overheating

**Jim Trekell (22375)** · June 25, 2006, 10:32 AM

Re: overheating

John at idle your vacuum advance unit should advance the ignition timing the maximum amount the vacuum can is manufactured for. If it is not doing it, this is the most likely the cause of the rise in temp rise when you are letting the engine run. If you remove the vacuum line from the vacuum advance at normal idle speed, your engine should loose rpm. If it does not and you have full time vacuum to the unit the vacuum advance unit has ruptured and you need a new one.

**Duke Williams (22045)** · June 25, 2006, 11:19 AM

Re: overheating

When you remove the hose from the vacuum advance, plug it! Before you plug it revs will actually increase because it's a vacuum leak.

Total idle timing with the vacuum can connected should be 16 plus whatever your initial is set at.

Page down and read the thread "'66 SB vacuum advance question", and post the code stamped on the bracket.

When cold (engine not running) you should be able to easily turn the fan by hand. After shutdown with the temp at 200, it should offer much more resistance. That's a basic functional test for the fan clutch.

Duke

**Bill Richards** · June 25, 2006, 01:07 PM

Re: overheating

Duke, seems like my fan clutch works exactly opposite as you described, stiff when cold and loose when hot. It`s brand new as well. What gives?
Bill

**Duke Williams (22045)** · June 25, 2006, 01:19 PM

Re: overheating

Did you read the thread I refered to? If so, you should have some ideas, like:

What's the vacuum can ID number?

Does it meet spec?

Does it see full manifold vacuum at idle?

How about the the dist. no.? Is it correct for your engine. Does the centrifugal meet spec?

What is the initial timing spec for your engine and where is it set?

Duke

**Duke Williams (22045)** · June 25, 2006, 01:40 PM

Re: overheating

Sounds to me like it is not functioning properly. The fan clutch thermostat keys off rediator exit air temperature. A high coolant temperature the exit air should be hot enough to tighten the clutch.

You need to talk to the vendor who sold you the fan, but first check that the fan is installed to pull air from the front to the rear. I have heard reports of fans being installed "backwards" so they push air through the radiator from the rear, which will obviously cause problems.

Duke

**John Hinckley (29964)** · June 25, 2006, 04:00 PM

Re: overheating

Is the shroud in place? Is the fan positioned so the blade tips are half-in/half-out of the rear edge of the shroud? How "full" is the expansion tank - it should only be half-full, cold. If you "top it off", there's no space for coolant to expand when it heats up and it WILL "puke" out the overflow.

**John Orefice (30543)** · June 25, 2006, 05:31 PM

Re: overheating

Hi Guys
The shroud is in place. The fan and clutch are original and have not been rebuilt. I think I had the expansion tank full and that caused the leaking.But the gauge still reads up in the 200 plus degrees.One guy here mentioned the fan should turn harder when cold and the other guy mentioned it should turn harder hot. Who is right? I always believed it should turn harder when hot so it can pull more air. I'll have to check mine hot and cold. What would the vacuum can have anything to do with over heating? I thought that can was for the windshield washers. Well anyways thanks to all for responses..Does anyone know who rebuilds the fan clutches in I need it done?

Thanks...........John

**Duke Williams (22045)** · June 25, 2006, 06:36 PM

Re: overheating

The "vacuum can" I was referring to is the "vacuum advance control" on the distributor. From now on I will refer to it as "VAC".

The nearby thread explains for the zillionth time why an inoperable or improper VAC will cause overheating.

Duke

**John Orefice (30543)** · June 25, 2006, 06:57 PM

Thanks Duke, i'll read that other post *NM*

overheating

overheating

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