Disappearing coolant in reservoir mystery...

Where does it go ? 11 Crewmax 5.7
240k
I fill to cold mark and in a week or two it's gone...no mas.
I can't be the only one going thru this.
Surely it's a gasket. But Wich one ?
Anyone know ??

 

Take a look around the engine bay and look for the telltale pink crusties of evaporated tundra coolant. Look at the plastic seems on the radiator especially.

If you don’t see any of those check for signs of water in the oil and the exhaust.

Is it overheating at all?

 

Check all the usual suspects -

• Rad hoses / clamps
• Faulty rad cap
• Signs of leak near transmission / bell housing (valley plate leak)

When is the last time the coolant was drained?

 

All good suggestions. The weep hole for the water pump is best seen from under the truck although if it is leaking enough to lower your reservoir it should be noticeable coming down on the parts below. Peak under the black plastic intake manifold for the valley plate leak.

 

Does not over heat imo (Houston area)
Cruises at 190-200°F per Scan Gauge 2
Wich to me seems normal.
July 2023 when I bought it was already loosing coolant, I still did a total coolant flush with distilled water Wich I still have 4 gallons laying around in my garage & I believe Zerex Asian Pink coolant with Toyota vehicles listed on its safe chart.
The factory analog gauge points dead center as does the tranny.
I'm gonna be under the truck very soon changing my atf fluid it will be jacked up where I can crawl easily to inspect said areas & wp weep hole... Thanks guys.

 

There's a coolant by pass hose, that is under the intake manifold. If that was leaking you wouldn't see evidence of it, except
maybe by checking to see if the oil was being contaminated .

 

I just bought my 2012 CM at the end of November. Love the truck. Having the same issue with the reservoir dropping after I top it off to the 'full' mark with Zerex Asian Red. It doesn't overheat, but the outside temps hover between 20 and 40 degrees F here in Montana. It still has coolant up to the top in the radiator.
I notice the exhaust is very damp, even after the truck is warmed up. Not thick white smoke, just a lot of condensation. It smells ever so slightly 'eggy', a tiny bit like sulfur. Not sure if I'm imagining the smell or what. The radiator cap doesn't get hot to the touch even though the radiator gets hot. I plan to crawl under tomorrow and look for pink crystals. Hoping it's not a head gasket or heater core leak. I bought an extended powertrain warranty for 5 yr/60K at the Toyota dealership. It had 149K miles when I bought it 2 weeks ago. I've been tempted to take the truck up to the dealership and tell them to fix it, but I'm sure they'll say I bought a high mileage vehicle 'as-is'. The truck seems perfect otherwise.

 

Sulfur smell is usually the catalytic converter.

 

True story. Last night I got the bug to go out and inspect my engine bay. I found that the lower radiator hose clamp at the base of the water pump was improperly installed and was about 3 inches too low. I got my visegrips, pinched it open and slowly worked it up where it once had been (grooves were still in the rubber), then topped it off to the 'FULL' line. This morning, took my son to school and definitely got it warmed up, then popped the hood when I got home and took a peek. It was up past FULL. Hoping that's all it was. Gonna get in there some more today and see what else I can find.