Quote:
Originally Posted by Pete_89T2
The 1" extra coolant in the overflow bottle 30 minutes after a hot shutdown sounds about normal. When you shut down the engine the radiator cap allows pressurized/expanding coolant to flow into the overflow tank, raising its level. When the system cools down enough, the resulting vacuum should suck the coolant back into the radiator, leaving the overflow bottle around the full mark.
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When I get home I'll check it out again to see if it went down. I know the radiator pulled a good amount back in at the track as it cooled down, which isn't looking too good for the "there's a leak somewhere" theory.
Quote:
Originally Posted by Pete_89T2
If air is getting into the system, from either a leaky radiator cap or anywhere else in the system, it could explain the bubbles you're seeing. And it would explain the added difficulty in getting the system fully "burped" and keeping the buzzer quiet.
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I have noticed there is a tiny tear in one of the rubber seals in the radiator cap. I though it too small to make a difference but who knows. I always figured with the car running the pressure generated by the water pump would be more than sufficient to keep air from being sucked in, even at idle. If air is getting into the system with the car off, I'd expect to see the bubbles stop at some point as well.
Quote:
Originally Posted by Pete_89T2
If you're going to throw parts at it, I'd suggest getting a new Mazda radiator cap & thermostat regardless, especially if you don't know what's in there now. Don't bother buying a Stant or aftermarket thermostat - for some reason the ones the make for rotaries are crap.
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This I know. The rad. cap is the original I believe, but I'm almost certain the thermostat was replaced at one point (I have the records from the previous owners) and it's likely it's not an OEM Mazda unit. I'll do the pressure test and if that passes, change the radiator cap and go from there. If it fails, well I've got some exploring to do...
Quote:
Originally Posted by Pete_89T2
If your system is all stock, the cooling system is barely sufficient for track duty - it has very little excess cooling capacity, and a just a little bit of pump cavitation due to the prolonged high revs can easily boil things over. The buzzer sensor needs to be immersed in coolant at all times to keep it quiet - just one air bubble under it and BUZZZZZZZZZ. The temperature of the coolant has no effect on the buzzer - it's a level sensor.
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Yep, cooling system is all stock. I had no issues during the other runs over the weekend but I did stay in 3rd gear a lot more for this particular run so perhaps that was the proverbial straw. Aside from an upgraded radiator what other modifications would bring the cooling system up to track-ready levels? It's not a track-only car and I maybe drive it 25% of the time. I've seen underdrive main pullies but those make me nervous with the stock alternator's output.
Is there any way to "officially" bleed the S5 cooling systems? I open up the heater, turn the car off, then fill the radiator and overflow bottles. I squeeze the upper radiator hose to get as many air bubbles out as possible.