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I fought overheating and coolant system leaks on my 06 SV8 over two years and have replaced the thermostat, water pump, expansion tank cap, top radiator hose, top heater hose, replaced brushes in the auxiliary coolant pump, and added a coil ground to the relay for the IC coolant pump when the computer was not grounding the coil to run the pump.
I think I eventually got all the leaks fixed, but while sorting things out there were several over temperature incidents (the little red light over the gauge) and one low coolant message incident while driving out in the boonies when the top radiator hose backed off. I re-clamped the hose and added the gallon of coolant I carried with me but I had to drive some distance to find enough coolant to top it up and my Ultragauge got up as high as 230 degrees F coolant temp.
Now I have coolant being expelled from under the expansion tank's 20 PSI cap and a tendency to push the top radiator hose off even when double clamped with worm clamps. I did a system sniffer test that verified combustion gas in the coolant so there is a head gasket leak somewhere causing high coolant system pressure.
As others suggested, you might want to do the sniff test or compression test to see if previous overheat incidents may have compromised your head gaskets.
Last edited by philwarner; 07-17-2019 at 02:26 PM.
Red/pink antifreeze looks brown like rusty water which is odd as in the engine its lovely and clear,it seems as soon as its outside and dripping on things it does look brown...it can lead you up the garden path if you don't realise its anti freeze you might think something is blocking ,,its not ..
Interesting to see this thread come back again just when I have a further development with my 06 SV8. I had not driven it in some time because of the head gasket leak and lack of time to do a head gasket change (and driving my "new" 04 Mini Cooper S JCW is a blast), but when I recently took it for a warm-up drive around the local country roads I got the low coolant message and back at home found a sizeable leak of coolant all over the right side of the engine bay and it made a pool underneath that side. It was not coming from under the expansion tank cap as it had in the past and the upper radiator hose had not backed off of the top radiator bib as it had in the past, so there is apparently a new leak that is bleeding off the combustion pressure from the gasket leak. Maybe it's the tank itself this time, but I haven't had time to investigate further and was a bit bummed by the new development. I do have tracer in the coolant so I plan to pressurize the system to the 20 PSI cap relief pressure (if it will go that high) and check for leaks at night with my black light flash light (or torch for you Brits). At least on the short drive I was reminded of what a magnificent car this is when it is well. Nothing from the cap and top radiator hose is still tight, tank showing low level But spray back here and here and here and here
I'd get the car up to operating temperature and then rev the car whilst looking around those coolant hoses. It's clearly coming from near one of them as they are covered in coolant. Good luck and I hope you find the cause. I had a bad leak a little like that and it was the thermostat housing throttle feed pipe that was cracked and spraying coolant near that part of the engine and all down the front of the engine.