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Off Topic, 66 289 stang overheating HELP!


Guest Richard D

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Guest Richard D

I don't know where else to turn, the Ford forum stops at 1953. I will be brief. My friend is a collector and one of his cars is a 66 Mustang with 289, auto, factory air and pony interior with factory gauges including tach. Car has new 4 row radiator, new thermostat, fan clutch and water pump feel tight, no leaks at pump, and about 50,000 miles since new. When car is idled with A/C on temp stays below half way and you can see coolant flowing past filler neck when thermostat opens, will not overheat at idle. When driving car at 40-45 MPH temp slowly goes above half way, up to hot but does not pin gauge. When engine is shut off coolant sprays out of over flow tube for about 8 minutes. After pressure is released and fres coolant put in car runs cool and can be put away. I wanted to test it by removing the thermostat but due to design I would have to remove distributer to remove housing. Even though fluid is flowing well at fast idle could stat be closing ?

Sorry to ask here but don't know where else to go.

Many Thank's

Richard.

Edited by Richard D (see edit history)
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Guest re-reatta

Richard,

I believe the first place to look is the thermostat. Also check to see if the radiator hoses are in good shape. They may be collapsing which would prevent circulation.

Good luck,

Kevin

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There are two other possibilities that can cause the overheating.

1. Bottom radiator hose is being sucked together (collapsing) due to the wire inside it being rusted away. It won't collapse at idle. Only when the engine is running at higher speeds. Squeeze the hose and see if has any spots that can be mashed together.

2. The engine could have a blown head gasket. Hot gases being forced into the water will cause the engine to overheat. Any steam coming out of the exhaust? It may not be much. Put your hand over the exhaust pipe and see if gets excessively wet after the engine is warmed up. Any signs of coolant in the oil?

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Guest Richard D

Hi Ronnie, I checked the oil for any contamination, it is clean, and the car has dual factory exaust and could not detect ant steam or moisture. I thought about the bottom hose on the way home. I am going to recommend that he has it put on a flat bed and taken to his mechanics shop who can remove the distributer and reinstall it without messing up the timing and putting in another new Stant thermostat and replace the bottom hose. I could not see any bubbles in the radiator when running, if head gasket was leaking would there not be bubbles coming to the surface? Engine runs perfect.

THANK YOU FOR YOUR HELP.

Richard.

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You can't always see bubbles in the coolant when the head gasket is bad. Sometimes you can see moisture on a spark plug after the engine has cooled off. The moisture trapped in a cylinder will condense and wet the spark plug.

If he takes it to a mechanic, the mechanic should have the equipment to pressure test the cooling system. That should show up a blown head gasket. He should ask the mechanic to do a pressure test.

Let us know how it turns out.

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My Mustang was running hot and I just changed all of the hoses and the t-stat. Problem solved. If you are not showing any foaming your head gaskets are most likely ok. Go for the s-stat. Not much on the Mustang can go wrong as long at the fan is turning and you dont have a blockage. If you need more information look at the Falcon Club of America they are very helpful and the drive line is the same.

Chuck

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One other thing to do, and this is something nobody ever thinks about, is the radiator cap. Had a buddy with an old Cougar that was having an overheating problem that he couldn't nail, replaced everything else on the car, but it wasn't until he replaced the rad cap that the problem was solved. If the spring is weak it won't hold the pressure needed to manage heat.

A second possibility is a failing clutch fan. This one is simple to check, have him try spinning it by hand first thing in the morning, after it's run for a minute, and when the engine is hot. It should be stiff first thing, easy to turn after run, and impossible to turn when hot. If it fails these three tests then it's bad.

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Hey, what can I say... I'm not a Ford guy so if a 66 Mustang doesn't have one, I'd not know. And, if I had a car with no clutch fan on it, and wasn't planning to go with an electric fan, I'd install a clutch fan on it. So, if the car has one, it could be the problem.

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Fine at idle/low speed and gradual increase as speed goes up is typical of a bad fan clutch particularly with a/c & automatic. Will spin the fan, just not fast enough. Sometimes unhooking the spring will help but look for traces of leakage on the back side of the clutch.

A good fan clutch will make the fan howl above 2000 rpm.

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Guest Richard D

It does have a fan clutch, it was turning the fan and moving a lot of air at fast idle when hot so I assumed it was ok. It looks brand new. Since I do not feel comfortable removing the distributer (no timing light) I think the best thing is for a real Ford mechanic to look at it. Speaking of timing when driven it would not knock or ping even when trying to lug the engine.

Once Again Thank You All,

Richard.

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Ahh didnt think of a clutch fan as the orig car didnt have one but a lot of folks have chosen to replace orig with aftermarket. That could be part of the issue but the radiator cap would be a good place to start also and Ronnie is right, check the bottom hose as the RPMs increase the hose could be sucked flat.

Chuck

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BTW, an engine that is far retarded won't knock or ping either but will overheat, be down on power, and get lousy MPG.

Back in the day I used to hand tune a distributer by ear. Wanted to get just a trace of ping when the throttle was opened and then back off a touch. This was back when unleaded came out, octane went into the toilet, and none of the factory specs were right anymore.

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Guest Richard D

The 289 in this car has plenty of power, even at 45 years old. Plus I had forgotten how fast a up to spec R-12 A/C system gets down to freezing even when it is 90 degrees. My Reatta is still R-12 and takes about 10 minutes instead of 1 minute for vent temp to get to 38 degrees.

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