Where to take a temp reading to see if the car is really overheating?
08-03-2016, 01:12 AM
#1
Instructor
Thread Starter
Where to take a temp reading to see if the car is really overheating?
Post number 1 billion on overheating.
So my new-to-me 924s gauge creeps up. I was told by the PO that *he* was told the problem is the gauge by his mechanic. Now, it doesn't always happen, so having an intermittent gauge problem is plausible. Most of the time the gauge is at the 1/2 way mark.
On the occasions where I've seen the gauge hit the red, I've taken an IR thermometer to the water pump, top of the radiator, and thermostat housing and readings all seem normal - in the 190 - 195 range give or take.
Anecdotally, the underhood temps seem super normal. I own a ton of cars and when your engine is overheating you can really tell. Never felt anything like that. In fact, I would say the 924 seems to run pretty cool.
I have tried bleeding the cooling system but I have not done so with the nose in the air as some have suggested.
So this is a long way to a short question - where is the best place to take a temp reading to see if I'm really having an overheating problem, and what temp should I expect in normal operation?
Thanks!
So my new-to-me 924s gauge creeps up. I was told by the PO that *he* was told the problem is the gauge by his mechanic. Now, it doesn't always happen, so having an intermittent gauge problem is plausible. Most of the time the gauge is at the 1/2 way mark.
On the occasions where I've seen the gauge hit the red, I've taken an IR thermometer to the water pump, top of the radiator, and thermostat housing and readings all seem normal - in the 190 - 195 range give or take.
Anecdotally, the underhood temps seem super normal. I own a ton of cars and when your engine is overheating you can really tell. Never felt anything like that. In fact, I would say the 924 seems to run pretty cool.
I have tried bleeding the cooling system but I have not done so with the nose in the air as some have suggested.
So this is a long way to a short question - where is the best place to take a temp reading to see if I'm really having an overheating problem, and what temp should I expect in normal operation?
Thanks!
08-03-2016, 09:33 AM
#2
A infrared temperature gun only gives you surface temperature so you can be 10-15 degrees Fahrenheit off of the water temperature.
Just remember the temperature gauge on these cars are a bit different. The half way mark is 192 degrees and the three quarter mark is 206 degrees Fahrenheit. Most cars of the 80's the the radiator fan didn't come on until about 210 degrees Fahrenheit. Our cars the radiator fan comes on before the three quarter mark.
Just remember the temperature gauge on these cars are a bit different. The half way mark is 192 degrees and the three quarter mark is 206 degrees Fahrenheit. Most cars of the 80's the the radiator fan didn't come on until about 210 degrees Fahrenheit. Our cars the radiator fan comes on before the three quarter mark.
08-03-2016, 07:41 PM
#3
Instructor
Thread Starter
Yup, I get that. When I see ~190-ish on an IR gauge I know I'm still well within operating range.
My question is, if there is some sort of blockage or air bubble, is there another place on the motor I should take a reading to see if there is really a problem.
My experience is that my fan (1988 924s) goes on right when the temp gauge reaches the red mark.
I have seen the needle go well into the red mark. When I check the cooling system at that point, I still see coolant readings in the 190 range. Nothing about the motor or engine compartment feels excessive regardless of how far up the gauge I go.
So I suspect I simply have a gauge problem or a ground problem or a sender problem. BUT I want to see if there is a better place to take a reading to see if I really am running hot.
My question is, if there is some sort of blockage or air bubble, is there another place on the motor I should take a reading to see if there is really a problem.
My experience is that my fan (1988 924s) goes on right when the temp gauge reaches the red mark.
I have seen the needle go well into the red mark. When I check the cooling system at that point, I still see coolant readings in the 190 range. Nothing about the motor or engine compartment feels excessive regardless of how far up the gauge I go.
So I suspect I simply have a gauge problem or a ground problem or a sender problem. BUT I want to see if there is a better place to take a reading to see if I really am running hot.
08-04-2016, 12:50 AM
#5
Instructor
Thread Starter
Not knowing the electronics - does the gauge control the fan? Doesn't the ECU control the fan?
It's possible that the fan is coming on at the correct real temperature, but the gauge is just completely wrong.
It's possible that the fan is coming on at the correct real temperature, but the gauge is just completely wrong.
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08-04-2016, 06:01 PM
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08-05-2016, 02:05 AM
#10
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i would suspect the lower radiator hose to be a decent indicator of actual coolant temps, take an IR reading of the surface of the hose and then add 10 degrees or so and that aught to be pretty accurate in my opinion. Sounds to me like you have a gauge issue, probably related to shoddy grounds behind the cluster. I have a similar issue in my 86 NA, the voltmeter is pegged half the time at 16+ volts and half the time reads normal at ~13.5. My fuel gauge also can't be trusted and the low fuel light comes on whenever it wants, even with a full tank of fuel. I've tried cleaning all the grounds and have simply determined its a gauge fault and live with it since all my other instruments work fine. One of these days I might get around to replacing the cluster.
08-05-2016, 08:04 AM
#11
Doug, the coolant flows out though the water outlet on top of the engine and returns though the water pump. I thought these cars are reversed cool also because of the thermostat location. I was shocked when I found out that the coolant flow in the normal direction.
08-05-2016, 12:33 PM
#12
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Running into the same issue on my new to me 944. Biting the bullet and replacing the thermofan switch/ thermostat with their 75 & 71deg equivalents.
My low speed fans kick in @ the 3rd white line, just below the red warning in the temp gauge, and the high fan's never kick in which is too close for comfort for me.
I'm spending the $30 for the 2 new parts and be done with high coolant temps.
My low speed fans kick in @ the 3rd white line, just below the red warning in the temp gauge, and the high fan's never kick in which is too close for comfort for me.
I'm spending the $30 for the 2 new parts and be done with high coolant temps.
08-05-2016, 09:14 PM
#13
Running into the same issue on my new to me 944. Biting the bullet and replacing the thermofan switch/ thermostat with their 75 & 71deg equivalents.
My low speed fans kick in @ the 3rd white line, just below the red warning in the temp gauge, and the high fan's never kick in which is too close for comfort for me.
I'm spending the $30 for the 2 new parts and be done with high coolant temps.
My low speed fans kick in @ the 3rd white line, just below the red warning in the temp gauge, and the high fan's never kick in which is too close for comfort for me.
I'm spending the $30 for the 2 new parts and be done with high coolant temps.
08-05-2016, 10:11 PM
#14
Three Wheelin'
Post number 1 billion on overheating.
So my new-to-me 924s gauge creeps up. I was told by the PO that *he* was told the problem is the gauge by his mechanic. Now, it doesn't always happen, so having an intermittent gauge problem is plausible. Most of the time the gauge is at the 1/2 way mark.
On the occasions where I've seen the gauge hit the red, I've taken an IR thermometer to the water pump, top of the radiator, and thermostat housing and readings all seem normal - in the 190 - 195 range give or take.
Anecdotally, the underhood temps seem super normal. I own a ton of cars and when your engine is overheating you can really tell. Never felt anything like that. In fact, I would say the 924 seems to run pretty cool.
I have tried bleeding the cooling system but I have not done so with the nose in the air as some have suggested.
So this is a long way to a short question - where is the best place to take a temp reading to see if I'm really having an overheating problem, and what temp should I expect in normal operation?
Thanks!
So my new-to-me 924s gauge creeps up. I was told by the PO that *he* was told the problem is the gauge by his mechanic. Now, it doesn't always happen, so having an intermittent gauge problem is plausible. Most of the time the gauge is at the 1/2 way mark.
On the occasions where I've seen the gauge hit the red, I've taken an IR thermometer to the water pump, top of the radiator, and thermostat housing and readings all seem normal - in the 190 - 195 range give or take.
Anecdotally, the underhood temps seem super normal. I own a ton of cars and when your engine is overheating you can really tell. Never felt anything like that. In fact, I would say the 924 seems to run pretty cool.
I have tried bleeding the cooling system but I have not done so with the nose in the air as some have suggested.
So this is a long way to a short question - where is the best place to take a temp reading to see if I'm really having an overheating problem, and what temp should I expect in normal operation?
Thanks!
You could use a nice FLIR thermographic camera but you probably don't have access to one like the $200K camera we have at work...
Cheers,
Mike