Engine overheat and cool air -thermostat?

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

Reply to
gpagmail-news
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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

Reply to
Jonathan

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.)

Reply to
<HLS

I don't see where you have both. The symptoms you describe seem to indicate the thermostat is sticking closed and it's taking increasing temperature and pressure to get it to open. The "no heat in car so thermostat is stuck in open position" doesn't always mean that. Actually, you will have very slow heating with an open t-stat. That's how I knew my La Sabre's needed replacement. No heat at all (and a red lined temp gauge) sounds like it's sticking closed and not opening. I had an '86 Isuzu Pickup do that to me.

Any reputable auto parts store should be sufficient. Be sure you get the right temperature t-stat for your truck.

Since you didn't indicate what kind of truck you have, it's hard to say, but an hour or less is about average for the DIY'er. For the cost of a t-stat and it's relative ease of replacement, I'd start with that. And I'd go ahead and do a flush and hose check, too.

Reply to
The Ghost of General Lee

So if the thermostat is stuck open and the coolant is constantly being cooled by flowing through the radiator how would you have any heat ?

Wouldn't any of those cause more heat from the heater core and not less heat, which is his complaint ?

But he has no heat from the heater core. Wouldn't those problems you mention give him more heat ? I would suspect a low coolant level would produce the symptoms he is having.

Well, water pumps rarely work fine one day and fail the next. How do you get a complete blockage in the cooling system overnight ?

How about checking for low coolant ?

Reply to
Mike

Greetings,

Responses in-line...

It's the combination of cold ambient temps and overheating he is complaining about. There are conditions where a thermostat that is stuck open (or running without a thermostat) will cause the engine to overheat as well because the coolant is passing through the radiator too quickly and isn't bleeding enough of the heat off to the atmosphere. This is why it is not recommended to run without a thermostat. However, since he is in a very cold climate (which could be anywhere above the Florida-Georgia border right now...) then I don't suspect that his thermostat is stuck open and is the cause of his overheating. Stuck closed I could see with that kind of low ambient temperature.

No, especially if the thermostat is stuck closed and the piping for the heater core is plumbed to the downstream side of it. A blockage or stoppage to coolant flow could also stop heat because no coolant is getting to the heater core. I always recommend checking the air path through the radiator because that could cause the overheating that gets better as he turns on his heater (which he mentioned), but there is always the possibility that the air flow could be blocked causing the overheating and he has a seperate issue with his heater altogether (like snow jammed in the air intake - it is -10C where he is after all).

I agree that low coolant could be a possibility. However, if he had a blockage or bad water pump then he won't get any heat out of the heater because there is no hot coolant flowing through it. Yes, the engine will heat up (excessively, like he mentions) but he won't see any of that heat out of the heater because none of the fluid is moving through the heater core. Simple enough.

Let's see... He doesn't mention what make/model/year of truck he has so it is possible that he snapped a belt. Broken shaft on the pump, stripped impeller, to mention a few "catastrophic" water pump failures that could happen overnight. As for a complete blockage, how about a collapsed hose or a clogged radiator from rust or other junk. I never said his was an overnight condition - he relates that unusual symptoms have been building for a week.

Good idea. I agree.

Reply to
Jonathan

But you still haven't explained how a stuck closed thermostat could cause a NO HEAT condition. How can an engine be running hot and yet you have no interior heat ???????

Better hit the books again. Heater core lines operate independently from the thermostat. Think about this one a bit. Do you have to wait for the thermostat to open before you get heat in the car ???? Uh.......... NO

A blockage or stoppage

I always recommend checking the air path through the radiator

How does a water pump suddenly fail to stop pumping water ???

Doesn't really matter.

so it

Would overheat but would also likely lose alternator or power steering.

As for a complete blockage, how about a collapsed hose or

Would overheat but would have real good cabin heat.

I never said his was an

Which rules out most of your above answers. He said the temp would run hot, then come back down. Until the last day when it overheated and he had no heat. This would indicate, to me, a low coolant level caused by a slow leak.

Reply to
Mike

Reply to
JRL

It depends on where the lines to the heater core are plumbed. If they are after the thermostat then a stuck closed thermostat will also stop flow to the core. However, that is unusual since modern heater lines are plumbed on the upstream side of the thermostat. Also, a hot running engine can have no interior heat if it's running hot because of either no coolant flow (failed pump, for example) or a clogged heater core (which could be a possibility if the radiator was clogged also. What clogs the radiator will also clog the core). Simple.

Looks like you better hit some older books. Not all vehicles were plumbed this way, although they are in today's vehicles. While you don't have to wait for a modern thermostat to open to get heat in the cabin, you DO have to have coolant flow to get heat in the cabin. Low coolant, bad pump, or blocked heater core will create this problem.

OK, I'll spell it out...again. A stripped impellor or snapped shaft where the pulley is turning but the impellor isn't. Can happen from the fluid inside the pump being frozen solid when he goes to start the truck. If you recall, he did mention that he was in a place where he was experiencing -10C temps. I'm not assuming that he has the proper mixture of antifreeze in his cooling system or other issues, but I hope he does and that a bad pump is not the case (although I would still check it out as a source for a leak).

Again, depends on the truck. Not all in the past have the same belt turning the water pump, alternator and power steering like the modern single serpentine belts do. Not too long ago there were seperate belts for the pump, and another for the alternator so a loss of the pump belt wouldn't affect the alternator. Heck, my Duramax doesn't even have a belt to turn the water pump - it's gear driven.

Not really, because whatever is clogging the radiator would most likely be clogging the heather core as well - which is just another, smaller radiator after all.

I'm not disputing this, but while low coolant is an excellent possibility it's not the only possibility.

Reply to
Jonathan

How about some examples. I have worked on cars from early 60's vintage to

2006 vintage and have not noticed any differnece in the plumbing.

While you don't have to

It pretty much is when you consider that he actually has TWO problems, not just one. He states that it was running hot before it overheated and he lost his cabin heat. Turns out his problem was low coolant. He is now checking for leaks.

While most of your possible causes would be possible if he had just one problem they are contradictory being he has two problems. Example: Plugged radiator - While this would cause the car to overheat it would provide excellent cabin heat. I've worked on cars for a long time and never seen a water pump shaft just snap off. I also doubt it would do this silently, it would probable make one hell of a noise. I've worked with guys that have removed water pumps because they also thought the impeller was worn or broken, but once apart it was fine.( I never have actually seen one fail in this manner, yet.)

My point is that when trouble shooting ANY problem keep it simple. Always check the basics first, no mattrer how simple it may seem, and work your way up from there. It took this fellow several days to figure out his problem when several of us had recomended he check his coolant level FIRST. ( He also posted this in several different news groups) This is meant to help out the next guy having problems when he searches the newsgroup looking for answers.

Reply to
Mike

Are you a TROLL??????? If the water pump is not working (or some other issue is preventing coolant flow), the coolant around the block will get VERY hot (and this indicate an over temp condtion), but hardly any of it will make it to your heater core so you wont get any heat inside the cabin.

Now then, is it not possible that before when you said that the temp was going up but turning on the heater helped bring your temp down, that the water pump or other flow restriction issue was beginning to be a problem but later flow has stopped completely? Seems to make sense to me and that none of it happened OVER NIGHT as you put it.

Reply to
SgtSilicon

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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Reply to
Mike

Typically a stuck *open* thermostat will cause poor cabin heat.

Reply to
jcr

But would also have a low engine temp as the coolant is being cooled too efficiently.

Reply to
SgtSilicon

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

Reply to
Jonathan

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.

Reply to
Mike

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.

Reply to
SgtSilicon

Reply to
SgtSilicon

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...

Reply to
Mike Marlow

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

Reply to
Jonathan

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