So loud! So high pitched! It's driving me crazy. Here's a recording; https://soundcloud.com/doctormowinckel/volvo The recording doesn't do it justice, it's LOUD!

It's a whine that gets louder the faster I go, starts at about 15MPH and hits peak loud at about 65MPH. I'd think it was a problem with a bearing or something else if the noise didn't go away when I went off the throttle! If I go off the throttle on the highway, at 65, 70, the noise goes away, and picks up again when I put my foot back on the throttle.

I've replaced all the fuses, and the fuel pump relay, and the air intake hose, hoping that one of those would be the problem, but they weren't! Still noisy!

Plan F or whatever plan I'm currently on is to replace the fuel pump that's not in the tank. After that comes plan G, which is to re-replace the in-tank fuel pump, but I don't wanna do that again. That's a lot of work, and cursing at my car!

What do ya all reckon?

Also, if I were to replace the not-in-tank fuel pump, is that the same part as the in tank fuel pump, or is that a different one?

 

go about 60mph or whatever, where its nice and loud, put the car in neutral and coast, and rev up the engine to about the same RPM as it was when you were cruising. does the noise come back or not?

 

the main fuel pump is a completely different beast than the intank transfer pump.

 

In neutral the noise goes away, but in drive in comes back.

 

no squeal even if you rev up the engine while coasting in neutral?

turn off OD so you stay in 3rd gear, and go a steady 60 or 65MPH, noting the pitch and loudness of this squeal or howl... then enable OD so you drop into 4th, continue to drive a steady 60 or 65MPH. does the pitch or volume of the sound change significantly with the engine RPMs, or is it purely road speed?

(don't worry about speed in 3rd, a 240/740/940 automatic can go 80+ in 3rd gear without any harm, it just wastes gas)

 

It sounds nominal when I'm coasting in neutral. Going on the throttle does not make the howl come back when coasting in neutral.

Speed, and influenced by throttle. When I was doing 65 in third, it didn't change in any appreciable way. When I'm barely on the throttle, it will get louder. When I'm in park, and rev it a bit, there's no banshee howl. If it helps any, the sound is coming from the drivers side rear.

I'd like to think it was just a bearing, or the fuel pump, but the in tank pump was just replaced, and I have no idea why a bearing would get noisy based on throttle input, but I'm open to the idea that it would! It's confusing, is what it is.

Definitely appreciate the troubleshooting help, pierce.

Edit: Drove to the post this morning and found that when I coast around 40MPH, whether or not I'm not in neutral, it turns to a sort of high pitched gurgling sound? That's the best way I can describe it! I can get a recording of it if you'd like.

 

I think you should check out the driveshaft center bearing, its a ball bearing that rides in a rubber donut. both the donut and hte bearing can need replacing, na dit can make all kinda ugly speed dependent noises, and quite possibly only when you're on the throttle, thus applying lateral torque to it

 

It's not a fuel pump. Check the whole drive line, driveshaft, U joints, center bearings, etc. It should be apparent once you are under there...

 

yeah, I should have made that clear that it doesn't seem like its even remotely possible it could be a fuel pump. they run at a constant speed no matter what the engine is doing, the fuel is in a closed loop being pumped through the fuel rail, regulator, and back to the tank.

 

That makes sense! I never would have considered that option!

Thanks for the suggestion, guys!

 

Uh, it was a wheel bearing! Ha! I was so fixated on it being a fuel problem I hadn't considered other options! I took a look at the centre bearing, and it looked fine, no appreciable wear. My brother's a car geek and Volvo enthusiast as well, so I drove to his place, told him "Get in there's no time to explain!", or I was more like "Hey man, I'm gonna swing by today and borrow your ears for some troubleshooting in my 240", and he was like "Yeah sure man, no problem, what time?". He got in, we drove off, and immediately said "Wheel bearing, duh", then I felt foolish, because it's very obviously the wheel bearing!

Thanks for the suggestions! Getting other opinions is always good for getting the brain moving and motivation. I probably would have replaced the external fuel pump and wondered why the noise was still there if I hadn't joined this forum!