Overheating on a 170 in a 1961

[Notar61]

Hello,

I seem to be having some overheating issues. The 61 I'm working on has a new 2-row original style radiator, new water pump, new hoses, and a new 180 degree thermostat. Back at the end of May I had been driving it around a local town and it didn't seem to have any problems, temperature stayed right in the middle all day. Yesterday I was driving it at a steady 40 mph and the temperature gauge pegged out fairly quick after about 4 miles. It is warmer out now since it is going on July, but I don't understand what could make it drive so well last month and now it seems to overheat so badly? I haven't really messed with anything recently.

Based on some research I did, maybe I should check the timing? Also the fuel to air ratio on the carb? I also heard that a blown head gasket could be the culprit.

Does anyone else have any leads or maybe something I'm over looking? Thanks for any help!

-Andrew

[ew1usnr]

Hello, Andrew.

I don't understand what could make it drive so well last month and now it seems to overheat so badly?

Maybe the thermostat is stuck closed?

Is your fan belt tight?

When the radiator cap is off and the the engine is is running, can you see that the coolant is moving (circulating) in the radiator?

Thanks, Dennis.

[Notar61]

Dennis,

Thanks for the ideas.

Hopefully it's not a stuck thermostat. It's brand new. But I guess anything is possible.

The fan belt might be something though. I did put a new one on after I replaced all the cooling system parts. Maybe I didn't get it tight enough? That would make sense in that it was fine right when I put it on, but it might of slowly loosened up over time......thus making it overheat recently. I will have to check that today when I get home. Does anyone know the torque spec on the tensioner bolt?

I can also open up the radiator and verify if the coolant is moving around in there too.

Thanks again!

-Andrew

[Luva65wagon]

In addition to Dennis' great spot-on suggestions, you may want to verify your lower hose has a spring inside of it. With the motor off reach down and see if you can squeeze it to the point of collapse. Lower hoses are under suction and at a steady speed the lower hose may have got sucked closed.

I assume also the car actually did overheat with some evidence other than the temp gauge? Make sure that it isn't just a faulty sender.

Checking for flow does two thing at different points in time. When you start the car cold, cap off, there will be very little, if any flow and movement. Once the thermostat starts to open (if it opens) you will see the flow of coolant begin as you are looking down into the radiator.

Regarding a blown head gasket, this is, of course, possible, but would be the last thing to check for. Though there are testing tools for this - sniffers for combustible fumes out the radiator - there is also a potential for the water as you're running it to begin to bubble and froth like Old Faithful just running it there in the garage. If that doesn't happen, I would probably rule that out.

Also A/F mixture would be almost a non issue on a stock-ish Falcon.

[Notar61]

Roger,

I don't think my new lower radiator hose had a spring in it. If it did I may not of noticed. I can check though tonight. Do you know anywhere I can get a spring to put in there? I saw some for the V8 engines that some places sold, but not one for the six cylinder engine.

I'll do the radiator "cap off test" and let you guys know the results once I get the chance.

Hopefully its just something simple like the belt being loose or the lower radiator hose needing that spring.

-Andrew

[Luva65wagon]

You can get springs. In fact I bought a lower hose and spring (for something) once thinking the lower spring was "optional" and the hose came with a spring too...

... not sure if I still have said spring.

But check first and see. Hopefully it is simple. If all your changing was because it was overheating before, you may have simply not fixed yet what was wrong.

Keep us posted.

[doghows]

Not to be a smart *** but is the thermostat in the correct way? I only bring it up because I did put mine in backwards before and she blew her top.
Just looking for the simple stuff. Good luck.

[Notar61]

Yeah I guess some sensor testing is in order. Hopefully I can get to the bottom of this.

And Dogshows, no worries on the thermostat question, but the old one was in the correct way and the new one I just installed went in the same way as well.
(Spring towards the engine, pointy end towards the radiator).

I may be grabbing at straws here, but is it possible my oil pump is dead or in the process of dying? I had a flickering oil pressure light lately, but just figured the oil pressure switch/sensor needed to be replaced. I read somewhere that if it was on the fritz it could cause the engine to overheat pretty quick. Just a thought, although I read that it is rare that they ever go out.

Thanks again everyone for all the help on this!
-Andrew

[Luva65wagon]

Andrew,

The temperature and fuel gauge both operate off a 5-volt voltage regulator on the back of the gauge cluster. Is the fuel gauge working well? If it too is misbehaving, then this regulator may need to be changed. It's a crude device at best and they will seriously alter your gauge readings if bad.

Also, there is overheating and there is high temperature gauge readings. Overheating is blowing coolant out somewhere. High temp readings can be checked for using any of the things like Dennis suggested checking for.

Of course, if the water is flowing, the thermostat has to be opening. You can often use that point, at which it opens and water begins to flow, as a "read" for what the gauge is showing. Stock gauges have no temps written on them, so if you have a 180° thermostat and you watch the gauge, when you see water just start to flow look at the needle on the gauge. If it is already pegged at that point, you can rest knowing it is not reading right. If it is reading low at that point, yet continues to climb - then you may have something totally unusual causing the overheating. These would include everything from a shot water pump, leaky head gasket, cracked block, cracked head, or the engine is on its last leg. But really, as a motor gets old and sloppy, it tends to make less heat than more of it. Ring friction is at a minimum as is cam-lobe friction, which causes a lot of heat.

By now it sounds as though you have changed all the obvious things, so the question I guess I'm asking, is it a blow its lid overheating or simply an indication via temp gauge of overheating, but nothing is spewing?

[Notar61]

Just installed a new thermostat. No luck though. Car still overheats. I can see coolant circulating in the raradiator but the temp gauge pegs out after idling for about 5 mins. Is this a sign of something way worse....maybe engine wise??? I'm at a loss at what else to try......

[ew1usnr]

Just installed a new thermostat. No luck though. Car still overheats. I can see coolant circulating in the raradiator but the temp gauge pegs out after idling for about 5 mins. Is this a sign of something way worse....maybe engine wise??? I'm at a loss at what else to try......

Could it be that the temperature gauge is bad? Unless the cooling system was dry it almost does not seem possible to peg the temperature gauge after only idling for five minutes.

Maybe you could try a ThermoCap to get an independent verification as to what the temperature in the radiator actually is.

ThermoCap1.jpg

See: https://www.amazon.com/Mr-Gasket-247...hermocap+2470R

[Notar61]

Dennis,

Yeah maybe it is the gauge or the sending unit. I feel like I've gone over everything else at least 2 or 3 times now.

I bought a new sending unit when I started throwing on all the other new cooling system parts. I just got it at a local parts store....looked the same as the old one. Is there something wrong with the new one maybe? Maybe its producing an incorrect reading, if it is the wrong sending unit for the car? Is that possible? Maybe I should get a sending unit from a resto-mod place....that way I know its the correct type for sure?

Guess I will try that radiator cap with the temperature gauge too.

Could the overheating be indicative of a bigger, more serious problem? My older brother seems to think the engine is on its last leg or something....but he always throws this suggestion out at the sign of any issue.

Hopefully I can get this figured out really soon. It's driving me up the walls.


thanks,
Andrew

[ew1usnr]

Yeah maybe it is the gauge or the sending unit. I bought a new sending unit when I started throwing on all the other new cooling system parts.

I am just putting out ideas:

Ground the sensor while it is cool and have it connected to the gauge. The gauge should read cool. If the gauge pegs hot there is a probably problem with the sensor, or possibly the gauge.

You could test the accuracy of the sending unit by putting it in hot water. Heat the water to about 180 degrees and use a thermometer to measure it. 180 degrees should be mid-range on your cars temperature gauge. Then ground the sensor and have it connected to the gauge and drop the sensor in the hot water. The gauge should read mid-range. If it pegs hot there is a problem.

Or, just buy another temperature sending unit to replace the one you have, and see if the new sensor pegs hot the same as the previous one. If not, the problem is solved. If it reads the same, the problem is not with the sensor.

Just look at this philosphically and keep telling yourself "This is a hobby. This is a hobby." Avoid thinking about presidential politics and do not get stressed.