Antifreeze: Cooling System Flush
Good clean antifreeze not only protects your engine from freezing in the winter, but of course also acts as a coolant that keeps the engine from overheating year round. Good clean antifreeze not only protects your engine from freezing in the winter, but of course also acts as a coolant that keeps the engine from overheating year round.
In addition, it has corrosion inhibitors to prevent the metal in the cooling system from being eaten away by the water in the coolant.
It also has ingredients that act as lubricants to prolong the life of the water pump seals. As long as it isn’t diluted with water, the freeze protection and the ability to cool your engine stays good forever.
When flushing the cooling system, we drain the radiator and the block and run fresh water through the system until there’s clean water running out of both the radiator and the engine block drains prior to refilling the system with new coolant.
However, the corrosion inhibitors break down with time and heat. Antifreeze that gets too old will begin to eat away at important internal engine components and plug up internal cooling passages, which can lead to overheating and cause additional damage, expense, and inconvenience.
This may be putting a fine point on things, but Toyota specifies the use of deionized water (water that’s had the minerals stripped out of it) in its cooling systems. This is a more important concern in areas with a hard water supply. Deionized water (or distilled water) is recommended for both 1st and 2nd generation coolants, as the minerals in the water can precipitate out and restrict coolant passages. This issue is intensified with coolants that have silicates in them, as the silicates combine with the minerals and together they precipitate out of solution and restrict coolant passages. In this instance, it also results in increased corrosion due to a lowered concentration of silicates.
We’re fortunate to have soft water in Portland, and this is what we use along with antifreeze when we are filling a cooling system. In systems that require Toyota Super Long Life coolant this is a moot point, as it comes premixed with deionized water.
Types of coolant: Red, pink or green? The short answer: The simplest most straight forward recommendation we can make is to use Toyota’s red, Long Life Coolant where specified, and their pink Super Long Life Coolant where specified. On vehicles older than 1998, Toyota’s recommendations are very general. We have come to believe that the Toyota Long Life Coolant is preferable for these vehicles as well in order to reduce clogged radiators.
Types of coolant: Red, pink or green? The longer answer: Regarding generic green coolant versus Toyota’s red coolant in the older Toyotas (see section on older Toyotas through 1998 for broader discussion) although I’m willing to use either as per customer preferences, I have come to have a definite preference for Toyota’s Long Life red coolant. It was designed with full engineering knowledge of the various materials (seals and alloyed metals) it needs to be compatible with. It was also deliberately designed with zero silicates. While the silicates in other coolants provide excellent corrosion protection, over the long haul they tend to precipitate out and contribute to restricting coolant passages. This can eventually result in overheating and/or having to replace the radiator. The additional cost of Toyota’s coolant is minimal if you consider that the cost is amortized over a two to three year period and that the superior coolant may save having to replace your radiator.
I should note a balancing concern: On some engines where the timing belt runs the water pump, a red coolant leak with its build-up of crystals can cause the timing-belt tensioner bearing to seize up at the pivot. This can result in the timing belt going slack and hopping out of time. Usually this happens in cases where the timing belt was past due for replacement anyway. I’ve never seen that happen with the green coolant. Obviously there’s a trade off of concerns at play here.
The older Toyotas and Lexus (through 1998) (for which we recommend Toyota’s Long Life red coolant) simply call for ethylene glycol coolant. Ethylene glycol is the main antifreeze and heat-transferring ingredient in all three generations of Toyota coolant. To specify ethylene glycol doesn’t say anything about which additives and corrosion inhibitors are best. Although Toyota sold its own red stuff, I’m not aware that they published any specifications that would overtly steer people away from using the common green generic alternative. However, my recent understanding is that even at that time Toyota was using zero silicates in their coolant. (See section on 1999 and newer Toyotas for further discussion on the use of silicates and their tendency to clog coolant passages.)
Toyota called for a coolant change every two years or every 30k miles. We encourage the same, although I’m comfortable with 3 years or 30k. For years I actively preferred the green antifreeze to the red due to my strong impression that the red coolant more actively finds its way past seals and gaskets. I still have no question that I see red crystallized coolant deposits oozing past gaskets and seals more often than I see signs of the green coolant leaking. However, Ryan here recently raised the possibility that the red coolant may not leak any more aggressively, but may simply leave more visible tracks. This may be the case, and in fact seems likely to be so. I know that on older water pumps we always see some staining below the weep-hole on vehicles that use green coolant. This staining may represent a similar amount of seepage that would have shown up as a mass of crystals on a water pump that was using red coolant. I really can’t say for sure—in either case it’s a slow seepage that dries out as is emerges.
Within the first year after Ryan came on board he mentioned that since he’d left Lexus where they exclusively used Toyota coolant he was seeing a lot more radiators plugged up. He said he’d virtually never seen clogged radiators even on cars that had over 200k on them. The clincher came for me when we encountered a radiator that we had replaced maybe 30k prior that was already showing visible clogging of the passages. On that day I became a believer in using Toyota’s Long Life red coolant, and that’s what we promote to all our customers now who have vehicles that are 2003 or older.
In 1999 Toyota and Lexus came out with their red long-life coolant, which is definitely what we want to use in these vehicles. They still recommended coolant replacement every two years or every 30k, and this is the recommendation we follow, although I’m comfortable with 3 years and 30k. Toyota calls for coolant with zero-silicate, zero-amine, and zero-borate content. They specify that “use of improper coolants may damage the cooling system” and specify that their coolant is designed so that it “will not clog radiators from silicone gelling” and “will not corrode aluminum surfaces like coolants that contain borate.” When I’ve seen charts displaying the chemical profiles of brand new coolants, the Toyota long-life coolant is clearly different than Prestone’s green-colored alternative, with the Prestone coolant clearly having the silicon and borate content that Toyota engineers specifically want to avoid.
In 2004 Toyota and Lexus came out with their pink super-long-life coolant. This is what we use for these vehicles. Their recommendation on this coolant is that it be replaced the first time at ten years or 100k miles. Their recommendation thereafter is that it be replaced every 5 years or 50k miles. This puzzles me, and though I’m not characteristically cynical, I find that a cynical part of me speculating that possibly Toyota has taken this route as part of an effort to keep their advertised cost of ownership lower in order to enhance new car sales. This coolant comes premixed with a 50% of it being deionized water. I haven’t seen any chemical profiles comparing this coolant to the previous generation Toyota red long-life coolant, but they aren’t incompatible, because Toyota specifies that you can add the Toyota red long-life coolant to top off systems that have the Toyota pink super-long-life coolant. Different dealers have opted for different schedules on flushing this coolant. Some do it exactly by the book with the first being at 100k and the second at 50k. At the time of this writing, the Lexus dealership I’m acquainted with was recommending coolant being flushed every 30k, and observed that they always get some particulate sediment coming out of the system with the coolant.
Toyota’s recommendations assume a perfectly maintained coolant system, i.e. proper mixture, proper pressure, and continually full. Obviously if the mixture is off—diluted from adding water—that will decrease the effectiveness of the corrosion inhibitors and shorten the effective life of the coolant. Same with pressures: too low a pressure due to a faulty radiator cap increases the likelihood of internal metal erosion due to cavitation. Even allowing the system to go low increases corrosion, as the mixture of air and steam in the system is much more corrosive than being constantly bathed in coolant. This is apparently more especially so for coolants with organic-acid-technology based corrosion inhibitors, which is the class of inhibitors that Toyota’s Super Long Life coolant uses.
Regarding the service interval, I’m increasingly impressed that just to look at it, the coolant typically doesn’t look bad even at 100k. If customers prefer to go exactly with Toyota’s recommendations, I have no quarrel with that, although I at this point I still have some reservations that it’s ultimately for the best to wait 100,000 miles and/or ten years before replacing the coolant for the first time. Time will tell.
There seems to be some rationale for flushing the Super-Long-Life coolant every five years or 50k miles. It’s not a hard recommendation, but I think it may make sense in light of the fact that:
Toyota makes the same recommendation of five years and 50k miles from there on after the first 100k, and also because
Toyota recommends coolant changes at 30k with their older (not-premixed) coolant that is chemically similar enough to be used as a top-off coolant.
Note: The Super Long Life coolant shouldn’t be used in the older Toyotas that came with brass & copper radiators, as it’s organic-acid-technology corrosion inhibitors aren’t effective for these metals or the soldering used in these radiators.
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