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Hi all, been gone awhile, doing the job hunting thing. Laid off from the semiconductor industry so I've been busy. Anyway, our 66' 289 is running hot now that it's warmed up in Phoenix. Reviewing some past posts, one of the things mentioned was the possiblity of air in the cooling system. I'm wondering if that is why our gauge is reading VERY hot, when the motor seems fine. I can almost hold my hand on the valve cover when the gauge is pegged! I'm wondering if I could have an air pocket in the manifold by the temp sending unit and if this could be causing the high temp reading? The sender is new, not from Ford, it's one of the 5 or 6 dollar units from Mustangs Unlimited. Brand new wiring harness and the gauge seemed to be working ok prior to us draining the coolant a couple times for various services. What is the procedure for purging all of the air out of the system's nooks and crannies? We have tried about everything else ie new hoses with internal springs, new t-stat, radiator like new, new 16 pound cap, 16 inch electric fan with shroud. Any other suggestions? Thanks and sorry about being so long winded!
 
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I don't know that I've ever ran across air pockets. You say you can put your hand on the valve cover, what about the Radiator how hot does it seem to get? Have you ever left the radiator cap off to see if the water starts flowing after the thermostat opens?

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There is no real way to purg air out of the system. One thing you can try is
to rev. the motor with the cap off, the water level will drop, but only a little,
add water while it is still reved (2krpm) and put the cap back on.
It could be the gauge is out of calibration. If you can hold your hand on the
top hose while the gauge says hi, it may need a different sender.
A 4-core radiator is the only way to go, and a overflow tank.
 

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hmmmm...what kind of overflow reactions are you getting? Puke and spit or just low flow? *G*

At the temps your guage is telling you, there should be a goodly amount of coolant showing up in the puke tank....is there?

Does it suck back in when the engine cools off?

Try burping your Pony with a lower pressure cap, say in the 10-12 lb range....once the air is out and the engine cools off, put the 16 lb unit back on...sometimes this can take a few good blasts down the freeway, but keep it under 100, OK? *G*

Sounds like you've got lots of company in the job hunt...stay cool!!



Pat
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Get the Ford sending unit...makes a world of difference. Trust me on this....

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Midlife helped me with the same problem three months ago. However, the ford units I purchased are mexican-made motorcraft pieces that fit many generic applications...and IMHO aren't the ideal fit for 30-year-old mustangs (calibration issues I guess). In my case, the mach's gauge read very hot after installing this motorcraft piece, when in actuality, my engine temp was right on (candy thermometer stuck in the operating-temped radiator opening). What I did, per another suggestion on the board, is hit my local wrecking yard and get a couple sending units from pre '77 or so ford v8s. Installing one of those really did the trick. I got the candy thermometer at kroger for a few bucks to verify my engine temp was where it was supposed to be. Good luck.

70 Mach 1 (351C 4V 4-speed) I've been restoring since '96. 95% complete. Also have a '68 HT (289 2-speed) that I restored between '97-98 and is FOR SALE! The VMF has proven to be an invaluable resource for information, humor and excellent advice.
 

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You can drill a 1/16 hole in the outer rim of the thermostat and install the hole in the thermostat in the "up" position. I've noticed better quality thermostats come with the purge hole now.... Ditto on the temp sender, Bought a Wells from Autozone, pegs the guage but is cool as a cucumber... Make sure the wire to the sender isn't grounding anywhere....

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Dude...its the sending unit. The aftermarket ones always show higher operating temperature. You'd really be dumbfounded if the sender was showing the temperature to be pegged on the gauge. That happened to me once with a aftermarket sensor. The Ford sensor,or a sensor from a local auto parts store cost a whopping $5.00. Swap it out. You'll see.
 

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The book used to say to leave the top heater hose loose and fill it until coolant came out. But I never did it that way. I just drill a couple of small holes in the thermostat plate to let air through, fill it up and run it. Then let it cool and check and fill it. A coolant recovery system makes this really easy and provides a closed system. Do you have a way to test the real temperature? I use a candy thermometer in the neck of the radiator. They are usually pretty accurate and cheaper than a mechanical water temp. gauge. Then you can check that reading against your gauge.

...modified '65 convertible...
 
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