Engine cooling

Tiny
PACK1973
  • MEMBER
  • 1992 MERCURY COUGAR
  • 3.8L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 68,000 MILES
Had a problem this morning with an eratic temperature reading. Engine was getting hot, the cooling when I drove. I pulled thermostat, now the temperature is still rising to the red. This shouldn't be happening if there's no thermostat in correct? Is my water pump possibly bad? HELP
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Wednesday, February 10th, 2016 AT 12:44 PM

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Tiny
CARADIODOC
  • EXPERT
You don't fix anything by removing the thermostat. In some cases that can cause overheating because the hot coolant doesn't stay in the radiator long enough to give up its heat.

I don't know which engine you have, but if it uses an electric radiator fan, be sure that is turning on and the coolant level isn't low. The next step is to have your mechanic perform a chemical test at the radiator to check for a leaking cylinder head gasket. That involves drawing air from the radiator through a glass cylinder with two chambers partially-filled with a special dark blue liquid. If combustion gases are present, the liquid will turn bright yellow.
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Wednesday, February 10th, 2016 AT 12:54 PM
Tiny
PACK1973
  • MEMBER
Thanks for the quick response. It's the 3.8 engine. Fan is working properly. I was planning on replacing the thermostat, just put it back together and was going to try to make it to the auto store to buy one. Am I right though, if coolest level is good, and no thermostat, I should not get hot? By the way, it's around 15 degrees outside also. I was thinking the coolant wasn't getting to the motor because of the pump. Bad head gasket? Please no.
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Wednesday, February 10th, 2016 AT 1:02 PM
Tiny
CARADIODOC
  • EXPERT
Rule the head gasket out first. That test just takes a few minutes.

Normally the thermostat keeps the coolant in the engine long enough to get it up to the right temperature, about 195 degrees. That's where parts expand to fit perfectly and the oil can carry away contaminants to the filter. While it's not common, a missing thermostat can cause overheating, especially with really big engines.

Feel across the radiator to see if all areas are warm. If there's a cold spot, some tubes could be plugged. More commonly, if the coolant got diluted with too much water over the warm summer months, the radiator could be frozen.

I really hate winter / cold / snow!
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Wednesday, February 10th, 2016 AT 1:12 PM
Tiny
PACK1973
  • MEMBER
I hope I'm not annoying you with questions. I'm trying to see if the water pump is bad first, as I have no way of getting it to a shop without an expensive tow. What some ways to check that? Doesn't leak, and no bearing noise. Is there a way to check it? I've felt hoses, top is hot bottom is cold. If it was a head gasket, wouldn't I have antifreeze in my oil? I checked that already, and it's fine. Thanks again
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Wednesday, February 10th, 2016 AT 1:18 PM
Tiny
CARADIODOC
  • EXPERT
Oil and coolant mixing is the least common symptom of a leaking head gasket. There's 15 pounds of pressure in the coolant passages and about 40 pounds of oil pressure in the oil pressure passages. 0 pounds in the oil drain-back passages. There's WAY more pressure in the combustion chamber, and when you add the corrosive nature of ethanol, a leak between the combustion chamber and coolant passages is by far the most common place to leak. Also, each cylinder is surrounded by coolant and its passages so there's a lot of places the leakage can occur. There's usually only one or two pressurized oil passages and they aren't close to the hot cylinders.

Water pumps that fail to pump coolant are very rare. Only VW has had a lot of trouble with that because they used plastic impellers that crack and spin freely. If the water pump isn't circulating the coolant, it's more likely its drive belt is loose. I've seen a loose timing belt allow it to slip over a timing belt-driven water pump pulley. That can happen with serpentine belts too if the spring-loaded tensioner pulley is stuck in the retracted position, but those will usually squeal too.
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Wednesday, February 10th, 2016 AT 1:42 PM
Tiny
PACK1973
  • MEMBER
Ok, last question. When the engine was hot without thermostat, should I have been getting heat? I wasn't, and don't know what's normal. You think I could drive any distance as long as my temperature doesn't go in red, to make it to a shop?
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Wednesday, February 10th, 2016 AT 1:47 PM
Tiny
CARADIODOC
  • EXPERT
You can drive it as long as it doesn't overheat. No hot air means no coolant is circulating through the heater core. Check how far the upper radiator hose is hot and whether the top of the radiator is hot. If they're all cold, the coolant isn't moving at all.
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Wednesday, February 10th, 2016 AT 2:02 PM
Tiny
PACK1973
  • MEMBER
Ok, I'm hoping I'm just low on antifreeze now. Waiting for my daughter to bring me a gallon. I thought if you could see coolant in the radiator, it is low, that the engine would also be full. I feel pretty dumb if I'm wrong.
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Wednesday, February 10th, 2016 AT 3:24 PM

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