Exhaust leak, or blown headgasket

I recently fixed a vacuum problem, so now my engine is finally "alive" again, after beeing dead/sluggish for the last 8 months.

One day after this was fixed i got some vibrations, and a sound allmost like when a wastegate is opening and dumping exhaust without any muffler.
Could also sound like an old v8 diesel truck or motorbike..

I popped the hood and started up when warm, then i carn hear the "popping" sound the first 10-15 seconds before it fades away.

What worries me is that i think the coolant hose felt a bit hard. Could this be a blown head gasket, that leads cylinder pressure into the coolant system. And the popping exhaustsound i hear on WOT/load is exhaust pressure escaping through the expansion tank?

I have some videoclips with sound that will be uploaded in a moment.

(Engine is a AFN on a 1999 Passat)

Three short videoclips is available here:

https://plus.google.com/photos/1008...s/5797952451329408209?authkey=COmT5Ky-n6v7swE

Turn opp the volume to hear that "extra" exhaust tone

Here i have a log from yesterday, where everything was fine (40 samples to pull through 4th gear)


And i have a log from today, where the RPM line is jumpy, and i needed 80+ samples to get through the same RPM range as yesterday.

This sounds a bit like valve not closing leading the cylinder not working. This can also explain the RPM dips.

If it was mine car I would remove the valve cover and check the hydralic lifters and the valve stems. Also check the compression on each cylinder.

Why this is in the "TDI Power Enhancements" section? Looking at the logs the engine seems to be stock...

I didnt find any other section that fitted.
And since this started when i installed a bigger turbo and fixed a vacuum leak I figured this could be related to increased wear/stress on the engine with this increase in power over the ammount that it has been running with the last years.

Anyway, I have figured it out i think. The return lines from the injectors had started leaking at #3. I smelled diesel and removed engine cover. On idle i could see the spray/smoke was coming out at the same rate of the exhaust sound. So replaced those hoses, and also tightened the fuelline to #3 with 1/2 turn.

This fixed the sound on WOT, and vibrations are all gone.

But, i still have the same deep/loud exhaust sound the first few seconds after starting the car before it get quiet.

I also have a slight pressure in the coolant system, The big hose going from the radior to the engine gets a bit harder after a while, but still soft enough to squeeze flat with my hands. And when opening the cap on the expansion tank i can hear a bit air releasing. Is this normal, or should I continue looking for a broken headgasket?

Just for good measure, heres the last log, rpm plot seems smooth again, and the ammount of samples is down to <40.

Also check around the injector where it goes into the engine for soot... the injector itself could be not sealed well.

A little pressure is ok. Coolant vapor does make pressure when hot even if its not boiling.

Those who have head gasket issues usually Lose coolant and the container is pressurized like crazy. Also if the head gasket is leaking you can usually see dark soot in the coolant.