Hey guys, I finally have my own issue with the coolant system. I think I have an air bubble in my system, possibly a bad temp sensor, and pray to God not a blown head gasket. Is there a procedure for filling/bleeding the coolant system that someone can point me to?

If I drive a quarter mile the gauge spikes. I turn off the engine and none of the hoses are all that hot, no steam. In the meantime the fan runs like crazy. The GAP says the coolant temp is going as high as 110C, but if it's using the same temp sensor as the gauge and that's bad, them it may be erroneous data.

Any guidance is appreciated.

Cheers,
Houm

 

I had a similar issue, bad thermostat. Thermostats are inexpensive and easy to replace. Not a lot of time or money spent if that does not fix the issue.

 

It definitely feels like a thermostat, but I JUST had that checked last week, and changed maybe a year ago...it wasn't leaking or cracked, but I suppose it could still be "stuck" or have a bad sensor attached, right? I don't want to drive it, though, if the temp gauge is spiking like that. I guess I could have it towed and my insurance would cover that.

 

The large hose on the right - pump it by hand. It should be full of coolant. That is the most critical hose of them all in the circuit because its high up and a lot flows through it. If it feels empty, you are low on coolant - ignore the tank on these, they are not exactly accurate. Also when warm, if that hose feels firm then the system is pressurizing which is good.

Another thing you can do, with help, if to rev the engine a bit with the expansion tank cap removed. Coolant level should drop. If you stop revving with the cap off a bunch of coolant may come out - that generally means the pump is flowing good. The help is to put the cap back on before you let off the revving to prevent coolant from going all over.

 

OEMTOOLS 24444 Coolant System Refiller Kit, 5 Adapters, Eliminate Trapped Air, Test Radiator and Heating Core Lines for Leaks, Vacuum Fill Coolant Tool, Vacuum Leak Tester https://a.co/d/3KVI9sl

i bought this kit after having trouble bleeding the air. It works incredibly well.

 

The fan is running like crazy as a fail safe because the ECU is getting a reading from the temp sensor that your engine is overheating. There is only one temp sensor, it’s by the thermostat. The GAP tool is pulling info from the same sensor as the ECU. If the hoses are not hot but the temp sensor is reading 110C, then indeed the temp sensor is bad or you have air in the system.

Check for air via the methods identified above and check the sensor. The sensor is just a resistor, you should be able to check it by measuring resistance across it at varying temperatures. With some luck there are published values somewhere that you can compare to.

I’m curious what led you to have the thermostat inspected last week? How was this done? If air is in the system, it needs to be understood how it was introduced so that can be fixed.

 

If it is air, I'd recommend burping the system the next time the temp spikes. For all the bleeding I've done on these they almost never get rid of all the air.

Next time it spikes, pop the hood and unscrew the coolant cap. That will let out any air. Top off the coolant and you're good to go. You may have to burp it a couple times.

You can test the thermostat on your stove. Boil some water and put the thermostat in it, if it's working it will pop open. If not, you need a new one

 

https://a.co/d/9vy4NDS
About 4 years ago I used this test kit when confirming a head gasket leak on a Toyota forklift. It is pretty easy to use, and it's a definitive test for combustion gasses in the coolant system. You basically suck the air out of the coolant bottle and it diffuses through the colored liquid. If the liquid changes color, it is indicating the presence of combustion gas. I hope you don't need this, but it is a good test. You also want to check your dipstick for chocolate milk. Either would indicate a head gasket problem, or give you peace of mind that you're good.

The first time I did coolant work on this motor, I had to carefully remove the end of the hose that would normally have the bleeder T to let some air out. I eventually got it full. That's when I bought the Coolant Refiller kit above. When I changed out my crappy two-piece water pump a short time later, I used the refiller kit — easy!

 

Thanks guys, this is all very helpful.

@SeattleDriver I didn't have the thermostat inspected last week, but when in for some other work, my mechanic noticed that there is a coolant leak. He checked the usual suspects including the thermo and it was fine. The leak was at the water pump. Also, the thermo isn't that old. I think I replaced it last year. Probably 12 months + one day ago and hence out of warranty.

Anyway, slight update: I found an old thermostat assembly from my '05 that I had replaced for good measure in 2014 before my trip to the Yukon Territory. I am going to remove the thermostat housing itself and the temp sensor, and slap them on the '06, and then make sure the coolant is topped up, burping it along the way. We'll see how that goes!!!

 

An air bubble (air lock?) in your system sounds most probable since you had/have a leak.