After replacing thermostat and coolant temperature sensor car is overheating

Tiny
COOLOLDS85
  • MEMBER
  • 1989 BUICK REGAL
  • 2.8L
  • V6
  • 2WD
  • AUTOMATIC
  • 56,000 MILES
I just replaced a thermostat and coolant temperature sensor. I did a complete coolant flush of the entire system. I also just replaced the intake manifold gasket. So I know I had to drain all the coolant out of the system.

Intake manifold is leak free. But as soon as I started the car after adding coolant, I noticed along side the thermostat housing started overheating. I use rtv on the thermostat housing after putting the new thermostat in to seal for leaks. I am thinking maybe it’s overheating because I used concentrated coolant. I did mix water and used more coolant. I did some research and read that concentrated coolant is known to make an engine overheat if it’s not mixed properly. Many people recommended using straight coolant without adding water. Many had better results and increased the life of the coolant system parts in their cars lasting longer.

I am thinking it’s overheating because I used concentrated. I attempted to flush the coolant again today thinking maybe there was still air in the system somewhere. But when the engine started warming up it began to overheat in the same area again. I am lost. I know my heater core is okay because I have heat. It’s got to be something simple I did wrong for it to overheat like this. I hope it’s just the concentrated coolant. Let me know what I should do. I don’t want to drive it like this. Plus I am a beginner mechanic. If I can fix it myself without paying money I would appreciate how to correct this.
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Wednesday, May 22nd, 2019 AT 2:09 PM

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Tiny
COOLOLDS85
  • MEMBER
Here are some videos of where it s exactly overheating at and water pump inspection:
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Wednesday, May 22nd, 2019 AT 3:03 PM
Tiny
CARADIODOC
  • EXPERT
Did you replace the parts to solve this problem or for some other reason? Was the engine overheating before the repairs were done? I'm sorry, but I'm not able to view videos. What are the exact symptoms that lead you to believe the engine is overheating?

As for the coolant, the proper mixture is 50 percent water and 50 percent antifreeze. The antifreeze lowers the freeze point, but it has very little ability to carry heat to the radiator. That's what the water is needed for. It can contain a lot of BTUs of heat and move it efficiently.

Normally when you get hot air from the heater, the coolant has to be circulating to warm up the heater core in the dash, but GM often does things differently. Coolant might circulate through the heater core while an air pocket under the thermostat will prevent it from opening and coolant from getting to the radiator. Thermostats don't open in response to hot air. They have to be hit with hot liquid. If there is no bleeder screw on the thermostat housing, look for a coolant temperature sensor near it that you can remove. Add coolant until it reaches the top of the hole, then pop the sensor back in.

Feel across the radiator too to see if it's hot. If it is, the coolant is circulating. Then the two common things are to insure the radiator fan is turning on, and to perform a chemical test for a leaking cylinder head gasket. Here's a link to an article that explains it better than I can:

https://www.2carpros.com/articles/head-gasket-blown-test
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Wednesday, May 22nd, 2019 AT 3:36 PM
Tiny
COOLOLDS85
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The engine wasn t overheating before. I only replaces the thermostat and the coolant temperature sensor because I had to remove the intake manifold to replace the gasket. Every time I do a job with coolant I replace thermostat and coolant temperature sensor to maintain the cooling system. There isn t any head gasket leak, there isn t any milky wet shown in the oil and no white smoke is entering the tail pipe. It is just overheating near the thermostat housing. Like I said in the videos you couldn't see, is the water pump pulley has some play in it and makes noises when I freely spin it without the belt on. Also a symptom of a bad water pump seal would be coolant leaking out of the hole. This is doing so on mine. But if I were going to replace the gasket I rather replace the whole pump because it wasn t a new one. It was a re-manufactured part.

I mention the water pump because the engine is overheating. I want to make sure if the water pump relates to the over heating issue I am having. Like I said, the only thing that is over heating is the thermostat housing. I do have a bleeder screw, but the screw isn t bleeding when I open it. I don t know if there is air trapped in the system somewhere or the pump went out. I don t want to spend money buying more parts before I know what is it. That s why I asked for help how to fix it.
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Wednesday, May 22nd, 2019 AT 4:32 PM
Tiny
CARADIODOC
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Pop a sensor out to bleed any air out. A lot of cars don't even have bleeder screws, so we can work around that.

It doesn't make sense to say only the thermostat housing is overheating. It can only do that if the entire engine is overheating. Did you feel the radiator to see if coolant is circulating?

Milky oil is the least common symptom of a leaking head gasket. The most common ones are the white smoke from the tail pipe and bubbling in the reservoir. With neither of those, we'll assume the head gasket is okay, especially since it wasn't causing a problem before.

Is it possible you're seeing a problem where there really isn't one? A lot of GM engines have to get up to an uncomfortable 226 degrees before the radiator fan turns on. Before you spend any more of your valuable time chasing this, use a scanner to view live data and see what the Engine Computer is seeing for coolant temperature. You can also use the scanner to cycle the radiator fan relay on and off to verify the entire circuit is working.
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Wednesday, May 22nd, 2019 AT 4:59 PM
Tiny
COOLOLDS85
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I did a job where I had to drain the entire cooling system. Since I did a repair with the cooling system there must be air trapped in the system somewhere or I probably didn t bleed it properly or long enough. The entire engine isn t overheating, it s just in the one spot. I don t want to risk burning my engine out. So I was wondering what I should do next. I did use the scan tool a little while ago and noticed that the coolant temperature sensor was reading what it should be and wasn t going over specs. As for the cooling fans, my scan tool can t turn them on. I have the older model where you can only do tests on the sensors.

How about if I drain the coolant out of the system again, then refill it with a burp set?Maybe if I burp the system all the air bubbles will escape. I didn t burp the system because I don t have one of filler sets.
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Wednesday, May 22nd, 2019 AT 5:27 PM
Tiny
CARADIODOC
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The only place air will become trapped is right under the thermostat, and as I mentioned, that will prevent it from opening. If you remove a sensor near the thermostat hosing, then add coolant until it's about to run out, that should be sufficient. Sloshing hot coolant will hit the thermostat and cause it to open, then any remaining air will flow to the radiator, then into the reservoir as the coolant expands. That air isn't going to keep circulating through the system because it always floats back up to the top.

Understand no heat is generated near the thermostat or housing. The only heat is generated in the cylinders and passes through the cylinder walls into the coolant. If anything is too hot, the heat is getting there through the circulating coolant. Besides feeling the radiator, you can feel the upper radiator hose too, but do that near the radiator. Even when coolant is not circulating, that hose will feel hot near the engine end. That hose should be too hot to hold onto for very long.

An '89 model is going to have two coolant temperature sensors. The sensor with one wire is for the dash gauge or warning light. The sensor with two wires is for the Engine Computer. If you unplug that one with the engine running, the radiator fan should turn on. That's a fail safe design because the computer can't know if the engine is overheating, so it turns the fan on just in case. On most cars that will turn on the Check Engine light and set a fault code. Don't worry about that. On most models, once the sensor is reconnected, the light will go off the next time the ignition switch is turned on, and usually the fault code will self-erase after a certain number of engine starts. That's a quick test on most models to determine if the fan circuit is working.

Take a look at this article:

https://www.2carpros.com/articles/engine-overheating-or-running-hot

to see if it gives you more ideas. Is it possible you installed the thermostat backward? The spring and pellet goes toward the source where the heat is generated, usually meaning the other end is pointing toward the upper radiator hose. Usually you can't fit the thermostat into the housing the wrong way, but every now and then the engineers pull something to mess with us.
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Thursday, May 23rd, 2019 AT 9:15 PM
Tiny
COOLOLDS85
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So your saying if I take out the coolant temperature sensor and coolant comes out it should pull air out and open the thermostat making air come out to the top of the radiator and than will eliminate the overheating issue? I am going to burp the system too because I didn t do so.
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Sunday, May 26th, 2019 AT 7:53 AM
Tiny
CARADIODOC
  • EXPERT
Removing a sensor, then adding coolant, is burping the system. There might be a little air left when you put the sensor back in, but that is insignificant. It will work its way out to the reservoir the next time the engine warms up.

Keep me posted on your progress.
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Sunday, May 26th, 2019 AT 11:27 PM
Tiny
COOLOLDS85
  • MEMBER
To be on the safe side and probably will save me more time than having to remove the sensor because it s hard to take off with throttle body and air box there. I was told, you can jack the front side of the vehicle where the radiator cap is at, with the cap off and the air will escape out of the system faster forcing it out the coolant system because the front of the car or side will be in the air rushing air trap in coolant system out. The air in the system will start to gargle and when it reaches operate temp the air will be out of the system and I will just have to add more coolant to the correct level.

I already drained coolant system again and I squeezed the hose of the thermostat housing. It still felt like there was a lot of air trapped because coolant bubbles was just coming out of the bleed valve and the way it works is the coolant should be shooting out telling you the system is full and hose isn t spongy anymore. I kept adding coolant, the radiator kept overflowing so it was full, but the bleed valve on the thermostat just kept having bubbles come out and was barely shooting coolant out like it s supposed to when you know the system is full.

I already replaced the intake manifold gaskets, coolant temp sensor, thermostat, water pump, and radiator cap. I know when replacing parts in the coolant system it opens the coolant system and traps a lot of air in there. So I found out this is why it s overheating in the first place.

I want to make sure I can still run the engine to operate temp preventing damaging head gaskets ect. I take good care of the coolant system and always drain and clean the system putting fresh coolant because this isn t my daily driver and it sits a lot.

Thank you, your help will save me time and I would appreciate it.
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Thursday, June 13th, 2019 AT 7:31 PM
Tiny
CARADIODOC
  • EXPERT
The first paragraph is totally incorrect. The air is not trapped in the radiator; it's trapped under the thermostat. A lot of GM cars don't even have radiator caps any more. Any air that finds its way there goes to the high point, then gets pushed into the reservoir. When the engine cools down, the coolant contracts and draws liquid back in from the reservoir.

From what you described, it sounds like a cylinder head gasket is leaking. You might be able to see a steady stream of very small air bubbles if you remove the radiator cap, but the better test is described in this article starting with step 4:

https://www.2carpros.com/articles/head-gasket-blown-test

It might be less expensive to have this done by your mechanic. You can borrow this tool from an auto parts store that rents or borrows tools, but they will make you buy your own bottle of fluid. That's because it is rendered ineffective if it becomes contaminated with antifreeze, or if it freezes. They don't want to risk borrowing the tool to you with fluid that was contaminated by the last person, so they made that person buy their own fluid too.
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Friday, June 14th, 2019 AT 3:57 PM
Tiny
COOLOLDS85
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Sorry about the misunderstanding from the first paragraph, you are right Air is trapped in the thermostat housing, not the radiator because I would be seeing bubbles coming in front near radiator, which I don t see.

But I did read the article and from inspecting the vehicle, nothing in that article is even close to what the symptoms I am having and the antifreeze is not containmented, I just flushed the antifreeze out last week with fresh antifreeze. Also engine is running smooth and better than before because I had to replace the spark plug wires because it had loud idle, than started running rough and had a misfire and it mentioned misfire issues in the article. But replacing the spark plug wires made the idle run a lot better. The car isn t emitting a lot of white smoke. It s only coming from thermostat housing area. No smoke wasn t even coming out of the tail pipe heavily. This car only has 56,300. I always made sure I took care of the coolant and at that low of mileage the head gaskets should last me a lot longer because I never lack on maintenance when I spot a coolant leak and right now it s bone dry. That is surprising to me that you would point that out after I always maintained everything carefully even after spending all that money replacing the following parts. There isn t coolant in the oil, stating from the article, and in the radiator coolant wasn t even bubbling and wasn t rising over to the top. When the thermostat housing started smoking, the tail pipe didn t have excessive smoke coming out and coolant reservoir and radiator wasn t even bubbling or rising to the top.

Are you sure it s a head gasket blown when such little smoke is only smoking from one area? If it was a head gasket wouldn t there be excessive smoke everywhere in the engine bay? I have watched numerous videos on YouTube of what a blown head gasket looks like and I am not seeing a lot of smoke like that, only that small trail like I told you. There is no coolant leaks on the ground or oil around the engine block leaking out because I would see it on the manifolds or on the ground, stating from the article if there was a blown gasket. I checked when the engine was cool. Car sat for 6 months almost, even tho I started it real fast than shut the car off after 5 mins when it started smoking. Are you sure it s just not a cold start smoke because the engine wasn t running all that time, I thought doing coolant repairs opening the coolant system and draining the coolant out making air get in there would make the engine smoke a little bit.

Please understand, I am here to learn and give you a better idea why it s doing this, the intake manifolds were replaced, a lot of components were replaced and the coolant system was service. The whole system was open and exposed to a lot of air getting inside the engine. Wouldn t that just be a common symptom of not bleeding the system properly?
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Sunday, June 16th, 2019 AT 2:35 PM
Tiny
CARADIODOC
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Your logic makes sense, but let me share a few tidbits of value. In the late '90s, there was a service bulletin pertaining to one car model with one engine, and how to inspect the cylinder head and head gasket, then how to perform the repair. Many of those started leaking before 20,000 miles or two years. Most of those same engines went well over 100,000 without a head gasket problem. That shows age and mileage aren't the only factors. Also, a family member bought a new 1980 Chevy Citation with the V-6 engine. That one used a quart of coolant every month since the car was brand new. There were no external leaks, but back then, leaking head gaskets were something we had never yet heard of and had no experience with. Today they are real common.

A lot of head gasket jobs are performed at the new-car dealerships because the vehicles are still under warranty. Some manufacturers are very picky and demand to see maintenance records as a way to get out of paying for warranty repairs. That includes regular cooling system service. Even with that scheduled maintenance, head gaskets can corrode through and start to leak.

The biggest area of confusion has to do with symptoms. It all depends on where the head gasket is leaking and how badly it's leaking. Too many people put all their faith in looking for milky-colored engine oil, but that is by far the least common failure. The cooling system won't have more the 16 pounds of pressure in any passage through the heads, and the oil in the drain-back holes has 0 pounds of pressure, and oil in the supply passages rarely has more than 50 pounds. That little difference in pressures is easy for a head gasket to seal. When oil and antifreeze mix, it forms a mud-colored slop with the consistency of light oil. If the driver does excessive short-trip driving where the engine never gets fully warmed up, you'll find a cream-colored goo under the oil fill cap, (looks like Elmer's Wood Glue), and often water droplets under the cap. The clue here is those drops of water are clear, not mud-colored, and they aren't mixing with the oil. That water is condensation from the humidity in the air that is pulled though the engine, then through the PCV valve. When you can shake the water drops off the cap, suspect short-trip driving before a leaking head gasket.

The biggest pressure difference is between the cylinder and anything else. When the fuel burns, the resulting real high pressure can be forced through a weak spot in the head gasket, and while that could go into an oil passage, it is far more likely to sneak into the cooling system because it's those passages that surround the cylinder and are closest to it.

When the leak is small between the cylinder and coolant passage, it takes the high pressure of combustion to force combustion gases through the leak, into the cooling system. This is what I suspect you have. If that occurs slowly enough or only after the engine has warmed up, the thermostat may already be open, then you'd see the stream of tiny bubbles in the radiator. That air is constantly getting past the thermostat so it's not pooling under it. At this point there may be no other symptoms.

As the leak becomes worse, during the intake stroke, the vacuum in the cylinder and the pressure in the cooling system can be enough to pull some coolant into the cylinder where it will be burned and go out the tail pipe as white smoke. There's a chemical test for this I'll describe in a minute. Another point of confusion is water vapor is a byproduct of a properly-working catalytic converter, so water dripping from the tail pipe, or a little steam from the tail pipe is normal. It's also common to see water dripping from a drain hole made for this purpose, in the bottom of the muffler.

Another place for a head gasket leak is from a coolant passage to outside the engine. My assumption is while those are not real common, I'd blame it on lack of maintenance of the cooling system. One of the additives in antifreeze is corrosion inhibitors, and those additives wear out in about two years. There will always be some combustion gases that sneak into the cooling system, and those are what promotes acid build-up and corroded head gaskets. I've only seen this type of external leak a few times, and those were on Ford four-cylinder engines in the late '90s. I did see this once on an early GM Quad-4 engine, but when the new gasket didn't solve the problem, the frustrated mechanic discovered the cylinder head was cracked in that corner. That was a one-time deal that we never saw again.

The chemical test I mentioned involves adding a small bottle of dark purple dye to the coolant, then checking a day later with a black light. Auto parts stores have the dye for the liquid being tested, and they should have a black light to borrow. The dye will show up as a bright yellow stain that you can follow back to the source of the leak. In this case, check for that inside the tail pipe. This is useful when you can't tell where the steam is coming from. If liquid is dripping from the tail pipe and it has a color, it is antifreeze.

For that chemical test to be effective, the leak has to be bad enough that the level in the reservoir will be going down. When that type of leak gets real bad, it can cause a failure of the engine to crank due to "hydro-lock". When the engine is stopped, the cooling system is still under pressure, and that fills the affected cylinder with coolant. That liquid can't be compressed, so if that piston is just coming up on top dead center on the compression stroke when you start to crank the engine, the piston will be stopped from moving. We just ran into this here last week with a Nissan.

It's mostly four-cylinder engine cooling systems that seem to have to be manually bled, but when that is done to any engine, it's a one-time thing. If air could be trapped in a pocket inside the engine, it would tend to stay there all the time, and bleeding wouldn't get it out. In reality, the only other place for it to become trapped is inside the heater core, but coolant circulates through that even when the thermostat isn't open. All the air is going to float to the thermostat and sit under it. Once removed, the thermostat will open normally, then any remaining small bubbles will rush right through to the radiator, then into the reservoir.

There's a more subtle clue you can look for. As soon as you stop a hot engine, look at the level in the reservoir, then check it again five minutes later. You'll see it has gone up a little. That's because the heat in the coolant was being carried away to the radiator, but now, with the engine off, heat is still coming off the cylinder walls into the coolant, but not being dispersed. That causes it to expand even more and get pushed into the reservoir. If you see a few bubbles showing up in the reservoir, that's the last remaining air in the radiator being pushed out. As the engine cools down, coolant will be drawn back in, and the reservoir level will go down.

If you continue to see those vapor bubbles in the reservoir after multiple warm-up / cool-down cycles, it has to be coming from somewhere, and that can only be through the head gasket. This is where the chemical test at the radiator is appropriate. When the leak is still small, you may have to vary the conditions to make the leak be detected. That could mean performing the test while the engine is still cold, or only when it is hot. You might need to raise engine speed to 1500 rpm, or it might only occur under load, meaning in gear, with engine speed raised slightly.

For my parting thought, engine parts normally get way too hot to touch, but they don't smoke. When you see smoke, it is either steam, vaporizing oil, or exhaust gases. When you see that, it has to be caused by the fluid leaking at that point and boiling off, or residue that collected in that area after a recent service. Residue evaporates away, then that's the last you'll see of it. If you continue to see smoke or steam, you have to look at where it came from and how it got there.
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Sunday, June 16th, 2019 AT 6:08 PM

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