Engine noise under heavy load

[DMerryman]

Problem: A "whop, whop, whop" (kinda like a pump sound) under heavy load. Appears to be coming from within the engine.

Running a 2000 3500 Quad Cab Dually, Auto Tranney, 410 rear end loaded with a Bigfoot Cab over camper and towing a Jeep Wrangler..... total rig with my wife and I weighed out at 15,700 lbs. Of course dealer said he had never heard of this??? Anyone

else with some thoughts???

 

[Alan Reagan]

You may be trying to suck the snorkel closed (between the airbox and fender). Try removing that little piece of rubber snorkel from inside the airbox (it slips right out) and see it that stops your problem. Now if it is a slow groaning repetitive type sound, that's engine resonance. It was more pronounced on the 12 V with the mechanical pump. But it wasn't a Whop sound. Just a groan.

 

[John Berger]

That snorkel could definitely cause that sound. I don't run with mine, but decided to experiment with it last weekend, by drilling holes all around the lip that goes into the fender. I took it out for a test drive and when I got back and checked under the hood, the snorkel was resting comfortably in the bottom of the air box. Like I said before, my engine really sucks

 

[merryman]

The snorkel is NOT it. I removed mine (running a cone K&N), and I still get the whap, whap, whap, on most significant pull with a load--towing a 12 fiver.

Another approach that apparently worked for one member-Bill Stockard- (I have been trying to get around to it), is to reroute one of the heater hoses from the rear of the head to the front.

Bill posted a picture of the mod. but I can't come up with the thread right now. Seems he said a Dodge dealer in Wyo. did it for him and he has not had the noise since.



Vaughn

 

[David Wheeler]

Snorkel question please

One night while taking on fuel, I noticed the "snorkel" (plastic piece coming from the fender well to the air box) was separated from the air box. Looking at it, it has a flange on the end closest to the box. I assumed this flange was supposed to be inside the box and there to hold the snorkel on the box. I stuffed the flange inside the box, closed the hood and went on my merry way. I've looked in the service manual, but can't find a reference to the assembly. The question (finally ): is the flange supposed to be inside the box at the intake or did I make a poor assumption?



Thanks in advance,



David

 

[Alan Reagan]

David, It doesn't really matter. Supposedly, the snorkel provides cooler air from inside the fender. The down side to getting this air is the restriction of the snorkel.



Merryman, I had forgotten about the heater hose. Before you reroute everything, I believe there is a plastic orifice of some type at the rear in the heater hose. That caused some strange noises for some. I had a post last winter where I had stopped for fuel one very cold night. When I started back on the Interstate, under accleration, there was a sudden "whump" sound that came from the rear of the engine that scared the stew out of me. At that time I thought that might have been the heater system. The truck has never done it again.



You may be on to something. Let us know.