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Running great until I flushed the system and then it started to overheat?

Tiny
ROBERTBARNES62
  • MEMBER
  • 1999 FORD EXPEDITION
  • 4.6L
  • V8
  • 2WD
  • AUTOMATIC
  • 200,000 MILES
It was running great until I flushed the system and then it started to overheat. I replaced the thermostat a couple times and it would drive good for a day or two and then overheat again. I finally got tired of it overheating and just removed the thermostat. It then never overheated. This was just a temporary fix until I could figure out why it was overheating. So today I finally got some time to start trying to figure out why it was overheating and when I took the radiator cap off the cap and inside of the overfill tank is loaded with brown/red gunk. I figure it is rust cause I was only running water until I figured out why it was overheating. After I get all the gunk out the system I plan to bypass the heater core and see if that is clogged up and causing the overheating. But I want to get all the gunk out first.

So, what is the best and most aggressive flush I can use to flush the system?
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Wednesday, October 17th, 2018 AT 3:15 PM

9 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi and thanks for using 2CarPros.com.

A plugged heater core will not make the engine overheat. Since you have a build up of debris in the cooling system, I suggest doing a flush again. Perhaps the debris was plugging the thermostat and not allowing coolant to flow properly. As far as a brand, discuss that with the people at the parts store. There are many to choose from, and from experience, they all do pretty much the same.

Here is a link that shows how to properly drain and flush the system. As far as replacing the thermostat, it needs to be there.

https://www.2carpros.com/articles/coolant-flush-and-refill-all-cars

Let me know if this helps or if you have other questions.

Take care,
Joe
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Monday, June 28th, 2021 AT 5:11 PM
Tiny
ROBERTBARNES62
  • MEMBER
  • 83 POSTS
Thank you for the quick reply.

Here is a link to another question where I was trying to figure out why my SUV was overheating.

https://www.2carpros.com/questions/over-heating-22870572

I am lost as to why my SUV can be overheating so if you can help lead me in the right direction I would love your help. I will flush it again and see what it does.
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Monday, June 28th, 2021 AT 5:11 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi again. It took some time to read through the other link. It seems you have tried about everything there is with the cooling system, which makes me question if it is another issue.

Just for the heck of it, when the engine is hot (overheating) look at the lower radiator hose and make sure it is not collapsed. Next, I need to know if you checked for a head gasket issue. I noticed it was mentioned, but no results. Finally, a loss of power and overheating can be caused by other things as well. A plugged catalytic converter can cause it. If it over heats, confirm that the converter is not glowing red hot. Here are links that show head gasket and converter checking directions:

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

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

Check the simple things first. I know it sounds crazy, but I have seen lower hoses collapse causing a restriction and overheating.

Let me know.

Joe
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Monday, June 28th, 2021 AT 5:11 PM
Tiny
ROBERTBARNES62
  • MEMBER
  • 83 POSTS
Thank you for taking the time to go through the other thread. And yes, I have tried almost everything and that is why I removed the thermostat as that was the only thing that stopped it from overheating for the moment. I did not do a head gasket check because the other guy said he did not think that was the problem. I will do a head gasket check, lower radiator hose check as well as the catalytic converter check as well. I will be a few days before I get a chance to do these checks but I will get back to you.
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Monday, June 28th, 2021 AT 5:11 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
No problem. Let me know what you find. Also, when you installed the thermostat, are you certain it was facing the right direction? If it does not overheat without one, if a thermostat is properly installed and working, it should not overheat.

Let me know.
Take care,
Joe
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Monday, June 28th, 2021 AT 5:11 PM
Tiny
ROBERTBARNES62
  • MEMBER
  • 83 POSTS
Yes, I made sure I am putting it in just as the last came out which is with the pointed end facing up.
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Monday, June 28th, 2021 AT 5:11 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Just for the heck of it and since you already have the thermostat out, test it. Here is a link that shows how to do it:

https://www.2carpros.com/articles/how-an-engine-thermostat-works

If you go to the bottom of the link, it explains how to test one.

Let me know.

Joe
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Monday, June 28th, 2021 AT 5:11 PM
Tiny
ROBERTBARNES62
  • MEMBER
  • 83 POSTS
I bypassed the heater cores and it does not overheat but it stutters when hitting the gas. At around 60 mph the service engine soon light flashes. Any idea what causes that?
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Monday, June 28th, 2021 AT 5:11 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Welcome back:

If the engine light is flashing, that indicates a cylinder misfire. If you have a scanner, see which one it is or let me know the code and I will identify it for you and we will focus on that cylinder. If you don't have a scanner, most parts stores will scan it for free.

Also, make sure nothing was bumped at one of the coils or saturated with coolant.

Let me know,
Joe
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Monday, June 28th, 2021 AT 5:11 PM

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