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Discussion Starter #1
I'm having some problems with my 89 GT running VERY hot on the highway. Car has a Vortech blower and some other improvements adding up to about 350 HP at the wheels. Since these mods, the car runs cool as can be sitting at idle, even here in southern Florida. However, once you get out on the highway, the temp gauge just continues to climb until it's pinned. Hasn't boiled over but it sure is scary. Here's what we've tried so far -

Change to Edelbrock water pump, no change from stock. Bought a new Ford water pump, no change.
We've tried 160 and 180 degree thermostats. No difference.
The car has a brand new Mashimoto radiator with matching double electric fans.

By the way, the car is automatic with AC. AC condenser looks a little funky so I thought about changing that out too, but I can't imagine that would cause the problem I'm having.

For comparison, I've also got an LX with the 500 HP Boss 363 and AC. That never runs hot.

I'm really at my wits end here and don't know what else to change out. The Mashimoto people aren't terribly helpful so I thought of contact the Griffin people as I have their radiators in my other cars. Any ideas here, aside from moving up north?

Sure could use some advice. Thanks.
 

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Rent Asunder!
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I'm curious what other improvements. Did that include removing the heads? If so, make sure the head gaskets are installed the right way. If you install them backwards, you'll block the rear coolant passages causing an overheating issue similar to what you're experiencing.
 

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What's telling you it's running hot? Got an actual temp? Are you burping your system really well?
 

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Discussion Starter #4
I'm curious what other improvements. Did that include removing the heads? If so, make sure the head gaskets are installed the right way. If you install them backwards, you'll block the rear coolant passages causing an overheating issue similar to what you're experiencing.
Heads are stock, as is the long block. All mods are external. Car always ran perfectly cool until the blower. Car will idle all day in 90 degree heat and the temp gauge doesn't budge. But, that's idling. Once your out on the road and turning some revs (2500 RPM), that's when the trouble begins.

---------- Post added at 02:28 PM ---------- Previous post was at 02:24 PM ----------

What's telling you it's running hot? Got an actual temp? Are you burping your system really well?
Actually, I don't have an actual temp; just going by the relative position of the factory gauge. We should eliminate any possibility of a gauge issue but using an actual gauge when driving to see just how high the temp actually gets. Thanks for pointing that out. System is thoroughly burped.
 

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Rent Asunder!
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Do not trust the factory gauge. Get an actual temp gauge. The factory gauge in my Bronco would never go above the "N" in normal but read 195-200*F steady on an actual gauge.
 

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Discussion Starter #6
Do not trust the factory gauge. Get an actual temp gauge. The factory gauge in my Bronco would never go above the "N" in normal but read 195-200*F steady on an actual gauge.
Good point - going to check that MOnday.
 

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Qwik Enuff
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Check your secondary ground too.Its the ground strap located between the driver cylinder head (rear) or intake and the firewall.Its the ground for the interior/exterior lights,ac clutch,alternator & the gauges.Make sure the ground is tight and corrosion free.If this ground is loose,corroded or disconnected,it will cause the temp gauge to read high,especially when turning accessories (ac,blower motor,etc) on.
Read the following link for some detailed info about ground upgrades,paying attention to the very last paragraph.

How Important are Grounds in a Ford

You normally experience an overheat condition when an engine is idling or stopped at a red light vs when moving at highway speeds.
If your ac condenser fins are dirty or smashed in from previous repairs,that can cause a large portion of the radiator to be blocked with no airflow because of the condenser,but it should affect the engine at idle too.

Have you checked the temp sender in the intake?? If you remove the wire from the sender and touch it directly to a good ground,with the key on,the gauge should peg I believe.If it does,that indicates the gauge & sender wire are good,so the temp sender would be the only thing left which could be faulty,unless the engine truly is overheating.
If youre engine was truly running at the temp shown on your gauges red zone,the engine would be running pretty rough,most likely pinging and if you shut the engine down,you'd be hearing some strange noises like boiling sounds,etc.
The parts store didnt give you a standard rotation vs reverse rotation water pump did they??
 
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