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Overheating/Loss of water 99 VS 3.8

Mikado

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Hi all,
May I ask for your assistance? Might be a bit longwinded but history important. Picked up a 99 VS 3.8 Commodore Ute for my young fella's 1st car.. On picking the car up it started to run fairly warm ( 2 marks down from hot on the gauge ) & just feathered it home. Gauge fluctuated from hot to the middle of temp gauge. In the morning I checked the water, none was visible in the radiator. Filled up and ran again & checked, looked like mud. Drained radiator and brown crap came out, removed thermostat - all gunked up - so I flushed out for 30 min, put back together without thermostat - put a can of radiator cleaner in & ran for an hour or so & took for a run around the block. Temp gauge rose 4 points. before shutting down, checked all hoses & radiator cap for leaks - none detected. After cooling down pull hoses off - flush radiator & block via thermostat housing - heaps of crap again & flushed & reverse flush until clean. SCA did not have a new thermostat in stock, so buttoned up again and did a lap along M4. Without a thermostat, the temp gauge went up to 3/4 ( which I found strange ) Took it easy & got back home & left overnight. Removed plugs 1 at a time & replaced them. Wanted to check to see if any moisture in the cylinder. All dry. We took for a run yesterday & gauge rose to 3 marks from hot - without thermostat. Thermo fan activated when stationary. I really need some help, please. Could it be the temp gauge faulty or the coolant sensor faulty ???? When we checked again today, no sign of water in the radiator - none in the overflow tank ( Where did that water go ??? ) and importantly, no leaks in hoses or on the ground. Your advice & knowledge will be much appreciated.
 

Pollushon

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Most likely candidate is the lower intake manifold gaskets, the Eco is notorious for them as they are plastic with silicone seals. The brown sludge is usually a giveaway and lack of obvious external leaks. It's never enough water to leave cylinders wet but you end up with some oil and bypass gunk in the water system. Worth a look. Could also be as simple as a dud rad cap but you'd likely see steam
 

Harvs82

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Get the system pressure tested for a start, try a new radiator cap, and don't run it without a thermostat. The coolant will circulate too quickly. Ecotec are notorious for having dirty muddy cooling systems due to everything being cast iron, plus if the inlet gasket is leaking that only makes it worse. You'll probably need to flush the system with a good 100 litres of water if not more to get all the crap out. Run a good quality coolant too, not premixed crap. 50/50 ratio. Might be worth bunging a new water pump on too, they're cheap as.
 
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