Thermostat/ Temp Guage?

[JRBECK64]

What temp thermostat are you running in your Small Blocks and where does the temp guage read on the stock guages with the engine up to speed? I think I may have a problem with my Stock Temp Guage. Thanks for any help you can give with this.

JRBECK64

[Andy4639]

I have a 1986 HO 305 in mine and had to put the 307 temp gauge sendor in it to get the right reading for the factory gauge. It stay's right at the hash mark in the gauge. That's where I like it, have no idea what temp it's running though!

[Shyguy]

My '71 350 has a 180 degree thermostat and the stock temp gage up to temperature was at the first hash mark.

[GASoline71]

My '72 350 is exactly the same...

Gary

[sjarrett71]

My 72 GMC with stock everything and a 180 degree thermostate is at the hash mark also. Although I don't know what temp it is and I would like to know. I might add an aftermarket gauge somewhere down the road.

[JRBECK64]

Thanks for the info. My guage is pegging out and I dont know if its the guage or if the truck is really getting that hot. I am going to put an Aftermarket under the dash guage in it today with actual temp readings. I am running a 180 Degree Thermostat and Im not sure but I dont think the truck is running as hot as the temp guage is saying so I guess I need to figure it out before I do some damage to this Brand New Engine. Luckily my Thermostat cover has a port in it for a Temp guage bulb so Thats where I am going to hook that up. I guess I could take the Thermostat out and see if maybe its just a bad Thermostat as well. All the little things you have to Iron out when you put a truck back together is crazy. I bought a Brand New Power Steering Kit from CPP and the pump is leaking, now I have to take it out and send it back to them so they can check it before I can get a new one sent to me. That equates to two weeks of mail time to get another Power Steering Pump. It never ends.

JRBECK64

[blime81]

My electric fan cuts on at 200 degrees which is above the hashmark but not quite straight up. More like 11:00 or so. With a 180 and a belt driven fan it was the hash mark.

Are you sure the sender isn't grounding out? Check your wire.

If you ground the wire to the block it will peg out the guage if everything is working right. A fray in the wire allowing it to ground could be your issue. Sometimes a header can burn it and let it ground.

[JRBECK64]

Originally Posted by blime81

My electric fan cuts on at 200 degrees which is above the hashmark but not quite straight up. More like 11:00 or so. With a 180 and a belt driven fan it was the hash mark.

Are you sure the sender isn't grounding out? Check your wire.

If you ground the wire to the block it will peg out the guage if everything is working right. A fray in the wire allowing it to ground could be your issue. Sometimes a header can burn it and let it ground.

blime81,
I put a new harness and a new sending unit on the truck. What it does is come up slowely and it will eventually peg if I let it set and Idle. I am wondering if I have the wrong sending unit for the application? I bought an under the dash guage with actual temp readings so I wont be guessing. I also bought a Thermostat that fails to the open posistion so there wont be the possiblity of an overheat situation.

JRBECK64

[JRBECK64]

Does anyone know if there is a certian Sending Unit that is supposed to be used with the guages that are in these trucks? Like is there a certian ohm rating that the sending unit is supposed be? I would really like to get the Stock Guage working properly. Thanks for any info you can help me with.

JRBECK64

[72supermike]

I have a 72 4wd 1/2 ton that I just put a new sending unit in cause the gauge wasn't working at all. Now it will warm up to the top of the red zone and then cool down to the hashmark before the red zone once the thermostat opens up. Kinda wondering that same thing as you. Thanks!

[blime81]

If it comes up slowly you don't have a ground issue.

Not sure on the ohm rating. The sure shot will be to try with a real temp guage. Factory gauge could be messed up.

Another thought I had was if you recently put the sender in you could have let air in the block. What can happen is the air can pool under the thermostat and get you real hot as the air won't transfer enough heat to open the thermostat but the water will still be in the head passage making your temp sender go hot.

I drill a small hole in the thermostat when I install them to relieve that air. Could pull the thermostat to be sure there isn't a bubble under it.

[JRBECK64]

Just to let everyone know I put an after market under the dash temp guage in it and its running at 185 Degrees. I also put a fail safe thermostat that fails to the open position so you dont overheat the engine if it fails. Im thinking when I put the dash in my 67 ShortWide Im going to put an aftermarket bezel in it and put in real guages. Cold and Hot dont make it for me.

JRBECK64

[JRBECK64]

Originally Posted by 72supermike

I have a 72 4wd 1/2 ton that I just put a new sending unit in cause the gauge wasn't working at all. Now it will warm up to the top of the red zone and then cool down to the hashmark before the red zone once the thermostat opens up. Kinda wondering that same thing as you. Thanks!

72supermike,
That is exactly what mine is doing. Im guessing that the sending unit is bad so Im going to take a chance being they are pretty cheap and replace it. I hope that will fix it but now that I have the aftermarket under the dash its not a huge priority.

JRBECK64

[72supermike]

I just put a new sending unit in to make the gauge work. I hope the sending unit isn't bad since it's brand new. Oh-well. I bought the truck cause I can work on it without hooking up a computer so work on it I will.

[JRBECK64]

Originally Posted by 72supermike

I just put a new sending unit in to make the gauge work. I hope the sending unit isn't bad since it's brand new. Oh-well. I bought the truck cause I can work on it without hooking up a computer so work on it I will.

72supermike,
The beauty of these old trucks are their simplicity. For the most part their pretty cheap when it comes to parts as well. Now all I have to do is get the Front brakes working properly (Cant get the front Drivers Side to Bleed Properly). I Guess that should be another Subject.

JRBECK64

[kevmic28]

Originally Posted by 72supermike

I have a 72 4wd 1/2 ton that I just put a new sending unit in cause the gauge wasn't working at all. Now it will warm up to the top of the red zone and then cool down to the hashmark before the red zone once the thermostat opens up. Kinda wondering that same thing as you. Thanks!

Mine does the same thing. I need to replace the sending unit.