temp climbs to 230

[71MACH-1]

My 71 Mach 1 gets too hot with the AC on. I have a 2 core but the shroud is only a chrome decorative top piece........

Sorry about the thread hijacking

 

[goodnigh]

I bought one of those digital infared thermometers and I took some

Those thermometers are pretty cool, huh?

You can tell which cylinder is mis-firing by

aiming the thermometer at the base of a spark

plug.

mike

 

[midlife]

Aha! I was right* all along: that your temperatures are not correctly reading on your gauge. My bet is on the sending unit not compatible with your aftermarket gauges.

*A blind squirrel can get an acorn once in a while...

 

[TheJ]

Simple way to test BOTH your new IR meter as well as automotive gauge:

Boil some water.

Obviously you can point the meter to the water.

But, to test your sender, you can:

0. Boil a pot of water...say 1 quart. Make sure to pick out your wife's nicest pot, or maybe even Tea Kettle...I went for the tea kettle last time because she would never suspect I would use that.

1. Remove the water temp sender from your car.

2. GROUND the water temp sender to your cars chassis.

3. Make sure the sender's electrical wire is attached.

4. Stick the sender in the pot of boiling water with the electrical wire attached.

5. Turn your ignition key to ON, and see where your gage goes.

The water will tend to cool pretty fast, so you might want to grab your wife's oven or meat thermometer to confirm the water temperature.

You will lose water removing the water sender, so either drain your radiator or go buy a plug. You can look at a sender at the auto parts store to get an idea of the thread you need, unless someone here knows off hand.

This is also a good way to check a new sender/new gage.

This would work but instead of boiling water you could get a cup of ice water and test the sender and the thermometer. Let the ice water sit a minute to get to temperature. They both should read 32 deg F.

 

[ramair]

Aha! I was right* all along: that your temperatures are not correctly reading on your gauge. My bet is on the sending unit not compatible with your aftermarket gauges.

The gauges I am using are Sunpros that have their own sending units. My car originally only had the idiot lights, I have them hooked up too. I am thinking the Sunpro gauge is defective or the sending unit is.

 

[Wolverine]

The reason I use boiling/hot water is the temperature is close to the operating temperature of the engine. I don't think a cars temp gauge goes down to freezing, does it?

 

[Jeff73Mach1]

The reason I use boiling/hot water is the temperature is close to the operating temperature of the engine. I don't think a cars temp gauge goes down to freezing, does it?

Correct

32 is way off of the operating range and would not provide any relevant information.

I see no reason that an infrared thermometer aimed at the sensor should not provide a logical and valid basis for gauge calibration.

Most gauges operate by resistance across a ground circuit. Improper wiring will also lead to improper readings (including poorly designed factory wiring) I did own one ford whose temperature gauge would go from in the middle to on the high side, just by the act of turning on the radio. It was an aftermarket radio and after relocating the ground the temperature gauge stopped its aberrant behavior.

 

[TheJ]

The reason I use boiling/hot water is the temperature is close to the operating temperature of the engine. I don't think a cars temp gauge goes down to freezing, does it?

This is true, a slight oversight on my part. This is how you test full range thermometers, I didn't even think that his gauge won't go that far. You could also do this test on newer cars with the help of a scan tool.

 

[Wolverine]

This is true, a slight oversight on my part.

Were you by any chance staring into a cool glass of The Knot on ice?

 

[stevemach1ford]

well no one wanted to scare u but i had the exact same symptoms with my 2v clev ft lauderdale stop n go was terrible i would drive thru parking lots in cricles to beat the traffic lights turned out cracked valve bowls in head no water in oil no funny noises nothing but watching the needle go up and then back down.had 4v heads done instead of repairing and bam it was fixed good luck hope its ur sunpros auto meter has never let me down

 

[ramair]

The Sunpro temp gauge has no ground, it just had the sending unit attached to the the coiled wire that as attached to the gauge. I doubt it is a cracked head, 351W are not known for cracking heads and my car is not loosing any coolant. I will check the plugs to be sure, but I doubt I have a cracked head or blown head gasket.

 

[Jeff73Mach1]

I know what it is! Seriously!

Gauges use ground to give you readings. The sensor essentially allows more or less current to be drawn, thus giving you your reading.

I'd be willing to bet $2.41 that you used teflon tape on the sending unit. This affects the ground and causes readings to be off. The senders are a tapered pipe thread and need no teflon tape.

 

[TheJ]

Get yourself a multimeter and check to make sure the sender has a good ground. With the battery hooked up measure the voltage at the battery terminals. Then put the positive lead on the positive side of the battery and the negative lead to the base of the sender, not the terminal. The to readings should be close together, I'd say with in a half a volt.

Hope this helps.

 

[ramair]

I know what it is! Seriously!

Gauges use ground to give you readings. The sensor essentially allows more or less current to be drawn, thus giving you your reading.

I'd be willing to bet $2.41 that you used teflon tape on the sending unit. This affects the ground and causes readings to be off. The senders are a tapered pipe thread and need no teflon tape.

I did use teflon tape on the fitting, I will take it off and recheck the gauge.