Changed thermostat, Coolant temperature stays at 185 degrees

[SpaceBaller01]

Crickets are a PITA.

My apologies, I thought I set this to notify me when I got a reply.

 

[SpaceBaller01]

Correction, depending on the year of your vehicle they could have used a 195F as well. I do know that there are different temp options for performance or industrial applications of the same engine.

I'd double check to make sure what the OEM one you removed has stamped on it, or check with a dealership parts dept to see if they can give you the exact spec from new.

This is a 2004. Unfortunately the thermostat has no degree rating on it. I just know what I put in was 185, from the Amazon page. I'll have to give them a call on that one.

I do have another thermostat I ordered (but forgot to return, it's Gates (185°) instead of GM. I could try this one, but I'd rather not dump the coolant if I don't have to from changing the thermostat.

 

[SpaceBaller01]

When this "too cool" problem started, what work had been done just prior? Any chance you're running an aftermarket radiator?

Read this: https://www.tahoeyukonforum.com/threads/cold-case-radiator.135572/post-1699853

You could try pinching the small return line that goes from the radiator to the surge tank to see if that makes any difference.

Unfortunately I have no idea. Bought the truck earlier this year with virtually no history. I'll try that return line trick though.

 

[SpaceBaller01]

Did you change the settings in the ECM to make fans come on sooner? If not, it will always run the same temp.

Nope that's wayyy too ahead of the stuff I do lol

It went to temp a few.months ago then noticed it stopped going up all the way (before the weather started cooling).

 

[SpaceBaller01]

If the weather where you are is already cool, a thermostat stuck open could explain your heat feeling cooler than normal.

Is it possible the thermostat is stuck open or backwards?
Is that possible on the GM stats @OR VietVet?

I know I saw some people on Wrangler forum did not pay attention to how the original stat was positioned in their 4.0L and ended up putting the new one in backwards. But I forget what the exact implications of that reversal was. I am not sure, but I think they started off cold, then overheated after the stat opened (which was closed because it was in backwards...).

Honestly I'd be surprised I pretty much followed it as It came out. Has not overheated at any point. It did go to temp on like the 2nd or third time I drive it after Installing it a day or two after. But hasn't come back since.

 

[MassHoe04]

Honestly I'd be surprised I pretty much followed it as It came out. Has not overheated at any point. It did go to temp on like the 2nd or third time I drive it after Installing it a day or two after. But hasn't come back since.

Yeah... I wasn't insulting your mechanical abilities. I haven't found out if the casting for the thermostat housing would even allow the part to be flipped like it could on the Jeeps. I was just trying to talk out some of the possibilities and an open stat was one of the things I was thinking of as at least being remotely possible. Even then, the engine would get up to the normal operating temperature of somewhere close to 210 F +/- a few...

Cooler than normal most all the time and occasionally almost normal random other times.
This is a head-scratcher, but I am sure someone can help walk you through this diagnosis.

 

[Fless]

Does this have electric cooling fans, or a clutch fan?

 

[OR VietVet]

Could you clarify what you mean by heat soak?

A heat soak takes place every time you get the engine to operating temp and then shut off. The engine temp climbs higher then because there is no air flow. Then when it hits its peak temp, it drops. If you have electric fans they can stay on after shut engine off till a temp sensor sees the temp drop to a certain point.

 

[mattbta]

Coulda called someone on the rotary phone... BR-549?

Hee-haw was always on after the Dukes Friday night when I was a kid. I was too young to pay attention to skimpy dressed ladies.

Here's another to show my age....Pennsylvania 6-5000! I'm middle aged, but old soul'd.

My bets on too cool operating are also on missing restrictor.

 

[B-train]

So, running with the cap off at operating temp will allow coolant to flow freely and encourage air pockets to move through the system. Running the rpm up to a steady 1500 to 1800 rpm for about 5 minutes helps as well.

Heat soak is shutting down the motor hot (preferably after higher than idle rpm). It allows the engine heat to increase due to lack of coolant or air movement. Basically it allows fhe coolant to "grow" due to the increase in temp, therfore giving you a hot reading that can be topped off as needed.

An IR gun will verify this as well.

 

[SpaceBaller01]

Does this have electric cooling fans, or a clutch fan?

I'm guessing it's clutch driven. It does have a shaft driving those fans.

 

[Fless]

I'm guessing it's clutch driven. It does have a shaft driving those fans.

If the shaft is driven by the water pump, it's a clutch fan (one). The electric fans are dual and are not connected to the water pump.

 

[SpaceBaller01]

Yeah... I wasn't insulting your mechanical abilities. I haven't found out if the casting for the thermostat housing would even allow the part to be flipped like it could on the Jeeps. I was just trying to talk out some of the possibilities and an open stat was one of the things I was thinking of as at least being remotely possible. Even then, the engine would get up to the normal operating temperature of somewhere close to 210 F +/- a few...

Cooler than normal most all the time and occasionally almost normal random other times.
This is a head-scratcher, but I am sure someone can help walk you through this diagnosis.

Don't worry I didn't think you were meaning to there. Like you've mentioned we're trying to rule out some possibilities and no harm to ask .

Honestly I'm pretty tempted to go ahead and just try another thermostat. I happen to have one forgot, just didn't want to change out the coolant again if I don't have to.

 

[SpaceBaller01]

If the shaft is driven by the water pump, it's a clutch fan (one). The electric fans are dual and are not connected to the water pump.

In this case, yep it's definitely clutch driven. Just checked, connected to water pump, single fan.

 

[MassHoe04]

Don't worry I didn't think you were meaning to there. Like you've mentioned we're trying to rule out some possibilities and no harm to ask .

Honestly I'm pretty tempted to go ahead and just try another thermostat. I happen to have one forgot, just didn't want to change out the coolant again if I don't have to.

Unless the coolant is dirty or has big chunks of rust coming out with it when you drain down, I would pour it back in.
You may lose some while disconnecting hoses, but why throw it out if it looks good and clean.

If it doesn't look as good as when it came out of the jug, by all means new fluid.
But, save a few bucks if you can.

 

[SpaceBaller01]

Ok IR thermometer came in.
around 140-150 w heat off, 160 - 170 on
lower hose 105
upper 164 - 170

 

[SpaceBaller01]

So I changed the thermostat. I'm trying to fill it back up with coolant. Reservoir is full. None of the hoses are obstructed. However, I thought I saw smoke coming from the engine (had a burning smell too) and new popping sounds, it was dark outside though so not 100% at this point.. Not sure if it's just trying to burn the spilled coolant off or not What is the best thing to do here?

I tried squeezing the radiator hoses to try to get more of the air out (and so I can remove my funnel from the tank). Not sure how much that helped. I have 1 gallon in, I'm pretty sure 3 came out.

 

[MassHoe04]

You could try this...
Disconnect the upper radiator hose and fill until it starts coming out the upper hose. That should allow free flow to fill the radiator to near capacity.
Connect the upper hose.
Fill the coolant reservoir to the top (it will go down).
Run the engine.
When the thermostat opens, the level will go down and you will need to top off to the fill line on the reservoir.
You may need to top off more than once.
Just keep checking the levels after driving some.

I bet as soon as you disconnect the upper hose, the coolant in the reservoir will rush right out and be empty.

 

[SpaceBaller01]

Ok false alarm. The popping went away after a few minutes. No smoke. I've been able to get some coolant. It has bubbled down a bit, not significantly. Was able to drive up the road and get heat with no signs of overheat.

Thermostat is still going up only partway. I have a new sending unit coming in tomorrow. If that doesn't work I'll probably just have it looked at.

 

[OR VietVet]

Haven't we recommended an infra-red temp gun check at the thermostat housing, somewhere in this thread?