LS 180 just started overheating but cools down suddenly.

[Bonesbrand]

Hi guys I'm new to the Forum. I have an ls180 that's been running fine and all of a sudden then started overheating but then it cooled off quickly and then overheated again. My coolant recovery Reservoir is practically full and looks like it might be leaking a little bit. Any ideas? Thanks

 

[flyerdan]

Is it actuallyoverheating, or just indicating overheat? Quick temperature changes like that often are due to spurious signals, but if you have physical symptoms like steam or secondary temp readings, check the obvious: radiator clean and good air flow, water pump belt snug and turning proper, coolant level and condition.
The recovery tank should be between the hot and cold marks; you'll want to adjust the level with everything cold and the block and radiator completely filled, the recovery tank to the cold mark. Its purpose is to let the water expand out of the radiator, and draw it back after it cools so you always have a full radiator. It's important to keep it at the correct level so the siphon continuity is intact. It also lets you know at a glance the coolant level without opening the cap. Also, if it starts to overflow, that would indicate a bigger problem where something is getting into the cooling system, like oil or compression gasses.

 

[Bonesbrand]

Is it actuallyoverheating, or just indicating overheat? Quick temperature changes like that often are due to spurious signals, but if you have physical symptoms like steam or secondary temp readings, check the obvious: radiator clean and good air flow, water pump belt snug and turning proper, coolant level and condition.
The recovery tank should be between the hot and cold marks; you'll want to adjust the level with everything cold and the block and radiator completely filled, the recovery tank to the cold mark. Its purpose is to let the water expand out of the radiator, and draw it back after it cools so you always have a full radiator. It's important to keep it at the correct level so the siphon continuity is intact. It also lets you know at a glance the coolant level without opening the cap. Also, if it starts to overflow, that would indicate a bigger problem where something is getting into the cooling system, like oil or compression gasses.

Thanks for getting back to me so quickly. I did check the belt and it does seem loose I'm going to adjust it tomorrow. It looks like there are two radiators I guess one is an oil cooler? The one closest to the fan actually is pretty gummed up so I'm going to pressure wash it is well. Could a stuck thermostat prevent the coolant from returning to the radiator and cause the reservoir to stay full?