I need help identifying a noise that started while I was driving yesterday. I was driving my '97 F250 home with the windows down. I stopped at a red light and noted a loud roaring type noise coming from the front of my truck. The light changed and I pulled off and the noise went away. At the next light I heard the noise again and it continued intermittently for the next 3 or 4 miles to my home. There was no indication of any problem on the gauges and no loss of power at all. Initially I thought it might be the fan blade hitting the shroud. I pulled into my driveway and left the engine running while I popped the hood. It was pretty apparent that the noise was coming from the area of the turbo. It's pretty loud. Any ideas what it might be? Is there anything within the turbo that might fail and create a noise like this?

 

If the sound sounded like a whooshing sound made by rushing air, it sounds like your EBPV (Exhaust Back Pressure Valve) is closing when it shouldn't be. Did you notice any loss of power when you were hearing that noise? There are a couple things you can try to do to alleviate the issue.

The first would be to remove the EBPS (Exhaust Back Pressure Sensor) from the tube that it attaches to. The tube brings it up beside the HPOP reservoir and leads down to the passenger side exhaust manifold. If you remove the sensor I am guessing that you will see that the tube is plugged (or it may be cracked). You can either remove and replace the tube or try to clean it out using solvent, compressed air, or a drill with a piece of old speedometer cable or aircraft cable in it. This sensor is responsible for sensing the back pressure in the exhaust system and keeping the EBPV from closing when the engine is under load.

The other thing you could do is to just unplug the EBPV. There is a 2 wire connector under the intake side of the turbo. If you unplug that the EBPV should stay open under spring pressure from its internal spring. A lot of guy either unplug it or eliminate it all together (like myself). It is really just there to aid in cold warmup and it is debatable whether it even does that.

That's my best guess though.

 

Nate,

Not to high jack , but did or could you tell any difference when you removed the EBPV, mine is still in.

 

I don't know if I would say that there is a seat of the pants gain in power or not, but you could hear the turbo scream a lot better with it out of there. It wasn't a "WOW that made a HUGE difference" type of moment, but I think it helps. The truck runs good for sure.

 

DIYMechanic, I tried undoing the EBPV but that didn't change the noise. It's actually more of a knocking than a whooshing. I did notice that with the truck sitting in the driveway that when I rev the engine the knocking goes away. It's still pretty loud in idle. Any other ideas?

 

Is it a 5spd. or auto? Pull the inspection cover on the bottom of the bell housing and check the flywheel or flex plate, which ever it is. If it's a 5spd., do you still have the dual mass flywheel?

 

^^2x if this is a manual transmission truck you may be hearing the death song of the dual mass flywheel.

 

It's an automatic. I started the truck up this morning and there was no sign of the noise. I drove it to work (about 5 miles mostly on the freeway) and no noise. When I started it up to go to lunch, the noise was back. It almost feels like it's in the firewall.

 

Does this truck has the stock (flat) downpipe on it or does it have an aftermarket (round) downpipe? If it is an aftermarket pipe, It may be rubbing the firewall slightly causing the sound you're hearing. If you get under it you should be able to see at least 1/2" or so of clearance between the pipe and the firewall. If it is less than that, you need to either adjust the pipe or push the firewall pinch weld back some more.

 

I second that.

 

It still has the flat pipe that came as original equipment. I was thinking about the downpipe being the culprit also; I'm gonna take a look at that after work.

I have another question, if you don't mind? I might have put about a quart too much oil in when I changed it a week ago. Could that be causing part of this problem?

 

I'm not sure if the oil could be the problem or not, but I guess you could try to let a quart or so out and see if it fixes the issue.

On the downpipe, look and see if there is a chance that the insulation on the firewall or the pipe has come loose and is rubbing in there too.