Help me diagnose something 

"zeontestpilot" (zeontestpilot) 03/27/2015 at 09:10 • Filed to: Question, help

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Ok, so I drive a '08 PT cruiser, auto. I noticed when I drive > 60 mph, I hear a 'squeaking' noise in the rear. It doesn't sound like metal scraping, but like a mouse squeaking. It's more prevalent when the rpms are around 3k and when I'm pressing the gas.

The noise had multiple pitches, and seems to jump around with the pitch (it might be consistent, but it's too quick for me to hear). The noise also seems regular, except for the 1 or 2 second gaps which appear to occur at random. I can also hear it, when I press the brakes (to slow down in the hwy), but it's just random chirps followed by lengths of silence.

It isn't too loud, as anything from the engine to music will drown it out. My first guess was that maybe something wasn't lubed up enough, but the lack of sound at low speeds throws that idea out of the window.

Thoughts?

Twingo Tamer - About to descend into project car hell. > zeontestpilot 03/27/2015 at 09:11

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Maybe something loose on the exhaust?

zeontestpilot > Twingo Tamer - About to descend into project car hell. 03/27/2015 at 09:16

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It could be. It may be behind the drivers spot, but I'm not entirely sure. Would it only make sound at higher speeds though? Maybe more air being thrown against it?

CalzoneGolem > zeontestpilot 03/27/2015 at 09:16

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I'm gonna go with wheel bearing.

zeontestpilot > CalzoneGolem 03/27/2015 at 09:19

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If it is, what's a worst case scenario?

Aaron M - MasoFiST > zeontestpilot 03/27/2015 at 09:20

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So it's squeaks, at semi-regular intervals, coming from the rear of the car.

-Does engine speed affect the interval?

-Does suspension movement (hitting a bump, turning, anything else) affect the interval?

Things that squeak in the back of a FWD car are typically suspension components, though it may even be pieces of trim rubbing together (unlikely, though it's happened to me). I'm thinking a bushing...at highway speeds your suspension is a bit more compressed, and when you're braking the suspension is unloading as the weight of the car shifts forward (so you get the several chirps as the suspension unloads, then nothing). I don't know which bushing it would be, though if it's regular it's probably on the wheel side...control arm bushing or strut mount, I don't know. Have someone sit in the back of the car and try to pick out where it's coming from...first which side, and then maybe a height (top of strut, bottom of strut, somewhere else?).

CalzoneGolem > zeontestpilot 03/27/2015 at 09:21

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The noise will get worse until you replace it.

MazdaMonkey > zeontestpilot 03/27/2015 at 09:25

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You can easily rule this one out. Rev the engine in park. If it doesnt make the noise, its not a wheel bearing.

If it is a wheel bearing, you are going to want to replace it. It will eventually seize, and could cause an accident.

jariten1781 > zeontestpilot 03/27/2015 at 09:30

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Fuel pumps going out typically start by sounding like mice or crickets. That would be my guess if the sound doesn't change based on road surface/suspension loading.

Twingo Tamer - About to descend into project car hell. > zeontestpilot 03/27/2015 at 09:31

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Maybe just gets rattled about more. Our Micra had a metallic squeaking at speed because an exhaust hanger had half rusted through and rubbed against the body. Only happened with the greater vibrations at speed, at low speed you couldn't hear it.

Stephen the Canuck > MazdaMonkey 03/27/2015 at 09:36

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I think you wrote that backwards. It wouldn't make a noise if it was the wheel bearing. There would be no motion going through the wheel bearing with the car in park.

zeontestpilot > Twingo Tamer - About to descend into project car hell. 03/27/2015 at 09:37

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That makes a lot of sense. Our car used to shake a bit (haven't noticed it recently). I went to a couple mechabits, some said the engine mounts was bad, others said nothing was wrong.

nFamousCJ - Keeper of Stringbean, Gengars and a Deezul > CalzoneGolem 03/27/2015 at 09:37

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While we're on wheel bearings what would a bad one sound like?

Curious as I've noticed within the first hundred feet or so driving out of my neighborhood I get a slight metallic sliding noise - think if someone had a metal rod sliding along the ground or inside of your wheel. Its smooth sounding, not loud and can really only be heard when coasting (exhaust drones it out easily)

zeontestpilot > MazdaMonkey 03/27/2015 at 09:38

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Yay, more money to spend....

nFamousCJ - Keeper of Stringbean, Gengars and a Deezul > zeontestpilot 03/27/2015 at 09:42

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rockauto has bearings for <$30/each or the whole hub assembly for ~$40. I've seen mine ripped apart when we accidentally sheered off a wheel stud so it doesn't appear to be a too extensive task. If you have abs it may be different though. Check your ball joints while you're in there too, if having a shop do the work may just want them both knocked out at once plus they can do your alignment.

Twingo Tamer - About to descend into project car hell. > zeontestpilot 03/27/2015 at 09:42

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To be honest might be worth just ignoring the noise if there are no other symptoms. I'm an expert at ignoring irritating noises after the cars my family and me have had haha.

MazdaMonkey > Stephen the Canuck 03/27/2015 at 09:44

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Yep! Brain fart!

zeontestpilot > Aaron M - MasoFiST 03/27/2015 at 09:50

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Engine speed - maybe. About the time I realized that it was different for different mph, I had to get off the hwy and couldn't test it anymore.

Bumps - havent noticed it, but I spent most of my 40 minute commute listening to it. It seemed fairly regular.

The squeaking has been going on for a while now, but I usually play music so I dont notice it and forget about it. I had new tires put on last year, and had some other stuff fixed as well at a shop, but it was long after that I first heard the noise.

CalzoneGolem > nFamousCJ - Keeper of Stringbean, Gengars and a Deezul 03/27/2015 at 09:51

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They go squeak squeak.

zeontestpilot > jariten1781 03/27/2015 at 09:54

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Aren't fuel pumps toward the front of the car though?

Aaron M - MasoFiST > zeontestpilot 03/27/2015 at 09:55

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I think getting someone in the back of the car while you're driving is the next step if you want to diagnose this further. As I drive a car that's somewhat known for squeaking and rattling even on good days, my inclination would be to leave the radio on and not worry about it unless it got louder. You don't have any steering or driveline gear (I don't think they made AWD PT Cruisers) back there so it's pretty much just an NVH issue.

thebigbossyboss > zeontestpilot 03/27/2015 at 09:56

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Bad wheel bearing. Will get louder if left untreated.

thebigbossyboss > MazdaMonkey 03/27/2015 at 09:56

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Lol yes if it seized while going fast it could definitely cause an accident.

thebigbossyboss > zeontestpilot 03/27/2015 at 09:57

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Nay. They are near the gas tank (usually). Mine was like 3/4 back.

zeontestpilot > nFamousCJ - Keeper of Stringbean, Gengars and a Deezul 03/27/2015 at 09:58

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It seems I should take it onto a shop, see what they say.

zeontestpilot > Twingo Tamer - About to descend into project car hell. 03/27/2015 at 10:02

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Yeah, I've been doing that for a while now. I just figured I should stop being a driver, and start being a gearhead, and ask someone for their thoughts.

Sethersm > MazdaMonkey 03/27/2015 at 10:04

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What? Rev the engine in park and if it doesn't make the noise, it's not in the engine. Sitting still, I wouldn't expect a wheel bearing to make noise.

Wheel bearings also typically make a rumbling sort of "swoosh, swoosh, swoosh" sort of noise, not squeaking.

I would suspect suspension components. Or, if it is a regular/rhythmic sort of squeak, brakes. A warped drum can cause the shoes to rub against the backing plate causing a rhythmic squeak.

Twingo Tamer - About to descend into project car hell. > zeontestpilot 03/27/2015 at 10:04

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That's fair, if you want go a bit more gear head and someone doesn't get the answer on here, try getting a service manual and have a poke around yourself. It's the best way to learn.

nFamousCJ - Keeper of Stringbean, Gengars and a Deezul > CalzoneGolem 03/27/2015 at 10:07

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well crap I don't know what mine is. It's definitely coming from the front end. I've heard of ball joints dropping so thinking something may be rubbing but I just got an alignment done and they didn't say anything. But I'm honestly not surprised being that it is the Stringbean

zeontestpilot > Twingo Tamer - About to descend into project car hell. 03/27/2015 at 10:08

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Like those books you can buy at auto stores?

zeontestpilot > thebigbossyboss 03/27/2015 at 10:12

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What's the best way to confirm if it is or isn't?

jariten1781 > zeontestpilot 03/27/2015 at 10:13

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Many modern cars (most?) have their fuel pumps in the gas tank to take advantage of the liquid fuel as a heat sink. I imagine the Cruiser does, but I've never worked on it so I'm not sure. One disadvantage of that is that if the owner regularly runs the fuel down to near empty the pump can come uncovered and overheat leading to failure. It's rare, but not super rare. Usually recommend filling at 1/4 tank for that reason.

Twingo Tamer - About to descend into project car hell. > zeontestpilot 03/27/2015 at 10:13

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Yeah, I usually use haynes but I'm not sure if they're available in the US.

thebigbossyboss > zeontestpilot 03/27/2015 at 10:17

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If it's fuel pump related as another commenter suggested put the car in neutral or park (same thing in an auto kind of) and put your revs up to like 3-4k. See if the noise is present. If it is, then it's not the wheel bearing. If the noise is not present go drive around a bit and see if the noise comes back. If it does then it's most likely the wheel bearing.

If it's the fuel pump, catastrophic failure is not so bad. Your car just turns off whenever it goes, so keep your cool and safely steer yourself out of harms way. If it is the wheel bearing catastrophic failure is not so good as it will lock the wheel which makes loss of control likely.

zeontestpilot > Aaron M - MasoFiST 03/27/2015 at 10:18

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Correct, they only made a FWD. It's been the same loudness for thus whole time, really. I'll have to get a friend to drive the car while I sit in the back and figure the source.

zeontestpilot > MazdaMonkey 03/27/2015 at 10:20

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What about high revs period? I was going 20 mph but I got the rpms up to 6k, and there was no sound. Would that be a sufficient test?

RamblinRover Luxury-Yacht > Twingo Tamer - About to descend into project car hell. 03/27/2015 at 10:20

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They're very much available in the US. One might almost say endemic, like an infection.

Twingo Tamer - About to descend into project car hell. > RamblinRover Luxury-Yacht 03/27/2015 at 10:26

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But haynes is excellent.

RamblinRover Luxury-Yacht > Twingo Tamer - About to descend into project car hell. 03/27/2015 at 10:39

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Usually, yes. There are just so many they're like a garrison of very, very technically minded troops in the auto parts store, which makes one wonder if they're up to something.

zeontestpilot > thebigbossyboss 03/27/2015 at 10:45

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When I got off the hwy, I cruised around a bit at 20 mph, the rpm was up to 6k, but I heard nothing.

It also seems to only occur when I'm above 60 mph, nothing lower. Would wheel bearing still only make a sound at high speeds?

Twingo Tamer - About to descend into project car hell. > RamblinRover Luxury-Yacht 03/27/2015 at 10:45

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Making a lot of money is what they're up to, those things are expensive. I buy mine used.

and 100 more > zeontestpilot 03/27/2015 at 10:46

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When's the last time you had an alignment, rotation, & balance done? Also, have you ever had the struts replaced? Could be a tire bouncing due to being out-of-balance, or a blown strut, and the squeak is a rubber bushing that's worn out.

thebigbossyboss > zeontestpilot 03/27/2015 at 10:51

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Yes. A wheel bearing would get louder as you go faster. Sounds like yours is still "pretty" good. You could leave it a little while and see if it gets worse if you'd like.

zeontestpilot > jariten1781 03/27/2015 at 11:04

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I full it up religiously 1/2 or 1/4 of a tank. :).

zeontestpilot > and 100 more 03/27/2015 at 11:09

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Last year sometime. The tired are all new. The front suspension is original, and will be replaced in the summer when I get the money. The rear I think was replaced? The car had a lot of work done to it when i took it in last, so I cant remember it all right now.

zeontestpilot > thebigbossyboss 03/27/2015 at 11:15

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I wouldn't say it gets louder, more than it just appears and stays there. It tends to be the same loudness the entire time, like something is repeatedly rotating around.

thebigbossyboss > zeontestpilot 03/27/2015 at 11:20

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I dunno man. Something rotating around would be a wheel bearing because they do rotate. I cannot say definitively it is that, but if I was you that is the first thing I would ask the mechanic to check.

Or as I said leave it for a while, if in a few weeks it seems to be getting worse and worse and louder and louder than that is it. I would probably leave it for a while yet, but I don't have a baby and am also an idiot of sorts so there's that :P

Mattbob > RamblinRover Luxury-Yacht 03/27/2015 at 11:27

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an infection indeed, like syphilis.

Mattbob > CalzoneGolem 03/27/2015 at 11:28

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or until the wheel falls off!

zeontestpilot > thebigbossyboss 03/27/2015 at 11:30

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I'll probably take it to a few mechanics, see what they say. They figure out what im gonna do. Thanks for your two cents though!

CalzoneGolem > Mattbob 03/27/2015 at 11:36

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Right, no more squeaking then.

Mattbob > CalzoneGolem 03/27/2015 at 11:39

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I've heard them make a sort of grinding noise at speed. A subtle grinding. In my experience, its always my U-Joints that end up squeaking.

thebigbossyboss > zeontestpilot 03/27/2015 at 11:59

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No problem man. I really feel your pain. I had to learn everything myself from a pretty late start so it's really only in the last year or two that I have become somewhat able to get a better handle on the mechanical parts of cars.

jkm7680 > zeontestpilot 03/27/2015 at 14:49

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I had no clue they still made the PT Crusier in 2008.

zeontestpilot > jkm7680 03/27/2015 at 15:49

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Yep, they made them for 10 years. In '06 they redid the interior and exterior, which I think makes it look better. It doesn't have the stupid, gaudy plastic bumpers anymore. it's mechanically the same, but this gen they dropped the GT trim I believe (boooo).

jkm7680 > zeontestpilot 03/27/2015 at 15:54

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I thought they stopped making them in 2006 or something like that, haha. Never change Mopar.

zeontestpilot > jkm7680 03/27/2015 at 15:59

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Ha, when I bought the car, I figured I should know as much as I can about it, :)

jkm7680 > zeontestpilot 03/27/2015 at 15:59

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Haha, that's a good thing!