I have a restored 1966 Mustang GT.

It had sat for about 17 years untill recently and was started little.

It overheats and spews atifreeze. I have changed thermostat and fan clutch.

Could the radiator get cloged up just sitting for so long.

what do I try next.

Thanks so much

Jeff in NC


After sitting for 17 years you’ll likely have a few things wrong with it.

Where is the coolant coming from?

Rotted hoses?


Oh-oh. The car was restored THEN sat for 17 years?

OR, the car sat for 17 years and has just recently been restored?

Your answer will make a difference in our answers.

Where was the coolant spewing from?


Thanks guys for your reply.
as you figured out, I am not mechanical and am a “Newbie” to this chat thing.
The car was restored 17 years ago.
The coolant is coming out the overflow tube
Hope this helps .
Thanks again


Gotta start simple I think. I’d bet the hoses are shot, the thermostat is questionable, and the radiator is rusted. Maybe even a frozen bearing in the water pump. Was the engine re-built (complete) at the restoration? Does it run? Smoke? Oil leaks? How’s the idle? If it were MY car, I’d change the thermostat and hoses, and flush the old coolant. Careful running it, pay attention to the water pump and radiator. What size engine is in the GT? BTW . . . . what a cool project!


Hey Dude!
Thanks for the reply.
Let me be more clear. I talked to the guy in TN who did a Frame Off Restoration. It looks as good underneath as on top, but I have some concerns.
He said the engine and trans. were rebuilt but the carberator needed complete rebuild which really helped.
The fan clutch was wobbly so I replaced it , also the thermostat. It is a little confusing why a man would spend a reported 2000 + hours on it and be laxed in some areas. The hoses are new as are the belts. It is a 289 4V stock. Runs, starts and drives great with no smoke or noises. Factory A/C runs nice and cold also.
The guy who owned it has 14 other classics and I think this one got lost in the schuffle.
P.S. The coolant does have a funky brown color when I drained it. Again please bear with me for I am a “Dummy” when it comes to mechanic. I waited 45 years for my classic after retiring and I guess I got caught up in the cool looks of this car and the fact it was totlly restored. Guess I am the only one who has done this.
Thanks for the help ahead of time


Brown coolant can mean a rusty rad. It MAY be feasible to re-core this one if it has never been done before.
I fear a flush may simply loosen more rust (if it is rust) and will plug up again.

Now I’m also wondering if the rebuilt engine has had the block and head boiled clean.


Try the KISS technique, first (Keep It Simple, Stud). Walmart, and auto parts stores, have the Prestone (or, Zerex) Coolant Flush kits, and a Coolant Cleaner kit for under $20. When used as directed, they can do great stuff. The brown in the coolant, is usually rust from the engine coolant passages.


I agree, I would try flushing the cooling system first. If that doesn’t help, I would suspect the radiator. How available are correct replacement radiators for your car? If they are available, I would probably just replace it and see what happens (after flushing the system).


OK, Thanks guys. I’ll keep you posted