I completed the car last winter complete with a fresh 5.0L long block. We did about 5000 miles when we went south ,in march. for some reason the new motor occasionally runs hotter than the old one did. I put everything new on the front of the motor and it runs a good aluminum radiator. The old motor would rarely run the fan even during the summer but this one is all over the place. I have had the temp gauge hit 210 and the fan come on and other times the gauge has read 225 and the fan did not come on. I know about electric temp gauges, so yesterday I put a mechanical temp gauge in where the fan switch was so I can, maybe, get a better feel for whats going on. I tested the mech. gauge on the stove with a digital thermometer and it appeared to be spot on. I will take it out and run the crap out of it and see if I can make it act up. Cause when the temp gauge starts going up, I stop having fun.
Have you considered using a conventional engine driven fan? I hear of so many people who have issues with using electric fans on older cars. Yeah, a belt driven fan may use up a couple of HP, but I will gladly take that over overheating any day.
I had a similar problem with a non-Ford motor. I ended up being a poor quality "off shore" polished aluminum water pump with the impeller not pressed on the shaft enough. It would cool at highway speeds, and boil as it came back to idle. I even pulled the heads, before I found the bad impeller "inside the pump". In my case a Flowcooler pump fixed the problem. Did you change the original pump? Is it maybe a reverse rotation serpentine pump?
I have my electric fan turn on as soon as the motor starts, and just stays on.
Do you have a shroud around the fan?
SBFs have always had a problem with corrosion in the timing chain cover. It is very common to replace the cover. Add in late model swaps from EFI engines to carburetor applications needing a mechanical fuel pump, right outlet, left outlet, timing mark location, clockwise rotation, counter clockwise rotation, crank position sensor, etc. Finding good OEM covers is a major task. New, after market covers are common. As with many replacement parts, quality comes into question...'Caveat emptor' (buyer beware). Care in fitting and port matching is important. A little port matching can make huge flow improvements. Another rare condition not yet mentioned is trapped air. An air bubble in some systems can create intermittent temperature fluctuations. Unlikely with the number of miles you have driven but worth mentioning.
Ran the car to town this morning and did observe different readings between the two gauges a couple of times. It was not a very long drive but I plan on taking it to the Portland Roadster show on Friday. That will be close to a 500 mile loop so I should get some good information on what i going on. The mechanical gauge seemed to stay constant while the electric gage varied as much as 20 degrees. I want to get this part figured out before I start replacing parts.
Best to shoot the top of the radiator with an infrared temp reader. A Falcon Ranchero I built with a speed density EFI 302 seamed like it was running hot. Didn't loose any water, just read near hot on the stock gauge. Shot the top of the tank and found it was dead on 195 +/- 5. Could find no reason electrically why it would display on the high side of normal vice the middle of the normal range.
TO ford blue blood, where can u find one of those infra red readers your talking about?, i keep a close watch on my water temp , altho it never boils over, i still watch it!!!!!!!!!!!!, thanks jerry
Quote from: Ford Blue blood on 2017-03-14 08:11
Best to shoot the top of the radiator with an infrared temp reader. A Falcon Ranchero I built with a speed density EFI 302 seamed like it was running hot. Didn't loose any water, just read near hot on the stock gauge. Shot the top of the tank and found it was dead on 195 +/- 5. Could find no reason electrically why it would display on the high side of normal vice the middle of the normal range.
I had the same issue with a stock gauge in a 50 Ford. I was running a 195 stat and reading at the top of the temp gauge. Finally figured out that in 1950, 195 degrees was considered hot. Gauge was fine and the engine was working as it should. a resistor in the sender wire brought the needle down to the center of the gauge and fixed the problem
two things to look at, voltage regulator for the gauges and height of the engine. Voltage regulator is obvious, height of engine was a problem for me in fe exchanges, intake would be above the radiator and never rid itself of air.
Quote from: geraldchainsaw on 2017-03-14 10:39
TO ford blue blood, where can u find one of those infra red readers your talking about?, i keep a close watch on my water temp , altho it never boils over, i still watch it!!!!!!!!!!!!, thanks jerry
Jerry Lowes has them, about $19 on sale. I expect any tool supplier will have them. Never checked Harbor Freight as I have had mine for many years.
Napa has them
This may sound dumb, but are you sure all the air is out? I once had to drive my car up a hill in my back yard just to make the radiator the highest point
We just left the highest heater hose clamp loose while filling the coolant. Bleed the trapped air by moving the hose, when you get coolant, and not any more air, your done.
I loosen the temp sender to bleed out the block. On a 5.0 it is right at the thermostat so I think it is pretty effective. Need to drive it some more but it has been raining cats and dogs here. Trying to not have to do another spring cleaning before an event a week from Saturday.