Coolant flush. How to tell if thermostat open w/o temp gauge?

So, the temp gauge on my dash doesn't work. Spent about an hour trying to figure out why, but no luck.

I do need to change out the coolant. And the guides I've read/seen say to flush with distilled water a few times.

I understand that the thermostat opens when the engine reaches normal operating temperature. If the thermostat isn't open, the coolant isn't flowing through ALL the passages of the engine block, only some.

How can I tell if the engine has reached operating temps with a working temp gauge?

Would letting the truck idle for 5 mins be enough to get it up to operating temps in the summer?

 

I highly suggest a scan gauge. While the blue tooth devices and apps are nice.. I really like that my scan gauge is just ready to roll, and I don't have to deal with my phone to look at temps, etc.

Either route will work to give you an actual numerical value.

 

Once the upper and lower radiator hoses are the same temperature, that’s operating temperature. When you bleed the system, try to get the rad cap at the highest point by parking slightly uphill, on some ramps or something of that sort. It will help get the air out of the heater hoses at the back on the firewall.

 

Can't remember if...you had asked this before or something similar?

The gauge on the dash is useless and runs independent of the actual sensor that reads out to your ECM. With that said, use any tool that connects via OBDII.

The dash gauge runs off a single wire sensor at the rear of your intake manifold.

 

I just put my hand on the upper radiator hose. Once the tstat opens, it gets warm.

 

Ah the ghetto temp gauge.

 

Maybe. I sometimes make threads about future projects, forget that I made them, then make another one when I'm actually getting to the thing I was going to do. It's a bad habit and I'm in therapy to overcome this.

 

Not really, that literally is a sign of the thermostat either opening or not due to coolant flowing.

 

Well, you got good suggestions so far in this thread.

 

I thought the warm one was the top one and the bottom one would get hot. I wouldn' know. I never actually tested temp via that method.

 

I'm going to put in new coolant on Friday. I hope I can remember that I made this thread when the time comes.

 

You may already own an OBDII scan tool with live monitoring; that'll work to give you real-time temps.

 

I do own one. But, I don't think it does live temps. I will double check

 

An ultragauge or scantool can be programmed to monitor temps, check codes, etc. but with the intent to act as additional monitoring you leave connected to your vehicle.

Very useful if it's what you're into.

 

Get you a no spill funnel and keep it topped off for 10 minutes of idling. Should be good by then.

 

Do SG or UG pull a constant draw from the OBDII even when the truck is off?

I always tried confirming this but never found an answer.

 

It’s supposed to turn off. I’m not 100% sure that there aren’t conditions (like opening and closing the door multiple times with engine off) that can turn it on when you don’t want it. I disconnect it when I’m not towing.

 

Temp gun for the win!

My choice when working on different vehicles .

Just one vehicle I would have a scan gauge in a permanent mount!