Temperature Gauge Reads Extremely High (New 302)

tx65coupe · Apr 28, 2009

For those that don't know, I recently dropped a new 302 T5 etc into my 65 that started life as a 200 3 speed.

Anyway, The temperature gauge reads about 90 percent of the scale and the thermostat wasn't even open. This was the second time we ran it with the radiator cap on. After cooling down it doesn't appear that it took any more coolant in.

Keep in mind that this is all under initial startup with radiator cap off. We didn't have the cooling stystem completely full and were trying to fill it up. This time the gauge was pegged out at max H.

I am wondering if the sending unit is the problem. I have all new stock style gauges. They are the long speedo with the 120 mph speedo and fuel and temp gauges with warning lights for oil and alt. Could it be that the sending unit I got from CJ Pony part number HW1316 is the wrong one? It says 65 all for warning lights etc. I would link to their page, but the links never work for that website. Just search that part number at CJ if you want to see it.

Could the problem also be that my 302 has a 180 thermostat in it? I thought that the older engines had like 160 or 165 stats. If so, what sending unit can I use that will read close to right?

We used an infarred thermometer and could only get 160 degrees at the hotest spot on the motor. I'm not sure how accurate our test was though.

D.Hearne · Apr 28, 2009

Only way to know for sure is to install a mechanical temp gauge.

tx65coupe · Apr 28, 2009

I figured that would be a response. That would definitely tell what the actual temp is.

I was planning on installing a temp gauge and oil pressure gauge a little later, but that is not in the budget at the moment. We have spent far too much lately.

I just thought that someone else may have experienced the same thing when upgrading to a 302.

I have an Edelbrock intake and have the temp sensor in the front driverside corner. This is the best place I could find to put it. Is this a suitable place.

tx65coupe · Apr 28, 2009

On another note the heater doesn't seem to be working either. It has all new components as well.

When I turn the heater on only luke warm air comes out.

I think their is still air in the system, but maybe the heater core is clogged. I do know that when is was a 6 cylinder the heater didn't put out much heat either.

Maybe our Fluidyne radiator is keeping it cool and that is why the heater isn't putting out much heat.

It also seem like the thermostat will open and then close within a few seconds or so.

2+2GT · Apr 28, 2009

Anyway, The temperature gauge reads about 90 percent of the scale and the thermostat wasn't even open. This was the second time we ran it with the radiator cap on. After cooling down it doesn't appear that it took any more coolant in.
If it were actually as hot as that gauge says, it would have been boiling back out.

I am wondering if the sending unit is the problem. I have all new stock style gauges. They are the long speedo with the 120 mph speedo and fuel and temp gauges with warning lights for oil and alt. Could it be that the sending unit I got from CJ Pony part number HW1316 is the wrong one? It says 65 all for warning lights etc.
The warning light sender was on/off. The gauge senders all have the same nominal electrical value.

Could the problem also be that my 302 has a 180 thermostat in it? I thought that the older engines had like 160 or 165 stats.
NO, these engines were designed for a 190°F thermostat.

We used an infarred thermometer and could only get 160 degrees at the hotest spot on the motor. I'm not sure how accurate our test was though.
Duct tape your wife's digital cooking thermometer to the upper radiator hose. It'll be right within a few degrees. Don't get caught.

tx65coupe · Apr 28, 2009

Its got edelbrock aluminum heads intake and carb as well as an upgraded cam. I was told that the 180 was a good choice. Should I swap out the 180 for a 190 stat? My 95 F150 with efi 5.0 has a 195 stat I think.

Thats a good idea about the digital cooking thermometer. I am going to try that.

What does this statement mean?

The warning light sender was on/off. The gauge senders all have the same nominal electrical value.

Is there any way to make the temp gauge read correctly or close to it? My fuel gauge reads about 1/4 to 1/3 and has about 5 gallons in the tank. So, it reads about right. Usually if the regulator on the back of the cluster is the problem both gauges will read high or low. That doesn't seem to be the case here. I wonder if I have a defective sending unit.

2+2GT · Apr 28, 2009

Its got edelbrock aluminum heads intake and carb as well as an upgraded cam. I was told that the 180 was a good choice. Should I swap out the 180 for a 190 stat? My 95 F150 with efi 5.0 has a 195 stat I think.
I would. I always use the real Ford thermostat, it has a small bleed valve to let the air out when you refill the system, so you don't have to stand around for a half hour with the engine running.

Thats a good idea about the digital cooking thermometer. I am going to try that.

Is there any way to make the temp gauge read correctly or close to it? My fuel gauge reads about 1/4 to 1/3 and has about 5 gallons in the tank. So, it reads about right. Usually if the regulator on the back of the cluster is the problem both gauges will read high or low. That doesn't seem to be the case here. I wonder if I have a defective sending unit.
The gauge may be out of spec. The gauges can be calibrated, but it's a real pain. You may simply have a sending unit that's out of spec.

2nd Mustang · Apr 28, 2009

Is that suspected hot reading while the car is moving or when sitting still with the hood up?

I have a 302 with a mild build up. It has a 160 degree thermostat. If I remember correctly, a 160 thermostat will start to open at 160 and at 180 it will stay wide open. My car has never gotten over 190 degrees, even in the hottest So Cal summer days of stop and go driving.

My heater doesn't work efficiently either. It puts out warm air at the best but that could be due to old heater duct hoses.

Capt Dan · Apr 28, 2009

If you are running guages with a sending unit for lights, I would start there. I don't think they are interchangeable.

2+2GT · Apr 28, 2009

2nd Mustang said:
It has a 160 degree thermostat. If I remember correctly, a 160 thermostat will start to open at 160 and at 180 it will stay wide open. My car has never gotten over 190 degrees, even in the hottest So Cal summer days of stop and go driving.

My heater doesn't work efficiently either. It puts out warm air at the best but that could be due to old heater duct hoses.

No, the 160° 'stat = poor heater performance.

It's also not doing your engine performance any favor, either.

The thermostat has nothing to do with whether or not the car overheats (unless it jams closed, of course). Either the radiator is sufficient to the job, or it isn't. A 160° 'stat won't make your radiator any larger.

D.Hearne · Apr 28, 2009

2+2GT said:
No, the 160° 'stat = poor heater performance.

It's also not doing your engine performance any favor, either.

The thermostat has nothing to do with whether or not the car overheats. Either the radiator is sufficient to the job, or it isn't. A 160° 'stat won't make your radiator any larger.

That's not true. It would be only true if the engine ran at 160* with it.. I have a 160* T-stat in my V8 Ranger and it's normal operating temp is 210* with it. With a 180*, it'll stay at 230+ The 160 opens sooner and helps the radiator (which is really too small in my opinion) get an early start on cooling the engine.

2+2GT · Apr 28, 2009

D.Hearne said:
That's not true. It would be only true if the engine ran at 160* with it.. I have a 160* T-stat in my V8 Ranger and it's normal operating temp is 210* with it. With a 180*, it'll stay at 230+ The 160 opens sooner and helps the radiator (which is really too small in my opinion) get an early start on cooling the engine.

I'm trying to figure out how getting an early start will increase radiator efficiency. Do you have a rigid fan? Clutch? Electric? Fan shroud?

Getting an early start on cooling would help only if you only drive short distances. After that, you're done. Try a 190° sometime. Oddly, it sometimes helps the engine run cooler. Something about the temperature differential of the coolant in the radiator vs. the ambient air. I'm not very good at thermodynamics, though.

jlangholzj · Apr 28, 2009

i just put a 180 in my stang. It did have a 195 and ran at 215-220 on a regular day. After putting the 180 in, it sits comfortably at 185...i like.... much better performing and runs very good now.

2+2GT · Apr 28, 2009

jlangholzj said:
i just put a 180 in my stang. It did have a 195 and ran at 215-220 on a regular day. After putting the 180 in, it sits comfortably at 185...i like.... much better performing and runs very good now.

Sounds like your 195° wasn't operating properly.

ForceFed70 · Apr 28, 2009

Here's a cheap easy way to test:

All an electronic temp sensor is is a resistor that varies it's resistance depending on temp.

Pull your sensor out and put it in a pot of boiling water. Boiling water is always 100*C (or something like 220*F). Measure the resistance across the sensor while it's in the boiling water (1 lead of voltmeter on the threads, the other on the wire that goes to guage). Record this number for reference.

Now put the sensor back in the car, let it get up to temp, measure the resistance, and compare to what the resistance was when in the boiling water. This will give you a good idea of how hot your engine really is.

Keep in mind that as tempurature increases, resistance decreases.

2nd Mustang · Apr 28, 2009

Maybe I should add that my 302 has a mild hydraulic Crane cam, 600 Holley, long tube headers with H-pipe, 2.25" exhaust, turbo mufflers, 4 speed top loader, 3.25 limited slip rear end, no power steering, no A.C., stock water pump and a four row brass radiator.

After the thermostat opens fully at 180 degrees, it's not the thermostat controlling the maximum temperature but other items with the engine and car. Full open is full open no matter what temperature thermostat you have. All of the thermostats will stay at full open, just at different temperature settings.

If you want your car to run a hotter temperature level, that's, is IMO, a personal thing. My car runs very well at 180-190 degrees.

tx65coupe · Apr 29, 2009

Capt Dan said:
If you are running guages with a sending unit for lights, I would start there. I don't think they are interchangeable.

I am running a sending unit for the cluster with warning lights. This means that the cluster has fuel and temp gauges and alt and oil lights.

The other cluster is all gauges.

tx65coupe · Apr 29, 2009

2nd Mustang said:
Is that suspected hot reading while the car is moving or when sitting still with the hood up?

I have a 302 with a mild build up. It has a 160 degree thermostat. If I remember correctly, a 160 thermostat will start to open at 160 and at 180 it will stay wide open. My car has never gotten over 190 degrees, even in the hottest So Cal summer days of stop and go driving.

My heater doesn't work efficiently either. It puts out warm air at the best but that could be due to old heater duct hoses.

The hot reading is sitting still with no hood on the car.

We used an infarred thermometer and the hottest reading we could get was about 160. The thermostat does open, but doesn't stay open very long.

I know the engine isn't that hot because it feels about normal when touching the hoses etc.

I have discovered that my NEW heater core is clogged up. I don't really know how, since everything is new.

tx65coupe · Apr 29, 2009

ForceFed70 said:
Here's a cheap easy way to test:

All an electronic temp sensor is is a resistor that varies it's resistance depending on temp.

Pull your sensor out and put it in a pot of boiling water. Boiling water is always 100*C (or something like 220*F). Measure the resistance across the sensor while it's in the boiling water (1 lead of voltmeter on the threads, the other on the wire that goes to guage). Record this number for reference.

Now put the sensor back in the car, let it get up to temp, measure the resistance, and compare to what the resistance was when in the boiling water. This will give you a good idea of how hot your engine really is.

Keep in mind that as tempurature increases, resistance decreases.

I am going to try this and post back with results.

2+2GT · Apr 29, 2009

2nd Mustang said:
If you want your car to run a hotter temperature level, that's, is IMO, a personal thing.

Perhaps, but I knew a Ford engineer who was involved in engine and drivetrain development, and he assured me these engines were intended to run best with the 190° thermostat. Combustion, economy, power, corrosion resistance are all factors.

Temperature Gauge Reads Extremely High (New 302)

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