Not Another Overheating Thread!

jccpd

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I recently picked up a 93 Mark VIII with 97k on the clock from a police auction. It did not run and after doing work to it, I was able to get it running. I do not know the history behind the vehicle, but it looks like it had a hard life.
I currently have my original 93 Mark VIII, this 93 I purchased as well as a 94 and 95 parts cars.
When I began to drive the car, it overheats.
I know that these cars are temperamental, as I drove my original 93 from 2000, with 76k miles until retiring it in 2016 with 208k miles, and dealt with coolant changes several times.
I also searched this website, other Lincoln websites and social media for answers why this car is overheating.
Here is what it is doing, which has been consistent no matter what remedy I try.

1. The car runs great, does not miss and does not have any dreaded white smoke from the tailpipes.
2. There is no water in the oil, or oil in the water.
3. The fluid is fresh, about a 50/50 mixture.
4. The fan is running at full speed, but is not connected to the fan sensor at the intake manifold. It always runs full speed whenever the engine is running.
5. I can drive the car about 2 miles before it overheats.
6. When the car overheats, cool coolant comes out of the coolant reservoir, but not at a high rate.
7. On the temperature gauge, the needle slowly climbs to the "M" in NORMAL. Once it gets there, it immediately goes to the top of the scale, within seconds, indicating overheating and after a few moments, the engine warns to "Check Engine Temperature".
8. When checking the engine after turning it off, there is extreme pressure on the top radiator hose every time and the crossover tube and engine are hot.
9. This pressure on the radiator hose (and the system) will stay for 48 hours, slowly decreasing.
10. There is no bubbling in the crossover tube after replacing the fluid. Just the normal big bubbles when first replacing coolant and squeezing the upper radiator hose.
11. When filling the system, I can see the coolant flow in the crossover opening.

This is what I have done to fix the problem.
1. Replaced the thermostat with a new factory 195 degree version. I checked it prior to installing it and it opened at 195 degrees in water on the stove.
2. Replaced the water pump with a new one. The old pump seemed fine when looking at it afterward.
3. Replaced the radiator with one from one of the parts cars. Both the original radiator and the used one flowed water from the top to the bottom as fast as the garden hose would go. There seems to be no obstructions and the inside of the radiator looked very clean on both the original radiator and the "new" one.
4. Replaced the reservoir cap with a new cap.
5. Replaced the new thermostat with a new 96 Cobra thermostat at 180 degree (tested here as well) with the wide-opening inlet. Really, there is only one way to put in the thermostat. Putting it in backwards is pretty obvious.
6. Burped the system according to Ford procedures multiple times.
7. Burped the system according to Reinhart procedures multiple times.

Random thoughts:
1. I do not think it is the dreaded head gasket since the pressure remains in the system for days after shutdown. Also, there is no bubbling in the crossover tube after it is full. This would also negate testing for hydrocarbons in the coolant bubbles.
2. All of the hoses are in good shape and not obstructed.

It seems that no matter what I do, the result is the same.
I would be interested to see what I am missing and get some input from the Mark VIII group.
 

kTaLgsTo

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Looks like you've done a lot of work, I am leaning towards head gasket....

Few questions:
Is the heater blowing hot?
Have you done a proper chemical flush?

This stuff works great, when I got my mark it was bubbling out of the overflow, I did everything you did, then a few flushes (3) with this stuff fixed it, so I had a blockage somewhere....
https://www.amazon.com/gp/aw/d/B00B99U088?psc=1&ref=ppx_pop_mob_b_asin_title
 

xtriggerman

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Dont forget to let the air out of the top heater core pipe. Seems no one mentions that. I had an overheat after a rad change out and found quite alot of air there after several burping top offs. Seems the smallest amount of air in the system can stop water pump pressure.
 

jccpd

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Looks like you've done a lot of work, I am leaning towards head gasket....

Few questions:
Is the heater blowing hot?
Have you done a proper chemical flush?

This stuff works great, when I got my mark it was bubbling out of the overflow, I did everything you did, then a few flushes (3) with this stuff fixed it, so I had a blockage somewhere....
https://www.amazon.com/gp/aw/d/B00B99U088?psc=1&ref=ppx_pop_mob_b_asin_title
Yes, I have hot air. It only kinda filters through hot since I haven't troubleshot the blower motor yet. I have been focusing on the overheating issue...
However, I will order the stuff and give it a try. I post what happens.
Thank you for taking the time to respond.
 

jccpd

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Dont forget to let the air out of the top heater core pipe. Seems no one mentions that. I had an overheat after a rad change out and found quite alot of air there after several burping top offs. Seems the smallest amount of air in the system can stop water pump pressure.
By top heater core pipe, are you referring to the crossover tube at the front of the engine with the top that screws off?
I have bled that several times and have gotten the air out of it each time.
 

joegr

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...I have bled that several times and have gotten the air out of it each time.
If air builds back up in there each time, you have a leak somewhere that it letting the air in. Once air is there, it blocks flow. It's possible (ask the LS folks) for the leak to be too small to see any coolant, but still let air in each time the engine cools off.
 

xtriggerman

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By top heater core pipe, are you referring to the crossover tube at the front of the engine with the top that screws off?
I have bled that several times and have gotten the air out of it each time.

I'm referring to the top heater core pipe that comes out of the fire wall up by where the AC dryer can sits. The 2 heater core pipes are metal coming out to the rubber ones. Carefully take the top rubber one loose. I expected coolant to run out but there was none there after 2 or 3 burpings. The way I filled it is use a small funnel into just a slight opening of the rubber hose while the bottom mouth of the hose is still on the bottom half of the metal pipe. Hold a rag tight around the loose joint and pore coolant in until it over flows, flip out the funnel and push the hose back on. This is quite a high spot in the coolant system. I put in like 5 or 6 oz of coolant in that air pocket. The leak idea sounds like its worth looking at. In this article, I couldn't believe the rot in this coolant pipe. The car only had 67K miles on it but like they say, rust never sleeps....especially when inside where you cant see it.
 

jccpd

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I'm referring to the top heater core pipe that comes out of the fire wall up by where the AC dryer can sits. The 2 heater core pipes are metal coming out to the rubber ones. Carefully take the top rubber one loose. I expected coolant to run out but there was none there after 2 or 3 burpings. The way I filled it is use a small funnel into just a slight opening of the rubber hose while the bottom mouth of the hose is still on the bottom half of the metal pipe. Hold a rag tight around the loose joint and pore coolant in until it over flows, flip out the funnel and push the hose back on. This is quite a high spot in the coolant system. I put in like 5 or 6 oz of coolant in that air pocket. The leak idea sounds like its worth looking at. In this article, I couldn't believe the rot in this coolant pipe. The car only had 67K miles on it but like they say, rust never sleeps....especially when inside where you cant see it.
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Awesome! I never heard of that. I will definitely also try that this weekend when I do battle with the Mark VIII cooling system again.
 

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