Bad Temp Gauge?

GetX'd

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This is kind of an add on to the recent thermostat thread. I thought my stroked 440 was running too cool so I checked the thermostat and found it had a 160 in it. So I popped it out and replaced it with a 180. Thought it would run a bit warmer. I have a triple cored refreshed stock radiator too. I took the car for a good test run today and the gauge actually shows cooler than when I had the 160 stat in it. Dennis H recommended I get one of those laser temp guns which I picked up online. When I shoot the stat housing she reads a perfect 185 - 190. Pretty close to 185 mostly. The gauges were refreshed a few years ago and the temp has never run up to the normal operating range I would expect. I guess the car is running warm enough - so I’m left to think there’s something wrong with the gauge. Any thoughts or advice from anyone? I abhor the thought of taking that out - but how would I ever know if she is running to hot? What do you think?
 

gdrill

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Well personally, if I owned an engine that I had serious money into and truly worried about, I would definitely run aftermarket gauges aside from the factory setup. My engines are all relatively cheapos but I do believe the backup info to be priceless.
I know, not everyone likes the look of the gauges under the dash, but for me it's not about looks at this point.
 

Ranger16

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I would agree that the gauge is probably inaccurate and I think you have pretty much proved that with the IR thermometer.
 

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I would agree that the gauge is probably inaccurate and I think you have pretty much proved that with the IR thermometer.

Any way to fix those gauges? I’m not to swift with the elec part of the car. Are there wires running from the firewall to somewhere that I could double check?
 

PurpleBeeper

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Maybe start with the temperature sending unit? It's a lot cheaper & easier to install. There are probably some guys on this board (or online somewhere) who could help you rig up some type of "resistance adjuster" that would let you dial in your stock temp gage too (I've not seen this, but to me it makes sense).

Now that I think about it, maybe you could run a pipe thread tap up the temperature gage sending unit hole? I think that our gages work on resistance and that takes a good ground.

Any gage/electronic guru please jump in. I'm half guessing here.
 

PurpleBeeper

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Any way to fix those gauges? I’m not to swift with the elec part of the car. Are there wires running from the firewall to somewhere that I could double check?

yes, if you're running a big block, the temperature sending unit is screwed into the water pump housing, front of engine, passenger side (if I'm remembering correctly). It has one wire with an "L"-shaped push-on connector (white wire????) I believe it goes directly into its own connector in the bulkhead disconnect.
 

texas69bee

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Maybe start with the temperature sending unit? It's a lot cheaper & easier to install. There are probably some guys on this board (or online somewhere) who could help you rig up some type of "resistance adjuster" that would let you dial in your stock temp gage too (I've not seen this, but to me it makes sense).

Now that I think about it, maybe you could run a pipe thread tap up the temperature gage sending unit hole? I think that our gages work on resistance and that takes a good ground.

Any gage/electronic guru please jump in. I'm half guessing here.
^^^THIS^^^
Temp sending unit. I’m not sure what’s going on with them but I’ve had 2 fail already. I replace them, they work fine for a while then puke out. When new, temp is 190. When they fail, temp gauge barely moves.
 

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^^^THIS^^^
Temp sending unit. I’m not sure what’s going on with them but I’ve had 2 fail already. I replace them, they work fine for a while then puke out. When new, temp is 190. When they fail, temp gauge barely moves.
Where do you purchase a temp sending unit? Is that the one wire that goes from the water pump housing to the bulkhead that purple beeper is mentioning above?
 

miller

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Pretty much any parts house 'should' have the sending unit.

One little side note, like mentioned, the gauge works off of signal sent to it, AND ground.
The needed ground is where the sending unit threads into the pump housing. Use only a liquid type thread sealer, and still check for good ground contact, from sender to pump housing.

Gauge can be tested, by using the sending unit wire, simply to ground. Moves slow, but if good, the needle will move it's full range.
 

Ranger16

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Is that the one wire that goes from the water pump housing to the bulkhead that purple beeper is mentioning above?
Yes. Here is the best picture I have of mine. It's a 383, but they are the same.
You can see the single (factory gauge) wire below the heater hose. The silver cable above the heater hose is for the more accurate aftermarket gauge installed below the dash.
Road Runner 2   383 Motor.JPG

Road Runner 2 Interior 2.png


The factory sending unit will look something like this. The connector shown slides onto the nipple on top.
c-1150-3.jpg


Any way to fix those gauges?
I doubt if there is any way to make them more accurate. I think they are just dampened down to show "normal range". Just the nature of the beast.
 
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Yatzee

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This is kind of an add on to the recent thermostat thread. I thought my stroked 440 was running too cool so I checked the thermostat and found it had a 160 in it. So I popped it out and replaced it with a 180. Thought it would run a bit warmer. I have a triple cored refreshed stock radiator too. I took the car for a good test run today and the gauge actually shows cooler than when I had the 160 stat in it. Dennis H recommended I get one of those laser temp guns which I picked up online. When I shoot the stat housing she reads a perfect 185 - 190. Pretty close to 185 mostly. The gauges were refreshed a few years ago and the temp has never run up to the normal operating range I would expect. I guess the car is running warm enough - so I’m left to think there’s something wrong with the gauge. Any thoughts or advice from anyone? I abhor the thought of taking that out - but how would I ever know if she is running to hot? What do you think?
If what you see on the gauge needle is confirmed to be 185 actually then if the needle moves above that point you're creating more heat. Sometimes a hotter stat can make a car run cooler because of higher temps which "steams" out minute air bubbles in the block and a higher pressure rad cap can have the same effect. To my knowledge, manufacturers gauges needles sit pretty much in the center of their total travel at the correct operating temperature. It's an esthetic thing I believe.
 

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I think I just took what I’d hope was a minor problem and turned it into a bigger one. I bought a new sending unit and went to install it. Appears that the one that’s in there has been since the car was stock. Or at least the better part of the last 50 years. Tried to get the 1/2 out of the water pump housing and it’s in there so tight I stripped the head on it. It’s sooooo old that I had to force it and now the wrench won’t grasp it. Any ideas on how to get that thing out of there?
 

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Can you get a small pipe wrench on it? A cheater pipe will help, just don't get too heavy handed.
 

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Drill out with a succession of bigger bits.
 

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Well I got the sending unit out of the pump housing and replaced it with a Borg Warner sending unit. Drove until it should have been warmed up and the gauge needle still only moves a short distance. Checked the temp at the stat housing with my laser temp gun and it read 190. I guess this means the gauge is bad or the wire is not grounding properly. Any additional thoughts on this since I’ve got a new sending unit in there?
 

oldbee

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Wellll to check grd on the sender, add a grd wire and then that's out of equation. Personally I'd try someone else's sender first after the grd check. I just don't trust anyone anymore(especially Chinesium).
 

miller

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General rule on checking the gauge itself is, to put the sending wire directly to ground. The gauge needle should slowly move, all the way to the opposite (high) stop. Of course, connections at the gauge need to be in good shape, and the wires themselves.
 
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