On my 05 F350 6.0, I just installed an EGR cooler bypass kit that essentially leaves the old cooler in place but prevents exhaust from entering. I mentioned this to the diesel mechanic at my local Ford dealer and he said I will be coming to see him for new head gaskets soon. According to him, this turbo has no waste gate and the EGR system is the only way for an "overboost" to be relieved. Mine is welded shut and does not allow anything through. The EGR cooler is on the inlet side of the turbo and could only bypass excess back pressure it would seem to me. Being a variable vane turbo, I can only see an "overboost" if the vanes were to fail in one position, and worst case scenario would be blown intercooler components. I researched the 6.0 bible and numerous other sources and cannot find any relation between the turbo and the EGR cooler system. Any Thoughts appreciated.

 

overboost when the vanes stick can cause more than just a blown intercooler boot, head gaskets can pop too. i'm not a tech but i don't really think your tech is right about this. we don't have waste gates but if you have ever hear "turbo fart" that's the air getting forced out the air filter not the egr cooler.

 

Did the same thing when I had the oil and egr coolers replaced. Had a ss freeze plug welded into the inlet side of the egr cooler so no exhaust flow into it anymore. Oil cooler was plugged with casting sand passing very little coolant on to the egr cooler. Old style round body cooler (egr) that pressure tested fine but put the new on on just to be safe. No problems so far and just went through NJ inspection with no conflicts. Next will be rod out the cat but tough to get it off to do it . That aft connection has been on since new (04) and won't budge without special tricks. Bought mine in Mar 09 with 85000 on her, only problem what the burping and constant engine fan running when pulling a load. Since the repair none of that happens. Also put the NAPA coolant filter on her to make sure the coolant stays clear.

 

Your tech is wrong, egr valves are not used as a wastegate for the turbo. Here is the description of turbo operation straight from the Ford manual.

Vanes mounted around the internal circumference of the turbine housing are connected to a unison ring. The unison ring links all the vanes together and when the unison ring moves, all the vanes move. The unison ring is moved by exposing either side of an actuator piston to pressurized engine oil. Oil flow to the appropriate side of the piston is regulated by the turbocharger variable control valve whose winding is part of a pulse width modulated (PWM) circuit regulated by the powertrain control module (PCM). An increase in duty cycle of the PWM circuit will route oil through the turbocharger variable control valve in a way that will cause piston movement that increases manifold pressure (BOOST). Decreasing the pulse width will direct oil such that the manifold pressure (BOOST) will be decreased. Turbocharger control is a closed-loop system using the exhaust pressure (EP) sensor to provide feedback to the PCM. In response to engine speed, engine load, manifold pressure and barometric pressure, the PCM provides a duty cycle to the turbocharger variable control valve to cause it to match manifold pressure (BOOST) to the requirements of the engine.

And these are the only symptoms for overboost in the same manual.

High boost

Leak in exhaust system before muffler.
REPAIR as required.

Malfunctioning turbocharger variable vane hydraulic control valve.
REFER to the Powertrain Control/Emissions Diagnosis (PC/ED) manual.