screeching noise on corolla with 7a-fe engine

hi,
car is a 2001 corolla with 7a-fe engine, manual trans, 90,000 km on the odo. Made in Brazil, last year for the 7a-fe engine.
bought this car last month. It is impeccable, but it makes a very irritating noise:
When engine is cold (room temperature), it starts ok, no unusual noise, but after about 20 seconds, it starts making a screeching high pitched noise that gradually goes away after a couple minutes. If the engine is warm, it does not make any noise. After the noise goes away, it is the quietest car engine I've owned. Engine responsiveness seems ok, no change while it makes "the noise". Power steering also works with no problems. Noise gets louder following engine speed (rpm). Steering right and left does not change noise in any way. It definitely doesn't sound like slipping belts, it is a metallic screeching noise... What really puzzles me is that it only starts making the noise about 20 seconds after the engine is started and only with cold engine!!
What I already did: I replaced all the belts and the hi-pressure hose from power steering. First, the mechanic wanted me to change the hose, it wasn't the original hose toyota put in there back in 2001. Changed it along with all power steering fluid, no effect on noise. Then he claimed that this was belt/pulley related, I replaced all the belts and the noise is still there. Bearings related to these belts were checked and are all good. It's getting expensive to track the failure by replacing parts!
I am very aware that noises are hard problems to diagnose through writing, but if this problem sounds (no pun intended!!) familiar to anyone, I will be glad if you could give me pointers about what to look for. I really do not want to be stranded late at night on a deserted hwy (nobody wants, right?).
thanks and hope you all have a good week
-- Tiago
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Tiago Rocha wrote:

Take all the belts off and start it. Then you will know whether it is belt / accessory noise or engine noise. When you say "I" do you mean you or your mech/tech?
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Some stuff I did, some, the mech did... I don't really trust mechs, they are always trying to diagnose by swapping parts :-( Mech replaced the hose and checked the bearings, I replaced the belts, but I did not start engine w/o belts. Will try that... If it's belt, why, then, it only start making noise after a few seconds after engine is started? This does not make any sense (to me at least)!
-- Tiago
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On Tue, 9 Sep 2008 08:36:35 -0700 (PDT), Tiago Rocha

Probably a bearing. They can squeal when cold. Try using a stethoscope when the squeal occurs. Eventually the bearing will get worse. I had a water pump weep hole leak a little water on the belt when cold causing belt squeal for a few seconds after starting, then all evidence would disappear. Took about a week for the leak to get bad enough to show up on the ground under the car. That was pretty flukey, though.
--Vic
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Tiago Rocha wrote:

There is a pretty simple answer to that. That is when the most load is on the belt from the altenator. When starting cold is when the most drain on the battery plus you may have a battery that is losing some charge while sitting. A few seconds delay before going into maximum charge is normal. Also the belts are a little stiffer when cold and that might also contribute. It could also be a bearing connected to the belt (idler or altenator). What type of belt drives the altenator?
-jim

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jim wrote:

Hmm, now, that you mention it, it makes sense... It might be a bearing, even though the mech I hired to check it reassured the bearings are good, he used a stethoscope. He suggested that "when the belts are hot, they get softer and because of that there's no noise, maybe you have pulley damage", but I don't buy it, the pulleys doesn't look damaged or bent, or out of position or anything. When engine is hot it doesn't make the noise at all, even if I start/stop the engine multiple times. I don't think that I have anything that drains the battery when engine is off, even the radio is switched off automatically when I remove the ignition key, only thing that works w/ o ignition key on is headlight, interior light and trunk light, that last I double checked and it is turning off when trunk lid is down, but it's easy to confirm a parasite battery drain with a simple multimeter. Will check that too.
The belts on this car are V belts, three of them, including the one that drive the alternator.
-- Tiago
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That's the way to do it, but the problem is that there are a lot of things with bearings on them.
If you have a bearing that is failing, either on a belt tensioner, or a water pump, or the AC compressor or alternator, you should be able to tell with a hose stuck in your ear. Maybe not, but probably.
Also, if you squirt a little Super-Lube into the thing while it's running and the noise goes away, you have found the problem.
He suggested that "when the

It can happen. It's also possible that changing to a different brand of belt could fix everything, if it's a belt slipping problem.
Sometimes pulleys with rough surfaces get smoothed out and they slip a bit more. They can sometimes be roughed up with sandpaper.

This is good because it means you can take them off one at a time, or put a little belt soap on them one at a time, and see if one of them is at fault. --scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

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On Mon, 8 Sep 2008 13:22:13 -0700 (PDT), Tiago Rocha

What you describe is a classic symptom for a belt slipping at the alternator. When you first start the car the alternator is under heavy load recharging the battery. Once the battery is topped off again the load drops so the alternator isn't working so hard and the belt quits slipping. If you have already replaced the belt with a quality belt I would check the tensioner to make sure it is working properly. Also make sure the belt isn't getting oil or water dripped on it over night by something else that is leaking.
Steve B.
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Does that engine have a timing belt? Check the timing belt tensioner pulley. It is probably hidden under the timing belt cover, and hard to get to. It's not the same thing as an accessory belt pulley!
Your description and symptoms are very close to mine from last winter, right down to the start-up interval. Installing a new tensioner pulley worked like a charm.
Furthermore, I will hazard a guess that your vehicle has 80K to 160K miles on it, and to your knowledge the timing belt tensioner pulley has never been changed or looked at. Let us know! ;-)
--Dave
Tiago Rocha wrote:

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That was the only bearing that wasn't inspected... Might be it.
Car has almost 90 thousand kilometers (88600 to be more accurate) and that translates to roughly 56 thousand miles. Accordingly to maintenance schedule, I still have many miles before timing belt change deadline, but close inspection won't hurt, right? I am *sure* that the timing belt cover was never ever removed from where it is... :-)
Thanks for the help!
-- Tiago
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Tiago Rocha wrote:

Paul's previous suggestion to take off all the outside belts and start it is good. Do this first because it's easy and a clean diagnosis. Do it only on a cold engine, and of course don't run it up to hot without the water pump turning.
I do not know your engine. On my Geo Metro I had to remove the following in order, to be able to change the tensioner pulley:
1. Accessory belt. 2. Crankshaft pulley. 3. Timing belt cover. 4. Timing belt.
(4) meant that I had to re-align the cam shaft sprocket on assembly, and I screwed it up and had trouble getting it re-aligned. Mark the crank sprocket and the cam shaft sprocket very carefully before disassembling, and follow the book instructions for cam shaft timing. My mistake was I thought I could eyeball it without markings, and I was wrong.
The conventional wisdom on timing belts, I think, is to put a new one in whenever you are inside that cover, unless the old one is almost new. They are inexpensive compared to the cost of getting inside.
Also this far in, there were a number of bolts that required precise torque. So getting to that pulley is a bigger job than you might think, but a good one for do it yourself, with time and patience.
--Dave
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