'98 S70: Screeching when Reving at Cold Start

[WhatAmIDoing]

I suppose that could be the problem, but does anyone have an actual recording of this "moaning noise"? Some people have also described it as a buzzing noise (which it is not). I have not been able to do any work on the car due to bad weather, and high winds have ruined every recording I've tried to take. If only I had access to a garage.

I'm not convinced the problem is an oil thermostat. Even on warm days it makes the noise. Only when the outside temp is over 27 Celsius and I'm parked in full sunlight do I usually not notice the noise (but sometimes in the cold it goes away too). And threads have said they only hear it at idle, but I'm only hearing it above 1000rpm.

I had a brief break today to try and look at the serpentine belt again. I noticed a lot of rubber dust and what felt like some oil/grease on the tensioner pulley (stained my hands really black). I did not notice this on any of the other pulleys. I can also turn the idler pulley some without relieving tension on the belt. So maybe the tensioner is bad?

edit: sorry I'm not providing a lot of helpful information, but the weather has not been cooperating and I do not have access to a garage.

[erikv11]

I'm betting the farm on oil cooler thermostat. Unless it's that serp belt, which I am betting the other farm on.

[bmdubya1198]

I took a video yesterday, but I'm not sure if it actually caught anything. I'll post it if it's audible.
There is a brief period once I'm already driving (maybe a mile down the road) where it gets VERY loud and low frequency, then gets higher in frequency and goes away.
Mine is also noisy on warmer days. Here in NC we've been having plenty of 70+ degree days, and I've started the car for the first time of the day when it's already at or above 70, and it makes the noise.
I've also already replaced my serp belt and tensioner. The tensioner was used, but it feels nice and tight still.

[abscate]

I'm still bettng eriks farm on the oil thermostat

[1998v70xcbill]

The oil thermostat opens at a temperature way above outside temp. So you can get the noise in the summer. The noise will increase with oil pressure (1000 rpm). The noise always goes away after the oil warms up.
Start the car cold without the serpentine belt, and see if you get the noise. Spin the pulleys with the belt off, to check bearings.

The thermostat is (i think) located just behind the crank pulley. (If your oil cooler is in the radiator).
This drove me nuts for awhile. My noise sounded like a low frequency bearing noise.

[1998v70xcbill]

The oil thermostat opens at a temperature way above outside temp. So you can get the noise in the summer. The noise will increase with oil pressure (1000 rpm). The noise always goes away after the oil warms up.
Start the car cold without the serpentine belt, and see if you get the noise. Spin the pulleys with the belt off, to check bearings.

The thermostat is (i think) located just behind the crank pulley. (If your oil cooler is in the radiator).
This drove me nuts for awhile. My noise sounded like a low frequency bearing noise.

[scot850]

Both suggestions are good suggestions. Quickest way to see if either is correct is to remove the serpentine belt and start the car up from cold. My serpentine belt made a horrible bearing failing type noise when it got coolant on it when the top radiator connector broke off. I had to clean all the pulleys and replace the belt and it went quiet. However, the belt was noisy all the time which makes me think that may not be the issue unless when the engine warms up it grips better. Other option is the serpentine belt tensioner is maybe starting to go.

On the oil cooler thermostat, they do get noisy and make a weird noise, but be aware I believe they are now obsolete as a part. Used may be the only way to go. The thermostat is closed when cold and if it is leaking it kind of whistles until it opens when the oil heats up.

Other option is to swap the oil pan out for a later one with the oil cooler on the back and get a blanking plate from the same engine for the old cooler thermostat under the crank pulley. I may have an old style thermostat kicking around in the garage, but as it was donated to my stash I have no idea if it is good or not. Free but for shipping costs if I can find it. PM if you want to take a chance on it.

Neil.

[WhatAmIDoing]

So, I got a friend to help me this morning, and guess what... no noise... well, not at first like usual. Ambient temp was around 4-5C. Noise showed up after the car had started to warm up (maybe there is a min temp?). Could only be heard when my friend stepped on the accelerator. Noise was definitely coming from the passenger side (closer to the radiator I think). I now believe pretty firmly its the serpentine belt or a bad pulley. Noise was only heard for about 10-15 seconds, and was not quite the same as heard before (higher pitch and quieter). I manged to get a video which I will try to put up shortly. It's starting to get into a pattern of every other time I start the car in the morning.

I also pulled off the timing belt cover to see how honest the PO was about doing the timing belt, rollers, tensioner, and water pump. He claims it was done around 200-210k. The water pump looks new-er, but the tensioner definitely looks old and rusty (how easily do these rust?). The friction surface looks and feels kind of like sandpaper, is that normal? Pictures below. Debating if I should have a real mechanic check out all the timing parts and put a new belt on just to be safe.

[bmdubya1198]

So, I got a friend to help me this morning, and guess what... no noise... well, not at first like usual. Ambient temp was around 4-5C. Noise showed up after the car had started to warm up (maybe there is a min temp?). Could only be heard when my friend stepped on the accelerator. Noise was definitely coming from the passenger side (closer to the radiator I think). I now believe pretty firmly its the serpentine belt or a bad pulley. Noise was only heard for about 10-15 seconds, and was not quite the same as heard before (higher pitch and quieter). I manged to get a video which I will try to put up shortly. It's starting to get into a pattern of every other time I start the car in the morning.

I also pulled off the timing belt cover to see how honest the PO was about doing the timing belt, rollers, tensioner, and water pump. He claims it was done around 200-210k. The water pump looks new-er, but the tensioner definitely looks old and rusty (how easily do these rust?). The friction surface looks and feels kind of like sandpaper, is that normal? Pictures below. Debating if I should have a real mechanic check out all the timing parts and put a new belt on just to be safe.

Everything in there looks fine to me. Mine may have a little bit less rust, but it looks similar. Then again, my car has been in the Carolinas since the day it was brought to the States.

[bmdubya1198]

You can hear it a little bit this video I took: