High Pitched Rattle Coming From Front Under Accel....

ANIGAV Inc. · Post by **ANIGAV Inc.** » 06 Sep 2009, 16:04

Not a whine but an actual rattle

Hello all,
I'm hearing a strange noise coming from my car nad wanted to know if you all could help me.
Ok I know my cv axles are deader than jimmy hoffa but i dont think this is coming from them, correct me if i'm wrong.

The car idles fine and accelerates just like it should but i keep hearing this strange rattle coming from under the hood. It's noticeable because i think the sound it bouncing off the ground.
My friend is scaring me saying it may be teh bottom end of the engine spinning its last few spins.

It's hard to actually describe teh sound but if you were to have a childs rattle and put it under the car thats what it sounds like. No i havent run over any babies...today.

If this sounds like anything you've experienced please let me know.

Post by **Ozark Lee** » 07 Sep 2009, 04:09

Check the heat shield above the catalytic converter. It is in that general area and it gets very noisy if it gets loose.

...Lee

ANIGAV Inc. · Post by **ANIGAV Inc.** » 07 Sep 2009, 22:27

wow, i didnt think of that.

thanks

Post by **FlyingVolvo** » 07 Sep 2009, 22:47

I had a really bad metallic rattle in the car. It started as an intermittent noise that eventually ended up being at nearly every speed. Turned out to be the drive shaft dying.

But definitely start with the less expensive stuff!

Jesus · Post by **Jesus** » 08 Sep 2009, 01:52

I had a nasty rattle once under hard acceleration in my old 850. The mechanic, once the car stopped working, explained the reason for the rattle was the same reason for the smoke and the fact I need a new engine. - The head gasket had gone and taken the alloy head with it.

ANIGAV Inc. · Post by **ANIGAV Inc.** » 08 Sep 2009, 08:05

ecbsykes wrote:I had a really bad metallic rattle in the car. It started as an intermittent noise that eventually ended up being at nearly every speed. Turned out to be the drive shaft dying.

But definitely start with the less expensive stuff!

I see you have awd so i can kinda breathe easy. Although My cv axles are done, i'm replacing them on friday and will cross my fingers

Jesus wrote:I had a nasty rattle once under hard acceleration in my old 850. The mechanic, once the car stopped working, explained the reason for the rattle was the same reason for the smoke and the fact I need a new engine. - The head gasket had gone and taken the alloy head with it.

:gulp: i'm getting smoke from my exhaust and dip stick but an chalking up to my PCV needing to be replaced, also doing this friday.

I'm getting nervous now. She has 186,xxx on her and oil changes have been done like clock work. I bought it from a volvo mechanic at a volvo dealership so i would assume it was in halfway decent shape when i got it.

I'll keep you all posted.

FCPEURO · Post by **FCPEURO** » 08 Sep 2009, 09:28

What kind of gas are you running in it? I hope it is not the engine knocking.

Jesus · Post by **Jesus** » 08 Sep 2009, 11:48

ANIGAV Inc. wrote:
:gulp: i'm getting smoke from my exhaust and dip stick but an chalking up to my PCV needing to be replaced, also doing this friday.

I'm getting nervous now. She has 186,xxx on her and oil changes have been done like clock work. I bought it from a volvo mechanic at a volvo dealership so i would assume it was in halfway decent shape when i got it.

I'll keep you all posted.

The smoke wasn't from the exhaust it was from out of the wheel arches and round the bonnet once blown!

My post was tongue in cheek, sorry for worrying you. That is actually what happened to me, but in the space of about 20 seconds not a period of days or anything. I just got some horrible rattley metallic noises, a loss of power then 850 death + much smoke.

It had 136k on the clock, but the mechanic had some how missed the blowing gasket when i went in to find a water leak. The writing was on the wall when he couldn't find the leak and sent me on my way with a new radiator cap. (Mine had blown off!)

Brutus Maximus · Post by **Brutus Maximus** » 08 Sep 2009, 12:05

It could be the fuel/air mixture detonating (aka pinging) in the cylinders. Detonation can sound exactly like a baby's rattle, and it usually happens only during acceleration. Have you recently changed brands of gasoline? I'd try filling the tank with some 91-octane premium, or at least adding a dose of octane booster to the tank. If that doesn't quiet the noise, you'll only be out a few bucks. If it does stop the noise, you need to determine why it started detonating. You could have a bad knock sensor, or you could have excessive carbon deposits in the combustion chamber.

Either way, don't let it go on for an extended period, or it can blow a hole right through the piston crown. Then you'd be in a world of hurt.

Good luck, and let us know what you find out!

Here are some links with additional information on detonation:

http://www.tuninglinx.com/html/detonation.html
http://www.motorcycle.com/how-to/wrench ... -3420.html
http://www.kb-silvolite.com/feature.php ... ction=read

ANIGAV Inc. · Post by **ANIGAV Inc.** » 08 Sep 2009, 12:51

FCPGroton wrote:What kind of gas are you running in it? I hope it is not the engine knocking.

I've been using 87 from Wawa for the past few months. I'm at a half tank so i'll grab an octane booster on my way to school.

Jesus wrote: The smoke wasn't from the exhaust it was from out of the wheel arches and round the bonnet once blown!

My post was tongue in cheek, sorry for worrying you. That is actually what happened to me, but in the space of about 20 seconds not a period of days or anything. I just got some horrible rattley metallic noises, a loss of power then 850 death + much smoke.

It had 136k on the clock, but the mechanic had some how missed the blowing gasket when i went in to find a water leak. The writing was on the wall when he couldn't find the leak and sent me on my way with a new radiator cap. (Mine had blown off!)

Phew thanks for that clearing that up. No water leaks so far.

Brutus Maximus wrote:It could be the fuel/air mixture detonating (aka pinging) in the cylinders. Detonation can sound exactly like a baby's rattle, and it usually happens only during acceleration. Have you recently changed brands of gasoline? I'd try filling the tank with some 91-octane premium, or at least adding a dose of octane booster to the tank. If that doesn't quiet the noise, you'll only be out a few bucks. If it does stop the noise, you need to determine why it started detonating. You could have a bad knock sensor, or you could have excessive carbon deposits in the combustion chamber.

Either way, don't let it go on for an extended period, or it can blow a hole right through the piston crown. Then you'd be in a world of hurt.

Good luck, and let us know what you find out!

Here are some links with additional information on detonation:

http://www.tuninglinx.com/html/detonation.html
http://www.motorcycle.com/how-to/wrench ... -3420.html
http://www.kb-silvolite.com/feature.php ... ction=read

Thank you Thank you Thank you. Going to get the booster in a few. It's possible I have a bad knock sensor, the car has a few years on it. How do I check the sensor?

ANd as far as excessive carbon deposits wouldnt that get cleared up by using seafoam?