I have a 2002 1500 QC 4.7L.

The truck was being driven from Albuquerque NM to Portland OR by some friends of ours. At Nampa ID he said that after filling up it acts as if it was out of gas and the engine light comes on. There was a dealer ship near by so they took it in. Dealership finds a blow up spark plug in 5 and no compression. They had the valve cover off and said their theory was a pin had fallen out of my piston.

Now I don't know much about engines, but the pin coming out from the piston to connecting rod did not seem very likely to me. Especially when it idles and drives up to about 45mph without any indication of a problem, then it starts shaking.

I am in Portland and drive to Nampa and talk to them. The problem being that I live in the Portland area but I travel 3 out of 4 weeks, and my wife was 7mo pregnant at the time. The people driving it had our 2 dogs and their 2 kids, so that is why I drove over to get them.

So I just dont trust the dealerships explanation, sounds like they are just trying to screw a family traveling to me.

I tell the dealer that there is no way it can be handled at their dealer, I would just get a truck to transport it more local. So just put it all back together. Well he was not happy about that.

Anyways got it back, had to drive it a little to get it on the truck and back.

I took the valve cover off, the thing appears to run fine. It does have no compression on 5. 1,3,7 are 140. I did not see anything wrong with the valve or the rocker.

The truck has sat for 2.5 weeks and I got a leak down gauge ordered and sitting around somewhere.

Looks like most likely going to have to pull the head off, I am sure its going to be some valve problem from what I have read on the forums.

It does not overheat, and the person driving from NM said it did not over heat the whole way.

 

My first guess would have been head crack or gasket around #5 due to an overheat. Still could be even though it hasn't overheated, just less likely.

Leak down test should give you a good idea what's going on with that cylinder...

 

Reasons for no compression would be a hole in the piston, a broken rod, thrown rockers or a really really bad head leak. I dont see the head leaking that much and that fast. I also dont see the piston coming off the rod by means of the pin coming out. However, I have seen pistons break lose from the rod and holes in pistons. Normally from the things we see here on the site with your issue are thrown rockers as you know.

With that being said and just to make sure, did you pull the valve cover and rotate the engine by hand or with the starter and watch BOTH valves on #5 move??

You could get a flex cam and look down the cylinder bore or drop the pan and look up at the piston maybe.

Whatever you do, please let us know what you find and take pics.

 

I must be doing this leak down check wrong. It seems you can get the % gauge to read anything you want.

 

I can definitely hear air flowing through the cylinder.

Amazingly the instructions for the gauge and on the internet are still confusing me. Nothing says what the input pressure should be. At around 10-20 psi it reads loss, but if I go higher it shows no loss. Even if I just push in the valve to act as a complete open the gauge does not show a loss.

But with 90 psi to the gauge and closed, when I plug it into the cylinder it drops to 70psi, but the % gauge doesnt move. I checked with smoke around the valves and the spark plug and as much as I could around the head and nothing. 20% loss does not sound enormous, but the compression gauge reads 0.

Also even at 90psi in and all the spark plugs out, its not enough to turn push the piston, which from what I read it should be doing easily, which is why they instruct to keep the other plugs in. So says the interwebz.

I am just going to work on pulling the head off to take a look.

I will post pictures of the grenaded plug and what I could get of the valve train here in a minute.

 

Got the intake and exhaust manifold off. Hooked the leak gauge again, and you can clearly hear the air leaking from the intake.

Also notice all the intake ports on the heads are dark and covered with whatever gets in there, oil? But Cyl 5, the failing one, is almost clean. Not sure what that says.

 

That means its been "washed out" by coolant and likely means a cracked head or head gasket failed.

 

Head gasket is fine. Cant see nothing wrong with the head housing.

The only thing I see is that the intake valve does not seat fully, looking down the intake runner I can see light around the edge of the valve. Trying to get a picture of that.

 

It looks like the seat is gone ?

 

The only thing I can notice visually is the amount of hard carbon around the valve seat area, and all the valves are that way. I know the same look around the bolt of the AR15/M16 and it usually is having feeding problems.

So I will see what I can do about cleaning that all up and see how it seats. If still no good, then maybe have to hand it over to a shop to take a look.