Coolant Mix

If you have chosen not to use Toyota's own coolant, you have to decide what concentration you should use. The more concentrated the coolant is, the more protection from freezing. The antifreeze additives also raise the boiling temperature. This is marginal however.

In many cases of overheating, the obvious question is "why is it overheating?" A better question to ask is "why does it not overheat all the time?" Then the answer is quite simple, pressure.

For every 1psi of pressure, the boiling point is raised by 1.66C. The preferred radiator cap to use is the Toyota one with the float. Failing that it must be a Toyota cap that is rated to 0.9Bar or 13psi. Not the TRD cap that some garages have inadvertently fitted, that's 19psi and will blow every hose, and find every weak point in the system causing it to leak like a sieve.

As you can see from this table any loss or reduction in pressure will reduce the boiling point of the coolant.

Dave Bright, 25 Sep 2003.