Coolant temperature on car

[QueBert]

I got a used Saturn Sky Redline yesterday, on the way home the coolant light came on, my friend was driving with me and we pulled over. He's good with cars so he looked under the hood and the level was fine, so we got back on the freeway and it went off and back on a few more times. He researched the hell out of it today and came to the conclusion it was the Coolant temperature sensor. I poked around a bit and saw quite a few people with the same issue. He's generally really good with cars so I took his advice and had him swap out the sensor. Tonight I went to JiTB to get some dinner, I was flipping thru the info button and ended up leaving it on the coolant temp one. It was about 199 when I 1st got in the drive thru, there was a really long line. 5 or 6 minutes later it has crept up to 128, it went up a few more degrees. Now I don't remember the exact temp when I finally was out of the drive thru, but I believe it was about 138. I was about a mile from home. On the drive home it dropped and dropped and was at 212 when I got home.

1st thing I did was hop on the Saturn web site and download the manual, I searched, but unless I'm blind it doesn't touch on the normal temps. I know it has a temperature warning light that comes in when it's overheating. But, I'm not sure if the sensor he replaced is faulty, or just not connected right. I Googled this and apparently 235 is high, but not a FUCK there's a problem point. The problem is people were saying at above 215 the fans should kick in, unless I just don't know what to listen for, I didn't notice any fans come in.

I can't go back to the dealer because the car was sold as is (out of warranty) And I'm maybe being a bit overly concerned here. But should I be worrying? It's a pretty mild night and I wasn't running the AC or heater. 238 seems like it's too high, while idling it will be higher due to the cold air intake not doing much right? If 238's above where it should be, then something's wrong with the sensor. It was steady going up every minute I was in the drive thru line, I'm not sure it would have stopped at 238. I just know about 10 seconds after I took off it started to steadily go down.

ideas here? Perhaps I'm making too much out of nothing, but this is my new baby and I'm overly anxious while I adjust to having a turbo sports car.

 

[phucheneh]

238 is bad.

While it's obviously not going to be a 100% rule, in general:

Climbing temps at a stop: bad cooling fan

Climbing temps on the freeway: restricted coolant flow. Usually a stuck thermostat.

edit: to check the fan, turn the AC on. If the AC compressor is running and the cooling fan is not on, there's an issue.

 

[nerp]

If you JUST bought it, the dealer might be receptive to fixing it even if it was sold as is. Not all places are willing to say FU to a customer who just plunked down money. Their reputation is at stake. Let them know that.

 

[SearchMaster]

I'm not sure what the normal operating temperature is for your engine, but mine (98 Accord) is ~190 when moving and ~205-210 when stationary but running. So 238 seems very high.

I recently had a coolant hose break when I was pretty close to home, so I gambled and drove home with it. The temp got as high as 240, so I would be concerned with 238 especially if the idiot light came on. phucheneh gave the general rule, and it sounds like it's rising while stopped and dropping while moving, so check your fans first.

But I think nerp is spot on also - it wouldn't hurt to run it by the dealer and see what they say.

 

[SpatiallyAware]

Many modern engines, especially turbos, run hotter than you might think.

I agree with phuc, ~240 would be too hot for me to be comfortable. What are your ambient temps?


I have seen a number of coolant temp sensors bad right out of the box.. I had a ducati 1098 and ended up buying some white box sensor from napa to get correct readings since the 3 I bought from ducati were all off by 10% (which is considered acceptable to them). That 10% margin of error seems common, which is ridiculous IMHO. I ended up bringing a meter to napa and testing a couple, but that was for a motorcycle with a super sensitive engine.

You can test them with hot water by measuring resistance across the leads. Try googling the part number of the sensor itself to get the readings.

Also clean the connector with deoxit or contact cleaner, then after it's dry fill with dilectric grease. I've seen dirty ones give goofy readings. Since coolant comes out when it's removed it tends to gunk up connectors.


Also, some vehicles have a separate simple on/off temp sensor in the radiator just for the fan. So, it's possible you have a good temp sensor at the tstat (showing accurate dashboard temps), and a bad sensor in the rad which isn't telling the fan to turn on. You may be able to find that sensor and short it out to test (read up on that first...)


Past that, I would take it to the dealer if it's a GM place since you just bought it. They will likely cut you a deal on labor if not fix it for free.

 

[LTC8K6]

Did the fan(s) accidentally get unplugged during the sensor change?

The description matches the fan not coming on.

 

[iamwiz82]

238 is a bit out of range but not much for a modern turbo car. I have seen 225F on my turbo. The aux fan kicks in at that point. Check that your fan is kicking on.

 

[Vetterin]

238 is a bit out of range but not much for a modern turbo car. I have seen 225F on my turbo. The aux fan kicks in at that point. Check that your fan is kicking on.

My turbo cruises the hwy at 65 mph between 215-220 all day as the grill shudders close for fuel economy. Temps actually go down in city driving.

 

[exdeath]

190-210 is normal. Anything over 220 for extended periods off throttle is problem.

 

[QueBert]

Many modern engines, especially turbos, run hotter than you might think.

I agree with phuc, ~240 would be too hot for me to be comfortable. What are your ambient temps?

Ambiant temp was probably about 70 max.

Thanks to everyone for the replies, glad to know it wasn't me being paranoid. I thought it might be something with the fan because it went down as I drove. I'm of course going to call the dealer now I know it's more than likely an issue. I know there was a big "as is" box checked on my contract I signed, but as mentioned here they probably (hopefully) will help me. I gotta go putt around a few quick places before I go to work, I'll definitely be keeping an eye on my temp.

 

[SpatiallyAware]

Also check the oil/coolant for them mixing. Overheating can cause a blown headgasket, and that may be why the dealer ended up with the car....

If the oil or coolant looks like milkshake or chocolate milk that is not a good thing. Better to figure that out now in case you have to fight the dealer.

 

[Throckmorton]

First thing to do would be change the fan clutch or replace the fan if it's electric. Should be cheap and easy

 

[QueBert]

Fan's not coming on, I called the service center at the dealer and the service manager was super nice, he said bring it in Friday and they'd get it taken care of for me. Could be a bad fan, could be a bad relay, I don't know. I don't have the tools to troubleshoot it, and it doesn't look like it would be an easy fix. It's very cramped in the engine bay. I'm glad it at least sounds like they're going to fix it.

 

[phucheneh]

If the AC doesn't turn it on, it's probably going to be the fan (or 'fan controller,' if applicable- electronic module that manages fan via PWM) or a relay. Fuse is possible but would be indicative of a bad fan.

With regard to the mentioning of AC, the reason that's a good test is because the AC basically acts as an override to turn the fan on whenever the compressor runs. So it wouldn't be ECT or 'fan switch' related (fan switches are pretty old hat, I wouldn't guess it uses that kind of system).

 

[SpatiallyAware]

Check the oil/coolant first... You can check the oil while hot, just pull the dipstick. Should be dark oil, or possibly translucent. You don't want any whitish milkshake stuff.

When cold, take the rad cap off and look inside. Should be clear water fluid... Again, chocolate milkshake = bad

 

[Ronstang]

190-210 is normal. Anything over 220 for extended periods off throttle is problem.

That is not true according to the Ford engineers I spoke with on the phone about this very issue. They would like to run cars hotter because they are more efficient but get complaints like yours. Heat 220 or over is only a problem on old engines because of metallurgy and design along with the fact that carbureted cars have a problem with the fuel falling out of suspension in the intake manifold....EFI cars don't have this problem because the fuel does not travel the intake tract.

 

[Throckmorton]

That is not true according to the Ford engineers I spoke with on the phone about this very issue. They would like to run cars hotter because they are more efficient but get complaints like yours. Heat 220 or over is only a problem on old engines because of metallurgy and design along with the fact that carbureted cars have a problem with the fuel falling out of suspension in the intake manifold....EFI cars don't have this problem because the fuel does not travel the intake tract.

99.9% of drivers don't have a temperature gauge or a Scanguage, so how would they know what the temperature is? All they have is a needle that goes to red when the engine is catastrophically hot.

 

[tonyfreak215]

The location of the sensor makes a huge difference. In my miata there is a 30 degree difference between the hottest part of the coolant lines and the hot side of the radiator.

 

[QueBert]

Took most of the day, but the dealer fixed it. Car didn't hit above 205 on my way home, and the AC is blowing ice cold air.

 

[nerp]

Awesome. I had a feeling the dealer would take care of it for you. Generally there's a window of time after a sale that they'll try to keep you happy and prove they're worth doing business with, even if the car is sold as is or with no warranty. It's the places that sell you a broken car and then tell you to screw off 24 hours later when you come back with problems that give the industry a bad name. Fortunatley, not all are like that.

I had a similar experience at a local body shop that came highly recommended to me by a good friend who is an car insurance guy, so I trust his analysis of local body shops. They did spectacular work on the paint, far beyond what anyone was willing to do for the price (no bondo, actual metalwork, no blending of paint - painting the whole door and quarter panel instead. . . .
Well I got the car back and the weatherstripping inside the door and the door panel wasn't put back on perfectly, the fitment was a bit off and the rubber on the inside part of the window was bunched on one side. Took it back. The shop owner fixed it right there on the street with me standing there. You could tell he was pissed one of his employees let the car go without proper QC. Shook my hand and I drove off very happy. I know I'll take my and other cars back there. They messed up, but see, they FIXED it happily and stood by their work. This is why the place is so busy and has cars lined up around the block waiting to be fixed.