Over the summer I had a leaky water pump causing the car to overheat and obviously loose coolant. Once it was fixed it was fine for about a month. Now the low coolant light is on again and now that cold weather is here it takes forever for the heater to warm up. Also when driving for about 5 miles the temp will skyrocket to 230* then within 30 sec drop to 180 and stay there for the most part. There have been times where it will rise and fall quickly randomly.

Any idea what this is? There is no coolant leaking anywhere, oil is not milky, and no steam out of tailpipe???

Thermostat maybe?

 

Definitely sounds like a Thermostat sticking problem to me...

 

he is right it is the thermo sticking or is stuck, you can get a new one for around 10 bucks i guess the montes run what 180 degrees?

 

It could be an air pocket too. Follow the replacement steps to replace, then/or follow the coolant refill steps just to fix the air pocket

Replace

Take off the radiator cap, and squeeze the upper radiator hose slowly so the coolant tank fills up... you may need to lower the coolant tank, or take the hose off and put it in a coffee can under the car to collect the coolant.

Once the upper radiator hose is somewhat empty, take out the 2 nuts holding the thermostat cover (?) down. I think the nuts are 10 mm. Here is where the excess coolant will run on the engine so do this when the engine is cold.

Take the thermostat out and replace it with another. You may need a pliers or long handle screwdriver to pry it out as the gasket holds it in there nicely. Then put the cover back on, tighten the nuts back down.

Coolant Refill

With the radiator cap still off, open the little brass breather nut on the top of the thermostat. I think this is a 5 or 6 mm nut. Start adding coolant back into the system.

I had to work my system a bit by closing that valve, squeezing the upper hose a few times, loosening the valve, adding coolant, and repeating the process until coolant came out of the valve.

Works great for me now!

 

Thanks guys Ill try the thermostat and report back. Thanks!