Noise Help (long)

[Alan Reagan]

Last night I took on a project truck and I need some help with a noise. First let me tell you what I've done so we can eliminate all the normal problems.



The truck is a 99, quad cab, 4X4, 5 speed. Cummins replaced the short block under warranty and mileage is really low at 15. 9 mpg. I got out the torque wrench.



ALL of the intake manifold bolts were loose. Two were loose enough to turn by hand. Torqued them to spec.



When the boost system was reinstalled at the shop, the lower clamps at the intercooler were not tightened. After intercooler was about to blow off before long. Took care of all the clamps.



Cleaned the IAT.



All filters were already changed.



Truck now starts easy, idles smooth. Power is good and you can really tell when the boost starts coming up. These tweaks should increase mileage immediately.



One last problem that I couldn't figure out is where I need some help. There is a noise coming from the center of the dash, either from the back of the engine or inside the dash. It starts at 1200 RPMs and is worse at 1800. The first idea was that it is electrical. It is a whine similar to what you might here when your stereo system picks up alternator whine, only louder. To be clearer, it sounds like alternator whine from a car that has just been jump started and the alternator is working under heavy load. Then you listen some more and the sound doesn't change but it sounds almost like an air leak or water under pressure. Like when you pull out the tire valve stem and at a point the vibration sets up and makes noise. This is not a minor sound that you can barely hear. It's very annoying. At speed, I could push in the clutch, coast in neutral with no change so I'm sure it's not drive train. The sound will stay constant while coasting till RPMs drop to 1200 and then it disappears. Rev up the engine and the noise is back.



I'm posting here because I can't tell if it's engine or not. I sat on the passenger side while someone else driving. The sound definitely comes from the center of the dash around or behind the radio. The radio was off BTW. I even pulled fuses. There is no noise in the speakers.



I'm wondering about the heater hose lines. Anyone had a constant problem with them making noise. Second, I thought I had disconnected the vacuum lines that run to the heater switch to eliminate that but I'm not sure. I'll probably have to pull the dash and do it inside. This is the last little issue to bring a project truck back to its former pristine state.

 

[nps]

Alan,



To isolate the vacuum lines without going into/under the dash, try clamping the supply line shut under the hood and before the firewall with a pair of vice grips. Can also work to isolate the heater lines. I've got a pair with a 6" wide jaws intended for welding but work great as a line clamp. a small "C" clamp will also work.



Should at least change the noise, if not eliminating it completely.



Another source? Is the A/C compressor running? Maybe low on charge and there's bubbles running through evaporator.



Final suggestion would be something in the blower squirrel cage. But doubt it since the noise is engine-RPM dependent.



Neil

 

[RAMalama]

My money is on the vaccum lines based on what I've read. Then again, I have no money...

 

[Steve Campbell]

About a year ago there was a thread on the water lines to the heater core making a noise somewhat like you are experiencing. Being without the "problem", I took no note and do not even remember the title of the thread. Perhaps someone else will remember.

 

[John Berger]

Sounds like the heater hose that runs from the heater core to the motor. It's a 99 so it's probably the same thing that my truck did. There is an orifice or o-ring of some sort in the brass fitting where the heater hose connects to the engine manifold (passenger side). Take the heater hose off and pull that orifice/ring out and reconnect the hose. Your whining noise should disappear. Supposedly it was put in to regulate coolant flow/heat dissipation or something to that effect. I have had mine off since it was 6 months old and have not had any problems whatsoever. There are threads out there, but I would bet this will solve the problem. Let me know.

 

[Alan Reagan]

Thanks, guys. At least I hope I'm looking in the right direction.



NPS, Good idea on clamping them off. Didn't think of that. I was just going to remove.



John, is it the outside hose closest to the fender or the one closest to the valve cover that has the orifice?



I gotta say, this is the weirdest sound I have ever heard coming out of a vehicle. Gives me a new appreciation on what some of our members have been through in solving strange problems.

 

[Thomas]

Here's the heater hose noise TSB:



http://dodgeram.org/tech/tsb/1999/09-04-99.htm



Thanks Fritz!

 

[Alan Reagan]

Thanks for the research, Thomas. That's a big help.

 

[John Berger]

It's the hose closest to the valve cover and it's between injectors 4 and 5. You can't miss it.

 

[Alan Reagan]

Happy boy . I never would have believed that the noise I was hearing was coming from the heater line. You guys. We clamped off the line and the noise disappeared. It was loud, too, before the padded vice grips. Thanks for all your help. We be ridin' in a Dodge Red 4X4 looking good now. Just a couple more things to do and we're finished. The mileage was at 15. 8 before I overhauled the top end of the engine with a torque wrench. Now we're waiting on the results of my initial handiwork. Again, thanks to you all for the help. That's right, we bad, we bad.



Edit. Removed the washer or whatever you call that thing. Thanks for the right location, John Berger. Noise is gone. Thanks again, guys.