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54’ 3100 235 engine

Just replaced my stock non working gauge with aftermarket modern mechanical gauge. Truck seems to run cold I understand it is a relatively cold part of the engine but usually has to idle awhile after driving at a stop to show any temperature and after driving again usually goes back down to minimum reading.....thermostat issues or just common while drive in cold temps (20-50 degrees) at slow speeds to show cold temp

What temperature thermostat?

Where is your temperature sender attached to the engine?

I have a 61'235 in my truck with a mechanical temp gauge, and in 70 degree weather I drove 2 miles up hill then 2 miles back and about 5 minutes after I parked the truck the temp read at operating temp for a little while before dropping. I think that it takes a while to register the temp and those old 235's take a while to heat up. Overall I trust my mechanical gauge to let me know I'm too hot, but also follow your nose! like a certain toucan once said. You will smell it getting hot about the same time your gauge reads hot in my experience.

I checked my new mechanical gauge in a pot of boiling water before I put it in. It was pretty accurate. My LS setup runs about 199 all the time so the gauge is way up but I just wanted it working.

The temp sensor is the stock position on the 54’ 235. Top rear driver side of engine near firewall. I did test gauge in water before installing the gauge does work. If it sits long enough idle I can get 160-180 but once I start driving Again it pegs to minimum

I believe that is just air cooling the motor as you drive I bet if you drive longer that the needle will slowly start to creep up again.

First of all there is nothing "modern" about a mechanical gauge. An electric gauge would be more modern. Send pic of gauge face after it settles while driving. Or provide part number. It's all about perception, hash marks and thermostats....and you are in New England and we don't know the temperature (30-60) or how much antifreeze you put in.
You are seeing that it reaches 180 then cools off with forward motion. That's what it's supposed to do.

It settles at the peg the same if the engine was off, I mean modern as in not stock original and bought recently at any autozone, if it is normal to show no temperature while moving forward that is perfect and I have no worries that it’s running too cold

Also stated all my driving has been in minimum temp of 20 and Max
Of 50. I haven’t been able to test in warmer temperatures yet but hopefully in the next weeks

As long as experienced owners aren’t saying yes this is abnormal stop driving immediately that is a start

Once last note would be the radiator feels normal operating temp for a motor vehicle so my assumption is a mechanical gauge in that area of engine is prone to read colder but would definitely alert me if it became significantly hotter than it should?

If it actually stays pegged, I would be sure to have proper anti freeze. Your problem can indicate a thermostat stuck open. Easy to test. Pan of water on the stove with a thermometer. See what temp it opens and what temp it closes. Opening temp should near match the value stamped on T stat. You could also have one that is rated too low. You could have a bad new gauge. Tube kink somewhere. Pegging at left is worth doing these tests. It is good that it goes up to 150-180. How does your heater work? Good? Did gauge readings match thermometer when tested?

When you take out T stat, observe it, it should be closed. ALL THE WAY closed. Observe for crusty. Observe for upside down install.

If all checks out, run with radiator half covered with cardboard to see if things change.

All above is for peace of mind but may discover something.

What temperature thermostat are you running? I would think you want at least a 180* stat to keep the engine up to a safe operating temperature. If you allow the engine is running below 160* you run the rick of accelerating engine wear because the clearances are to tight.

Get a Infrared Laser Temperature Sensor (they're cheap and a good tool to have), then take a few readings on the block and radiator, that will tell the story.

https://www.amazon.com/Thermometer-SOVARCATE-Temperature-58%C2%B0F-1112%C2%B0F-Refrigerator/dp/B0878WB6HQ/ref=zg_bs_9931459011_6?_encoding=UTF8&psc=1&refRID=1P29GM4J708SKR9ZDAFD

Mike B

My ‘59 235 takes quite a while before the temperature gauge starts to move. At least ten minutes while driving and probably twenty while idling and that is not to operating temperature. Probably at least another ten minutes. Once it reaches 180 degrees, it stays there.

My temperature sensor is located in the same place as yours.

New gauge works tested in water, will test the thermostat next. Just wanted ask before I start tearing things apart since I’ve never used mechanical gauges before. The antifreeze in it now is regular 50/50 green filled to just cover the top inside radiator

How far does the replacement gauge stick into the head? The stock bulb is about 2-1/2” long and most of that is in the head.

They were identical length luckily

Mako 1975 My 51 6400 with a big radiator will come right on up to 185 in 3or 4 miles then stays there. Never offers to overheat in hot weather. Think your thermostat is kinda crazy .

Had a nice 65 degree day today went for long drive. Temp gauge stays at 140-150 while driving 35-40 mph. Stopped and took readings periodically with infra red......radiator always 140ish maximum, 140-165 in between spark plugs/heads 180 if stayed stopped for minute or so. Most spots on engine 160ish

First day temp gauge didn’t peg out at minimum since warmest day of year so far by at least 10 degrees

I would change the thermostat for one rated at 180 degrees. Its cheap and easy to do. 160 degrees is too cold.

Put in a 180 yesterday going to drive tomorrow when weather clears.

New thermostat works much better, it was free flow open before....gets up to temp and stays there, downside is need new radiator

+

Glad you solved your issue. One more success! One step closer!

mako, i have a 54' 3100 with a 57' 235 engine. my gauge sensor line is cut just outside the firewall & i was looking for where my sensor is and all i see is a pipe plug in the top of the head driver side just above the #5 intake manifold port. is that where your is located??

also if anyone now what the part number would be for a new sensor???

thanks

I will assume you are talking about a temperature gauge.
You will need to buy a new 54 gauge and capillary sensor. Sold as one unit. Click
Adapt it's sensor fitting to the 57 motor as necessary.
I assume when it broke/was cut off, someone plugged the sensor hole with a pipe plug.