overheating problem 1977 comet 302

alright everyone, this is my first time posting. but i bough a 1977 mercury comet 4 door with the 302 motor. ive been slowly rebuilding it but what is getting me right now is an overheating problem. i had to temporarily by-pass my heater core because it was steaming up my car. ive replace my thermostat, flushed the system 2-3 times. the car did sit for three years. i replaced all the hose's. i can drive around town at 30-45 all day. but right when i go slower or faster it starts overheating. SOMETIMES. and then randomly i can drive it down the freeway for 10 miles before it starts going up. normally i cannot make it to the other side of town. the cooling system is on a smaller loop then normal because i closed off the heater core by cutting the hose and looping it to the other hose area. any ideas on how to fix this? i did a block test and it came up good. but my fluid was a milky brown each time i flush it. and when i flush it i let the water run until theres no discoloration. and i even reverse flow the radiator. i need help. thanks everyone.

 

There is the possibility the water pump may not be working properly. Also, the brown colored water may indicate blockage in the radiator. Looping arnd the heat core shud not affect normal cooling.

 

alright. ive used my heat gun on the radiator and it runs even tempatures lowering where it needs to and up where it needs to be. i was going to check the water pump probably monday when i have time. its had me and a couple of other people stumped. because when the cap is off you can tell its flowing properly. well i mean you can atleast tell it is flowing. thank you very much for taking your time to read this

 

Welcome to the forum! Like u said, it is flowing - but may not be flowing enough to cool properly. Do u have a fan shroud? What type fan on the car?
I can't think of any other reason it wud be overheating

 

from Northeast Pennsylvania

If you have had this problem since you purchased the car check to see if the previous owner didn't have the fan mounted to the water pump backwards - I have seen it before and it will not cool an engine

 

Running lean or incorrect timing will cause overheating

 

to the site!!!!!

 

to the board...

 

my thoughts are head gasket too if its milky brown at each flush

 

I have checked for a blown head gasket. My oil has been fine I check it daily. I do not have a fan shroud. And its an aftermarket 5 blade fan. The heating problem started a few weeks after I bypassed the heater core. I'm going to pull the water pump this week and see if the blades are rusted out or not. And thanks for the welcomes everyone I'm loving the help and loving the car too!

 

Aftermarket Fan ??

Hello :
Just reading your posts .. if you're running a " flex fan" be careful !! One of
our friends lost his life when a blade let go when he was " winging" the throttle in his back yard. The blade severed his artery in his neck and He bled out before help could be rendered. His wife now drives their Grabber and she runs an " electric " fan . Just a word of caution.
Cometized

 

I also converted to an elec fan for safety reasons. And, that was prior to hearing abt the person who got killed by the fan explosion. Any kind of fan w/o a shroud is an accident waiting to happen IMO.
The heater core bypass shud not make much, if any difference in overheating. A lot of folks don't have cores hooked up w/o a problem. I bypassed mine for the first season I had the car cuz the core had been leaking and the PO had nothing going thru it.
I wud look for something else. After u inspect/replace the pump we will see what u come up with. If I removed a wp I wud replace it - they're not expensive and may eliminate a problem in nr future. Hope that is ur problem...

 

Do aftermarket fans come left or right hand rotation? I wonder if the blades are bent to pull air for a different rotation. Try changing over to a stock Maverick fan just to see if your over heating problem lessens.

Also are you running a shroud?

 

i do have one of those "flex" fans which is on my list of replacements its just time and money for me. i am planning on replacing the pump anyways just because why not when its off make it like new. i also am wanting to get a shroud because it is rather unsafe. and if i can find a replacement fan i am going to. but ive been even trying to find a new hood for it and NO where has the stuff i want unless i go brand new. and being 19 and a college student my funds are very very limited.

 

He stated he does not have a shroud. I don't think the blades are curved for a different rotation - I think it is mostly for noise control.