Hello, I just recently took on the challenge of doing a head job on my 2006 volvo s40.
Everything went smoothly, I took the head to the shop to get pressured checked and rebuilt. I bought new head bolts and torqued them down to sequence, they all grabbed. I torqued everything down to spec and went smoothly.
I went to turn on and turned on first try no problem... Only thing is that it was making a loud slapping noise, sounds like it was a diesel engine. lol maybe an exhaust leak?
I left it on for about 15 mins, no change to noise, and no water in oil. I turned it off and turned back on, the noise is still there. left on for 45 mins still no water in oil or over heating issues.
there is no check engine light on and shows no pending codes, but does say "reduced engine performance" on dash and does have low idle.
I will attempt to upload a video.
Any help is much appreciated.

 

Was the head machined down? If so, did you adjust the valves?

 

Yes, the heads where machined down. I did not adjust the valves, I thought the machine shop did that?
any help is much appreciated thanks!

 

Reduced engine performance can be the fuel pressure sensor. Check your fuel pressure.

 

Not sure what else is going on - but there HAS to be an exhaust leak there... once you get that fixed, you might get other more subtle audio clues about the problem.

 

What does the fuel pressure have to read? also would low fuel pressure cause the noisy engine? can't me not adjusting the valves after the heads where machined also cause the "reduced engine performance" and the noise? or is the noisy engine and the reduced engine performance two separate problems?
Any help is appreciated thanks!

 

I thought it did sound like an exhaust leak. But I torqued everything down to spec and there was no visual sings of any holes or anything on the headers before placing it all back together. How do I go about fixing it?
any help is appreciated thanks!

 

Sure does sound like an exhaust leak.

The reduced engine performance on my 2005 was because the fuel pressure sensor had failed. The fuel pressure is controlled through voltage on the newer 2004.5 and up 2.4L and 2.5L engines. When the sensor fails the fuel pump doesn't produce the correct pressure under load and the result is the reduced performance message.

 

The video wasn't loading for me before but it is now. It does sound like an exhaust leak. You sure the gaskets were installed correctly? I forgot which year had gaskets that would fit on the studs two ways. We had an apprentice who made that mistake once.

 

When you mounted up the exhaust manifold, did the studs stay in the heads or did the nuts come off the studs? You probably have either like suggested above the gaskets in the wrong place or something not tightened down.

The gaskets are a bit tricky.

 

The nuts came off with the studs, I have a feeling I placed the gaskets incorrectly, I did have trouble holding them in place while install.

 

the gaskets did seem to go on both ways, so I went with my gut feeling and placed the rigid side towards the head. I have a feeling I placed them wrong is there anyway to remove the headers without removing the head?

 

I went ahead and wiggled a the fuel pressure sensor connector and the "reduced engine performance" went away now it is throwing a p0121 code, and says to service the engine on dash. Still no check engine.

 

SOLVED! thanks everyone for your help. I re torqued the headers, noise went away. I cleaned the Throttle body and the code went away. Now i'm back on the road. Thanks!