98 V70 Squealing on the throttle, what in the world?

jsrnsis · Post by **jsrnsis** » 27 Jun 2024, 17:42

So after a steering rack replacement, this noise developed on a 98 v70.

The constant noise may or may not have been the SAS pump failing, but there is also another squeak and squeal when the throttle is blipped.

I just can't figure it out, it seems to come from the throttle body or intake manifold area. I changed out the idle air control valve, and got no change. Has anyone heard a sound like this before?

It sounds like a clown car horn, which would be comical if it wasn't driving us crazy trying to figure out.

dikidera · Post by **dikidera** » 27 Jun 2024, 23:39

That is actually pretty funny, almost like a clown nose. To me this sounds like a noise related to vacuum as air rushes past some seal or something. If you had a vacuum pump, this is the first thing I would've had you check. Remove the black plastic cover where the TB is and have a look see, it could be a torn vacuum hose say for EVAP(if your 98 has one).

On my older first gen S40 I had a similar noise, but not this pronounced with the PCV system having a torn membrane.

jsrnsis · Post by **jsrnsis** » 28 Jun 2024, 06:50

dikidera wrote: ↑27 Jun 2024, 23:39 That is actually pretty funny, almost like a clown nose. To me this sounds like a noise related to vacuum as air rushes past some seal or something. If you had a vacuum pump, this is the first thing I would've had you check. Remove the black plastic cover where the TB is and have a look see, it could be a torn vacuum hose say for EVAP(if your 98 has one).

On my older first gen S40 I had a similar noise, but not this pronounced with the PCV system having a torn membrane.

Can you clarify what you mean by PCV torn membrane? I need to test it, but thinking maybe it's air escaping from the "up and over" PCV hose that goes to the top of the engine. There's a joint there where the glue might be coming undone. Hopefully more glue and a hose clamp will solve this.

dikidera · Post by **dikidera** » 28 Jun 2024, 08:29

The early PCV systems(on first gen S40s/V40s) had this little membrane that would tear and cause a similar sounding noise. And excessive vacuum in the crankcase, so much so, I couldnt pull out the oil cap. Sometimes by blipping the throttle like you yourself do, would cause this noise to appear.

jsrnsis · Post by **jsrnsis** » 28 Jun 2024, 13:24

I glued and clamped the top PCV hose with no change. Will update with what I try to do today.

dikidera · Post by **dikidera** » 28 Jun 2024, 14:14

The PCV membrane is inside the PCV unit itself. If it is the same style as the early S40/v40s(first gen).

jsrnsis · Post by **jsrnsis** » 28 Jun 2024, 18:17

dikidera wrote: ↑28 Jun 2024, 14:14 The PCV membrane is inside the PCV unit itself. If it is the same style as the early S40/v40s(first gen).

Our P80 PCV boxes are literally just boxes with a baffle inside, very low-tech.

Post by **scot850** » 28 Jun 2024, 19:07

Your car is a 98. Does it still have the PCV system with the flame trap just behind the throttle body? Also if I recall correctly your car is an NA motor so it won't have the engine oil cooler thermostat that can whistle.

Neil.

jsrnsis · Post by **jsrnsis** » 29 Jun 2024, 08:00

scot850 wrote: ↑28 Jun 2024, 19:07 Your car is a 98. Does it still have the PCV system with the flame trap just behind the throttle body? Also if I recall correctly your car is an NA motor so it won't have the engine oil cooler thermostat that can whistle.

Neil.

Yes, it is an NA, but we didn't put the flame trap insert back in when we did the PCV. My dad thought it might have been the o-ring for the vacuum tree, and the little bolt broke off almost instantly flush with the manifold.

Replacing the o-ring made no change. Another problem that surfaced at the same time is slight difficulty starting. Longer cranking and steering wheel jerking when the engine starts.

The sound does seem to come from the front of the engine, and in the area of the throttle body. It's pretty hard to narrow down the location.

Post by **scot850** » 29 Jun 2024, 08:20

Although it is likely an outward blow rather than an inward suck, it may be worth trying spraying around that area with brake cleaner/WD-40 or the like with a long tube on and see if you can see any blow. Not tried it myself, but that is worth a try.

A cracked hose or seal like you suggest is most likely the issue. Although you removed the flame trap, is the holder still in place? They can crack where they attach to the throttle body area, or the 2 halves of the holder separate.

Neil.