Radiator expansion tank boils over while coolant guage reads 1/2!

Tiny
JMSUAREZ
  • MEMBER
  • 1999 SATURN SC1
  • 165,000 MILES
Just recently bought this vehicle, had a real bad coolant leak through the radiator. I went ahead and replaced the radiator, coolant hoses, 50/50 coolant and thermostat twice (twice becuase they can be faulty even though new) The vehicle after about 10 minutes begins to boil over out of the expansion tank but my gauge is reading around 1/2. I know the fan does not kick in till about 3/4 on these (it does) but its already boiling over by then. Also I turn on the ac when its around 1/4 & 1/2 (fan does work) but it still continues to boil over in a few minutes. Im not sure where to go from here, the weep hole on the water pump is not leaking and praying it is not a blown head gasket. Oh while running; the coolant hose from the (upper driver side) engine block/radiator is nice and hot but the hose thermostat/radiator (lower passanger side)is not hot at all, even while the reservoir is boiling over. Help!
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Tuesday, September 13th, 2011 AT 1:24 AM

3 Replies

Tiny
SATURNTECH9
  • EXPERT
Have you replaced the radiator cap yet?On that car the fan turns on at just over half way not 3/4 or a little higher. Have you checked the coolant temp sensor yet?Thats the most likely cause its really common for them to fail on those. Also inspect the terminals on the connector going to it they get corroded from the coolant temp sensor leaking coolant into the connector. If the terminals on the connector are blue or green its corroded and you will have to replace the connector. Have you checked for codes yet?
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Tuesday, September 13th, 2011 AT 1:40 AM
Tiny
JMSUAREZ
  • MEMBER
First thing tomorrow I'll replace the expansion tank cap, i'll do the sensor also but doesnt that control the fan? If my fan does come on with the AC then why does it not cool it down then? I would love to check the codes(no warning lights on. Yes they work) but the closes auto parts is about 15 minutes away. Car wont make it!
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Tuesday, September 13th, 2011 AT 1:52 AM
Tiny
SATURNTECH9
  • EXPERT
Make sure you inspect the connector also for coolant temp sensor. Make sure the sensor you get where the connector goes on that its brown. You could have a bad coolant cap and thats why its boiling over even with the ac and cooling fan on. The sensors are only 10-12 without using a temp we dont know what the actual temp is when it boils over could just be a coolant cap not holding pressure. Dont worry your in good hands though I know saturns inside and out.
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Tuesday, September 13th, 2011 AT 2:08 AM

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