Thermostat, or what?

[superedge88]

I have a 99 mountaineer with the 5.0 drove yesterday morning with the heat on and was getting no heat, then the temp gauge started to sky rocket, then after about 1 minute of being very high it then came back down into normal levels. Then on the way home from work it did the same thing but then stayed way up (barely made it home) I opened up the hood and could hear a hissing, seemed like it was coming from the area of the thermostat but couldn't see bubbling or trickling of antifreeze. There was antifreeze that had leaked somwhere near the thermostat, but I could not see the exact placment of the leak. Does this sound like a bad thermostat? The hissing happens after it has ran for a while, could it be that the system is not pressurized because of a small leak? I have to have the mountaineer up and running by tomorrow, but I'm running out of daylight!

 

[marragtop]

Sounds like a stuck thermostat. Put a new one in. Don't drive it if the temp gauge pegs to hot.

 

[exploded99]

Leak was probably the bypass hose right next to the thermostat - its a little hose with a 90 degree bend in it.

You should get a new bypass hose and a couple of new hose clamps for it when you do the thermostat.

 

[LuvMy98Ex]

Yeah, it sounds like a stuck thermostat. I had this happen to me about a year ago. Fortunately, my engine seems to be fine. Good luck!

 

[briwayjones]

Change the thermostat. I had a stuck one once that we kept putting off changing with very bad results.

 

[superedge88]

Leak was probably the bypass hose right next to the thermostat - its a little hose with a 90 degree bend in it.

You should get a new bypass hose and a couple of new hose clamps for it when you do the thermostat.

That was it, a leaky bypass hose, too bad the mechanic figured that out before I did.

 

[Tony H]

I'm not doubting the T-stat but NO heat? that sounds like very low on antifreeze. It's so low it can't get through the heater core hoses. Check anti freeze level

 

[superedge88]

The leaking bypass hose was the reason the antifreeze levels were low, would emkpty out most of the antifreeze while driving.