Hello , yesterday we installed a new aluminum rad 3 core and a 16" puller electric fan and a new thermostat on my sons 69 Mustang 351 w .It's running hotter than before .We're wondering if the fan is not enough pull for the three core or what the heck is going on . Any of you guys had problems like this ?
Thanks
Gary

 

What were you running before? If you were running a factory fan you could try putting that back on and see if it runs any cooler an if it does then you know that your electric fan doesn't have enough snot.

 

does it get hot above 50mph or only in traffic / below 50mph?

When did it last work right?

 

make sure that you have the fan spinning the right way, i have seen people get the polarity incorrect and end up pushing hot air from the engine bay out over the radiator

 

Yes it's going the right way we can feel a lot of air being pulled through .
Thanks for your reply .

 

This car has always run a little hot idling mainly city traffic . Thanks

 

It had a stock rad with a flex fan , we may try a stock fan or something like it . Thanks .

 

if its fine above 50mph then the issue is almost certainly a fan issue and independent of the rest of the cooling system which is probably working fine.

-Gun

 

When I was running my 20" radiator I never could get the cooling issue to completely go away but once I jumped up to the 24" the problems all disappeared.

I use a FoMoco factory flex fan I pulled from a 77 LTD and the proper shroud, I got it from CJ Pony and even now with the AC condenser in front of the radiator, it never gets above 190, I don't care how long it idles.

 

There's not much information here to make anything but general suggestions. Let's try this:

What are you measuring the temperature with? A factory gauge, aftermarket, how?

What temperature was it running before, and after? "Hotter" isn't that helpful.

Detail the changes: Same type and temp thermostat? Same hoses, or new hoses, and is there an anti-collapse spring inside the lower hose? Does the system include an expansion tank and is it just overflow, or is that pressure cap on the tank making it a true expansion tank? Pressure cap rating? Radiator differences. Fan differences. Before/after

Water pump: Was this changed? If not, when as the last time?

Coolant type? Ratio? Did you use distilled water and pre-mix? And did you use a wetting agent?

Does the car have AC and if so, are the condenser coils clean and flowing air?

How did you bleed the air from your system? Air pockets are a very common cause of over heating.

Before filling the system with coolant, did you check for pressure leaks and if so what system did you use?

I realize all this sounds like too much.. making it too complex.. but for the last 25 years I've been running later model mustangs and the cooling systems have almost evolved to the point where you need a degree to troubleshoot them. And in the process you learn most of this stuff applies to early model cars as well, but perhaps not as critical.. Properly setup an older car can run as cool and reliable in traffic as a new car.

One of the changes in how I approached cooling systems was to use an . I'd pre-mix my coolant, distilled water, and wetting agent into a 5-gallon bucket, pressurize the system to check for leaks, and then suck it in until it's filled to a perfect level with no air pockets or need to bleed. I've used this on cars with multiple radiators, or old style mustangs, and its great. I especially like how it reveals pressure leaks. It will even reveal a head gasket issue at a basic level, though you need to confirm head gasket issues. Curious to your responses.