Thermostat Going Bad?

Hey guys, I have a 2008 TRD OR 4.0l with 206000 miles and going strong! Absolutely love this truck! I feel like my truck takes a long time to get the water temp up. I'm thinking that my thermostat is either stuck open or never actually fully closes.

I can usually expect about 20 degrees F ambient temp each morning.

If I start the car and let it idle for 10 mins, I find that the water temp gauge is only barely above the bottom line (horizontal indicator).

If I start it and drive immediately, it can take about 10-13 mins to get to operating temp.

Does this sound like its taking too long to everybody?

 

This truck takes the longest to come up to temp of any vehicle I've owned and is only second to the Nissan Xterra/Frontier I've driven several times. That being said, do you have any codes? Are you low on coolant or experiencing any issues with your heater? If it is taking a long time, it is a good indicator your thermostat is the problem, but often times it'll trigger a code as well since the engine took longer than a specified amount of time to warm up.

If you're in doubt, go ahead and change it. It is a cheap part and at 206k miles, you're definitely not going to hurt anything by doing it.

 

Thanks for the insight. No codes of any kind, but I'm glad to know that I'm not totally crazy thinking its taking too long. I'll probably get to changing it out in time, but I just had the coolant changed about 6k miles ago, so I'm not keen on opening it all up and draining it yet.

 

10-13 minutes to get to operating temp was right about where my 09 took to get decently warm. Modern vehicles will throw a code for temperature not in range if something is really off. Idling does not warm a vehicle near as fast as there is no load. Now at this mileage it wouldn't hurt to swap it out as it's a whole unit if I remember correctly. Do yourself a favor and go OEM or a brand that is OEM like Aisin ($30 on Rock Auto).

 

When you say "operating temp" do you mean 190 ish degrees? or starts to move the needle?

 

I had this same issue and after replacing the thermostat the truck will now get up to operating temp in about 4-5 minutes of driving at temperatures below freezing. It can be stone cold in the morning and up to temp by the time I’m at the gym 2.5 miles away.

 

That is actually super encouraging and pushes me to replace the thermostat. I think its certainly in my future (spring time)!

 

It’s possible that the thermostat is failing to close all the way.
If it’s staying in an open (or partially open) state, it will take longer to heat the coolant.

Of that’s the case, good.
I’d rather have a thermostat fail in the open position.
Closed will cause the engine to get too hot.

I’d try a thermostat. It won’t hurt at 200+k miles.

 

this is what i like to hear, did you just change it out with the oem one?

 

Thermostat typically fail in 2 modes. Open or closed.

Open the engine takes forever to reach operating temperature. Sometimes it won't get warm enough. Ambient temps have a big impact.
Closed, the engine will overheat in fairly short order.

But at 206 Kmiles, the truck is due for a bit of service. Change the T-stat and the coolant.

A tip, don't sit idling for warm up. Get in the truck, start it, buckle up, drive off, easy on the gogo pedal until a little heat registers on the dash.

 

If you are going to change it I’d go OEM Toyota (AISIN) or AISIN branded.

 

In the middle where it should be for normal operation.

 

I’d say replace it , it’s shot

 

I think you're right.

 

I am actually in the same boat , the truck is taking awhile to heat up , and it’s having trouble staying at temp . Im just replacing the thermostat , it’s like $36 and some change

 

Agree,good insurance to at 208k