overheating issue

zwoman · Jul 19, 2009

My 68 is running very hot. The gauge pegged and would sometimes drop back down so I thought maybe the gauge was failing (suggestion from a different post). Put a mechanical gauge on and disconnected the original. When idoling it warms up to 190-195 and the thermostat begins circulating water in the radiator. It remained in the 190 range. Took it out for a road test and as soon as there is a load, the temp climbs all the way to 245 and it boils out into the overflow What next?

2+2GT · Jul 19, 2009

Sounds like you have the correct thermostat, and it is operating correctly. It also sounds like your cooling system can't handle the heat. has your engine been bored oversize? If so, a 3-row radiator is mandatory, as is a fan shroud and upgrade fan, such as rigid six-blade fan or better, a thermostatic clutch fan. A valve in the hose supplying coolant to the heater should have a vacuum shutoff valve for an AC car, make sure it's working. If you don't have AC, a manual valve in this hose will improve cooling efficiency.

First check to make sure the radiator isn't just clogged with gunk. It was that simple on a car I had years ago.

zwoman · Jul 19, 2009

Thanks but...

The radiator is less than two years old and this was not an issue from the get-go so I don't think it is the radiator. I'm wondering if the thermostat is not opening all the way (Am I just grasping at straws?). Maybe just enough to circulate the water but not cooling sufficiently???? HELP

2+2GT · Jul 19, 2009

zwoman said:
The radiator is less than two years old and this was not an issue from the get-go so I don't think it is the radiator. I'm wondering if the thermostat is not opening all the way (Am I just grasping at straws?). Maybe just enough to circulate the water but not cooling sufficiently???? HELP

Probly grasping. If the thermostat opens asi does at 190, it would have to somehow jam closed after you hit the road to drive. It's cheap, though, get a real Ford one, 190° stainless with an air bleed valve to make putting the coolant in easy. If that doesn't do it, start on my first list.

Platonic Solid · Jul 19, 2009

It might help if you answer 2+2GT's questions from your previous thread of the same topic:

1. Is your radiator a 2 row or 3 row?

2. Do you have a fan shroud?

Also, have you solved the carb/idle problem from your talk section thread?

zwoman · Jul 20, 2009

how do you know how many rows are in your radiator? No shroud. Wouldn't it overheat just sitting there if that was the problem? Regarding the carb/idle issue.....I have an Autolite 2100 on order. Thanks.

mhjo · Jul 20, 2009

2+2GT said:
. A valve in the hose supplying coolant to the heater should have a vacuum shutoff valve for an AC car, make sure it's working. If you don't have AC, a manual valve in this hose will improve cooling efficiency.

First check to make sure the radiator isn't just clogged with gunk. It was that simple on a car I had years ago.

Can you explain this more detailed? Where can I get this? Pic?
(I have AC in my car, but no shutoff valve)

Platonic Solid · Jul 20, 2009

mhjo said:
Can you explain this more detailed? Where can I get this? Pic?
(I have AC in my car, but no shutoff valve)

Picture links to part description:

Platonic Solid · Jul 20, 2009

zwoman said:
how do you know how many rows are in your radiator?

Open the radiator cap and count one row of visible tubes side to side.

S-Car-Go · Jul 20, 2009

With the car warmed up and idling, feel the FRONT of the radiator fins for hot or cold spots. You may have a partialy clogged radiator. Even if the radiator is only 2 years old, it can still catch junk from your motor.

BTW, how's the tune? Could timing be off?

mhjo · Jul 20, 2009

Platonic Solid said:
Picture links to part description:

OK. What does it do, and how will it contribute to better cooling?

Platonic Solid · Jul 20, 2009

mhjo said:
OK. What does it do, and how will it contribute to better cooling?

I always thought it was just to shut off the hot coolant to the heater-core on A/C cars so the evaporator-coil and heater-core weren't fighting against each other.

2+2GT will have to explain how shutting the coolant flow to the heater-core off improves engine cooling. Makes no sense to me.

I always though one method of getting a little extra cooling was to turn the heat UP (thus opening this valve) and turn the heater fan on high.

2+2GT · Jul 20, 2009

mhjo said:
OK. What does it do, and how will it contribute to better cooling?

The manual shutoff valve functions similarly to the automatic valve used on factory AC cars. Any coolant that goes to the heater when you aren't using it goes straight back into the engine, reducing the efficiency of the cooling system. By placing a valve in the hose from the intake manifold to the firewall, you increase the amount of coolant that actually gets to the radiator.

2+2GT · Jul 20, 2009

2+2GT said:
The manual shutoff valve functions similarly to the automatic valve used on factory AC cars. Any coolant that goes to the heater when you aren't using it goes straight back into the engine, reducing the efficiency of the cooling system. By placing a valve in the hose from the intake manifold to the firewall, you increase the amount of coolant that actually gets to the radiator.

I always though one method of getting a little extra cooling was to turn the heat UP (thus opening this valve) and turn the heater fan on high.

That increases cooling, but not very efficiently, and results in cooking you and your wife who is going to be a lot less likely to want to go to cruise night after you've cooked her. Send that hot coolant to the radiator where it can do more good.

BarnStang · Jul 20, 2009

Make sure the lower radiator hose isn't collapsing shut at higher rpms. THere should be a spring in the bottom hose to prevent this. You can run the throttle up and hold it and watch the hose to see if that's happening. Something to check.

Platonic Solid · Jul 20, 2009

BarnStang said:
Make sure the lower radiator hose isn't collapsing shut at higher rpms. THere should be a spring in the bottom hose to prevent this. You can run the throttle up and hold it and watch the hose to see if that's happening. Something to check.

And if the spring is missing, good luck finding a replacement. I ended up having to purchase one of those universal hoses just so I could cut it in half to get the spring out.

zwoman · Aug 2, 2009

YEAH:l That was totally it! The hose was collapsing Replaced the old hose and now it's running like a champ. Thanks sooooo much for the suggestion. I overlooked this completely.

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