Head and exhaust manifold questions / help

[sinstr]

Well... I think I may have some problems. Ive driven my H3 twice in the last 30 days. Both times, I throw the P0300 code every time I start it. Ive cleared the code, but it returns when I restart the truck. The truck seems to be running smooth, but is down on power, and my MPG have tanked to under 170 miles per tank. Now, I dont pay much attention to MPG, so that may be normal, as I have a winch, UCP, 35s, Gobi, etc etc. My ScanGuage shows Im getting 7-9mpg last I drove it on the highway.

Next problem, when the truck is cold, it makes a loud vibrating noise from the pass side of the motor. I think I have a bad exhaust manifold. I cant seem to find any crack. Once warmed up, the noise is gone. It does not sound like a typical exhaust leak (ticking)... so im confused.

Im still under my 100k powertrain warranty. Im getting a local shop I trust to handle the leak down test for me, as I dont trust the dealer.

Can anyone tell me if the dealer needs to remove any of the skid plates or UCP to replace the head?? I have repaired or replaced my crossmember EVERY time the dealer has removed my UCP because they zing the bolts with an airgun and strip them.

Should I remove my AirDoc before taking it in, as Im sure they will bitch about that or not re-install it correctly??

Has anyone had the exhaust manifold replaced under warranty??

Thanks

 

[sinstr]

Few bits of info on the truck

07 Adventure 3.7L / Auto
Winch
UCP
Rock Rails
AirDoc
PCM Tune
Ported Throttle Body
70k miles
35" Tires
Gobi

All the typical upgrades that add weight....

 

[f5moab]

There have been problems with exhaust manifold fasteners to the head.
Does the sound get quieter as the engine warms up? (If there is a small crack in the exhaust manifold, as the heat expands the metal it will usually get quieter.)
I would worry less about the skid plates than the head if it needs replacement. If they cannot get the skid plates on correctly, imagine what they will do to the cylinder head. And, if they don't have the chain holding tool, they have to remove the skid plates to replace the cylinder head.

As for the P0300, run a can of techron through it and change the place you purchase fuel. It could just be the fuel you are using. Not octane related, but additive related. Stations use different additives for the same basic fuel supply and this can affect how a vehicle runs.

 

[sinstr]

I was hoping you would chime in....

I only run Chevron or Mobile fuel, super unleaded. I do run techron, in fact last itme was before i parked it traveling to do some offroading. Ill keep an eye on it. Any idea what bolt/flange area cracks in the manifold?? Warranty or not??

 

[08SolarFlareH3]

I was hoping you would chime in....

I only run Chevron or Mobile fuel, super unleaded. I do run techron, in fact last itme was before i parked it traveling to do some offroading. Ill keep an eye on it. Any idea what bolt/flange area cracks in the manifold?? Warranty or not??

If you use Chevron gas, you are all ready getting Techron. Techron is in Chevron and Texaco fuel. Wish we had them in the north east.

 

[M22KLARS]

Whats the code for a stuck open t-stat?

 

[f5moab]

Not sure where, but it is noted that exhaust manifold fasteners have been known to snap. Exhaust manifold cracks can be hard to see, sometime they are on the bottom making it impossible to see until removed. However, small cracks will basically seal up as the manifold heats up (metal expands) thus the noise at start up that goes away when the engine warms.

You might want to head to the dealer and let them diagnose if under warranty. As for the skid plates, tell the service manager. Running the skid plate bolts with an airgun should hot strip them out, unless the tech keeps cranking away at them once tightened. The Chevy tech near me uses an impact and so far no problems; other than he always forgets to tighten the two front bolts.

 

[alrock]

I've had the exhaust manifold bolts crack and they did have the ticking noise; fixed under warranty. Didn't have an MPG issue though. Dealer only messed with the new crossmember once and they stripped it/broke it out when installing it as brand new. (That's the newer crossmember with the stud embedded in it)

Thermostat issue should be easy to spot just by watching the gauge. I never had a code or any noises. My truck just wouldn't warm up properly.

If they are going to do significant work it may be beneficial to put on the stock intake just to remove the headache, questions and worries.

 

[08SolarFlareH3]

If they are going to do significant work it may be beneficial to put on the stock intake just to remove the headache, questions and worries.

Agreed, don't give them an excuse to try and deny any claims. The less they know the better off you are.

 

[persius1]

I am getting that same ticking noise when in drive and a little when in park and revving the engine. Not sure what to make of it and I'm hesitant on taking it to the dealer for a warranty repair since they always give me a hard time about my mods.

 

[alrock]

The cost of replacing exhaust manifold bolts on your own is worth hassle over mods.