Overheating Root Cause

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Wabel

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I finished working on my 2004 V8 overheating problem a few days ago and think the root cause is worth sharing.

The following is based on OEM parts. I am a novice so I hope this makes sense.

Inside the thermostat housing the thermostat pin inserts into a hole that is on top of a column which is part of the thermostat housing mold. This column is about 1" tall. With the thermostat installed and fully closed about 1/2" of the pin is visible and the remaining 1" or so is pushed up inside the thermostat. When the thermostat opens the stopper pulls back exposing more of the pin. When the thermostat is fully open the entire pin is visible so it's open about 1".

Taking a close look at the old housing, with the thermostat still installed, I noticed that the column was only about 1/4" tall. At first I thought the new housing was the wrong part so I called a Lincoln dealer and verified that what I had was indeed the correct part.

The column must have crumbled in on itself losing about 3/4"!

With the thermostat installed and fully closed about 1 1/4" of the pin is visible with only about 1/4" pushed up inside the thermostat. This means when fully open the thermostat could only open about 1/4" and was restricting coolant flow.

My Theory:
Over time the column crumbles getting shorter and shorter. At first the car may not overheat but runs hotter and pressure builds much higher than normal. Under these conditions time takes a greater toll on the cooling system and eventually leads to the failure of the remaining plastic cooling parts.

So if your car is running too hot and/or is overheating or the cooling fan is running at higher speeds but there are no signs of a coolant leak and you have bled the system properly then consider checking inside the thermostat housing.
 
No I didn't sorry. I wasn't planning on posting but the more I thought about it I thought it to be interesting as well. If you like watch this video. At 15mins. 15secs. there is a good view inside the OEM housing. The gold colored cup-like washer is what the thermostat pin inserts into. That is on top of a column that's about 1" tall maybe a little less. It may not look that tall in the video but that's about how tall it is. Inside the OEM housing that I pulled off of my car that column had crumbled down to almost 1/4". The plastic flakes and bits drained out with the coolant. Hopefully all of them.

 
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You know, you'll be replacing all the rest of those plastic parts too. It's all made out of the same stuff, and it all degrades at about the same speed. All of this is well known to many of us.
 
I figured that to be the case so I have all parts but for a degas ready to go and all are OEM. I've enjoyed some great threads here on the subject.

However I'm wondering if the thermostat restricting coolant flow is what begins the degrading process. If the housing issue I mentioned occurs slowly over time then someone could be driving around a long time with elevated coolant temps and pressure way above normal and know nothing of it. Driving under those conditions for months maybe years I'm sure would take a toll on the other plastic in the system.

Either way I'm watching closely.
 
Perhaps for some that is the first symptom. For others, the plastic ears that hold the thermostat together fail, and still others have leaks and trapped air as their first problem. Personally for me, I've spotted leaks starting and never had any overheating.

I can tell you with complete certainly, that the parts will and do degrade without any overheating. (I do suspect that more heat makes it faster.)
 
I don't think the T-stat housing starts to fail and then causes all of the other parts to then fail. all of the parts just get brittle and start to fail after all of the time and heat cycles. the T-stat housing just tends to be the first part to fully fail because of on top of all of the other forces acting on the parts, that one part also has the added stress of holding the spring pressure together. in my case, the end of the coolant outlet pipe blew off letting all of the coolant get pumped right out. when taking it all apart I found that the ears holding the T-stat parts together had snapped off and most of the T-stat had turned sideways allowing plenty of flow 100% of the time.
 
My 2004 V8 is nearing 58K miles and I am not looking forward to all of these well documented cooling system issues. At least the PO had the cooling system flushed before I bought the car.
 
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Wabel said:
The column must have crumbled in on itself losing about 3/4"!
Click to expand...
What you saw is pretty indicative of what happens to the rest of the PLASTIC cooling system parts on the LS. You may think you have escaped disaster,,, but in reality... your cooling system "fun" is probably just beginning. Depends on if/what a previous owner has replaced.

joegr said:
You know, you'll be replacing all the rest of those plastic parts too. It's all made out of the same stuff, and it all degrades at about the same speed. All of this is well known to many of us.
Click to expand...
1LoudLS said:
I don't think the T-stat housing starts to fail and then causes all of the other parts to then fail. all of the parts just get brittle and start to fail after all of the time and heat cycles. the T-stat housing just tends to be the first part to fully fail because of on top of all of the other forces acting on the parts, that one part also has the added stress of holding the spring pressure together.
Click to expand...

I think everything has been said that can be said. There are hundreds of stories just like yours on LVC
 
Then you know what to expect. I suggest you take preventative measures... so you don't end up broken down on the highway somewhere. Remember the old saying... "an ounce of prevention,,, is worth a pound of cure".
 
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