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Old 07-16-2017, 12:00 AM   #1
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Overheating 305

1992 305 V8
Appears to be Overheating.

Parts replaced:

New Radiator
New radiator Cap
New hoses.
Thermostat housing.
New Thermostat
Water Pump.

On the Infared gun i'm getting readings of 160 180F
The Temp sensor and relay have both been replaced..

I am getting readings of 145-180F when the relay for the fan kicks on

The heat guage in the car was going about 3/4s or highter before relay kickin it on.

Last edited by phasevariance; 07-16-2017 at 01:44 PM.
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Old 07-16-2017, 12:20 AM   #2
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Re: Overheating 305

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Originally Posted by phasevariance View Post
1992 305 V8


The heat guage in the car was going about 3/4s or highter before relay kickin it on.
That sounds about right with the stock inaccurate gauge and 235F fan switch
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Old 07-16-2017, 08:53 AM   #3
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Re: Overheating 305

Sounds like the car is not "overheating" at all. Sounds quite normal in fact.

Replace the temp gauge sending unit; driver's side head, between #1 & #3 spark plugs.
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Old 07-16-2017, 01:42 PM   #4
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Re: Overheating 305

I remember changing something under the manifold between spark plugs and it was a pain in the ***, I thought it was for the fan to kick on at certain temps.

On a side note, this car has only one electric fan. The car does go into the red when going up hills.

It's difficult to tell if it's just a lying gauge.
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Old 07-16-2017, 04:46 PM   #5
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Re: Overheating 305

If it's going into the red on the gauge is it also bubbling out the coolant into the overflow tank?
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Old 07-16-2017, 05:47 PM   #6
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Re: Overheating 305

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Originally Posted by tealman92 View Post
If it's going into the red on the gauge is it also bubbling out the coolant into the overflow tank?
No, no bubbling no steam but the engine does seem hot. I didn't have my infrared gun on me. I really think it's a lying indicator at this point.

I'm gonna run it at idle after I swap out this sending unit sensor.

If I can post video snapshots I will.

Thanks for the response guys!
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Old 07-16-2017, 05:50 PM   #7
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Re: Overheating 305

Is your air dam under the front of the car intact and present?
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Old 07-16-2017, 08:38 PM   #8
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Re: Overheating 305

Yes, the air damn is fully intact. I am running these tests with the car in park. I noticed with the AC switched ON the temp gauge stays at or below the 1/2 way mark. But with the AC switched OFF the temp guage will jump all the way up to to 3/4 (close to red line) and then the fan switch will kick on and activate the fan and it will drop almost back to the 1/2 mark.

It's very unnerving to watch. The readings I had tonight were much lower 130-165 F

Should I just install a separate temp gauge? Not sure what's going on here.
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Old 07-16-2017, 08:43 PM   #9
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Re: Overheating 305

The fan is automatically activated with AC on, so your fan system seems to work fine. Perhaps a fan switch that is designed to turn the fan on at a lower temp would be a good plan
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Old 07-16-2017, 09:22 PM   #10
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Re: Overheating 305

Mine (87 GTA dual fans) acts the same way. Tons of info right here on tgo dealing with these issues. I've learned these stock gauges are unreliable. Put a aftermarket gauge on temporarily to check against your stock gauges.
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Old 07-16-2017, 10:22 PM   #11
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Re: Overheating 305

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Originally Posted by henryd3 View Post
The fan is automatically activated with AC on, so your fan system seems to work fine. Perhaps a fan switch that is designed to turn the fan on at a lower temp would be a good plan
I think you hit on something there. I think it's a reasonable explanation. I'll try a lower rated or after market fan switch.

I'll keep you guys posted.

p.s water pump was failing, the old puddle of antifreeze after sitting a bit then finally dripping at ide. It had to go.
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Old 07-17-2017, 07:10 AM   #12
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Re: Overheating 305

The temp gauge sending unit is on the driver's side. The fan switch is in the pass side head, same hole; which puts it between the #8 & #6 spark plugs.

The temp gauge one is a piece o cake. Right out in the open staring at you. Yours is farkled. Change it out. Your car is not "overheating" and your fan is working fine. Everything is doing what it's supposed to except the gauge.

Quote:
On the Infared gun i'm getting readings of 160 180F
Quote:
guage in the car was going about 3/4s or highter
You have a piece of genuine test equipment telling you one thing, and a "sporty" trim package telling you something else. Which word in the phrase "lying gauge" do you need explained more fully?
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Old 07-17-2017, 03:53 PM   #13
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Re: Overheating 305

Yes, I've already established the fact that the car is not actually overheating. When I was out for a drive the guage was indicating that the car was overheating.
Brought it home, took some readings, posted it here for some good camaro advise. =)

Lets not engage in trolling =)

So we have:

The temp gauge one is a piece o cake. Right out in the open staring at you. Yours is farkled. Change it out
Replace the temp gauge sending unit; driver's side head, between #1 & #3 spark plugs.

Last edited by phasevariance; 07-17-2017 at 04:05 PM.
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Old 07-18-2017, 07:57 AM   #14
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Re: Overheating 305

Nobody is "trolling" anything.

Quote:
with the AC switched OFF the temp guage will jump all the way up to to 3/4 (close to red line) and then the fan switch will kick on and activate the fan and it will drop almost back to the 1/2 mark.
That's EXACTLY what it should do. The REAL temp should climb gently (not really "jump": I hope that's not what yours does) to around 235, the fan should come on, it should cool the motor down to 210 or so, the fan should shut off, the temp should begin to climb again toward 235, the fan should come on, ... for as long as the car sits there idling. Until it runs out of gas. 235 is usually somewhere on up toward of the gauge on these things; and 210 is just a little above half, usually.

Cruising down the road however, there should be enough air forced through the rad to keep the engine at or just below the fan's shut-off temp. It should run pretty close to thermostat temp, which should be 195: the gauge should then read right at or just a little below the halfway mark.

With the AC on the fan should run constantly, but the fact that the air reaching the rad has already been SIGNIFICANTLY heated by the AC, will usually make the temp higher than the thermostat temp. Shouldn't be ALOT higher, and should reach a point and stabilize; but expect it to be higher. Maybe 5/8 of the gauge just as a rough guide. Then when driving it should drop back down nearer the center of the gauge again, as the forced air flow provides better cooling.

Quote:
Should I just install a separate temp gauge?
Why? That is, what good would it do? Will it change the temp the engine is REALLY running at?

Quote:
Not sure what's going on here.
What's going on here is, your car is working fine. Your gauge actually sounds like it's not too terribly far off. But you can replace the sending unit and make sure it's as "accurate" as it's ever going to be.

This shouldn't be that hard to understand. Go swap out the temp gauge sending unit and see if that makes the stock gauge read any different. If it doesn't, does it really matter? REALLY? If you know what it reads when the car is working right, then you will be able to tell when the car malfunctions; and that's really all it's ever good for anyway. Think of it as being just an "idiot light" in a different shape. It's simply not "accurate" to begin with and never really will be. It's a go/no-go kind of thing, not test equipment.
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Old 07-20-2017, 01:47 AM   #15
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Re: Overheating 305

Quote:
Originally Posted by sofakingdom View Post
The temp gauge one is a piece o cake. Right out in the open staring at you. Yours is farkled. Change it out
Quote:
Originally Posted by sofakingdom View Post
This shouldn't be that hard to understand. Go swap out the temp gauge sending unit and see if that makes the stock gauge read any different. If it doesn't, does it really matter? REALLY?
I swapped out the temp gauge sending unit and now the stock gauges work properly again. (inline with readings)

The good news is that the "farkled" coolant sensor did get a reprieve but his cousin did not.


Thanks sofakingdom for taking the time to respond and help out

I appreciate it, and maybe others will one day find this thread helpful too.

Last edited by phasevariance; 07-20-2017 at 01:59 AM.
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Old 07-20-2017, 06:55 AM   #16
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Re: Overheating 305



Out of curiosity, when it goes through the heat up / fan on / cool down / fan off cycle at idle, what are the points on the gauge that each event occurs at? And what indication does it show while cruising?
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Old 07-20-2017, 06:21 PM   #17
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Re: Overheating 305

Wait... are you guys serious about 235F being ok operating temp?? Whether factory programmed or not, isnt that a little hot?
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Old 07-20-2017, 06:22 PM   #18
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Re: Overheating 305

Unfortunately GM designed these cars to run on the warm side. They didn't have engine longevity in mind.
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Old 07-20-2017, 06:25 PM   #19
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Re: Overheating 305

Quote:
are you guys serious about 235F being ok operating temp??
Absolutely. Or at least, the upper limit of "normal", at which the cooling system goes to work. It doesn't sit at 235 100% of the time.

Quote:
isnt that a little hot?
Not really.

Quote:
They didn't have engine longevity in mind.
I guess that's why cars from the last 30 years or so, that ALL run at temps like that, will go 200,000 miles easily, while cars from the days of "cooler" operating temps, such as from the 50s, had a tough time going 100,000 without needing SERIOUS work. Or part of why, anyway.
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Old 07-20-2017, 10:22 PM   #20
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Re: Overheating 305

Yeah I'm sure nothing like crap Quaker State oil or advancements in bearing technology played a part in it. The newer cars I work on daily that All run at 210* or less and most are creeping up on 200k+ miles. Your elevator don't quite make it to the top floor if you say an engine will last longer running at 240* vs 190* or less. Common sense is heat deteriotes everything inside an engine beginning with breaking down oil. That said you don't want an engine running too cool either. You run yours at the 230-240 mark and I will keep mine at the 210.
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Old 07-22-2017, 02:54 PM   #21
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Re: Overheating 305

I'm having a similar issue. mine however is leaking at the radiator. I'm ordering an oem replacement. I'm also going to get the new fan switch that turns the fan on at the same temp that the thermostat opens. I never considered that the gauge wasn't correct.
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