I have a 2005 PT Cruiser non-turbo. A short time back, the tensioner bolt broke on the alternator and after spending several months going back and forth with the dealer, I was finally able to find the correct size bolt to replace it. Shortly afterwards, I began to hear a scraping sound coming from the engine compartment. The sound is sporadic, and only lasts for a short time. The sound only appears to happen when the engine is idling down when coming to a stop, and it doesn’t always do it. It doesn’t make the noise when accelerating, in fact, the noise quits when I accelerate. The noise sounds like metal being drug on concrete, or a grinding sound. Is this a possible bearing going out on the alternator or possibly the AC clutch/bearing? The noise is not present during normal driving conditions, just when the car is almost at a stop and stops as acceleration occurs. I have reached in to see if possibly a loose pulley/bad bearing on the alternator, but there is no slack there. Is it possible that I have the alternator belt too tight, or is this another issue? Does anyone have any ideas? It is driving my wife nuts, which in turn is driving me nuts. Thanks in advance for any help.
Does it happen when your braking or after you let off the brake? Could be brake pads are shot. I would not think it would only happen on deceleration it was a belt driven device.
The radiator cooling fan motor can get quite noisy if the motor bearings are worn/loose. Inspect the motor shaft for play.
Based on the description, I am thinking that the OP may be hearing the ABS activating…assuming that a 2005 PT Cruiser may actually have had ABS.
When ABS activates, it can be described as a “grinding” sound.
If you can get it to happen sitting in the driveway, ask your mechanic to use a mechanic’s stethoscope to narrow down the location. I just use a length of garden hose as my car-stethoscope, Tom and Ray suggest using vacuum hose, but the stethoscopes mechanics use are probably better.
Now about this bolt you mentioned above. It took the dealership several months to determine which is the correct size bolt to use for the alternator mounting bolt? That’s puzzling. I’d be sort of suspicious you still don’t have the correct bolt installed, and that’s what’s causing the problem. It may be that there are certain combinations of rpm and alternator loading that result in a clearance problem involving the alternator and associate pulleys.
Just because there is no slack in a tensioner pulley, alternator bearing, etc does not mean a bearing cannot be faulty. There is obviously some kind of issue due to the fact that a tensioner bolt broke. The odds of a bolt failing due to a metallurgical problem are so infinitesemally small as to not be a factor.
Another possibility is a loose or cracked heat shield on the exhaust.
Let me update my problem. After driving the car around without the family so I could actually hear and pay attention to what was going on, this is what I found. I don’t believe this is caused by a belt, but possibly a bearing. The noise starts when I slowly go forward, foot on the gas/brake or not, there is a grind or popping sound. When I increase speed, the sound stops and there is no noise when at cruising speed. It only appears to be when I am creeping along at a very slow speed, such as when you take your foot off the brake and the car eases forward without stepping on the gas or when I first start pulling off, and again, this isn’t all the time. Is this a wheel bearing, or maybe a bad CV joint? I am puzzled. Thanks for any ideas ahead of time. Oh, and as for the post of the tensioner bolt earlier, the local dealership couldn’t tell me what size it was. I had to call a dealership out of town to get the right size bolt.
To check for a bad bearing, jack the vehicle up so the tire is off the ground. Grab the tire at the 6:00 and 12:00 o-clock positions and try wiggling the tire.
If the tire wiggles that bearing is shot.
Your brake pad wear sensors are rubbing.
Ok, so the car has to be moving to hear the sound. hmmm … @Nevada_545 makes a good point. Be sure to have the brakes checked. You may just need a new set of pads. Another test you can do yourself for ruling in/out a wheel bearing problem is if the noise is considerably worse when turning in one direction vs the other. Worn rear wheel bearings on front wheel drive cars can exhibit this symptom, where the sound is most noticeable at slower speeds, like when driving around in parking lots. The thing that narrows it down further is if the noise is worse when turning in one direction.
A slightly warpped rotor can cause this as irt rubs the pad each time it comes arount at slow speeds. Just jack up the wheels and spin them to check it out.
After jacking the car up to replace a worn tire, I have discovered that the noise is, in fact, a very bad a and loose wheel bearing. Off to the machine shop to have a new one pressed in. Thanks to everyone for the input.