car issues

[Robb]

Son got home and woke me up at 10:00pm last night telling me of a radiator hissing or spewing, (his term, not mine) and said the heat gauge in his car would peg to the red, stay there for a few seconds and then drop back down to cold. He said the car would never warm up. I checked under the car on the way out the door this morning and there are no leaks.
Tonight when I get home I'll check fluid levels, make sure the heater core isn't leaking and then assume that I need to go buy and replace the thermostat.

Can you that are auto knowledgeable confirm I'm on the right track here? If not the thermostat, what else would cause the car to act like that? FYI: '98 Ford Mustang 3.8 auto.

[rbeau30]

Thermostat is easy and cheap to replace, I probably would start with that.

[Robb]

I'll pick one up at noon today. That's my guess to the issue, but any other advise on what to check for is appreciated. I'll check waterpump/belt, hoses and fluids. Other than that I'm out of ideas.
Just hoping it's a thermostat.

[Danimal]

If there is even a possibility that the antifreeze mix is not 50/50, or is old and burned up I would bet that your coolant is freezing. I did a lot of work on my Jeep last year and did not have a great mix in it and it froze this year. It did the exact same thing that you described, and it would appear to be the exact same thing as if the rheostat stopped working. I would first start the car and let it warm up until it starts to get above normal, then shut the car off for about 20 minutes. Then start it up again and let it warm up until it gets above normal and shut it off. If the thermostat is bad, the car will continue to over heat. If it is a frozen coolant system, (it was -3 here last night so I would not be too surprised) then after about 2 - 3 warmup cycles it will thaw out and run normally when the coolant has a chance to warm up the radiator.

I would give that a try first to avoid tearing into the thermostat only to find a green slushy in there. Also you can squeeze the radiator return hose and see if it feels like it is frozen. The lower engine supply hose is on the pump suction side and has a spring wire frame in it to prevent it from collapsing, so only the upper radiator return hose will be able to tell you and it will feel like a freeze pop.

[Robb]

Danimal,

Thanks for the tip, I'll check that top hose first.

[rbeau30]

Good catch Danimal, i never thought about that, I check all three cars' mix as part of the winterization every year so i've never actually had this problem.

[Jamnanc]

Tell him to be careful, a hard freeze will screw his block. If he overheated in the summer and added water to keep going, then the mixture won't stop freezing at these temps.

[mightiestmouse]

You can also remove the thermostat and place it in hot water to see if it is working properly. Just a quick check to see if you even need to spend the money on getting a new one.

[CHA-LEE]

That sounds exactly like the coolant freezing and not flowing properly through the block and radiator. How long has it been since you did a complete coolant flush and refill?

With the temps dipping in the -10 F or colder range it is cold enough to allow worn out coolant to actually freeze or partially freeze.

If the engine got hot enough to boil the coolant creating excessive pressure to vent (Hissing sound) then the coolant system needs to be flushed and refilled anyway to eliminate the air pockets in the system. Air pockets in the coolant system will cause overheating issues as well so its best to not even try to recover the coolant that is already in there, but to instead perform a complete coolant flush and refill.

[GunsRBadMMMMKay]

When the gauge hit red then dropped, it was because it overheated and blew out the coolant and got air in the area where the sensor is. It never got back up to temp again because there was no coolant touching the sensor. You could have a bad water pump, or if it did freeze you could have worse (sorry....). If it overheated, safe bet is to just change the thermostat - but you can test it first like previously suggested - if you put it in hot water (~180-200 degrees) it should open up all the way and smoothly, then close when removed and cooling down.