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Car Temperature Rising Past Normal

  • Thread starter jimscott
  • Start date

jimscott

Tropical Fish Enthusiast
The car's internal temperature has been scaring me of late. When the car is warming up from a cold start, it goes past what I consider the normal "warmed up" level on the gauge and then drops to a level lower than the typical warmed up temp. And then it pretty much stays, with minimal cycling, thereafter. Last night it went about 2/3 of the way on the gauge, one tic mark away from the red zone, and then I watched it drop real quick. And then it was stable for the rest of my 35 minute commute back home. It's like whatever regulates the temp, be it a fan or thermostat, is frozen and then it releases or turns on or opens up or something. Don't know if it needs more coolant or a new thermostat or a new fan or what. Any ideas?
 
I had an older car that did that exact same thing and it was the thermostat. It sounds like its sticking and not causing the coolant to cycle soon enough and then failing to close again once temps drop enough. Obviously I would check the coolant level but if there was insufficient it probably wouldn't be cooling back down once it got up there. I doubt its the fan as that wouldn't cause a quick drop in temperature like the movement of new cold coolant would and in the temperatures that your having in NY state this time of year, I cant see the fan being all that important unless you spend the entire 35min sitting still in traffic. I would start with a new thermostat and go from there, but this is based on my personal experience so maybe a mechanic can give you better advice.
 
Sounds like the thermostat. If your handy you should be ale to swap it out for $5. Just gotta find a warm place.
 
You can always check the thermostat... it's pretty easy to do... it's usually located in the elbow where the top radiator hose connects to the intake manifold or cylinder head. probably only two screws holding it in. Pop it out, and drop it into a pot of water on the stove. It should stay closed until around 180-190 degrees (forgive me, I am a diesel mechanic, these temps may be a bit high for a car)... then it should open fairly rapidly. Once the water is allowed to cool, it should snap shut again...

Of course, you will have to replace the coolant when you pull the t-stat out, and a thermostat is only $5-15 dollars, so go ahead and throw a new one in while you're there... just nice to do the stove test to verify if that was the problem or not.

Sounds like a t-stat....
 
It might be no big deal. The thermostat is basically a valve that stays closed until it reaches a certain temperature and opens. At that point, hot water flows into the radiator and the cold water that was in the radiator mixes into the hot water and the gauge sees the temperature drop. With the thermostat closed and no coolant flowing through, it's slow to react to the rising engine temperature, which is why you see the temperature go high before dropping. The effect seems to be more pronounced in cold weather. I've never had a car go as high as you describe, but that doesn't mean that you have a problem. My father, who's a retired mechanical engineer gearhead, says a thermostat always fails in the open, never in the closed position. Methinks it can't be "always" vs "never", but every thermostat failure I've had was in the open position and the symptom was that the engine took forever to warm up this time of year. Your mileage may vary.
 
I was a mechanic at my dads autoshop for a number of years growing up. Thermostats absolutely can get stuck closed or respond too slowly opening up. Whenever there is a coolant temperature problem we always started with the thermostat and checked that first. If you are going to bother even taking the housing off to check it you might as well toss a new one in. They are real cheap and odds are that is the problem. Before you check that though you should at least make sure the antifreeze isn't low and the radiator and reserver tank are filled to the proper level.
 
Thank you all for the feedback! Of course I can't get a repair shop on the weekend and it will have to wait until Monday. Meanwhile, I bought antifreeze at a local NAPA and asked the clerk a few questions about it. He also indicated the thermostat, fan, air pocket, and possibly being low on coolant. I poured 2/3 of the fluid before it started coming out of the overflow. I couldn't see the level from the resevoir. That didn't resolve the issue, so all roads point to the thermostat. Again, thanks.
 
You should fill the reservoir, not the radiator. Why can't you see the level in the reservoir? It should be visible from some angle because that's how you gauge if the coolant is low. However, if you were able to pour 2/3 of the jug into the radiator, I think it was low. I wonder if you'd have to run through a full cold-hot-cold cycle before you'd see any change.
 
Jim,
it could be related to the extreme cold this past week..
is the car kept outside?

the cold could be messing with things, perhaps causing something to stick that wouldn't stick if it wasnt so cold.. and once the car warms up, things return to normal..

was it doing this before the cold-snap?
or just during it?

Scot
 
  • #10
I did fill the resevoir. It is too opaque to see fluid. It is kept in an unheated garage by night and outside for my second shift job. So yeah, it is getting a lot of unavoidable cold. It corresponds with the cold snap or is at least more pronounced. It is definitely a recent phenomenon.
 
  • #11
I wonder if you'd have to run through a full cold-hot-cold cycle before you'd see any change.

Upon driving off, after filling the resevoir, the temp rose to the edge of the red zone of the guage.... and then immediately went back down to the midline. Presumbaly, the thermostat just then opened. I went home and turned off the car. A half hour later my wife took me into work and the car behaved normally. She came home and later went out to do some shopping, before picking me up again. The car behaved normally. I took the car to church this morning, now with the outside temps recovering into the mid-20's and the car behaved totally normally. So for the moment, if I wasn't looking for a problem... I wouldn't be perceiving any. It is quite possible that the fluid hadn't circulated long enough to take effect, upon driving off. It is also quite possible that the warmer temps alone solved the thermostat issue. It is also quite possible that the lack of coolant led to this so-called "air pocket" situation and the recent frigid weather contributed / exacerbated the situation. All I have is a lot of variables, correlation, and observances - but little in the way of cause-and-effect. I still wouldn't trust the thermostat as far as I can throw it and as the clerk indicated, the radiator is a closed system... which begs the question as to why the coolant was low in the first place (hole in radiator? loose clamp? cracked hose?) and whether this was a temporary fix.
 
  • #12
The forecast is for warmer temperatures this week so, to continue this experiment, you'll need to head up around Hudson Bay to get cold enough temperatures for a valid comparison when you start it in the morning. Let us know how it goes.
 
  • #13
Hard to say exactly what the problem is. I doubt that the extreame cold would make the thermostat stick closed. Even in 20 degree weather though it will take a few hours for the engine block to cool down to air temperature and fully close the thermostat. We always used to see sticking thermostats during the Summer months not the Winter. It's quite possible there is nothing wrong with the thermostat and your problems were with low fluid and the waterpump unable to circulate the fluid properly because of it.

For now I would make sure the fluid stays topped up and keep an eye on things.

One thing you should have a look at though..
If you let the car sit and idle for a while does the temperature get higher?
 
  • #14
One thing you should have a look at though..
If you let the car sit and idle for a while does the temperature get higher?

Oddly enough, never, once the car went through what it was doing, did it ever rise while idling. I though that was strange.

What about the concept of low fluid leading to an "air pocket"? One thing I'd like to keep an eye on , and it will be obvious if it is parked in snow, is to see if there are green spots. Mind you, we've owned the car for now 4 years and never did anything with the cooling system. Is it possible for the fluid to slowly diminish over time?

Somewhere between Saturday afternoon, when Lynn took control of the car, and Sunday, when I went to church, the car was declared to be healthy again. And so on Monday, instead of a trip to the repair shop, we took a trip to the laundromat. Withing 2 hours we loaded and unloaded 12 washers and driers and scampered back home so that I could get to work on time.
 
  • #15
In some cars (definitely the minority) they have higher spots in the system that can hold air. These spots need to be purged... This is typically the thermostat housing (a small screw/bolt on top of it) you just crack it open till only fluid is coming out. Once the fluid goes low air gets to this spot and doesn't purge itself. Why is that a problem? Fluid doesn't allow for compression while air does. so with a completely sealed system as the fluid heats up it builds pressure, this pressure helps prevent the water from boiling. Once the water is boiling it is harder to get it to let go of the heat through the radiator. If there is air in the system as the heat builds instead of building pressure it compresses the air in that air pocket allowing the fluid to boil.
The fluid can diminish over time, but not in the way of it would not cool your vehicle. Here we barely see freezing temps so most of us don't even use anti-freeze. Or at least much less than recommended. Anti-freeze has no cooling properties, if you filled your car with pure anti-freeze it would over heat. All it does is helps prevent the fluid from freezing. (it may do something for the boiling point too, but I recall that being minimal if at all it's been a few years now since I was a mechanic by profession... now it's just a hobby :p )

Andrew

Andrew
 
  • #16
So I may have a real leak? Should I mix a little water in there at some point (obviously before the car is warmed up)? I have experienced a cracked hose and loosened clamp before, so maybe that's happening?
 
  • #17
If fluid is missing you have a leak. Sometimes these leaks temporarily seal them selves. You should fill it in both the radiator and reservoir tank. Drive it for a decent amount of time (to allow it to heat and cool a few times as it heats it will push excess water into the reservoir and as it cools suck that water back in so the radiator has no air in it) after that monitor it to see if the fluid is going down. If it is you have a leak somewhere... either internally or externally. I've only skimmed this topic but if you've done this already (and checked for a bleeder as I described above) and it's still heating up- I agree with most here that this sounds like a thermostat.

It sounds to me like the thermostat is doing two things wrong... sticking so it's not opening right away, and when it does open, not opening all the way... This would explain it getting very warm before cooling (late to open) and getting warm when being driven but not when idle (the slower flow can keep up with cooling the heat of an idling motor but not a driving one). That's my best guess anyway. :) did you cover what kind of vehicle this is?

When adding fluid, you should try to mix it in at 50/50 (or whatever the container recommends for your temps)
 
  • #18
You might want to put a clean piece of cardboard under the engine compartment when you pull it into the garage at night. Try to do this right after you get done driving it. If you have leak in a hose or radiator or something external if its bad enough to leak it will be easily noticeable. The nice thing with cardboard is that the antifreeze will stain it if its dripping so even if its minor or dries before the next day you will still see some indication of a leak of something. This doesnt work as well if you have had recent snow falls etc that would make the bottom of the car wet as that water may appear to be a leak when its really not.
 
  • #19
I would also recommend squeezing the top radiator hose and see if the system is pressurized when hot, it should be. If not and no obvious leak is found, try replacing the radiator cap. They are the pressure regulation control for the cooling system. If bad you can slowly loose coolant out the overflow without any obvious leak.

(prob thermostat time, and a good flush for PM sake)

Av
 
  • #20
I took the car in for a routine oil change. The coolant I put in on Saturday was gone. So they poured in the remaining fluid I had, as well as water. He didn't see any leaks, per se, but sees a lot of fluid behind the assembly - a mix of oil a coolant. He thinks it might be a head gasket and suggested I take the car to our mechanic an they would introduce a dye into the system as well as a pressure test.
 
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