With my 351W, the gauge used to stay right in the middle or slightly below last Fall/Winter. Creeps up when 80+ degrees out and after driving for 30-40 minutes or in traffic. Now, in the Fall/Winter I do have a Heater Core switch which I open to let more hot air into the cabin…that is currently closed. Will try again with it open. FYI, a new 160 degree thermo and system flush were just installed/completed (before that it was going right up to the red line but never passed it when really hot out…90+).
Running too hot or is my gauge just not accurate??? Do I need a new sending unit???
To diagnose this issue you need to measure temperature at the sender. That is where the gauge gets it’s information. Putting 160 degree thermostat in doesn’t improve cooling ability it actually places greater demands on the cooling system. It’s like turning the AC down lower when it can’t keep up with where it is already set. With that thermostat you should be seeing right around 160 at the sender.
Most likely you have two problems. First the sender or the gauge may be inaccurate. I developed a gauge tester to let you verify the reading of the gauge. It is $30 shipped and works with fuel temp and oil pressure gauges for all Fords from '56 to '86.
Since all of the temp readings appear to be higher than expected most likely cause is that the radiator flow is restricted. Look at the size of the radiator hoses. They are very large to accommodate a huge amount of coolant flow. At the point where the tubes are soldered to the core the solder oxidizes and expands. It is called solder bloom. That can restrict flow quite a bit. This used to be cleaned out by a process called “rodding out”. An abrasive rod was run through each tube to open them back up. If you have an old school radiator shop they can still do this. Aluminum radiators are not serviceable so this only applies to original brass / copper types.
I wish I had a good answer for a reproduction sender. My best recommendation is an OEM sender. They are sometimes available on eBay. Since they have no moving parts they seldom fail.
If you still have the stock 2 row radiator get rid of it. It is probably clogged and or leaks. Replace it with an aluminum 3 row. I did and it solved my over heating issues. I got one that the top looks like OEM and with some black heat resistant spray paint looks good too. I was even able to get the stock fan shroud to bolt on.
Thanks…when they flushed it out and replaced the thermostat they thought it was fine. Since the weather is getting a little cooler I flipped the heater core switch in the engine compartment pushing more into the cabin…it is running around 180-190 now but sometimes the gauge still pops up towards the red…I am starting to think it is the sending unit or the gauge itself just reading inaccurately???
There is yet one more variable if your engine has never been rebuilt - engine block cooling passages can get full of crud. Nothing I did solved my 351C overheating problem until they rodded out the block.
It is now running at 180-190 with the heater core switch opened up…that is not really overheating, is it??? I drove for 30+ minutes the other night and it did not even get to halfway on the temp gauge…so weird…
No, 190 is about right. But, what happens with the heater off? If you need the heater on to hold 190 with a 160 deg thermostat, something isn’t quite right.
