I took a chance on a 2007 volvo s40 and was told it has an engine knock, the older gentleman that sold it to me for dirt cheap said it sat a while. I immediately checked the oil and it was less then a quarter in there, so I added some oil and noticed it got quiet a little. I towed it home and immediately put the computer on it and it states there is "no codes" which is weird because on the dash it states "maintaince airbag/urgent" or something like that. To me the motor seems to run rich but actually doesnt, kind of got a go-kart sound/feel to it. Car has a 150K miles on it

Anyways, where should I start with trying to determine how bad this knock is or where it's coming from? My dad is a mechanic but can't make it out for 2 weeks, and I would like to get something started on it. Any ideas on how to proceed?

 

What kind of code reader are you using? A general OBDII reader will not read the SRS codes. The Volvo VIDA/DICE is needed.

Do you have any of the history of car (maintenance, when it started knocking)?

 

No history of any kind, I got it off a 70 year old who said it was running and just started knocking then sat.....unfortunately. I'll check the reader when I get in, it was a standard one from autozone but I'll find out

 

are you hearing pinging or a rod knock or perhaps a manifold or exhaust leak? Does it only happen under hard acceleration / going up a hill? Does it change sound if you run 93 octane?

 

I could be wrong but it sounds like a pinging type sound to me, and you can hear it while revving/accelerating and driving. Nothing noticeable when idling (but I'll confirm that whenables I get back in). Haven't had the chance to put 93 octane in yetas it had a half tank.

 

Update: so I changed the oil, oil filter, and added risoline, HOPING it would lower the sound and crossing my fingers that it would work but then when I started the car the knocking was even LOUDER.
I now believe they used a thicker oil to help with the sound, but I could be wrong.

Now when the car is cold it runs fine but as it warms up, it dies....HELP.

Tried to check the compression, but couldn't figure it out as the manifold comes off?

 

Update: we found this hose that had tape on it, appears there is a hole or rip on it.



Goes down to here...


Which also had tape on the other end, what hose is that?

 

Local mechanic said to rebuild the head, to solve the knock but dam without me doing a compression test I'm at a loss.

 

That is the PCV breather hose. Some hack decided to tape it instead of replace it.

 

Got it, thank you.

 

Yes, change the hose and see how it sounds.