Coolant Overflowing From Reservoir

[bigmitch]

Having a problem with my son's '04 Lexus ES330 losing coolant from overflow vent tube. Got a call from his wife last night said the car overheated. Went and looked at it today and coolant level was about a gallon low. No leaks noted but did notice that there is evidence of dried coolant around overflow vent tube and surrounding areas of the car. After driving the car and coming back to the house noticed that with the car running the reservoir was starting to fill up and slight amount of bubbles coming out of overflow tube at bottom of reservoir . Before it more then 3/4 of the way full the fan came on and the coolant level started to drop until the reservoir was almost empty. When the fan shut off the reservoir would start to fill again. Back in January I replaced the water pump when I did the timing belt and also the thermostat. Car has ran fine up until this point. Also didn't notice any evidence of coolant in the oil when I pulled the dip stick. Not sure if maybe the radiator is somewhat clogged but looking for some input on what to check and a possible culprit. I'm going to try and get a coolant pressure tester and block tester from auto zone tomorrow to check for leaks and possible head gasket problem. Thanks in advance for all your help and input.

Scott

[gbhrps]

Scott,

From what you describe the news is not good. You could have a whole raft of different things that are causing the symptoms. You may have a blown head gasket (hence the bubbles in the overflow tank), a collapsed radiator hose, plugged radiator, bad thermostat, or the water pump has gone south. The radiator fan may not be working or the block may even be plugged at some point. I'm sure there may even be one or two areas that I haven't even mentioned.

The only way to know for sure is to start with the simple things that can be checked, and then go on to the next one, and so on until the culprit rears its ugly head. Good Luck!

[bigmitch]

Scott,

From what you describe the news is not good. You could have a whole raft of different things that are causing the symptoms. You may have a blown head gasket (hence the bubbles in the overflow tank), a collapsed radiator hose, plugged radiator, bad thermostat, or the water pump has gone south. The radiator fan may not be working or the block may even be plugged at some point. I'm sure there may even be one or two areas that I haven't even mentioned.

The only way to know for sure is to start with the simple things that can be checked, and then go on to the next one, and so on until the culprit rears its ugly head. Good Luck!

Well the news is better then I thought, I landed up finding a leak around the thermostat housing and after pulling the housing found the thermostat stuck open. Changed the thermostat and gasket put on a new radiator cap, burped the system real good and so far everything seems good, no more bubbling into the reservoir. Also did a pressure check and held pressure solid for 20 mins until I bled it off. Also started the car with the pressure gauge hooked up and pressure built up slowly, where as I think it would've built up quickly with a blown head gasket. Also got a block tester and checked for gasses in the coolant for signs of a blown head gasket and the test fluid stayed blue where it would've turned yellow if combustion/exhaust gasses were present. Hopefully that was the culprit of my problems, if it was I consider myself lucky. Temp indicator never went above half way with outside temps at 110 degrees. I'll be driving it the next couple of days to make sure everything is functioning properly before I turn it back over to my daughter in-law.