overheating on freeway?

[phinkel26]

Ok here is what I have, 289 bored to a 302, stock heads, new water pump, 195 thermostat, flex fan straight, no clutch, with the big shroud. The problem is it heats up on the freeway to like 240, and around town runs 190-200. also timing is set at lke 10 degrees at idle, and I have a brand new 4 core radioator. Oh and my head gaskets are good, checked no trace of admissions in my coolant, and no trace of coolant in my exhaust. What is making me run hot? Also what should my temp be at, on the street as well as on the freeway.

 

[Blown4.6]

Hmmmmm, that's very, very odd. You're way hotter with more air flowing through the radiator pulling heat away from the water? Interesting. Well, first, your temp should run around 185-195 (ideally) on the highway. I don't like to see it go higher than 210-215 under any conditions.

Are you certain that your timing is in fact advancing with vacuume? Late timing can cause overheating under load. Beyond that, I'm stumped. Are you 100% certain your pump is working properly? I have never seen it happen, but I guess one could work at low speeds and not work very well at high speed (about to fail alltogether).....?

Sorry to respond without better answers. I'll give this one some thought.

 

[phinkel26]

Thanks for your reply, I just replaiced the water pump this past week to rule that out. I was thinking possible the timing chain is streched, or the timing marks arent lined up but......correct me if I am wrong the car would run hot no matter what, not just heat up ont he freeway. Is there a way to check that the distributor is advancing? I wonder if it could be the lil diaphram on the side of my distributor, "the vacume advance". I just dont know what the heck could be causing this. Also on a 65 automatic what options do i have as far as transmissions go. I am running a c4 now and i am wondering whta i can do to get mor out of the transmission.

 

[rbohm]

there are a number of things that will cause overheating at freeway speeds, but not be a problem at city driving speeds. things like the lower rad hose collapsing, air not getting out of the engine compartment, too much advance at freeway speeds, rad core not flowing properly.

 

[1969mach1351]

Since you know what temp it is running I would guess you have aftermarket gauges? When I bought my car the oil pressure and water temp. gauge wires were switched and gave me the apperance of what you are describing. As the oil pressure went up on the freeway the temp would show an increase and reverse when I was in traffic.
Too get a rough guess on how acurate your gauge is I would assume around about 140* it would start to boil over? Is your gauge reading right? Can't think of anything else

 

[gp001]

If you have an auto trans check the condition and the level of your fluid. If its low the trans could be pumping the fluid back through the system without it getting a chance to cool off.

 

[302 coupe]

my car used to do the same thing, it would run about 230 on the highway, then sitting in traffic it would cool down to about 180-190. I could never figure it out. Thermostat, hoses(bottom has a spring to prevent collapsing), radiator(3 core), pump, everything was good. I had a belt driven fan, about an inch away from the radiator and no shroud. I reasoned that airflow wasn't a problem since it cooled off in traffic. I decided to switch to an electric fan and ditch the stock fan. I mounted the electric one in front of the radiator and hooked it to a thermoswitch so it would come on at 180*. Somehow it solved my problem, even when the fan isn't running going down the highway, it runs 185.

 

[67bluestang]

Ok here is what I have, 289 bored to a 302, stock heads, new water pump, 195 thermostat, flex fan straight, no clutch, with the big shroud. The problem is it heats up on the freeway to like 240, and around town runs 190-200. also timing is set at lke 10 degrees at idle, and I have a brand new 4 core radioator. Oh and my head gaskets are good, checked no trace of admissions in my coolant, and no trace of coolant in my exhaust. What is making me run hot? Also what should my temp be at, on the street as well as on the freeway.

I'd say, make sure the thermostat is closing as it should. If it stays open all the time, at highway speeds (higher rpm) the coolant won't stay in the radiator long enough to cool down. One other thing, it's probably ok, but make sure the fan is on correctly. I bought a truck once and it was heating up and while checking it out, i felt air coming out the front. They had put the fan on backwards.

 

[phinkel26]

oil pressure sending unit is on the driver side of my block, and the water temperature comes from the intake manifold up by the distributor? however I could move it to the rear of my manifold back behind the carb. The manifold is a generic edlebrock.