Squeeking sound from throttle?

bmw335d · 02-05-2018, 08:35 AM

Hey Guys,

I recently started hearing a squeeking / chirping sound when I tap the gas pedal.

It goes away when the engine warms up.

Could it be the throttle body causing this?

Anyone else experience this?

Torqu3 · 02-05-2018, 09:47 AM

"Throttle body" only moves on startup and shutdown. It isn't really like a traditional throttle body on a gasoline car. So it's not that. Belt Squeal as the serpentine belt warms up?

PerfectAce · 02-05-2018, 10:28 AM

Squeaking/chirping on cold start would have me looking into the belts and pulleys.

bmw335d, how many miles on your car? Have the belts ever been changed? More importantly, has the harmonic balancer (crankshaft pulley) ever been replaced on your car? If it hasn't, I'd would bet money that it's failed.

A few days before mine catastrophically failed (leaving no doubt what the culprit was) I had noticed a slight squeaking on cold start ups, obviously coming from the belt(s). In hindsight I figure that the inner rubber of the HB was just starting to let go, doing some funky spinning on start up causing the belts to slip and squeal. Once the rubber in the HB via friction got warm enough to stay temporarily "glued" together and let it operate seemingly normally, the belt squeal stopped.

I'm thinking something similar might be happening here. OP applies a bit of throttle when cold --> increases torsional load on the HB --> compromised inner rubber of HB gives way --> belt slips causing squeal. Once warmed up and "settled in", slippage and squeal stops.

Top tip to OP: on next cold start up, before cranking, open hood. Then start engine, immediately get out and observe belt behavior. Take a good whiff as well. If you smell burnt rubber, HB is definitely kaput.

Owen81 · 02-05-2018, 02:41 PM

Possible boost leak or valve cover gasket leak?

AlpineX · 02-05-2018, 06:26 PM

If it is happening when applying initial throttle, I would think it could be belt or vacuum/boost related. I believe that a chirp is one of the first signs of HB failure, as is burning rubber smell, visual cracks can also show wear.

Lot of people changing out harmonic balancers these days.

bmw335d · 02-05-2018, 08:51 PM

Hey so I have an 09 model with 210k kms on it. I had the HB and belts changed at 120k.

So I took off the cover today and had my friend tap the gas while I listened and the sound seems to be coming from the swirl flaps, I can see the shaft move and the sound seems to be coming from right under the intake manifold.

I'm planning to do the swirl flap delete so hopefully this will fix the issue, i'll post back once done

thanks

02-05-2018, 08:35 AM	#1
bmw335d Second Lieutenant 104 Rep 247 Posts Drives: X3 M40i, 335d Join Date: Sep 2010 Location: Toronto, Ontario iTrader: (0)	Squeeking sound from throttle? Hey Guys, I recently started hearing a squeeking / chirping sound when I tap the gas pedal. It goes away when the engine warms up. Could it be the throttle body causing this? Anyone else experience this?
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02-05-2018, 09:47 AM	#2
Torqu3 Major 322 Rep 1,157 Posts Drives: 2011 335d Join Date: Sep 2016 Location: Centralish Texas iTrader: (0)	"Throttle body" only moves on startup and shutdown. It isn't really like a traditional throttle body on a gasoline car. So it's not that. Belt Squeal as the serpentine belt warms up?
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02-05-2018, 10:28 AM	#3
PerfectAce Second Lieutenant 107 Rep 202 Posts Drives: 2011 335d Sport Join Date: Jun 2017 Location: Austin, Texas iTrader: (0)	Squeaking/chirping on cold start would have me looking into the belts and pulleys. bmw335d, how many miles on your car? Have the belts ever been changed? More importantly, has the harmonic balancer (crankshaft pulley) ever been replaced on your car? If it hasn't, I'd would bet money that it's failed. A few days before mine catastrophically failed (leaving no doubt what the culprit was) I had noticed a slight squeaking on cold start ups, obviously coming from the belt(s). In hindsight I figure that the inner rubber of the HB was just starting to let go, doing some funky spinning on start up causing the belts to slip and squeal. Once the rubber in the HB via friction got warm enough to stay temporarily "glued" together and let it operate seemingly normally, the belt squeal stopped. I'm thinking something similar might be happening here. OP applies a bit of throttle when cold --> increases torsional load on the HB --> compromised inner rubber of HB gives way --> belt slips causing squeal. Once warmed up and "settled in", slippage and squeal stops. Top tip to OP: on next cold start up, before cranking, open hood. Then start engine, immediately get out and observe belt behavior. Take a good whiff as well. If you smell burnt rubber, HB is definitely kaput.
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02-05-2018, 02:41 PM	#4
Owen81 Lieutenant 83 Rep 431 Posts Drives: 335d, 17/22 TDI Join Date: May 2015 Location: Alberta, Canada iTrader: (0)	Possible boost leak or valve cover gasket leak?
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02-05-2018, 06:26 PM	#5
AlpineX Captain 247 Rep 776 Posts Drives: Diesel Join Date: Sep 2015 Location: US iTrader: (0)	If it is happening when applying initial throttle, I would think it could be belt or vacuum/boost related. I believe that a chirp is one of the first signs of HB failure, as is burning rubber smell, visual cracks can also show wear. Lot of people changing out harmonic balancers these days.
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02-05-2018, 08:51 PM	#6
bmw335d Second Lieutenant 104 Rep 247 Posts Drives: X3 M40i, 335d Join Date: Sep 2010 Location: Toronto, Ontario iTrader: (0)	Hey so I have an 09 model with 210k kms on it. I had the HB and belts changed at 120k. So I took off the cover today and had my friend tap the gas while I listened and the sound seems to be coming from the swirl flaps, I can see the shaft move and the sound seems to be coming from right under the intake manifold. I'm planning to do the swirl flap delete so hopefully this will fix the issue, i'll post back once done thanks
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