Coolant reservoir bubbling over at high altitude

[Greg1112]

Hello! I am new here.
I have an interesting. Issue. I have a 2011 Toyota Tacoma that overflows its reservoir when it is above 8,000’ and I shut the engine off. There is no indication on the gauge it is overheating. I have noticed if I keep the engine running the bubbling is minimal. I tried replacing the aftermarket radiator cap with a factory one. I think my other option is to make sure the reservoir is dry before I head to altitude.

 

[Vercingetorix]

Is there an electric coolant pump that could be bad? One that’s supposed to run after shutdown.

 

[dishdude]

The only time I've seen this happen was a head gasket allowing compression gases into the cooling system.

 

[Coolant Kid]

The only time I've seen this happen was a head gasket allowing compression gases into the cooling system.

Same here...head gasket.

 

[Chris142]

Make sure the place where the cap seats to the radiator is smooth.

 

[hemitom]

Doubt it's a head gasket ! if it was wouldn't it do it all the time and not only at high altitude ?

 

[HemiBenny]

Find the leak in your cooling system. Altitude won’t make a difference in a cooling system that’s working properly.

 

[dishdude]

Doubt it's a head gasket ! if it was wouldn't it do it all the time and not only at high altitude ?

Head gaskets can leak only under certain conditions, especially when it comes to compression gases.

 

[slacktide_bitog]

Maybe it can't keep enough pressure at high altitude? Lower pressure, lower boiling point

 

[Japanese]

There is no indication on the gauge it is overheating.

Does your cooling fan work all the time?
Make sure your cooling system doesn't have any leaks. Coolant boiling point is highest when is under preassure. When the cooling system have a leak the coolant boiling point drops.

I'm not an expert, but it looks like a common issue at high altitudes:
https://www.google.com/search?q=car...yNTU2ajBqMTWoAgCwAgA&sourceid=chrome&ie=UTF-8

"As altitude increases and atmospheric pressure decreases, the boiling point of water decreases."
https://mountainhouse.com/blogs/bac...Xm0iU_1xufsFetNvlaWK0asfB_ntAl87920UNIG_wnJ9F

 

[clinebarger]

OE Radiator?

 

[Astro14]

“No indication of overheating” - from the factory gauge? It’s “normalized” to show in the center, despite any variation in engine temperature. So, even though it shows in the middle, your engine could be running significantly hotter, and that would cause the overheating. Got a scan tool? I’d be curious what the actual, not dash gauge, temperature is when this happens. Bet it is, actually, much hotter than normal.

 

[Lubener]

Had my coolant bottle overflow when I blew a head gasket. The temperature gauge didn't even reach normal when it happened.

 

[Jetronic]

what's the concentration of coolant? Is it high enough? the boiling point of water is 197°F at that altitude, so you will get bubbling if the fluid going to the overflow tank is hotter than it (with pure water) a slightly higher concentration of anti-freeze could prevent that.

 

[oldcodger]

Pressure test your cooling system.

 

[69GTX]

Maybe run the reservoir level lower.....closer to 1/2 full....leaving more room for expansion.

 

[Astro14]

Maybe run the reservoir level lower.....closer to 1/2 full....leaving more room for expansion.

If this truck is like mine, full cold is about 1/3 full. Lots of room for expansion. I think the engine is actually overheating despite what the dashboard gauge reads. Most temperature gauges are idiot lights - they don’t show the actual temp any more.

 

[50yr Street Mech]

Something overheating somewhere. I'm no expert, but a bad head gasket would bubble all the time, and you would be getting oil/coolant mix in the oil or coolant. I would check temp sensor, or change coolant & thermostat, flush cooling system, clean exterior of radiator, check fans to make sure they are coming on when their supposed to, check fuses on cooling fans, check fans to make sure they are working. One may be burnt out. I've had that problem before on my Honda and Nissan. One bad fan. Pressure test cooling system. Don't go by the stupid gauge. Nothing more than a glorified idiot light. Best of luck

 

[incognito_2u]

Pressure test the system and work your way up from there…..

 

[f355spider]

I would get a cheap ELM327 scan tool and a free app and then you can read the actual coolant temperature.
They are useful for scanning and clearing codes too. They are like $5 on fleabay. I keep one in each car.