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Old September 5th, 2009, 22:06
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5-90 5-90 is offline
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Re: Renix Cooling Tips

Originally Posted by SFW516 View Post
Thank you very much for all the helpful advice, I will do some more investigation on the fan first and get back to you. I have a feeling its either the relay or the sensor. So if I do put in a 180 thermostat it won't cause any problems? I just might do that if it continues to run warm.

The thing is everytime I open it up and take a look the upper radiator house is always pretty stiff and there is a good bit of pressure build up on the overflow bottle. So much so that it will spew coolant if I open it up. I just think if I let it continue it will damage the overflow for sure and who knows what else.
It's going to spew coolant. Water boils at 212*F at STP, but that point is increased by 3*F for each psi of pressure added above atmospheric (14.7psia.) So, if the pressure is 15.7psia, water will boil at 215*. 16.7psia? 218*F.

RENIX caps are spec'd for 13-16psig, or 1ATM (14.7psia) + 13-16psi, or 27.7-30.7psia. Round up, call it 28-31psia (close enough for illustration.) At 3*F per 1psi increase, you're looking at an increase of 39-48*F increase, or a new boiling point of 251-260*F.

When you remove the cap, you effectively remove that pressure - and the water (210-215* design operating temperature) is now allowed to boil freely. Recall that "antifreeze" serves to lower the freezing point of coolant, but does little for the boiling point - that's done by the system pressure.

So, it's no surprise that your coolant starts boiling as soon as you remove the cap - that pressure (that you've released) is the only thing that prevented it from happening in the first place!

If you want to play with the fan actuation temperature, there are some adjustable sensors that will fit a 3/8" NPT port, and you can replace the RENIX thermostat housing with an HO version (same shape, but adds a 3/8" NPT port for a sensor that the HO uses but the RENIX does not.) Leave the RENIX TFS in place as a plug, and that takes care of that hole. You'll want to get a sensor that can be adjusted for an "ON" range of 215-230*F, and an "OFF" range of 190-195*F or so. These are actual, absolute values - I'd forgotten to mention that the values given earlier were "relative" values, and the actual operating values for the TFS are somewhat lower - to reflect its position in the "cold-side" radiator tank.
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