Compression leak?
 

Ladies and gentlemen:
Hello!
My problem is this. Some time ago, my 94 3.9L DI developed a noise that sounded sort of like a squeak. I was told that it shouldn't be anything.
[I should say that this truck overheated about a year ago, but I had it checked and several mechanics thought that the only problem was in the cooling system (I posted on this before). Last october the radiator was rodded and flushed. No problems at all since then.]
Now back to my issue. The noise worsened and I thought that it was an exhaust leak somewhere around the manifold on the passenger's side. When I got to the muffler shop he said it was a spark plug that was loose. So nothing was done by him.
Another mechanic also said that I had a loose spark plug so we changed all spark plugs but the noise is still there. The truck runs smoothly and it actually has increased its mileage since this. I has power and pep and no overheating or anything like it. I feel it actually runs better than before. Any clues as to what it can be?
I will post this in other fora as well.

Thanks in advance.
Alfredo

Can you perform a leak down test on your cylinders?

I will find someone who can (hopefully)
Thanks

Actually, the first thing you should do is have your exhaust manifolds checked for cracks. I was thinking a leak down test to check for bad exhaust valves, but the more I think about it, the more I lean towards a cracked manifold. The sound gets worse because the crack is slowly growing.

If an exhaust leak you seek, SeaFoam induction treatment will show it with minimal delay as a side benefit. Makes a gray smoke while cleaning out intake gunk, ehis comes out of the exhaust pipe and every exhaust leak you have, smoke lasts just a few minutes. Could also restrict the tail pipe (not fully) and increase the squeal to find it.

I replied on the other forum.
In a nut shell, just have the exhaust leak fixed.
Either cracked manifold (weld shut) or a bad gasket (replace), no big deal.

I've seen a 3.9 with a bad head gasket that leaked combustion gasses out the side of the engine.