Strange Engine Noise

[PUFF00]

Last night I had been pulling my trailer (~7K lbs. ) for about 1 hour and I was cruising in 6th when I came to a hill, I down shifted and the tach went to about 2,300. As soon as I downshifted I heard this low frequency Brrrrrrrrrrrrrr. It almost sounded like the exhaust had changed pitch, as if something in the exhaust system changed. It continued to happen every time I was in 5th gear and above 2,200 rpm—mostly pulling hills. After a while I decided it was coming from the engine and not the exhaust. I pulled over and checked for loose exhaust manifold bolts, loose oil filter, loose anything. Everything seemed ok.

By the time I got home today it seemed to have stopped—the noise was not there when I pulled the last hill on the way home.

To try and describe the sound a bit more, it almost sounded like a very muffled exhaust brake, but it happened when the engine was under load.

The truck did not loose power, and I just kept pulling hard. The truck has 4,500 miles on it.

Any thoughts?


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2001. 5 3500 QC 4X4 6-speed HO 3. 55 black
1998 Jeep TJ black http://www.nm4w.org/members/puffer.htm

[This message has been edited by PUFF (edited 04-08-2001). ]

[This message has been edited by PUFF (edited 04-08-2001). ]

 

[Bad340fish]

Its getting warmer outside, I wonder if your fan was coming on?? The truck is new maybe you never heard it before?
Clark

 

[PUFF00]

This was at night and the temp was ~45 F. I think the fan would have come on before this—I’ve had the truck for a month and have towed in hotter weather. I don’t think it was the fan. It was an engine/exhaust sound. It sounded like the exhaust just “opened up” or something. It was a deep low frequency sound that kept pace with the rpm, but sounded like it was coming from the engine, and only happened when pulling hard and the rpm was over 2,200.

Nothing seems wrong. No check engine light. Power still good. Boost comes on like normal. No loose bolts that I can see.

It’s just strange when you hear new noises like this. Since I’m not familiar with diesels, these things worry me.


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2001. 5 3500 QC 4X4 6-speed HO 3. 55 black
1998 Jeep TJ black http://www.nm4w.org/members/puffer.htm

[This message has been edited by PUFF (edited 04-08-2001). ]

 

[Guest00]

Have you bombed the exhaust ????

Do you have the infamous rrrrRRRRrrrrRRRRrrrrRRRRrrrr above 60 mph ??

[This message has been edited by JNutter (edited 04-08-2001). ]

 

[PUFF00]

No, unfortunately I have not modified the exhaust--see my post on the product page "5" Exhaust Big Bummer. "

So it's not the infamous drone. This was from the engine, I'm pretty sure.

It's just strange. All of the sudden the engine had this deep growl that I had never heard before. It seems to be gone now. I'll be listening for it though.

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2001. 5 3500 QC 4X4 6-speed HO 3. 55 black
1998 Jeep TJ black http://www.nm4w.org/members/puffer.htm

 

[Alan Reagan]

Puff, Mine did that after a fillup coming out of Florida at Christmas. Not only did it make the noise but I could feel it. It was about 30 degrees out and I had been running pretty hard, stopped for about 10 minutes to refuel and started back. In 5th gear merging back onto 75 it did it and scared the crap out of me. I let off, it stopped and never did it again. I think it has something to do with the heater lines coming into the firewall. There had been discussions here before about removing a piece of plastic out of the incoming heater line because of the growling noise it made. I've heard similar noises come through steam and return lines to boilers when a hydraulic shock vibration starts in the system. Mine has never done it again.

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2001 HO 6 spd 2500, 4. 10 LSD, Towing Package, Electric Brakes, SPA EGT/Boost Gauges, Fog Lights, Real Backup Lights, Molded Running Boards

 

[PUFF00]

Interesting…thanks Alan.

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2001. 5 3500 QC 4X4 6-speed HO 3. 55 black
1998 Jeep TJ black http://www.nm4w.org/members/puffer.htm

 

[Alan Reagan]

It's that feeling like you almost turned over backwards in your chair..... but you didn't #ad
. I don't think its the pump or anything like that. It's like a thermostat trying to decide whether to open or close or open or close. Mine definitely came from under the hood but I don't think it was an engine thing. Had to be a support system. The closest thing I've found to the sound and feeling is recently, I let my truck roll down a slight incline without cranking it. Of course when I went to stop, it didn't want to. I had plenty of room so it was no big deal. When I started the truck and stopped at the street before pulling out, it make a similar growling noise like somehow it got air in the steering pump (which supplies braking power). It growled and I felt it through the floorboard. I won't do that again.