Temp gauge help needed.

[78SierraGrande]

I have a 1978 C20 454 with a TH400. I have a 4 core radiator. I suspect my temperature gauge is not reading correctly. It runs "normally" between the "c" and the first hash mark. It has never ran "hot", so I don't suspect I have a cooling issue.

My question is, how do I determine if my temp gauge is accurate? Where does the mechanical connection enter the block or water jacket? How would one go about installing an aftermarket mechanical temp gauge?

 

[Honky Kong jr]

I have a 1978 C20 454 with a TH400. I have a 4 core radiator. I suspect my temperature gauge is not reading correctly. It runs "normally" between the "c" and the first hash mark. It has never ran "hot", so I don't suspect I have a cooling issue.

My question is, how do I determine if my temp gauge is accurate? Where does the mechanical connection enter the block or water jacket? How would one go about installing an aftermarket mechanical temp gauge?

I wanna say the sensor is screwed into the cylinder head inbetween the exhaust ports. Or in the intake it will be a single wire sensor. Just remove the sensor and install your mechanical gauge adapter in there in which ever location your current sensor lives.

 

[MrMarty51]

At the work shop, they have a red box that has a bunch of potentiometers in it. There is also a card with different settings listed for the various makes and models of wehicles. Hook that to the temp sending wire then adjust the resistance and read the gauge to see if it is accurate.
The temp sender unit is screwed into the head on the drivers side.
There is a plug on the passenger side head that can be removed and a mechanical gauge installed into it.
do You know what temp of a thermostat is in the engine now ? If it is a 180 then the temp gauge might be accurate.

 

[1987 GMC Jimmy]

Get you one of those laser sighted non-contact thermometers from Hope Depot. I bought the green one, and it works well. Point it at the side of the head where the sender is to get an accurate reading so you can compare it to your gauge.

 

[78SierraGrande]

At the work shop, they have a red box that has a bunch of potentiometers in it. There is also a card with different settings listed for the various makes and models of wehicles. Hook that to the temp sending wire then adjust the resistance and read the gauge to see if it is accurate.
The temp sender unit is screwed into the head on the drivers side.
There is a plug on the passenger side head that can be removed and a mechanical gauge installed into it.
do You know what temp of a thermostat is in the engine now ? If it is a 180 then the temp gauge might be accurate.

It is 180 degrees. I changed it JIC when I got it back on the road. It had sat for about 10 years. I've had the truck since 1993, and it has always run very cool. I now have a wife who I really like, lol, so I don't want to risk her being stranded somewhere due to a faulty gauge. Thank you for your reply.

 

[75gmck25]

There appears to be a problem with getting the right senders for some of the older gauges, and it throws them off a little. I've run across articles that provide parts numbers for the right sending unit, but I haven't kept track of the URLs with the info.

On my '75 GMC I have the stock gauge and an under-dash mechanical temp gauge. With a 195 degree thermostat the stock gauge reads a little under the first hash mark when warmed up, and that is about 195 degrees on the mechanical gauge. At about 200 degrees the stock gauge has just reached the hash mark.

Bruce

 

[highdesertrange]

a note on the IR thermometers. the reading you get through metal will be 5-10 degrees cooler then the actual water temp. highdesertranger

 

[Tobe's84Jimmy]

i love how you said you now have a wife you really like. i was married before, divorced, and yes NOW I TOO HAVE A WIFE I REALLY LIKE, ha!!