View Full Version : '75 Grand Am Running Hot

May 29th, 2012, 10:01
My '75 Grand Am with a 400 4-barrel and factory air is running hot whenever I pull the A/C. At Highway speeds it will hit 210-220 degrees. In slow traffic it will jump between 220-230. Turning the A/C off helps but what's the point of having working A/C if you can't use it?

My friend who is a full time mechanic and has worked on the car suggested installing a new OEM style 4-core radiator. The car has it's original radiator in it (Harrison stamped on the side). It doesn't leak or anything but I suspect after 37 years, it may be plugged some. We have already installed a new factory water pump. The original clutch fan seems to work fine (kicks in and out when it should). Should I also replace the clutch fan assembly? I don't want to go to an electric fan or aluminum radiator to keep the engine compartment as stock OEM as possible.

Any thoughts on getting the 400 to run between 210-220 would be great!

August 8th, 2012, 13:33
The 4 core should solve your heating up issue, even with the A/C on. The three core was barely adequate when new, and with years of barnacle buildup would render it ineffective. I have used the Spectra CU165 radiator in my cars and for a Chinese built unit, it is of good quality. On E-BAY one can be had for $240 inc. shipping. With it, your 400 should never exceed 205 with properly mixed 50/50 green coolant.

August 17th, 2012, 21:24
Was it running at a lower temperature, and then one day started running hot? That might indicate the fan clutch let go, or the vacuum advance canister failed. If it has been gradually running hotter (or the car is new to you) then I'd vote for a clogged radiator. The passages in the radiator can clog up over time, and if the coolant isn't changed regularly, it can be worse. I'm not sure if they still rod radiators anymore. That is when the remove the tanks and run rods the same shape and size as the passages through the core, to push out all the deposits and corrosion And open up the radiator, then re-solder the tanks back on. Kind of like a heart bypass operation.

I would think your car originally had a 4 core radiator. Iwould stick with a stock replacement and a new clutch if you need it. Those cars had no problem cooling when new, and don't need any modifications if everything is working correctly.

I bought a 1974 Grand Am new back in 1974. One of my favorite cars. Mine was admiralty blue with burgandy interior and special order white seats, with honsycomb wheels. I cried when my ex-wife drove off in it.