I own a '77 Cutlass, and I keep having the same problem with the car overheating. I replaced the radiator with a new one, thinking that this would solve my problem, and made sure I flushed out the old gunk in the cooling system, but it keeps overheating!! A friend told me to replace the thermostat, do you think that, thats the problem? I need some suggestions, any advice would help!!!! Thanks.

 

1 way to find out, is to remove it and put it in a heating pot of water on the stove. If it opens up around 170-200 degrees, it's ok. I'd Probably just end up putting in a new one in since it's already apart though, and keeping the used one for a spare if it works.

Check your water pump and make sure there's a belt on it lol.

 

I had problems with mines as well in the past.I replaced the radiator but that didn't help totally.I gave it a good flush and that seemed to do the trick.I finally got my heater working so now I have to flush it again because I didnt get all the rust color coolant out when I flushed it the first time.
A new thermostat could definitely help plus they're cheap anyways.Maybe your belts were loose and that may have helped with overheating the first time.
Good luck with the problem!!!

 

That car is nice man! I just saw your car ironically on Youtube, before you put the rims on it. my 77 is the same color. I appreciate the advise.

 

Check the clutch fan first. If it's not functioning properly, car is going to overheat in slow or city driving. It should roar whenever the car is first started and then quiet down, and should also roar way before the car overheats. If you never hear it roar, it's not working.

Next- make sure all the radiator shrouds and seals are in place. If airflow is bypassing the radiator, cooling is not going to be up to snuff.

Is it visibly overheating? Steam, puking out the overflow, knocking? Check the pressure cap making sure it is for a closed system and the right lift pressure.

If it's just the light coming on, check the temp sending unit on the intake. I've seen many of them get the sensing bulb cocked off to one side and ground out against the block, making the hot light come on when car isn't even close to hot. Gage senderswill do the same thing.

For that matter, make sure you have the right sender for your instrumentation. You'd be surprised at the number of cars I've seen with the wrong one installed.

 

Does it overheat at low speeds or at high speeds?

As suggested above, check the things that don't cost anything before spending money. I've had a thermostat get stuck and cause an overheat. Check the clutch fan and the sending unit. Check for indications that the engine is runnign lean. Be sure the engine is properly tuned and that the advance is working. There isn't much to a cooling system and the problem usually becomes obvious with a little checking.

 

Thanks guys! I'm going to put in a new thermostat this weekend, and see if that fixes the problem, I do hear the roaring when the car is on and it overheats when idling. I'm so fustrated that I'm thinking of just tearing the whole engine apart and rebuilding it. Theres an oil leak on the motor, which i think may be bad valve cover gaskets, and when I started it last night it was sputtering a bit after i put in new antifreeze and coolant. I put in the 50/50 mixture, so i dont know. I think I might just tear it down and rebuild it.