Thermostat stays closed after idle 30mins

[UltTrail runner]

Just replaced heater Ts. I was going to top/burp coolant to replace what was lost. But it seems the thermostat just does not open even after 30mins of idling with heater on most of the time. Is this normal? The thermostat was replaced new about 30k miles ago with timing belt and the water temperature has been always in the middle of the gage. Thanks in advance.

 

[AlpineAccess]

So your vehicle is overheating?

More likely, your thermostat is not closing all the way and so the vehicle is not reaching operating temp?

 

[UltTrail runner]

So your vehicle is overheating?

More likely, your thermostat is not closing all the way and so the vehicle is not reaching operating temp?

No I don’t think it’s overheating as the temperature gage stays normal. I was waiting the coolant to circulate to the return hose to the radiator while I have a funnel full of coolant attached to the radiator. I was anticipating the amount of coolant in the funnel to reduce as I lost about 1-2 cups of coolant when changing the heater Ts. But the coolant in the funnel did not reduce after 30mins idling and the return hose does not feel hot while touching it compared to the supply. So my guess is that thermostat was not open. I believe there is probably some air in the coolant system now, would that be okay? Or should I wait longer for the thermostat to open to release the air?

 

[AlpineAccess]

No I don’t think it’s overheating as the temperature gage stays normal. I was waiting the coolant to circulate to the return hose to the radiator while I have a funnel full of coolant attached to the radiator. I was anticipating the amount of coolant in the funnel to reduce as I lost about 1-2 cups of coolant when changing the heater Ts. But the coolant in the funnel did not reduce after 30mins idling and the return hose does not feel hot while touching it compared to the supply. So my guess is that thermostat was not open. I believe there is probably some air in the coolant system now, would that be okay? Or should I wait longer for the thermostat to open to release the air?

If the thermostat was installed correctly (with the little air bleeder jiggle valve at 12 oclock, you would start with a cold engine and the radiator cap off.

Set heat to high in the cab and fan speed high (not auto). Start the motor and "burp" the radiator hoses by squeezing them, and add coolant to the system until topped off, but don't let engine heat up. Turn off, put cap on. Turn back on and let warm up to operating temp and then turn off.

When everything is fully cooled again and no pressure in system, open radiator cap again and try to burp. When you have successfully filled the system there will be no air in the top of the radiator when cold and the reservoir will have a gone up slightly from excess purging from the system.

This is just how I have always done it (when not using a vacuum tool) and I'm sure there are other ways!

 

[2001LC]

Just replaced heater Ts. I was going to top/burp coolant to replace what was lost. But it seems the thermostat just does not open even after 30mins of idling with heater on most of the time. Is this normal? The thermostat was replaced new about 30k miles ago with timing belt and the water temperature has been always in the middle of the gage. Thanks in advance.

Coolant systems topped properly and not moving through radiator after warm-up. Does indicate blockage. Which in most cases is a stuck closed thermostat. Which would result in a high engine coolant temp (ECT). ECT should be check through tech-stream to confirm. Dash gauge, is only good as indicator.

Gauge on dash can be misleading. For a few reasons:
1) Coolant in system is low. Resulting in, coolant below water temp sensor.
2) Fault in water temps sensor circuit.
3) Dash gauge only gives approximate range.

One indicator system is low on coolant and air in system. Is cabin heaters don't blow hot, just warm or cool. They should blow hot, after about 10 to 15 minutes of idling.

Try this:
Engine cold and off, squeezed the upper rad hose a few times, with cap on. Than check to makes sure radiator full. Start with cap on, than after running 10 minutes or more take RPMs up to ~3K. Squeeze hose again, it should now feel hard/full. Both cabin heaters should now blow hot. Let sit over night to cool down for 8 hours. It must be parked level, or better yet, with front end higher than rear of vehicle. Before sun comes up, heating the outside air (OAT) or starting. Check under radiator cap, making sure coolant to the top. If not; top, and repeat.

The morning you find the radiator full to the top. Than start with rad cap off ( I only recommend this, because you're not seeing flow now). Check to see that coolant is flowing after warm-up of about 10 or more minutes of idling. It's best you check ECT through techs stream. You'll want to see above ~180. If you still do not see flow after ECT above 184f. I'd than inspect thermostat, by removing it.

 

[UltTrail runner]

If the thermostat was installed correctly (with the little air bleeder jiggle valve at 12 oclock, you would start with a cold engine and the radiator cap off.

Set heat to high in the cab and fan speed high (not auto). Start the motor and "burp" the radiator hoses by squeezing them, and add coolant to the system until topped off, but don't let engine heat up. Turn off, put cap on. Turn back on and let warm up to operating temp and then turn off.

When everything is fully cooled again and no pressure in system, open radiator cap again and try to burp. When you have successfully filled the system there will be no air in the top of the radiator when cold and the reservoir will have a gone up slightly from excess purging from the system.

This is just how I have always done it (when not using a vacuum tool) and I'm sure there are other ways!

great. I will try this method. Thanks!

 

[DBULL]

Just watch your overflow tank.As the system cools it will draw coolant back into the radiator.Two cups of coolant shouldn’t cause any overheating.