Ok I have a 2006 hummer h3. It was built after they fixed the head issue. Last 6 are 332769.

We were driving down the road when all of a sudden it started missing on cylinder #3. I limped it home and started with the basics.

Swapped coils. Swapped plugs. Checked voltage to coils. Everything was ok so I did the next easiest step and checked conpression.

Starting at radiator
C#1 160psi
C#2 170psi
C#3 0psi
C#4 180psi
C#5 190psi

After doing a little research it appears that #3 going bad isn't very common but does happen. Most of what I have seen is for #5

I don't have a way to do a leak down test but I blew into the head and didn't hear anything from the dipstick, exhaust, or from the intake. It sounds like the air is just blowing out somewhere in the head area but I can't find it.

What I find strange is that pressure increases at each cylinder as you head towards the back of the engine.

What do yall think is the most common cause of this and how should I go about fixing it?

 

I would start by checking for a broken valve spring

 

OK I pulled the valve cover off and all the springs are fine. Nothing looks odd or out of place. I am going to continue on and remove the head and see what it looks like. I hear there is a tool or something for the timing chain? Where can I make one or maybe rent one at?
I have been following a guide from http://www.gm.oemdtc.com/1742/removalinstallation-of-lk5-or-l52-cylinder-head-2004-2006-chevrolet-gmc-hummer/2

It seems to be lined up with the h3
Also wanted to note that this engine has 223k on it.

 

lots of hard detail work/torque specs/ new bolts, and its still a hi mile engine.
find a low mile used one. its ezr.

"car-part" lists all usa junkyards ,,,lots of h3 being parted out.
check prices and decide.

 

Are there any special tools I need to do an engine swap

 

Ok I got the head off. And it is most definitely a bad valve. I'm not sure how to upload pics but there is a pea sized hole in one of the exhaust valves on the #3 cylinder.

I am going to order a new head from the parts store. And install it some time this week or next weekend.

However I broke one head bolt off just bellow the face of the block. Is there a special tool to remove it without damaging the block?

And I did shock the bolts with a punch and a hammer however I still broke one.

 

This is really cool that you know how to do all this stuff. As far as the bolt if it is flush with block you could weld washer then nut to that and cross fingers. If your the pray'n type may be start with that or tribal dance lol.

J/k

 

It is about a 1/4th of an inch below the face of the block and I don't have a welder of any kind. So I don't think welding it will work. I have a set of ezouts but I have heard bad things when it comes to them and bolts broke off it heads.

It is currently soaking in xp 101 penetrating oil (best stuff I have ever found even better then pb blaster)

 

lots of hard detail work/torque specs/ new bolts, and its still a hi mile engine.
find a low mile used one. its ezr. top end gasket set expense and the bottom may go bad in 2000 miles!!

"car-part" lists all usa junkyards ,,,lots of h3 being parted out.
check prices and decide.

yrs ago i had a 4 banger mileage mustang, lost head gasket/oil leaker.
did the junkyard swap with tranny cheap. it was ezer in my mind than a head swap, no complications, one weekend.

 

This is the best penetrating oil I've ever seen.


https://www.amazon.com/Kano-Kroil-Pe...enetrating+oil