The one you've picture and link The King.
When I got that 01LC around 2003, coolant was ~1/2" low and radiator looked a little darker as I recall at 60K miles. It, The King, after ~13 years ~100K miles more, was still fine. That radiator isn't a radiator I even consider scheduling for replacement. I started babying that coolant system around 90K miles with Toyota red and flushing every 2 to 3 years. It's where I cut my teeth on Land Cruisers, learning the value of flushing and burping.
If every radiator in a Toyota that turned brown blew, we'd have a worldwide shortage of radiators.
It's more important to replace thermostat & cap, as those can blow radiator if stuck closed.
So yes, brown plastic is and indicator, but don't freak out just for that. Tees are a little different in that torque of engine could pull apart and they tend to leak with age. Leaks (any) need addressing! Tees are something I just do as a PM these days, not so two years ago (learning).
Here's the Tee's from The King after ~16 years and 165K miles. They are hard and still usable.
View attachment 1788500
So why am I seeing Heater Tees in 06 and 07 w/~60K miles that breaking apart. Is it a difference in plastic?, difference in coolant? (LL 2yr vs SSL 10 yrs/5 yr), years coolant in system before flushing or a combination of?
I think leading cause is length of time coolant remains in system. That fresh coolant has all it properties (additives) intact like the plasticizer, which age depletes.
Secondary is heat speeding up loss of plasticizer.
Thirdly, that a system low of coolant will dry plastic parts in air pockets after every cool down, leaching out plasticizer faster.
2006 at 60K miles. ~60k to 200K miles in 06-07 all have been falling apart. Higher mileage tend to be lighter (brown) in color. Note: only ~1 in 4 of these had coolant leaks and ran system low.
View attachment 1788506
So here's 19yrs and 350K miles from a system that was 2 " low on first inspection. Lexus reported coolant low when they replaced the front water bypass pipe hoses (oil cooler) about 70K miles ~3yrs earlier, with aftermarket hoses and clamps. I had to R&R all those hoses & clamps with OEM as they where leaky. This is same radiator upper inlet gooseneck picture earlier w/350K, that I've "schedule" for replacement (along with upper & lower hoses, and transmission cooler hoses and water bypass joint front). In fact I drove around yesterday 93 F OAT, terrible stop and go traffic for 6 hours. I've zero leaks now, so rad can wait!
View attachment 1788508
Here's the top of the 350K 19 yrs old, not all that bad except the strange marks/corrosion spots.
View attachment 1788638
It's the goose neck
gouge,
pits and
chips that put this on replacement schedule, more so than color.
View attachment 1788645
I've a neighbor with a 98 w/250K that never knew he needed to maintain his rig, just drove. It had factory timing belt, water pump until I convinced him to replace recently. He still has factory Tee's and radiator. Tees are covered with pink gunk and radiator is browner than any I've seen. I've press on him hard to change out the tee's.
Here's what I see happening to his tees. First I could grab with my hand and pull apart if I tried. With age engine & trany mounts they will be soft. A hard stomp on the gas pedal and engine may move just enough to pull tees apart. Also coolant is leaky from them which all leaks need addressing.
His radiator is not leaking, so neither I nor Slee (Just in Slee for a bunch of stuff) has recommended more than be aware of and keep eye on radiator & coolant level.
Yes @medtro you've seen me replace a lot of parts, I'm now averaging 300 parts (7 qts of oil = 7 parts). Many because they are out of service (don't meet spec of FSM) other because of incremental benefit it gives, and some depend on objective of project.
But I've only replace two radiators, one was leaking at seam in front, which is the most reported failure/leak point. The other is in post #37 above as it was cracked gooseneck, additional it had exhaust gas blowing in it. I believe that one was run low on coolant for 20K miles and had air flow blockage. I think (but will never know) the head gasket blew before taking out the Heater Tee. That radiator showed zero signs of leaks.
As much as I may like to replace ever parts on a rig, it's not practical nor necessary. A rigs intended use is also considered when deciding what to R&R. Is it a DD, going deep into backcountry or a third word country far away from any assistances.
Bottom line, color is indicator of condition but not what I base final call for replacement on.
Keep coolant topped and fresh and be alert to smells and sounds regardless of color.
