Good day guys, I am new to the forum and have been a hummer 2006 H3 3.5l early number owner for many years. My check engine light has been on and off all on its own for the last year. Being not to concerned with it, it really started to act up a few weeks ago. Started with codes for tac and b camshaft position over advanced. Clean throttle body and checked cam sensors cleared code and it never came back. Next was open injector circuit followed with a P302 then P304. Cleaned injectors/ bench tested good, installed new ac Delco plugs. Rough idle persisted almost like a surge idle but ran smooth over 800rpm. Then P0172 system too rich with a P300 over and over. Next was my compression test cyl 1-140 psi, 2-120 psi, 3 170 psi, 4 140 psi and 5 has 170 psi. added oil to cylinder 2 retested at 155psi. Performed leakage test and all were in red excess leakage. Decided that the intake valves were faulted. Dis assembled the top off the engine, valve cover and manifolds to investigate further. Cylinder TDC with 50psi and oil sprayed in intake valves confirmed all intake valves tested one at a time are leaking. All of these codes all associated to that is bizarre to me. Removing the cylinder head and replacing complete assembly cams and all. Anyone else experience similar problems to what I just explained? how do all the intake valves leak at the same time kind of bizarre!!!

 

Is your Vin# within the range of the 3.5Ls under recall as built prior to the hardened valve seats????

The S/Ns affected is any 2006 H3 lower than 287591 .... the first one started with 100,001, your truck build date will be Nov. 06 or earlier. Not all have the problem, but some could. The head issue affected not only the I5, 4s and 6s were subject to the same issues.

 

Here is the head assembly and progress today.

 

in your last picture it looks like your valve seats might be protruding or dropping. the bottom ones closest to the floor in the picture orientation.

 

Carbon buildup. SeafoamWorks!

 

Unfortunately we are a little bit passed seafoam lol. And yeah it is protruding a bit. I am still shocked that I could not get any of the intake valves to seal at all. I am just deciding between full cam and head replacement vs rebuild as the price is pretty similar.

 

if the valves do not seal then you might have bent valves or need to remove the valves and aggressively clean them.

 

Almost cleaned and back to carbon free.

 

I can definitely give a valve cleaning a try before going ahead with a new cylinder head. I was just nervous that none of the intake valves would seat and had leaks due to the bad valve seals I kept hearing about. If it was as simple as cleaning them I would go that route 100 percent.

 

You haven't heard anything about valve "seals" except from yourself. They last forever in Atlas motors. The valve "seats" are the issue of contention with 06 3.5L motors