Automotive

Radiator broken or just really hot weather?

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Deal Fanatic
Dec 31, 2007
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Richmond Hill

Radiator broken or just really hot weather?

So for the last few days, the temp gauge has been jumping from 90 to 100-105 during the afternoon commute. Especially when it's stop and go traffic. The max temp is 125.

At first I thought it was due to the really hot weather, but am seeing similar behaviour during idle at a parking lot in the evening around 8pm ish.

It only cools back down to 90 when I'm getting good speed like 70 km/h+.

I've also noticed the occasional hissing while driving.

Is this a radiator issue? Or is it just because it's so hot out?

Should I take it to the shop asap?

Note: it's a 2004 pontiac sunfire
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Deal Addict
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May 18, 2002
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Brampton
enwhyRFD wrote: So for the last few days, the temp gauge has been jumping from 90 to 100-105 during the afternoon commute. Especially when it's stop and go traffic. The max temp is 125.

At first I thought it was due to the really hot weather, but am seeing similar behaviour during idle at a parking lot in the evening around 8pm ish.

It only cools back down to 90 when I'm getting good speed like 70 km/h+.

I've also noticed the occasional hissing while driving.

Is this a radiator issue? Or is it just because it's so hot out?

Should I take it to the shop asap?
These days a lot of cars will get up to 115-120 before the cooling fan comes on, check to see if it does.
Also see if there are any trouble lights on the dash.
Deal Fanatic
Dec 31, 2007
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Richmond Hill
prod wrote: These days a lot of cars will get up to 115-120 before the cooling fan comes on, check to see if it does.
Also see if there are any trouble lights on the dash.
115-120 is really cutting it close to the 125 max. Seems too small of a margin for the cooling fan to kick in?

There are no warning lights on the dash, no low coolant light on.
Deal Fanatic
Oct 26, 2008
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Victoria, BC
enwhyRFD wrote:
Is this a radiator issue? Or is it just because it's so hot out?
It's a cooling system issue (of which the radiator is just one part). Very hot weather should have little bearing on it.

The engine/radiator fan is most likely not working as intended.
Assuming it's an electric one and not driven by the engine, it may have a bad electrical connection, not receiving a signal from a sensor, or its motor has high resistance or just worn out.

If it has AC the fan should probably come on whenever the compressor engages which is easy to check visually or audibly. (Keep hands down by side.)

Hissing sound is not good. Someone needs to take a look at it.
Deal Expert
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May 10, 2005
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Ottawa
To add to macnut, have you checked the coolant level? Is it a 50/50 mix of coolant and water? Is is old coolant?
Could also be a thermostat.
“Those people who think they know everything are a great annoyance to those of us who do.”
Deal Addict
Dec 27, 2007
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Edmonton
I worked on a couple of those. Check the relay on the driver side. Had issues with en both times
warming up the earth 1 gas fill-up at a time...
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Deal Addict
Mar 30, 2010
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GTA
90c while driving *at highway speeds* in hot weather is normal.
Above that while idling or doing stop and go isn't abnormal either.
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Feb 16, 2016
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Casselman, Ontario
The same thing happened to me about 3 years ago on my 2001 Sunfire. I checked the coolant level, for leaks, everything seemed ok. The week after, my water pump died. My 2 cents.
Deal Guru
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Mar 31, 2008
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Likely temperature sensor in the waterpump. My GM car did that. Temp guage rise during stop, and goes back down during movement. It caused the fan to not work properly. Also caused some start-up issues.
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Jun 12, 2007
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I think in those GM cars (cavilier/Sunfire), the cooling fan is set to come on at about 105C which seem to coincide with your observations. (3/4 of the temp gauge scale)
. When the fan comes on, it runs till the temp drops back to something like 100C
(1/2 of the temp scale)

Car likely is working normal

To test the fan, turn the AC on and the fan likely will startup

Or

If you idle in a parking lot (with AC off), the electric cooling fan should be off until the temp gauge gets to 3/4. Once the fan starts, the temp should drop to 1/2 scale where the fan stops. The process then repeats
Deal Guru
Feb 9, 2006
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Brampton
Get someone who knows what they're doing to look at it. Those cars are known for leaky water pumps, issues with the head gasket, and fan relay failures.
Deal Fanatic
Jul 26, 2007
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If you are still dingling around with issue, pop the hood or listen for the rad fan each time you get out of the car. If you can see the fan working just once, cross that out of your list.
Sr. Member
Oct 18, 2013
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Brampton
PUT the AC on and see if the rad fan is spinning when its hot out, if its spinning the rad fan is OK.
Thats how it works in my Mercedes, maybe pontiac is a tiny bit different.
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May 18, 2002
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l69norm wrote: I think in those GM cars (cavilier/Sunfire), the cooling fan is set to come on at about 105C which seem to coincide with your observations. (3/4 of the temp gauge scale)
. When the fan comes on, it runs till the temp drops back to something like 100C
(1/2 of the temp scale)

Car likely is working normal

To test the fan, turn the AC on and the fan likely will startup

Or

If you idle in a parking lot (with AC off), the electric cooling fan should be off until the temp gauge gets to 3/4. Once the fan starts, the temp should drop to 1/2 scale where the fan stops. The process then repeats
Maybe in other cars. I have had two cavaliers, and seen many other GM cars of the time in operation. The temp gauge stays in the middle, or very slightly above. If the gauge gets to 3/4 you have likely already overheated the engine and may have caused damage.
It could be many things, collapsed hose, partially blocked rad, sticking thermostat, relay, fan, expired coolant etc. You need a full test of the cooling system.
Deal Fanatic
Apr 20, 2011
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ON
If you're barely moving it will go above 90 a bit. Experienced this after a 6hr summer drive and then stopped waiting in line at the border. (05 sunfire that was ~6yrs old at the time but basically new in operation)
If it's going to the end of the gauge, then you have serious issues. But a bit above 90 while not moving/moving slowly, I would not be concerned yet.
Deal Addict
Dec 27, 2007
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tebore wrote: Get someone who knows what they're doing to look at it. Those cars are known for leaky water pumps, issues with the head gasket, and fan relay failures.
I believe the head gasket was not an issue on the 2.2 ecotec which he has (2003+ and some 2002)

Relay yes. Replaced a couple
warming up the earth 1 gas fill-up at a time...
You only live once, get a v8
Deal Fanatic
Dec 31, 2007
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Richmond Hill
So I did a few tests yesterday during the afternoon commute.

1. I turned off the AC.

When I kept the AC off, temps didn't go past 110. It fluctuated between 95-105. The cooling fan did not seem to get engaged. It was a bit windier than usual, so that may have helped drive air in.

2. I turned on the heater to the bottom vents and opened the windows.

Temps looked like it dropped a few degrees. Not a large drop, but at least it didn't keep the temps from increasing.

So, it doesn't look like a radiator issue? And moreso due to a combination of heavy AC usage and hot weather?
Deal Guru
Feb 9, 2006
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Brampton
tmkf_patryk wrote: I believe the head gasket was not an issue on the 2.2 ecotec which he has (2003+ and some 2002)

Relay yes. Replaced a couple
Right. The 2.2 was the chain tensioner right?
Deal Addict
Dec 27, 2007
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tebore wrote: Right. The 2.2 was the chain tensioner right?
Yup
warming up the earth 1 gas fill-up at a time...
You only live once, get a v8
Deal Expert
Jan 15, 2006
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Richmond Hill
Pete_Coach wrote: To add to macnut, have you checked the coolant level? Is it a 50/50 mix of coolant and water? Is is old coolant?
Could also be a thermostat.
Won't be tstat as those are designed to fail open. My guess is water pump is on its way out. OP check under the car to see if there is a puddle of coolant. If so its most likely the water pump.

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