2009 4cyl 2.7 coolant loss

Driving my new to me 2009 Tacoma 5 lug base 2.7 auto across the country. Had no issues in the previous 2 months of city driving-- truck was zealously maintained by previous owner. 172,000 miles. Long list of replacement parts & maintenance from previous owner.

About 2000 miles into my trip, temp gauge goes up to 3/4 high, pull over immediately. Look at my coolant and the reservoir is empty. Fill it with green Prestone (all I have), drive down the road and it start overheating-- reservoir is empty again. Fill it two more times like this, and then it stays full. Drove it 700 more miles to get to my destination and the reservoir has stayed full and no overheating.

My oil level has not changed, it is not cloudy, and I don't smell any sweetness. I haven't noticed any white smoke, and there are no obvious coolant leaks.

Any ideas?

 

Check the level in the radiator. Checking and filling via the reservoir isn’t the proper way.

Once the radiator and reservoir are full, all you can do is keep an eye on the level. Obviously you have a leak. But where? We don’t know.

The coolant bypass is a know issue.
Other than that, an exhaust gas test of the coolant system maybe be in order.

BTW, ALWAYS check the coolant in the radiator when the engine cool and been off for awhile.

never check it on a warm engine. The coolant is hot and under pressure.

 

Thanks for the response.

Edit: I just talked to the previous owner, he had the plastic bypass pipe replaced with the metal one, by Toyota. The water pump has also been replaced. The thermostat is likely original.


I had the truck off for ~30 minutes before I filled the reservoir, and only check the radiator level after it was cold.