SpeedyGeek

iTrader: (2)

Ok, so I read a lot of posts about the Coolant Temperature Sensor lately. But I still have a question I haven't found a good solid answer to. I have an 87 Formula. I took out the 305 computer controlled carbureted LG4 engine. I put in a 350, edelbrock intake and carb (non computer controlled). I put in a new MSD distributor, no ECM, no knock sensor, no computer controlled anything at all. Transmission has been taken care of in these respects as well. So my question is, do I still need the collant temp sensor? Is it only there for the ECM? Is it required for the fan to work even without the computer? Is the Fan Switch between 6 & 8 and the relay the only things I need for the fan to work?

ok, sorry, that's more than one question.

Thanks

//<86TA>\\

iTrader: (14)

you dont "need it", but you temp gauge wont work without it

i would keep it so you cant tell if the car is overheating, and when its properly warmed up

SpeedyGeek

iTrader: (2)

So, the temp gauge is controlled by the temp (switch?) on the drivers side head with one wire connected to it, then how does the coolant temp sensor come into play with the gauge? I'm just trying to figure all of this out. End result is getting my fan working again and removing anything 100% not needed. Right now the coolant temp sensor is in question. After this I'll move on to the relays.

By the way. Originally the sensor was in the thermostat housing. I once bought another housing and it had a 3/8 inch hole and a 1/2 inch hole. I had put the sensor in the 3/8 and plugged the 1/2 inch. The housing even came with a plug for each. But now that I have all this chrome on the engine I figured I'd take off the ugly housing and put a chrome one on. Funny thing is all of the chrome housings available have the 1/2 inch hole. But all temp sensors are 3/8 inch. Lame, absolutely lame. I tried an adapter but that was no good as the adapter surrounded the sensor so coolant couldn't properly flow past (around) it to get a good reading. So, I relocated it to the front of the intake. Coolant came out when I unplugged the hole to put the sensor in, but the question is, is it a reliable place for this sensor? Will it work correctly?

screeminchicken

iTrader: (2)

U can probabaly tap and put it on the inlet side of the radiator. Remember inlet side

tony_cogliandro

iTrader: (3)

im not absolutely sure but doesn't the water temp feed into the ecm and therefore help adjust the various factors in keeping the engine running within specs?
take a look here https://www.thirdgen.org/forums/elec...r-shorted.html

SpeedyGeek

iTrader: (2)

That's what I was guessing to, but again, I am just guessing. I am hoping someone on the board knows for sure. So I have no ECM, no computer controll. Is the fan switch and the relay all that controlls the fan? Or is there anything else involved?Is the guage switch in the drivers side head the only thing for the guage? With no computer can I toss the temp sensor?

Thanks guys. :-)

mtwlkn122

The temp sensor on the intake manifold is the one that controls the computer that one(if your new intake has a hole for it) just plug it or w/e you want to do with it. The sensor on the drivers side does the fan kick on and passenger side does the temp gauge. I might have the driver and passenger side mixed up. Like said above i would keep the one for the gauge as you will want to run a temp gauge.

tony_cogliandro

iTrader: (3)

well you might want to know the temp but if no computer at all it does not matter for computer control purposes, but i would think you might want to know if you are overheating.

87350IROC

iTrader: (2)

Tons of flaky info on this thread. The fact is you do not need the CTS if you are not using an ECM. All it does is feed temperature data to the ECM. You gauge is controlled by the sensor on the driver side head between 1 3 cylinders. The secondary fan, in a dual fan setup, is controlled by the swtich in the passenger head between 6-8 cylinder.

This is the correct info.

A-RON

ok well i was reading through this thread and i have a similar problem. my temp guage doesnt read anything. i replaced the sensor next to the thermostat housing. oh by the way i have a 92 Z28 with a 305. but i still dont get a reading. when im driving, the temp stays fine but as soon as i put it in park and let it run, it overheats and thats the only time my guage works. the coolant bubbles into the overfill and is extremely hot but this only happens when it is in park. i can be sitting in stop and go traffic and it wont over heat. both fans kick on and i have "burped" the system a number of times. i have no idea whats goin on. any help would be awesome!

deadbird

Just for clarity's sake (and somewhat repetitious of what 87350IROC stated),

The Temperature Sensor, located around or, on the thermostat housing (depending on engine type) and has two wires, is for the ECM - only.

The Temperature Sender, located in the drivers side head with a single wire, is for the temperature gauge - only.

The Fan Switch, located in the passenger side head, is for the cooling fan - only.

If your gauge does not work, it will be the Sender in the drivers side head or, an electrical fault.

As an indicator of the gauge even working, when you turn the key to crank the engine to start it, the gauge should do a sweep to full temperature.

A-RON

wow i feel more or less dumb....
but now i just have the issue of it overheating when it is in park. should that issue go away if i get that temp sender checked out? or does it sound like a different problem?

Kevin84Z28

iTrader: (3)

1. Make sure your thermostat is working.
2. Check to make sure your hoses aren't being crimped.
3. Make sure you have the correct radiator cap.
4. Make sure your electric fan works.
5. Use coolant.

deadbird

There isn't anything to feel dumb about. It gets hard to tell what is what when when you're not extremely familiar with the under hood wiring. It makes it even harder when looking for information and the wrong terms are used for parts.or, the information isn't very clear.

To add to what Kevin84Z28 stated,
Keep in mind as well that the preset temperature for the electric fan to run is around 220 °F (even hotter for the fan switch). So, as the car just sits and idles (be it driveway or stoplight), there is no air moving past the radiator and the temperature will climb until the car moves or, the fan turns on.

SpeedyGeek

iTrader: (2)

87350IROC was right. I knew the locations all along but wasn't 100% sure about the need of the CTS. He was right.

So after all of this and putting in a brand new Hypertech 176 on fan control switch and connector I still couldn't get the fan to come on. So I took the car to a shop in town. It's an excellent shop (Fryar's in Chattanooga, Tn). It's the only shop I will take my cars to these days. They take my extended warranty for my Trailblazer and they never ever do a bad job, always straight with me and does the best job. They just cost a lot. Anyway when I get to the point that I give up on something I take it to them.

The mechanic (Jimmy) hit the intake and heads with an infrared heat sensing gun. He said that he got the hottest readings from the intake just around the thermostat (duh), a 10 degree hotter difference than the heads where the sensors are. Also he said the new fan control switch I got was no good. He put a new one in. Also he said the knock sensor connector was plugged into it. The guy who did the original engine swap had the wrong connector on it all along. So, he took the old fan control switch out, plugged it. Took the temp gauge sender out and plugged it. I already had the knock sensor out and plugged when I put this new engine in. Jimmy took the coolant temp sensor out and tossed it, he said it definietly isn't needed if I have no computer just as 87350IROC said. He put the temp gauge sender in the front of the intake and put the fan control switch in the top of the intake right next to the thermostat housing.

My fans come on and my engine now stays cool :-)

Now I know there have been a lot of posts out there about everything listed in this post. There are a lot of really bad answers out there. So how can we get the following put into a sticky (if it's not already)?

This much is fact since I have had both...

87 Formula with a 305, computer controlled, carburetor engine
90 Formula with a 305, TBI engine

Factory cooling sensor locations...

• Coolant Temp Sensor - Thermostat Housing
• Temp Gauge Sender - Drivers side head between 1 and 3 exhaust
• Fan Control Switch - Passenger side head between 6 and 8 exhaust

Alternate (better) cooling sensor locations...

• Coolant Temp Sensor - Thermostat Housing (not needed if no computer is present)
  
• Temp Gauge Sender - Front of intake pointing forward
• Fan Control Switch - Top of intake next to thermostat housing

Thanks for the help everyone.

rtrevino

[quote=SpeedyGeek;4166486]
Factory cooling sensor locations...

• Coolant Temp Sensor - Thermostat Housing
• Temp Gauge Sender - Drivers side head between 1 and 3 exhaust
• Fan Control Switch - Passenger side head between 6 and 8 exhaust

quote]


Hello,

after reading this thread i have discovered that my CTS is located on the driver side head, and that the sender is in the place where the cts should be, should I relocate them to their correct places?

Thnks!

Raul

engineerit92

Figure id post here with my 2 pennies.

Basically GM was not to smart when the designed the location of the temperature gauge. Below the headers…..I just replaced mine and it is now worse than ever. It reads hot pretty much any time. Gauge loves to read 260 when it sits still for a bit.
What makes me think it is the gauge , well I use a thermo to measure the water when the car was running, I think the most it will pick up is 170. The manifold might hit 185-190. I think I might just need a better way to measure the temp to be sure. I figured as much as the gauge hits 260 the little old 5.0 would have blown up by now and my tranny would be a roast duck.

Basically I am just looking for someone with a similar problem and a solution to make sure my dummy gauge is working. What voltage does the sender line run? I know the typical resistance of the gauge. I do remember someone testing out there sender by putting it in water,, you need to complete the circuit before it will work on that note. As crazy as it sounds you need to run something to the negative battery to see just how well it works.

On a side note does anyone know if pressure is important for the sender? Like at 14.7 psi 100C will it read 100C or if it is 16psi will it read 140C etc.

As an answer to your question , well most of their sensors are trash anways. ECM<- yes FAN<- yes. Gauge <- up to you.
One thing you could do if you dont have the ECM is run a gauge to all three points and measure tempraures at different locations of the block. And a toggle for your fan.

87350IROC

iTrader: (2)

engineerit92,

I suspect either you got the wrong replacement or have a bad guage or have bad wiring. I have headers too and these are my results: When the CTS reads 170, I read 180 at the passenger side head, and am right above the line between the 0 and 220 lines on the gauge. This is the temp my car stays at in traffic.

deadbird

Considering the heads on an engine run the hottest (aside from the actual cylinders), that's probably the best place to put a gauge. That way, while the gauge might indicate overly hot temperatures, making you take caution, the engine it still within safe operating range.

Seems more like a safeguard. Gauge reading not giving a true accurate reading in the thought of safety.
Kind of like the gas gauges shows there is less gas then is truly there because some engineer realized there is some dumbass willing to see how far you can drive on empty.

I fail to see the stupidity in calibrating something to favor caution.

Just my opinion, too.

FreeSpirit

There is definitely a lot of misinformation going around. Ive been searching the boards for a few days, went to Oreillys, got some diagrams and the manual, and this is the first thread I found that really cleared up everything involved with the cooling fans, and which switch controls what. Thanks

titus78

good info in this thread!!

jeff1010

You guys are the best, Water temp gauge is working like a champ after you know where to look and connect the wire. Thanks