Weird hissing noise from under truck? (Warning: wall of text)

[skiffer]

I'm not sure if there's a better place to post about this, but this is the general forum so maybe I got it right. Starting a week or two ago I noticed a weird hissing noise when I was on the highway. It seemed to be paired with turbo spool and sounded kind of like an exhaust leak or something. I got under the truck and made sure the v band clamp that connects the down pipe was tightened all the way and it seemed to go away after that. So I thought I had fixed my "exhaust leak".

But, a couple days ago, it came back. Today it was especially noticable, but it definitely isn't linked with turbo boost. I tried giving the truck some more pedal on hills to spool it up a little more, and the sound wasn't there. I tried slowly building boost to see if there was a certain pressure, sound didn't correlate to that either. The only thing I know will make the sound get louder is when the truck shifts gears (specifically into 4th at about 30MPH and 5th at about 45MPH), the 68RFE does it's stupid RPM flare on the shift and the exhaust hits a different note. That specific thing seems to make the sound very loud. Gear shift followed by RPMs changing and the exhaust hitting a different note makes this hissing noise especially loud.

I also noticed that when it's doing it around 45MPH I can make the noise get very loud by giving the truck just a little touch of acceleration. When I'm doing that I noticed this: 43MPH - hardly notice, 44MPH - start hearing the noise over the exhaust, 45MPH - the noise sounds like a second turbo is spooling under my truck almost, 46MPH - starts fading away and quickly becomes unnoticeable again.

So....what in tarnation is going on? It isn't an exhaust leak that I can tell, I checked the clamps on my intake filter all the way down to the turbo, I checked all intercooler related clamps for tightness in case it was a boost leak, and I'm not losing boost or power when the noise comes around. I've heard power steering pumps make an odd noise on their way out but it doesn't matter if I'm going straight or taking a turn, the noise still comes around. The truck is also at 18K miles so I hope it isn't a power steering pump. If anyone has any ideas please give me some stuff to try and look at/fix. Thanks, and I apologize for the long winded post. I'm just trying to give every detail I can

 0 Comment(s)

[Power247]

Man, this is something! Wish I could help out. Hope you get it sorted quickly. Something like this would drive me nuts.

Greg
2012 | RAM 2500 | CCSB | Custom tuned by Double R Diesel
2016 | Heartland Pioneer | DS310

 0 Comment(s)

[Oil Stain]

My is a 2012 Ram, i had the same issue, turned out it was one of the booster lines went bad. The inner plastic tube inside the hose broke away from the crimped end and would make loud hissing sounds when i turned the wheel.

I remember now, it was the upper hydroboost / Line-Power Steering Pressure hose, part # 5154687AA. That part was for a 2012. Maybe you are having the same issue even though yours is a 2018. Just throwing it out there. Good luck!

 0 Comment(s)

[DDP]

My is a 2012 Ram, i had the same issue, turned out it was one of the booster lines went bad. The inner plastic tube inside the hose broke away from the crimped end and would make loud hissing sounds when i turned the wheel.

I remember now, it was the upper hydroboost / Line-Power Steering Pressure hose, part # 5154687AA. That part was for a 2012. Maybe you are having the same issue even though yours is a 2018. Just throwing it out there. Good luck!

I have heard a few people having the same issue. Hopefully this is it!!!

 0 Comment(s)

[DIESELWRKS]

So you have no signature so I don’t know if your deleted or stock. If you are stock you want to check all flange bolts on the exhaust, if you see anything funny, you may want to loosen the exhaust to retighten this way you know its correct. Check also the sensors and make sure they are tight.

I have seen a couple late 2500’s that have loosened the flange bolts and have had finger tight sensors.
For boost leaks, this is not a boost leak. If you had any cracked boots or loose clamps for the inter-cooler cold or hot side this would be a big woosh sound and very little power to the truck. And if you ever are around when a inter-cooler boot blows. They sound like a gun.

check your air filter and air path to the turbo, If you are not deleted, check the EGR/exhaust manifold-flange connections for any soot present. If its present then there is a leak.

Now if you are deleted and put on a exhaust. Is it new? Is it a dump exhaust tip style? So new that you are getting sound reflection off of things ? likely not this but thought I would ask, I had a past truck that I had the exhaust dumped 2 feet past the down pipe right under the passenger butt and that would make sound bounce and echo off everything.

 0 Comment(s)