Earlier this week I pulled my travel trailer (approx 10K) from south of Austin to Dallas. I was running 70 - 80 with my Quad on the lowest setting, 70hp. I was in T/H with OD lockout only when in traffic or pulling hills. I have H2 tires and wheels, so it's easy to run high EGTs in 5th gear if you don't have enough RPMs on certain hills.


After pulling a couple hills I noticed the check engine light and pulled over to check the code. It was the 0234, Overboost. No big deal, reset it with the Quad and got back on the highway. A few miles and hills later set the overboost again. I was running pretty hard and didn't bother to reset it this time.


About this time I noticed when RPMs got over 2800 or so, I would hear a constant whoosh or air rushing sound coming from under the hood. Happened every time I was near WOT and over 2800 or so. I've pulled this trailer a number of times, but can't recall hearing this noise. It wasn't pilot injection, or the fan roar either, though both of those happen all the time. Didn't sound like turbo whine. This was almost like the sound of airing up a tire with a compressor, though not as high pressure.


EGTs were OK, less than 1250 or so, under load. Boost wasn't as high as I would expect for those conditions, though, maybe 10-15psi max. Truck was running good despite the temps, traffic and me worrying about the noise.


Anyone heard this before? Does the wastegate make a noise when it activates? I did a visual check on all the intercooler hard/soft lines, nothing jumpeed out at me. Is it possible the 0234 - Overboost code had caused the ECM to open the wastegate more?

I am not sure how thorough a job you did on the intercooler conntections but that is one place I would start. On my old Dodge, I developed a small crack and could not find it for about 3 weeks because I was not pushing hard enough on the hose to show the crack. Just an option.

Since your were running that hard and with the Texas heat, my best guess it is your fan clutch engaging. Did you happen to notice any change in engine coolant temp? Mine has been cycling more than it did last summer, especially after a stop. My coolant temp has NEVER gotten over 180, even the other day when I towed 18,000lbs in 98 degree heat. It used to not cycle this often, so I am contemplating replacing it. I have 84,000 miles on it.





Gary

My intercooler hose blew off on me once under hard acceleration. There was a lose of power and the sound of forced air. Yes the turbo was supremely loud.


Nonetheless, I'd take turbospl311 suggestion and check all the intercooler connections and hoses for any cracks or holes.

I think Grey Ghost nailed it. Texas heat = engine fan coming on.

L8r

I'm used to the sound of the fan roaring, that sound was present as well. This was more like an air flow or blowing sound.


Does the fan clutch slip at high RPMs? I noticed the rush of air only at higher RPMs, while running at or near WOT.


I'll douple check the hoses again. The intercooler hoses and pipes are all post turbo, right?

yes, the inter-cooler is post turbo... If a hose popped off you would know it! POW!! WHOOSH! Then every time you move, even under slight throttle you would hear the WHOOSH of the turbo.


Sounds like the fan clutch or a small hole in the hose that opens up under boost.


IMHO

I just hauled a load of cattle (11,000lbs with trailer) yesterday afternoon and when the tranny was in fourth I could hear the roar of the engine plus the fan clutch cycling, but no noticable change in coolant temp.


Also a correction about the coolant temp in my previous post: I was reading the gauge wrong. The needle was 1 1/2 marks below the 210 mark. I'm assuming this is about 195-200 degrees. The bottom line is when I'm pulling, it never budges from this, with or without the fan clutch engaged. My previous '95 2500 with a 454 was a different story. The temp was always changing, usally to the HOT side. I'd have to replace the battery evey year just due to the heat cooking it! Glad I don't have that worry anymore.