[Kjones]

My 2004 heads where replaced by dealer under warranty about 70,000 miles, now it is at 180,000 and have replace all plugs coils, and the intake, still wont pass emissions still get a misfire code. Looks like another head replacement next again.

 

[Gold Country Russ]

Kjones, that is not surprising if the head was replaced before 2009. The valve guide issue was not resolved until 2009 production so all the heads before that date were built with substandard valve guides. The only good news is that replacing the valve guides & doing a valve job will fix it. There are no new heads available except for the "reconditioned" heads GM sells for something over $1,000 which is 3 times the machine shop price of installing new valve guides and a valve job on your head. The real expensive is the high labor cost for removing and replacing the head. At a minimum you would also need a new head bolt set, timing set, gasket set, and of course the head work.
A compression test is the best way to determine the condition of the valves and the cylinder sealing.
Good Luck!

 

[c0d3man]

I recently bought a 2012 Colorado, Automatic, 3.7L I5 with only 37.8k miles on it. Same as all used vehicles that I buy, I did the following almost immediately:

-Spark plugs
-Belt and Tensioner
-Air Filter
-Cleaned MAF and TB

When changing my plugs, the rear-most plug (Near the firewall) was fairly coated in oil on the plug threads. My guess (I hope) is this is just oil seeping around the valve cover gasket.

Also, and this is the most concerning for me - I am getting a VVT/Timing Chain rattle on cold starts. It only rattles until oil pressure builds up, then it goes away.

I am also getting what I believe is valve squeal for about 2-3 minutes after cold starts, which isn't a good sound. It's a slight squeaking that increases with throttle that didn't go away when I changed the belt/tensioner.

It's at 42.5k miles now - Hoping that it doesn't need a new head. Any insights would be great.

 

[CR>AUTODETAILING]

I own a 2008 chevy colorado Z71 4x4 and it misfires in Cylinder 5. It has been doing it since 30,000 miles and I am not currently at 139,000 miles and truck still has issues. Chevy dealership told me nothing was wrong until the warranty expired, then all of a sudden, the head issue was discovered. I still need to fix the issue. i just dont have the funds and time todo it.

 

[PARRCO11B]

I guess it's my turn to chime in. 2010 3.7l. 230k on the clock. Bad valve guide seals plus #3 & #4 valves not seating properly. Number #2 intake cam cap overheated. Scarred cam journals. So, it was time to refresh the head. Since my local shop doesn't line bore, I ordered a reman head. In this time I am also going through every other thing I can think of. So, I found a 2 row all aluminum radiator to keep thing cool (since the oe is obviously not up to the task). New harmonic balancer, new thermostat, new starter, new fi wire harness, ign coils, spark plugs, cam actuator, cam actuator solenoid, cam pos sensor, timing set w/ balancer shaft set. And since I had to take the rack and pinion out, new inner and outer tie rods plus ball joints and sway bar links. Amazon loves me right about now. This is all thanks to the endless research I have done through this site. If my truck will be down, it will only be down once! What I will say is the improved design on the head bolts....if you follow the crack, tap procedure come out just fine. I thankfully did not break a single head bolt.
PROST!

 

[ChecCol2008]

I just got my compression results in for my 2008 3.7L Colorado. I performed the test due to the fact that I am experiencing some of the issues posted on this thread. The compression falls between 172 and 180, a variance of about 4.6 percent well under the 15% that may indicate a valve leak. The variance seems okay but the pressure seems low compared to the 215 I have read to be normal on these engines. Any help would be greatly greatly appreciated! Thanks