Hello all. I have a 75 280z. The newest and baffling problem is a steady woo sound from what I believe the valve or head case. It only happens at start up when engine is cold at idle around 1000 rpm. Once warmed up to around 140 degrees it seems to go away. All input will be greatly appreciated.

Please provide more info about your Z. Year, Model, any mods. Then you'll get some replies from our experts. Thanks.

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Keith Hultmark
2009 370Z Touring - Sold (5 years owned)
1993 300ZX - Sold (5 years owned)
1976 Porsche 912E. #163 of 2200 - SOLD (3 years owned)
2018 BMW 330i GT xdrive daily driver
2004 BMW Z4 3.0i ….it is a Z

1975 Datsun 280z

Use a stethoscope to pinpoint the source of the noise. They're about $8 at any automotive store. If you can't get one, use a long screwdriver or metal rod instead. Hold it to your ear and "walk" it around the engine until you find the noise.

*BE CAREFUL*. Don't get your clothes or body parts involved in moving engine parts.

Try the areas of the front case (spinning pulleys/tensioners/belts/fan), the timing chain (bulge at the front of the cam cover) and the thermostat.

When the engine is off, spin and wobble the fan by hand. See if it has any bent vanes or if the bearing sounds weird or lets it wobble.

That year Z had a clutch fan. When it was cold the fan spun at maximum RPM, even at fast idle. As it warmed up, the fan disconnected when it wasn't needed. That may be the "WHOOOOO" noise you're hearing. If it is, it's normal.

Frank

It's a frozen fan clutch. Very common problem.

_________________
John Taddonio
1970 240Z
1977 530Z
1984 300ZXT
zcarnut@hotmail.com
FB: Zccr zcarclubofrochester

That's what I thought (fan clutch). I installed a brand new one last week and still the same .

Clutch fans depend upon proper storage to work correctly. As odd as it sounds, there is only one way to lay a clutch fan during storage to ensure it works OK when you use it again. It must lay flat, face up. Anything else causes the internal oil to collect where it doesn't belong.

There are only 4 screws holding the fan on, but it's a real chore getting them off without damaging the radiator. Then, there's not enough room btwn the fan face and the radiator core to remove the fan.

SO ~ to test your theory, you could loosen and remove the fan belt and run the engine briefly with the fan inoperational to zee if the mystery noise goes away.

Even if it doesn't, the relative "silence" without the whirring fan windstorm would make it easier to locate the noise.

Go point frank I will definitely try that. Thanks