Engine overheat and cool air -thermostat?

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Yesterday coming home from work in -10 C, a 26 km drive,
I was getting just cold air through the heater. I was watching the temp
guage all the way home and as I got near my home about 20 minutes in,
the temp guage on my pickup was at the red line.
Once parked in driveway, I noticed the rad pushingbubbling fluid into the overflow and could smell hot antifreeze.
I have noticed the past few weeks that the temp guage has been rising but then would suddenly start to go down esp. if I turned on the heater
and it seemed unusual at the time so I have been watching it. --yesterday was the first time, it did not go down. I went for a little drive later that evening and this time, the temp rose even faster -7 minute drive to move temp guage close to red and still no heat from heater.
I assumed/read that you would have one or the other, that is, engine overheats so thermostat is stuck in closed position No heat in car so thermostat is stuck in open position.
I seem to have both scenerio's going on.
Any thoughts -is it even the thermostat? if so, I know the thermostat is relatively inexpensive? should I buy 3rd party or from dealer and finally, how long/shop time to replace one (I am assuming one hour or so) and is it worth trying to do it myself?
Many thanks in advance
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Greetings,
Thermostats are cheap and easy to replace, but for some reason I don't suspect it's your thermostat. Since the heater lines on many vehicles are connected to the engine side of the cooling system, it should make no difference if the thermostat is open or closed in order to get hot coolant to the heater core.
However, since you have no heat at all in the cabin and a spiked temp gauge, then I suspect you either have a thermostat stuck closed, a blockage somewhere in your cooling system or even a failed water pump. You should also check the air path through the front grill and the radiator fins for blockage.
A temp gauge that rises steadily but goes back down when you turn on your heater tells me that either fluid is not getting to your radiator (thermostat stuck closed) or if it is then it's not being cooled (blocked air flow or clogged radiator).
A rapid temp rise with no heat from the heater says failed water pump or comlete blockage in the block.
You could try replacing the thermostat (and I recommend replacing the radiator cap at the same time). If it works then great, but if not then take it to the shop for a look at the water pump and flow test.
Good luck - Jonathan

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Greetings,
Responses in-line...

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No, are you an idiot???? Can you even read ???
If the water pump is not working (or some

I trimmed the rest of this post so that maybe you could see to who you are replying to. I was asking the above question to another person who claimed a stuck thermostat could be the cause of overheating AND no interior heat. See the "AND" , that means BOTH problems are occuring at the same time. You replied to my question. But........ What the hell does a water pump failure have to do with a stuck thermostat??????

Now you are replying to the original poster, I am not that person. You seem to be having a problem following this conversation.

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> On 3/22/2006 9:07 PM ... SgtSilicon wrote:

Typically a stuck *open* thermostat will cause poor cabin heat.
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But would also have a low engine temp as the coolant is being cooled too efficiently.
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Greetings,
Yes, but not in all circumstances. I've seen an engine overheat with the thermostat stuck open because the coolant was flowing too fast through the radiator due to high water pump RPM's to bleed enough heat off into the atmosphere (I've also seen this with no thermostat installed). The coolant wasn't staying in the radiator long enough to be cooled. Yet the same motor was over-cooled at lower RPM's because too much coolant was allowed into the radiator when it didn't need to be. This is the reason why it is not recommended to run without a thermostat - you need some control over the flow through the radiator.
Other than that I agree with what you are saying.
Cheers - Jonathan
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You seem to have alot of " book " knowledge but no hands on knowledge. The no thermostat will overheat the motor seems to be a text book only event. In all the years I have been around cars I have never seen this happen. I've ran dozens of cars without a thermostat for whatever reason and not once have I seen one overheat beacause of that. In fact most will never reach proper operating temp with the thermostat removed.
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In fact, "text" books and science dictates exactly what you observations have been. While I'm not an experienced mechanic, I have done well in physics.

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Not to mention that when a thermostat sticks open the flow rate is the same as when a thermostat is normally open. If it were to be the case that a stuck open thermostat will cause overheating, then a normally open thermostat would also cause overheating. I think what Jonathan observed was something else at fault which he mistakenly assigned to a faulty thermostat. Not that I haven't been bitten by such things...
--

-Mike-
snipped-for-privacy@alltel.net
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Wow, this is getting too out of hand. Your first assumption is that I'm saying this will always happen every time every day, etc. Bad assumption on your part. This is only a possibility that I've witnessed once and not an absolute. Why do you continue to make out like I'm stating it as a federal law or something? Do you actually believe that when I said "I've seen an engine overheat with the thermostat stuck open" that I saw it in a lab somewhere? Oy vey! There are some circumstances that exist that not everyone has seen - I don't lay claim to having seen all of them, but I have seen some. Just how do you think these things got into the textbooks anyway?
Anyway, I'll gladly concede the point that it is not a regular occurance or that it would be my first choice for the answer to a problem. As they say, "when you hear hoofbeats, don't think zebras!" so this is where I leave off.
Cheers - Jonathan

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Mike wrote:

Hey Mike....been following this thread. Apparently you "actually" know what you are talking about. I've seen/heard this baloney being spouted here on these newsgroups before and a number of people will believe anything if someone keeps repeating it.
It's amazing how complicated people will try to make these simple problems. Car overheats, no heat in cabin......99.9 percent of the time....low coolant. But no....we've got to come up with all sorts of other reasons.
Car will overheat if thermostat removed......hahahaha.....that's a good one! Unbelievable what people come up with when it has to do with operating principles of engines, cooling systems, and cars in general.
Ian
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Thanks Ian. It really is amazing, all the replies to this post with off the wall suggestions when all that was needed was to remove the radiator cap and check the coolant level. If most people would just start with the basics they would have better luck finding most problems. I really felt bad for the original poster with all the odd answers he was being given.
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On Fri, 24 Mar 2006 02:03:30 GMT, "Jonathan"

That just isn't scientifically sound. Basically the same amount of heat should be transferred to the atmosphere from the radiator regardless of flow rate of coolant. The determining factors are how much heat the coolant picks up from the engine and how much cool air is flowing over the radiator. A bit of coolant losing a measure of heat or losing half that heat but twice as often is the same over all transfer of heat. So yeah, a faster flow rate means the coolant doesn't drop as much heat in it's journey through the radiator, but it makes more of those journeys in a given time. It comes out the same.
To put it bluntly, if you think about what you said, then once thermostat opens up it would allow too much coolant to go through the radiator and over HEAT itself. Opening of the thermostat does just the opposite, and having one ALWAYS open keeps the coolant cooler than it should be for proper operating temperature of the engine. Removing a thermostat wont cause over heating, just under heating of the coolant in the jacket.
Now I do not doubt your observations, but I think the cause you attribute is mistaken. There must have been other factors in play, known or unknown.

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Using good quality thermostats from your local parts house is fine. Ditto radiator caps.
I have seen some cars where changing the thermostat is a 30 second job. On others it may take longer, but is seldom a complicated job.
I agree with Jonathan that you should change both cap and stat, and refill with the proper coolant. Be sure to get the air out of the system. Some cars have air bleed valves in the systems, others do not.
Then keep an eye on temperature and coolant.
Depending upon what engine you have, several GM models have engine weaknesses that can result in loss of coolant, and even destruction of the motor if left unaddressed. (We assume you have a GM of some sort.)
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