My newly purchased 1970 250c is driving me crazy. From the transmission/clutch area I get a unrelenting rpm-dependent chirping sound. It kinda sounds like an accessory belt, but you can make it go away with just a slight amount of pressure on the clutch pedal. It makes this sound in every gear and neutral with the clutch fully out. So much as breath on the clutch pedal and silence can be enjoyed again, this trick works in every gear and neutral.

Now I initially thought of the throwout bearing, and I think it's likely related to the problem but I don't think it's gone bad as the throwout bearing really only does work when the clutch is depressed. When it's not depressed the throwout really doesn't have any work to do and should happily spin on it's shaft. Every bad throwout bearing situation I've ever seen has been a throwout that makes terrible sounds when the clutch pedal is depressed, this is acting in the exact opposite.

I thought briefly of the clutch pilot bearing, but it really only does work when the clutch is spinning at a different rate than the flywheel, so that rules out anytime I'm in gear and driving/chirping down the road.

So right now I'm at a loss. I'm unfamiliar with the car and annoyed. Because my radio is out for refurbishment I can't even drown out the sound. If you have any ideas on what to check or perhaps adjust, I'd love to hear it. I don't even know if there is a way to inspect the clutch area, so if you know how to do that I'd love to hear it as well. Thanks.

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Own:
1970 Mercedes 250c, 1976 International Scout II, 1982 Mercedes 240d, 1997 Honda Accord Wagon, 1998 Acura Integra Type-R, 2009 Mazda5.
Owned:
1974 International 100 pickup, 1975 International Scout II, 1981 Mercedes 240d, 1985 Mercedes 300SD, 1988 Honda Accord, 1988 Ford Thunderbird, 1991 Honda Accord, 1996 Geo Metro, 1996 Ford F150, 1996 Dodge Grand Caravan, 1997 Honda Accord, 2003 Acura TL-S, 2003 Yamaha V-star.

did you check the transmission oil level. It may also be a rattling clutch friction plate hub

__________________
2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

I have not thought to check the transmission oil level. Do you know what transmission model would be in the car? It's a four-speed manual and I'm assuming Getrag something or rather. I know the transmission was replaced less than 1500 miles ago, but it was 1997 or so when that work was completed.

__________________
Own:
1970 Mercedes 250c, 1976 International Scout II, 1982 Mercedes 240d, 1997 Honda Accord Wagon, 1998 Acura Integra Type-R, 2009 Mazda5.
Owned:
1974 International 100 pickup, 1975 International Scout II, 1981 Mercedes 240d, 1985 Mercedes 300SD, 1988 Honda Accord, 1988 Ford Thunderbird, 1991 Honda Accord, 1996 Geo Metro, 1996 Ford F150, 1996 Dodge Grand Caravan, 1997 Honda Accord, 2003 Acura TL-S, 2003 Yamaha V-star.

The sound you describe is indeed from the throwout bearing. The bearing "runs" with zero clearance when released. A new bearing will spin freely, and quietly at zero clearance, however an old and somewhat sticky bearing will not be driven at engine speed when released (zero clearance), but will instead slip with respect to the fingers of the pressure plate, causing the audible "chirp".

The trans is a G76/18. Fill level is to the upper plug on the right side. ATF

So is there any solution other than pulling the transmission/replacing the throwout? Can I inspect it easily?

__________________
Own:
1970 Mercedes 250c, 1976 International Scout II, 1982 Mercedes 240d, 1997 Honda Accord Wagon, 1998 Acura Integra Type-R, 2009 Mazda5.
Owned:
1974 International 100 pickup, 1975 International Scout II, 1981 Mercedes 240d, 1985 Mercedes 300SD, 1988 Honda Accord, 1988 Ford Thunderbird, 1991 Honda Accord, 1996 Geo Metro, 1996 Ford F150, 1996 Dodge Grand Caravan, 1997 Honda Accord, 2003 Acura TL-S, 2003 Yamaha V-star.

No, and No.

would not a clutch thrust bearing cause loud screeching under load if it were not freely spinning.

but it maybe that way, In redoing manual transmission clutches I had experience of this noise when the transmission fluid was low and cold - hence I posted it.

__________________
2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)