I was towing up the Shasta's in northern Cali this weekend and my engine was acting (sounding) very strange for a few stints. I was towing an 11K enclosed trailer up some 6% grades at 55-65 mph with Predator programing in the Tow setting. I was closely monitoring EGT and boost levels. EGT never reached a questionalbe level. I will get to boost in a moment. When going up a few of these hills, the engine unmistakenly change in sound. The new sound mimic that of the noise a gas engine makes when the automatic choke is on during a cold startup (how it is a higher pitched engine noise, but returns to the normal operating noise when the engine is warm enough). Make sense? Basically it went from the normal diesel low growling noise to a higher pitched humming noise. This would last until I crested the hill and eased the load on the engine for a minute or two. Also while this phenomenon was occuring, occasionally I would hear and extremely high pitch noise, like say that of dragging a finger nail accross a chalkboard. This noise would come and go, lasting no more than a second at a time, and occuring no more than 2 times per hill. At no time during either of these symptoms did I lose power. It felt like I was still running a 100%. The boost needle however would bounce a little, like 2-3 lbs up and down. It may be normal for the boost to do that, I do not know since I did not pay much attention to it before my freak occurances.

Anyone know what this problem could be? It is an 03/03 F350, apprx. 15K miles. EGT was good. Boost was strong with minor bouncing. Oil level is good. Trans oil level is good. This was ONLY up long steep grades and would correct it self without the driver changing anything.

I am pretty sure that these engines have an auxilary radiator fan. I don't think the noise was that and I am sure that the infrequent chalkboard noise definitely was not an auxilary fan. I know what I am describing sure seems like it could be an auxilary fan, but I just don't think that is was.

Please anyone with a though respond. I have found that the people here are much more knowledgeable that the dealerships, so I like to have good possibilities of what the problem may be before I take it in to get fixed so that I can give them an idea of what to look for. (I hate it when the dealerships response is, "Oh, this is a 6 Liter")

TIA

 

The turbocharger spins at very high RPM so it makes sense that any noise associated with the turbo would tend to be high pitched. Manifold pressure will fluctuate a bit, primarily with changing load, but to describe it as bouncing makes one wonder if there was some kind of internal contact or bearing problem with the turbo. Something going on that would temporarily slow the turbo may account for the "bouncing" seen in the pressure. That's just one possibility. I'm sure there are many others.

Regards,

Morris

 

Thanks for the response!

The primary noise I described is definitely not anything turbo related. It is directly related to the engine itself, as the noise ajusts along with the rpms, just like normal engine would sound, just at a higher tone. If the diesel had a choke (and maybe it does, cause I don't know for sure one way or the other) I would definitely say that it was the choke coming on when it was not suppose to.

The blackboard noise I described very well could be turbo related. It was so infrequent and unpredictable that it was not possible to even come close to isolating it.

Any other theories??

 

One more thought, about the nails across a blackboard sound. The one thing that comes to mind is belt squeal. It's not necessarily logical that it would happen in the scenario you describe but it is about the only sound I have heard that could be described that way. If it ever happens again it may be worth trying turning the A/C off or on to change the belt load.

Regards,

Morris

 

I ASSume it's still under warranty
if so, detune the predator and bring it to a dealer with a CERTIFED 6.0 diesel tech ... call around, that really makes a difference !

What area are you in and the dealership name that you have littel confidence in so I won't waste my time there

good luck,
John