How to check proper coolant circulation....

Does this happen on a cold day as well?

Have you had the radiator flushed and/or rodded recently? What size radiator are you using?

What fan and shroud setup are you running?

Is the engine more than .030" overbored?

I checked flow on the race car by running a garden hose into the radiator cap and connected the top radiator hose to a scrap garden hose and leaving it loose....turn on the water pump (you'd start your engine) and timed how long it took to fill 5 gallon bucket...for me, it took about 20 seconds....a stock water pump will likely be faster...
Oh, you wouldn't get a true flow reading with the thermostat in place...I use a restrictor plate with no thermostat...





Pat
http://www.jps.net/binay/webdocs/strtmstng002_sml.JPG

I don't have the history of what was done to the car before I bought it other than the engine was rebuilt last year in Feb....

To answer your questions from the best of my knowledge:

1. Happens whether it is hot or cold, just takes longer when it is cold out....

2. The radiator might have been flushed when the engine was rebuilt. It hasn't been rodded, and the size of the radiator is stock for a 68 289 along with the original fan, but no shroud.

3. I wasn't told if the engine had been bored or not....the crank was turned ( I guess that's the meaning of a 10/10 crank with standard bore) and a performance cam was put in( only specs on the cam I could get were 260 advertised duration, 224/.465, meaning?).


RJ
68 Diamond Blue Coupe
Sprint Promotion A
289 2bbl with a C4

College Station, TX

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A while ago I was experimenting with the fan blade to achieve better mpg. What I did was take the fan-blade off the pulley and drive the car just as I normally would. I'm not afraid of overheating because I have an auxiliary electric fan that I can switch on and off manually.

The idea behind removing the blade was better fuel economy because the engine wasn't cooled unneccessarily (it was mid winter) and to eliminate the friction of the blade with the air.

I didn't drive the car like this for long because when I was sitting in traffic I constantly had to keep an eye on the temp gauge. After a few minutes of standing still at a traffic light the needle already came dangerously close to the red area. And after driving a somewhat longer stretch everything was OK again.
In the end I resorted to using the aux fan more often that I anticipated. In the end it didn't make any difference in mpg either, so I put the blade back on.
With the blade in place there's no need to keep looking at the temp gauge. After standing still for a while the gauge will have crept up a little, but nowhere near the red area.

I take it for granted that you have the fan blade installed and the belts are correctly tensioned.
The first thing that would come to mind in your case is that your radiator is partially blocked. The best way to flush a rad is to do it upside down. You can do it by sticking a hose in the bottom end and fill up the rest of the hole with a rag. Better is to remove the rad from the engine bay and put it upside down while you flush it.
Then flush the rest of the cooling system. Don't forget to flush the heater core too.
The themostat may also be the culprit. If it sticks closed or partially closed, it will restrict coolant flow.

Another possibility is that you have an air-lock somewhere in the system. Vent the air from cooling system in the highest spots (hoses running over the valve covers).

Then there is the possibility that you increased performance without increasing the cooling system as well...

I have heard before that Mustangs can be chronic overheaters. That's why many fit a higher capacity radiator.
In a stop and go traffic situation I would opt for an electric fan and/or a larger radiator.

<P ID="edit"><FONT SIZE=-1>Edited by HighVoltage on 04/07/01 02:45 PM (server time).</FONT></P>