A Toyota technician has a peculiar but rare find concerning Toyota Tundras with  4.6 liter or a 5.7 liter engines. While he had only run into the issue “one other time” during his career, it was still concerning enough for him to post a “tech tip of the day” to TikTok. 

Master Toyota technician Cameron (@mdttoyotech1.0) warns Toyota Tundra drivers about possible overheating when hitting highway speeds. This TikTok has received over 4,000 views as of this writing.

What Caused The Radiator Issue?

According to Cameron, Tundras that overheat when driving at highway speeds may accidentally have bits of an old radiator cap inside the vehicle’s coolant system. The Toyota Tundra, based on Cameron’s information, specifically has a coolant hose that is susceptible to small bits of debris. 

Cameron mentioned during his TikTok clip that he had only seen the diagnostic he provided in 2026 “one other time.” According to his video, the issue is specifically related to 4.6 liter or 5.7 liter Tundra vehicles, not other Toyota cars. 

The customer who received the diagnostic had installed a new radiator cap, which didn’t technically lead to the problem. Instead, bits and pieces of the old radiator cap broke and fell into the coolant overflow tube. From there, those pieces ended up lodging the vehicle’s thermostat housing. 

These vehicles’ coolant hoses are just small enough to fit small bits of debris from the radiator caps, hence creating a tricky to diagnose problem for technicians and mechanics. It’s an issue that even skilled mechanics may struggle to catch. 

But, the issue can eventually lead to the coolant system for the Toyota Tundra not working properly. The restriction reduces coolant flow to a degree where the system may overheat at highway speeds but be perfectly fine when moving slower. 

Cameron also described how he first ran into the issue in his TikTok’s comment section. “[With] the first [vehicle] I was dealing with, I was rather confused. I found that [issue] when I was pulling the upper hose off to see my water flow through the radiator because I was thinking a clogged radiator,” Cameron commented.

After he discovered the issue the first time, he had a much easier time diagnosing the one other car that had a similar problem.

How Susceptible are Radiator Caps to Coming Apart?

Radiator caps degrade over time, which can lead to coolant leaks or temperature fluctuations. Ultimately, radiator caps should be replaced regularly, as they erode and lose tension, which can eventually lead to coolant issues.

Corrosion from coolant can compromise the metal components in a radiator cap, eventually leading to issues like what Cameron discussed. The rubber lining used on many radiator caps may also crack and degrade over time, eventually leading a radiator cap to not seal properly.

There’s also risks when installing a new radiator cap, as they can come apart after consistent deterioration. One small movement may end up accidentally knocking bits of an older radiator cap right inside of a vehicle’s coolant hose. 

But, there are other issues when it comes to radiator caps. Consumers may purchase a brand new cap, only to discover that it is incapable of maintaining the correct coolant pressure due to a spring issue. 
Radiator caps should be replaced every four to five years, or 50,000 to 75,000 miles. But, for car owners living in hot climates or extreme weather conditions, it may be worth replacing a radiator cap earlier than that.

Does a Vehicle’s Mileage Directly Correlate to Issues with its Radiator Cap?

One commenter noticed that higher mileage 5.7 liter engine Tundras commonly received this technician diagnosis. 

“I’ve seen this twice in the past [two] years on high mileage 5.7’s,” shared another mechanic. 

“Same exact complaint. Nice find!” another added. 

But, it’s important to note that it’s not necessarily the vehicle’s mileage that causes this specific diagnosis. It’s the radiator cap’s erosion and general condition. Radiator caps generally erode over time, meaning that vehicles with higher mileage that haven’t received a new radiator cap are more likely to have a similar coolant diagnostic issue.

Radiator caps that have visible corrosion, dried residue on the outside, a sweet smell or are actively leaking coolant should be evaluated and replaced. Improper seals on radiator caps are a direct cause of coolant issues, regardless of a vehicle’s make and model.

Is This an Issue That Can Happen to Any Vehicle?

Cameron had only noticed this diagnosis with Toyota Tundras, but commenters added that it can technically happen with any vehicle, regardless of make and model.

“Seen that once. It can happen to any make and model with an actual radiator cap,” one commenter shared.

Issues with radiator clogs are surprisingly common, although they’re not commonly clogged by radiator cap debris. Similarly, issues with radiator caps also stretch across different car brands including pressures problems, corrosion and deterioration over time, and coolant leaks.

Regardless, the issue does seem to be prevalent for Toyota Tundras, making it something worthwhile for Tundra owners to look out for, especially as they start to have higher mileage on their vehicles. 

We’ve reached out to Cameron via TikTok direct message and Toyota’s corporate email for comment. We’ll let you know if either party responds. 

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