milky oil or white substance in coolant.

Best of luck finding what it is but if it is a head gasket dont go to a dealership for repair, a competent shop or mechanic can do the same work for far less $$.