the_lane

Hi,

Been driving my car all week (50 miles per day). A lot of it in traffic.

Today, temp gauage started acting wierd.

Driving steady (40 - 50mph) temp was at 1/4 on guage.

When I can to a stop, guage would creep up to 3/4 - took about 1 minute. When I started going again, it would drop right back down.

Any thoughts?

It is raining now so, haven't had a chance to look under the hood.

Boofers

You could start by checking your clutch fan. Spin it by hand as hard as you can & if it turns 360 degrees or more its probably worn out.

the_lane

what is the clutch fan? (sorry!!)

It is an auto btw

rcread

Take a look to make sure you haven't lost a piece of seal between the radiator and fan shroud.

Boofers

No need to apologize! We all help each other out here.

On the front of your engine there is a fan, it is driven by a belt. When the engine runs the fan spins and draws air through the radiator to cool the coolant. This is your clutch fan.

As your car moves faster, more air flows freely through the rad. This free flowing air can adequately cool the rad so there is less need to have the fan spinning. That is where the clutch comes in; when enough free air flows the clutch 'disengages' the fan from the engine, which frees up horsepower & improves fuel economy because the there is less load on the engine.

If the clutch is worn out (too loose) what will happen is the fan doesn't spin fast enough when you need it the most - when the car is not moving. This is why it looks to me like your clutch fan is worn out, not enough cooling at a stop.

When you spin the fan by hand (with the engine off of course) it should stop after about 180 to 270 degrees. If it spins more the clutch is worn, the more it spins the more worn the clutch is. This failure is not uncommon for these fans.

There are different types of clutch fans so hopefully you have the one I am talking about. What year is your vette?

the_lane

It is a 1979

David Ey

Where do you live? I will have a new clutch you can have for shipping in a few weeks if you can wait.
Well, almost new....less than 250 miles on it.

the_lane

Actually, I am in the UK!

I shall check my clutch fan in the morning and, let you know how I get on!

SanDiegoPaul

It is a FAN CLUTCH, not the other way around. (there's a clutch on the fan, but not a fan on the clutch!) It is the device that allows the fan to freewheel when necessary.

My first thought though, is the thermostat. It may be sticking every now and then causing the temp to fluctuate widely.

Boofers

So Lane have you had a chance to check your clutch fan yet?

MILO

Here's how I solved my heating issues with a fan clutch. The spin test only works with a RPM regulated fan cutch. For a thermostatic fan clutch, like our 1979's, there really is no test except what I posted. PS: I'm going to an electric fan. http://forums.corvetteforum.com/show...3&forum_id=119

Good Luck

TopGunn

You might want to check the radiator fluid level before you go too far into things.

Bill

Star79

simple things first! Your symptoms are the same as mine were after winter storage this year, added water/coolant all was fine.