Thread: Temp Sender?

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What or maybe were is the correct spot for the temp sender? On my 57 Chevy I just finished a Small Block 383 Build and install. Dumb me I didn't install the sender until after I got the engine bolted down all snug and secure. The easy place was to install the sender in the drivers side head between the number 1 and 3 plugs. You all know the place I am talking about there is a big old plug there in all 350 type heads, I assumed ( there's that word) that plug was actually for a sender. Now that spot seems to me to be a Hot Spot right in the head and between those two cylinders. Got me to wondering should I have installed the sender in the manifold? Plug there as well. Is there a temp difference? Reading from the sender I have installed in the head temps seem a little high, runs at 210 to 220 will get even hotter at times and cools down when I coast down a long hill in neutral to as low as 200. Just got me to wondering is there a big difference of the temp if taken from difference places?

RS

The gauge will show cooler using the location by the thermostat housing. I guess it's a matter of personal preference as to whether you want to see the reality of temp at the head.

The proper place is in the head.

Originally Posted by sg4356

The proper place is in the head.

How did you come to this conclusion? As tech said I believe it's a matter of personal preference and besides Chevy mounted them in the intake manifold for many moons.

When I put my 23 together I put the sender in the back of the intake manifold......highest temp it recorded there was 120 degrees. I moved it to the front, right by the thermostat housing and it went up to 150. Now, with a 190 thermostat it reads about 170 all the time. Not sure why it was so much cooler in the back of the intake.

Don

Thanks guys, I don't know were the correct place was thus the question. I do know that Chevy has used both locations at different times. It just never occured to me that there would be such a difference. It only makes sense if you think about it, the head location has just got's to be hotter governed by whats around it.

After reading what Tech and SG said I went and bought two more temp gauge and installed one in the Manifold by the Thermostat Housing, and the other in the passenger side head. I took the car out for a little drive I was really surprised at the different readings. The gauges are all Autometer manual gauges, the readings at cruising, and I was driving around on the country roads around here. Car is a 1957 2 Door Wagon, with a just rebuilt 383 and a Muncie M21 4 speed.



Car was driven around for about 20 min before I took these readings. Reading from Drivers side head 220 Degree's ( wish we had that little degree symbol) temp from passenger side head 230 degree's, temp from Intake Manifold 195 degree's. The readings being different bothered me some so I went back to the shop and changed the guages around. Drivers side to the manifold, passenger side to the drivers side, and the intake sender to the passenger side. A warning let the damn thing cool waaaay down before you do this, I was a little hasty and I am paying the price for my haste NOW.

Another little cruise and took the readings again. Drivers side head 220 degree's, passenger side head 235 degree's and the intake 190-200 degrees.

One interesting observation, while I was driving there is a big hill going into Guntersville on Hiway 69 down grade is about 3/4 or maybe a little more of a mile. When I topped the crest the readings were just about what is above. I shifted into neutral and let the car coast all the way to the bottom of the hill, I was doing right at 60 MPH and didn't loose much of that speed all the way down. The guages for both heads cooled way down to 195-200 degrees, the guage reading the intake manifold temp did not move and stayed right at 190.

I am going to leave all three gauges hooked up and watch this for a spell. I now believe that the head probably gives a hotter temp and for that reason alone may just be the correct place if you want to really know what is going on. Thanks again Folks!!

RS

Originally Posted by Hombre259

Car was driven around for about 20 min before I took these readings. Reading from Drivers side head 220º (wish we had that little degree symbol) temp from passenger side head 230º, temp from Intake Manifold 195º. The readings being different bothered me some so I went back to the shop and changed the guages around. Drivers side to the manifold, passenger side to the drivers side, and the intake sender to the passenger side. A warning let the damn thing cool waaaay down before you do this, I was a little hasty and I am paying the price for my haste NOW.

Another little cruise and took the readings again. Drivers side head 220º, passenger side head 235º and the intake 190º-200º.

One interesting observation, while I was driving there is a big hill going into Guntersville on Hiway 69 down grade is about 3/4 or maybe a little more of a mile. When I topped the crest the readings were just about what is above. I shifted into neutral and let the car coast all the way to the bottom of the hill, I was doing right at 60 MPH and didn't loose much of that speed all the way down. The guages for both heads cooled way down to 195º-200º, the guage reading the intake manifold temp did not move and stayed right at 190º.

I am going to leave all three gauges hooked up and watch this for a spell. I now believe that the head probably gives a hotter temp and for that reason alone may just be the correct place if you want to really know what is going on. Thanks again Folks!!

RS

Your wish has been granted, now you have it.

Mike

Most older EFI vehicles will use a temp sensor to tell the PCM engine temp & when to turn the fans on & off (if it has electrical fan). They will also have a temp sender that is for the temp gauge or light. The newer vehicles have only one sensor to do the job of one sensor & one sender. The one sensor will send one signal to the PCM & one signal to the BCM. The PCM will interpret the signal & make adjustment to air/fuel ratio, fans, ect The BCM control the gauges & also controls the fans when the a/c is turned on. These systems are networked together & also has a fail safe. If the engine starts to run hot then the PCM will advance timing & dump a little more fuel while the BCM will turn off the a/c & turn the cooling fans on high. Just about have to be an engineer to understand this stuff.

Mike that don`t work on a Mac....!

Originally Posted by 406Rich

Mike that don`t work on a Mac....!

Doesn't work on my Windows Vista either. Maybe there's some special way of entering it?

Good thread, we get customers all the time wondering why the temp is different at different spots on the engine.
I get many folks calling with their infrared heat guns pointing at their radiator saying thet their gauge is wrong. Please don't use a temp gun to check the temperature of the coolant inside the engine from the outside of the block, or radiator!
Mark

@ntfday well sir the general has always put the temp. sender in the head for the gauges. the one in the intake is for fans or computer. I just thought that GM may know more than Me or you do about this. I do believe the head would give a more accurate reading of the engine.

All i'am saying is this is how General Motors does it and Me myself being a line mechanic for 30 years I want to know what the most extreme wtr. temp. is so i dont blow head gasket or crack a head. Put it where ever you want LOL thats just where G.M. puts theres.

Originally Posted by sg4356

All i'am saying is this is how General Motors does it and Me myself being a line mechanic for 30 years I want to know what the most extreme wtr. temp. is so i dont blow head gasket or crack a head. Put it where ever you want LOL thats just where G.M. puts theres.

I guess in those 30 years you never had the chance or opportunity to work on an early sbc, say circa 57, since the heads had no provision for a temp sending unit. There are others on this board who probably remember it better than an I since I was only 13 at the time.

Yes i would say other things can cause heads to crack and gaskets to blow, but from my experience I would say nine out of ten was due to over heating. sense the engine has over heated, i would say nine out of ten it is because of low coolant level. the problem of cracked heads was more likely in 80's and newer small blocks due to thinner decks on the heads. I would say 230 degrees and up will cause these problems. which is why i would put it in the the head for a more accurate reading of engine temps. again put yours where you want me and G.M. will put ours in the head. lol You are correct ntfday not much work done on 57 LOL besides all 57s i see nowadays have blown big blocks install or fuel injected small blocks. lol Sorry if i made anyone mad with my thoughts on this matter. I was just saying