Turns out putting the temp sensor in the intake really is no good

[Swearbody]

Had the brand new sender in the intake and was overheating so it said. Tried a different thermo and same problem. Ran without and it was all good but only got to 110deg so couldnt tune or drive for that matter.
Decided to try a manual bosch gauge and sensor in the head and it matched the dash gauge....until it didnt.once it started rising the dash gauge read all the way hot and the manual read 190. So it was the gauge/sender the whole time and I never actually had an overheating issue. Verified with a infared thermo at radiator entrance.
So I cranked the truck and had to shut it off like 10 times during cam break in thinking It was overheating ( dont worry I shut it off immediatly each time and then ran it at 3000rpm to wear in the cam/lifters)

It is still possible that the new sender isnt right, but it is the correct gm sender. I just put it in the intake instead of the head. I have seen people say that problems arise when doing this and damn if they arent right IN THIS CASE.

 

[HotRodPC]

Keep in mind, your cylinder head temp can be quite a bit hotter than the intake temp. Cylinder heads is where all the combustion takes place and the sender is in between 2 cylinders generally. The intake is right next to the thermostat so as the thermostat pops it can be sitting next to cooler antifreeze.

 

[DoubleDingo]

I prefer the sending unit in the head, not the intake. To me it shows when the engine is getting hotter more accurately.

Back in 2015, when I got Crusty Biscuit, the PO had the sending unit in the intake. I relocated it to the port on the front of the driver's side head. But, I routed the wire around the back of the engine and up next to the block up to the sending unit. The gauge read almost maxed out hot just idling. If I was driving around it was pegged to the H. So replaced the two core radiator with a 3 core that I had, and it still pegged to the H. Baffled, I re-routed the wire along the top of the engine, dropped it down the front, and over to the sending unit, and it reads correctly. I told this to Pop and hes said the wire routing should make a difference. I agreed, but when I told him re-routing the wire along the top of the engine got the gauge to read the correct temperature, he couldn't believe it would change like that. I did my checking with it idling, cap off, and a thermometer dipped in the coolant. Weird that the wire routing made a difference. I would have put the sending unit in the back port of passenger side head, but I could get that plug out.

 

[Swearbody]

Keep in mind, your cylinder head temp can be quite a bit hotter than the intake temp. Cylinder heads is where all the combustion takes place and the sender is in between 2 cylinders generally. The intake is right next to the thermostat so as the thermostat pops it can be sitting next to cooler antifreeze.

It was the intake unit that was reading high in my case. The unit in the head reads perfect. So in my case the intake is giving the higher reading. My brother had the same issue with his and used the same intake. Mybe the eddy air gap has a problem witht hat....whoknows

I prefer the sending unit in the head, not the intake. To me it shows when the engine is getting hotter more accurately.

Back in 2015, when I got Crusty Biscuit, the PO had the sending unit in the intake. I relocated it to the port on the front of the driver's side head. But, I routed the wire around the back of the engine and up next to the block up to the sending unit. The gauge read almost maxed out hot just idling. If I was driving around it was pegged to the H. So replaced the two core radiator with a 3 core that I had, and it still pegged to the H. Baffled, I re-routed the wire along the top of the engine, dropped it down the front, and over to the sending unit, and it reads correctly. I told this to Pop and hes said the wire routing should make a difference. I agreed, but when I told him re-routing the wire along the top of the engine got the gauge to read the correct temperature, he couldn't believe it would change like that. I did my checking with it idling, cap off, and a thermometer dipped in the coolant. Weird that the wire routing made a difference. I would have put the sending unit in the back port of passenger side head, but I could get that plug out.

I thought about that as well. My temp wire had to be made longer and I wrapped it into the engine wiring harness with cloth tape to clean things up. I may have an issue there causing a higher resistance. I dont see how but I also dont know everything,LOL
For now im running the bosch unit in the head and will investigate further once ive worked out some of the other issues im having.
I couldnt time or tune without it being at temp so I have some work still to do.

 

[PrairieDrifter]

I highly doubt wire routing will change anything. Not saying the story is inaccurate or not true. But I don't believe there is a scientific explanation that would say that's how it works. You can't just move a wire and have it completely change the output, don't get me wrong that resistances and what not change but.... the only thing that could actually affect it, is its proximity to ignition components.

I would guess an air pocket or something along those lines. Also I might be thinking about this all wrong and am stupid too so... you know a grain of salt and all that lol

 

[Swearbody]

I highly doubt wire routing will change anything. Not saying the story is inaccurate or not true. But I don't believe there is a scientific explanation that would say that's how it works. You can't just move a wire and have it completely change the output, don't get me wrong that resistances and what not change but.... the only thing that could actually affect it, is its proximity to ignition components.

I would guess an air pocket or something along those lines. Also I might be thinking about this all wrong and am stupid too so... you know a grain of salt and all that lol

SO proximity to ignition you say...well It is ran along with the main harness(alternator,starter,ignition,etc) and branches out to go to the sender. I used cloth tape for making harnesses and ran it all together to clean up the engine bay. I may very well have some "noise" there interfering with the signal however I am fairy over cautious with wiring and the loom is actually pretty robust.

Thankfully I had the bosch sensor and gauge thats been sitting there on a shelf brand new still in the packaging for 2 years ,lol. Ill run that as a permanent backup and fit it into the dash cluster one day for a weekend project.
I will try and re route the original sensor wire and see if there are any results to speak of just since its so easy...why not.

 

[DoubleDingo]

I highly doubt wire routing will change anything. Not saying the story is inaccurate or not true. But I don't believe there is a scientific explanation that would say that's how it works. You can't just move a wire and have it completely change the output, don't get me wrong that resistances and what not change but.... the only thing that could actually affect it, is its proximity to ignition components.

I would guess an air pocket or something along those lines. Also I might be thinking about this all wrong and am stupid too so... you know a grain of salt and all that lol

It happened. No air pockets. If you saw it, you'd believe it. You didn't, so it's open to you to knock it.

 

[PrairieDrifter]

It happened. No air pockets. If you saw it, you'd believe it. You didn't, so it's open to you to knock it.

I don't doubt you. Just unprovable by known science. Now... if you really want to make me believe, move the wire all over the engine bay and if you get extremely different readings then I'd be swayed. Or if it could be replicated either by you or someone else

I'd say it's more like the wire was grounding out somewhere that's why it was pegged, and moving the wire around ungrounded it or something like that. Also not knocking on ya, but you can never be sure if you had an air pocket... especially if your switching sensors and plugs around on the system.

Crazy things happen sometimes, and most of the time we don't know the cause, not because we don't know things, but because we can't see the whole picture

Basically what I'm saying is yes, moving the wire may have fixed your issue, but how did it? Science says not because the wire likes to be in a certain position or twisted a certain way. But maybe because of something unseen.

 

[PrairieDrifter]

SO proximity to ignition you say...well It is ran along with the main harness(alternator,starter,ignition,etc) and branches out to go to the sender. I used cloth tape for making harnesses and ran it all together to clean up the engine bay. I may very well have some "noise" there interfering with the signal however I am fairy over cautious with wiring and the loom is actually pretty robust.

Thankfully I had the bosch sensor and gauge thats been sitting there on a shelf brand new still in the packaging for 2 years ,lol. Ill run that as a permanent backup and fit it into the dash cluster one day for a weekend project.
I will try and re route the original sensor wire and see if there are any results to speak of just since its so easy...why not.

Main thing would be like spark plug wires and alternator. Passenger side alternator trucks, usually have their temp sender on the drivers side head near cylinder 2, then a green wire comes out ALONE from the harness, right by where the distributor ign and tach wires would come out by the drivers side valve cover, then runs down the intake to the front of the engine and either over the valve cover straight down or down the front of the block then makes a little loop back to the sender under the manifold.

The sending unit has to be matched to the specific year range of your gauge in the cluster. Resistance changes.

 

[Swearbody]

Main thing would be like spark plug wires and alternator. Passenger side alternator trucks, usually have their temp sender on the drivers side head near cylinder 2, then a green wire comes out ALONE from the harness, right by where the distributor ign and tach wires would come out by the drivers side valve cover, then runs down the intake to the front of the engine and either over the valve cover straight down or down the front of the block then makes a little loop back to the sender under the manifold.

The sending unit has to be matched to the specific year range of your gauge in the cluster. Resistance changes.

That is exactly how mine was of course from the factory. It was my bad decision putting the temp wire with the rest. It was suspect from the get go and I knew that but did it anyway because I wanted the green wire to disappear . I know better now and actually think there is something to the whole ,wire on the passenger side away from other possible interference.
I certainly tried to match the sender to the gauge but may have the wrong part anyway. My gauge should be a 90ohm range and my truck info points to that sender. I should have taken the damn sender off the old engine before I gave it away. Live and learn... I will know more once I move the wire.

 

[Swearbody]

It could be as simple as my wire not being rated exactly what the OE wire is and that causing a resistance change. Makes perfect sense in theory.

 

[PrairieDrifter]

That is exactly how mine was of course from the factory. It was my bad decision putting the temp wire with the rest. It was suspect from the get go and I knew that but did it anyway because I wanted the green wire to disappear . I know better now and actually think there is something to the whole ,wire on the passenger side away from other possible interference.
I certainly tried to match the sender to the gauge but may have the wrong part anyway. My gauge should be a 90ohm range and my truck info points to that sender. I should have taken the damn sender off the old engine before I gave it away. Live and learn... I will know more once I move the wire.

Trust me I want a neat and tidy engine bay as much as the next guy but some things are the way they are because that's just the way it is lol. I would check it out though you know, make sure the reading actually changes if it's worth the work to you. I have my temp wire running close to my plug wires and my gauge is consistent, but I feel it's inaccurate sometimes, and some times not, if you wanted to, you can snake it down the back of the block under the manifold and go to the sending unit that way, I just didn't like that idea all that much myself so I didn't do it that way.

 

[Swearbody]

Trust me I want a neat and tidy engine bay as much as the next guy but some things are the way they are because that's just the way it is lol. I would check it out though you know, make sure the reading actually changes if it's worth the work to you. I have my temp wire running close to my plug wires and my gauge is consistent, but I feel it's inaccurate sometimes, and some times not, if you wanted to, you can snake it down the back of the block under the manifold and go to the sending unit that way, I just didn't like that idea all that much myself so I didn't do it that way.

Going in the head between 1-3 is out of the question due to the headers. I had to clearance my brand new stainless headers just to get #3 plug in and it touches the boot pretty solid still. Im using sleeves to protect them but it pushing on it pretty hard. I broke the first #3 plug if that tells you how close it is. also Im now running the bosch sender and gauge there in the head and it reads perfect so know...dont change it!!
Im gonna run the wire down the passenger side and see if that helps. If not then ill put the bosch gauge in the cluster one day as thats what I got it for anyway. My last square(that i sold) had a busted cluster and the bosch unit has been on a shelf collecting dust

 

[Swearbody]

Ok you two,LOL Also not to be a know it all but there is actually a lot of science backing his theory.


Resistance is actually a product of temperature in a wire. Thats actually how the sender works. As temp increases so does resistance; so a wire getting too hot will increase resistance. Its called temperature coefficient.
The resistance of a wire can be calculated at a temperature of 68deg using R=pl/a

where:R is the resistance, in ohms (Ω)ρ is the resistivity of the material in ohm meters (Ωm)L is the length of the conductor in meters (m)A is the cross-sectional area of the conductor in meters squared (m2).

Dont ask me to do any of this to the wire unless you plan to bring the beer. But I am down for doing it!!


And yes...I googled that ****. Fking sue me...LOve you guys..dont shoot me

 

[PrairieDrifter]

Ok you two,LOL Also not to be a know it all but there is actually a lot of science backing his theory.


Resistance is actually a product of temperature in a wire. Thats actually how the sender works. As temp increases so does resistance; so a wire getting too hot will increase resistance. Its called temperature coefficient.
The resistance of a wire can be calculated at a temperature of 68deg using R=pl/a

where:R is the resistance, in ohms (Ω)ρ is the resistivity of the material in ohm meters (Ωm)L is the length of the conductor in meters (m)A is the cross-sectional area of the conductor in meters squared (m2).

Dont ask me to do any of this to the wire unless you plan to bring the beer. But I am down for doing it!!


And yes...I googled that ****. Fking sue me...LOve you guys..dont shoot me

Not here to bash on anyone... unless called for....lol. We're here to learn and debate things to figure out what's what.

He didn't state what routing the wire had before he moved it so it's hard to compare, but if it was anything similar to factory it shouldn't have been an extreme difference. He was saying it was pegging but not when, was it always pegged or did the gauge work somewhat properly until engine temps came up and was just inaccurate? The extreme fluctuation is what leads me to believe it was an actual issue with the wire, that resolved itself after being moved around a bunch. If it was just small inn-accuracy then yes the wire for sure could have been the culprit. I believe when the temp wire becomes grounded the gauge pegs to H, I could be mistaking it for the oil pressure sending unit though. That's why I questioned it.