Bought a '66 289, 4 brrl, dual exhaust in Apr-12. Noticed stock temp guage showing it running a needle over half way in 90 degree Apr/May Arizona heat. When outside temp hit 100, stock guage hit 3/4. Removed radiator cap and stuck thermometer in coolant. Detemined midway on stock guage was about 220 degrees. Installed Sunpro temp guage and car idled at 200 and hit 240 degrees on highway. Installed 2300 cfm electric fan from Old Air and no relief, but cools quickly when engine off! Have since determined radiator was blocked as I have retrieved flakes of iron from radiator. Apparently it was sat at some point and now have crap in water jackets flacking. Have since installed Gano filter in top radiator hose, ran with prestone coolant flush, ran with and without thermostat, changed waterpump, and after Gano filter appeared to not be catching much grit flushed one last time and installed brand new 3 core aluminum radiator that local Mustang resto shop uses. It now seems to run about 195 in 100+ degree heat but if I drive over 40 mph, temp starts climbing. After 8 miles on highway at 65-70 temp hits 230. I've done compression test...all seem fine. Are my water jackets just clogged? Anyway solution without rebuild or new engine?

 

There's been a few threads about this lately. Don't know if search will bring it up or not. But one thread I remember the problem was the radiator needed to be re-cored.

 

Oh and welcome to TMS!

 

I did see one thread, but the guy determined it was his radiator. I however am essentially on my third radiator. Car came with 2 core aluminum (Northern sold through Summit). Wasn't sure it was the radiator, so made a $130 test with a 3 cored "heavy duty" brass/copper radiator from O'Reilys. The first 5 miles seemed good, but back to issues. Found a radiator shop and we determined the flaking water jacket issue clogging the cores. They flushed the aluminum that came with the car, I put that back in, but had trany lines strip in core (yes it's an automatic). Was able to drive for two weeks with same issues before swaping with 3 core aluminum from local stang resto shop. But still have the issues. Frickin frustrating. I have a hard time believing water jackets could be so clogged not allowing block to cool. I know I have flow b/c the Gano filter is clear plastic and I can see flow. 230 degrees seems way too hot to me. I had local tell me it should run 185/190 in AZ heat. What temp do others run? If stock temp guage is 215/220 at half way, and car runs at half with 180 thermostat, I'm wondering if locals think they are running 180 b/c of the thermostat when in reality it runs 220-ish. Which would mean I'm not that far off. But I think I'm just grabbing at straws b/c running at 230 makes me fear I'm about to blow a head gasket. I also have a hard time believing crap could make it past the Gano filter, but clog the cores in the new radiator.

 

So with that prestone flush, did you hook the hose up to it and force some water through the jacket? Was it clear?

 

make sure your upper and lower rad hoses have the metal expansion spring inside them .. sounds like suction from cruise speed may be collapsing a hose ..and make sure your thermostat isn`t stuck open ... too fast of flow will not allow heat transfer from the rad ..

 

Running hot at hwy speeds can be the worse. Possible transmission causing some of it. I would try a trans cooler just to be sure. They are cheap and easy to install. Make sure she's not running lean. Can also cause it. Thermostat shouldn't make a big difference(make sure it's not upside down).

 

Bottom radiator hose has expansion spring, haven't heard of upper having one (mine doesn't). But upper hose is brand new and wouldn't have room with the Gano filter. Been through two thermostats and ran without (when I was running with the Prestone flush). Ironically I didn't seem to see a difference with or without thermostat except it didn't come up to initial temp (180-190) as quickly w/out thermostat. Definately not running lean, but just readjusted the timing and idle air/fuel last night. I power timed it before and was at 15 degrees at idle and was advancing to over 40 upon rev. Backed it down to 8 degrees at idle and re-adjusted/air flow. Will see how it compares today. Not sure what size jets I have, I rebuilt the carb and don't recall markings. Drivability has been good...doesn't cut out or bog down so don't think initial float adjustments could be causing highway issues.

 

what does it do if you drive it at nite when the temp goes down .. or does it go down at nite in aridzona ? .. it`s not uncommon for a waterpump impeller to come loose .. and do you know if the engine has been bored out perhaps .060 or more .. they are called thin wall motors for a reason .. we will get to the bottum of this ...perhaps someone even has put a late reverse flow pump on it .. do you see coolant flow when the cap is off ..? and have you tried the coolant additives that advertise 20 degee reductions ..

 

Cdynaco - yess I hooked up the garden hose. But Prestone sells a flush which comes in a quart-1/2 gallon bottle. You put it in and drive for at least 10 hours, then flush. It seemed to work as I had "silt" in the bottom of my overflow bottle.

Hoss - I hear ya on the .60 bore. The car was jimmied with more than I originally thought, so it is possible but I just don't know.

When cap is off, I can see coolant flow across over cores. It has good flow. I drove at night yesterday after re-adjusting the timing and it was around 95 degrees with issue. This morning it was 85 degrees with 8 miles of hwy driving to work, temp hit 212. I will see when I go home...suppose to be mild day...only 105 today.

 

Just wanted to toss you my two cents. I had a mustang that was over heating my thread was the clogged radiator issue but even after the swap I was still a bit on the hot side I upgraded the fan to a flex fan and installed a shroud and it made a huge difference. And it is a fairly inexpensive upgrade. Hope that helps.

Les

 

Another little trick you can try is running thermostat less. I use to have overheating problems in my mustang just sitting in traffic. I tried running without a fan but the 80 degree summer bay area weather was too hot. I upgraded to an electric fan, flex fan, fan shroud and removing the thermostat. Problem solved.

Increasing airflow and making sure that coolant wasn't obstructed. Suggestions

Andres