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irregular metalic tapping-rattling noise


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Hello. I'm new to the forum, although I've visited a couple of times. Maybe someone can help me with my 93 Legacy, FWD, 148,000 mi. Last night it started making an irregular, metallic sounding tapping/rattling noise that seems to be coming from the lower part of the engine. By irregular I mean it's not rhythmic, it varies from several times a second to maybe a second or two between taps. I found that I was a quart low on oil, but adding a quart didn’t seem to make a difference - although it has been just about 2,000 miles and 2 months since my last oil change, and I never noticed using that much oil before. The noise wasn't there this morning when the engine was cold but I heard it again when I arrived at work, about 9 miles. I just tried changing the RPMs at idle, and above about 1,000-1,500 RPM I think it goes away, but I’m not positive because of the regular engine noise. When I let the idle back down, however, it started to make a racket. After doing that a few times, trying to find the point at which the noise abates, it stopped even at the regular idle of about 400 RPM, but I don’t suppose that magically fixed it for good. No idiot lights, temperature gauge is fine, seems to run fine - acceleration, etc., all normal. Oil looks fairly clean - no signs of coolant in it, and the coolant doesn’t look oily. Maybe the oil pump is bad? I'm hoping this sounds very simple to those who know more about engines than I do - maybe not easy or inexpensive, but simple. ... Sorry for the long post - I wanted to include as much info as possible so the resident experts can share their wisdom. :o

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Sounds to my ear like you have a loose heat shield or heat shields.

Since this is the least costly possibility, you could have a listen under the car while someone puts the engine thru the range of rpm where you hear the sound.

Hope it's only that.

In my limited experience, serious mechanical damage almost always produce a rythmic sound.

Good luck!

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I was thinking about maybe the heat shield after I posted, but then I had to drive home to let my son back in the house after he locked himself out. The whole drive home the noise wasn't there. Pulling in the driveway I heard a strange, squeeling-like sound. When I was ready to leave I restarted the car and started backing out when I heard more strange sounds, hard to describe, and the engine started to stall. Checked the oil and it was still OK, then started it again with the hood up and saw a small amount of smoke rising out of the area of the (not sure of terminology here) main engine pulley, where the alternator and a/c belt converge. So I left it in the driveway and had my son drive me back to work. Any ideas?

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You may have a bearing failing - either in the alternator, power steering pump if its external or in the timing belt drive or water pump if it is internal.

 

You can pull off your belts and rotate the alternator, power steering pump and AC compressor to see if they are binding. You can also start the car with the belts off (alternator light will be on) and see if the noise is gone. If not, you may have to pull the crank pulley and timing belt covers to investigate further.

 

I would not drive it until you can identify the cause of the smoke.

 

Gary

 

PS - just bought a 93 Legacy making a similar noise. Will post when I pull it apart - I think mine is a bad water pump or idler bearing in the timing belt drive.

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How much smoke? When the diode bridge in the alternator goes, there will be the distinct smell of burned electronics, and a small amount of smoke. Not thick, not belching, just like an idle cigarette.

 

There is likely to be an audible whine when the diodes go, because the AC current isn't being rectified. Should be easy to hear through the speakers with the radio on.

 

It could also be a seizing water pump bearing, which will cause the cambelt to drag on the water pump drive wheel, and eventually smoke - burning rubber smell.

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I hope it's an external item with a bad bearing and not an internal one. We (father-in-law and I) replaced the timing belt late last summer, but that didn't lead to any problems. However, it's been eating alternators at the rate of a couple a year (cheap but lifetime warranted Autozone ones, so the replacements are free). Maybe that's related - if the belt was too tight and the bearing on something else on the same belt was ready to go bad. Guess we'll be doing some investigating over the weekend. Thanks for the suggestions so far.

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Setright - not much smoke, but it was coming from down by the crankshaft pulley, not the alternator. But the belts definitely were turning. I don't remember any harsh electronic or rubber smell, but there may not have been enough to really notice.

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There are at least 2, maybe 3 (my memory fails me) idlers in the timing belt loop. When I did the belt in my 90 legacy, the bearings in 2 of these idlers were pretty dry. I popped the grease seals and relubricated them. This option will not work in your case - if it is a failed bearing, it is already toast.

 

Getting to the timing belt is pretty easy. The only trick is getting the crank pulley off. I thread a coat hanger twice through the one of the holes in the cranl pulley and wrap it around the alternator mounting bracket.

 

Once the pulley is off, it's just a matter of unscrewing the covers. Sometimes the lower screws do not come out - the nut insert breaks loose instead. If so, just pry it off at the failed nut, then remove it from the cover and epoxy it back in place.

 

Working on the timing belt is pretty straight forward, too - the only trick is the belt tensioner. It needs to be removed, compressed in a vice and locked in the compressed position with a small pin or drill bit.

 

Good luck!

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Smoke coming from the timing belt covers + mechanical noises is a bad thing.

Have a look there ASAP. Like someone said, it's probably something mechanical in there (idler pulley, water pump, tensioner, crank or cam bearing) that's going bad and that could mean broken timing belt and being stranded somewhere.

The good news is you have a 2.2L engine which is not interferential. A broken belt would not ruin the engine.

Good luck!

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I had an afterthought just after writing the previous post. Another possibility is maybe you did'nt torque the crank pulley bolt tight enough when you did the belt last summer (60 ftlbs in some manual when it should be more than a 100 ftlbs according to experts at CCR) and the pulley is loose and slowly eating away at the crank = noise, heat, smoke...

Look at the pulley when the engine is idling to see if it's wobbling.

Also slack the drive belt and pull and push it with some force to see if it's loose.

Just an idea.

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Turns out it was the water pump. Thanks for everyone's input. Luckily one of the local dealers has Saturday hours for parts - I figured I should go with a factory water pump, not Cheapyzone, because I only want to do this once. The only problems I had were, one, I overtorqued one of the water pump bolts and it sheared (and yes, I know overtorquing will compress the gasket), but luckily it wasn't hard to remove and a local parts store had a perfect match; and two, I had a tough time getting trapped air out of the cooling system. I don't know if this is the preferred method, but I ended up putting the front up on ramps to help bleed the air out through the bleeding screw.

 

Thanks again for everyone who shared their thoughts.

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