Low temps and boiling sounds from 3.8

[Ivycon]

Hi everyone,

2010 3.8L 170k miles

My gauge is reading that my engine isn’t reaching operating temps for a couple of weeks now. (It’ll be at like 160ish.) then one day I was idling at lunch and my water started boiling over and the temp got up to operating and a little more. Once I was in drive that issue went away but still ran cool.

So I replaced the thermostat and water pump but am still seeing this issue. I got home from work today and I could hear the water boiling in the radiator. and my fan doesn’t kick on while driving.

If I put the ac on the engine will create a weird feeling when sitting at a traffic life.

Ive dug into this some and haven’t seen anything similar. Does anyone have any thoughts on where to start or what could be wrong?

Thanks in advance!

 

[BLACKJKU]

If you had the coolant drained out you'll need to burp the cooling system, remove the cap raise the front up about 6" and start the Jeep. Then as the coolant lowers add some more to it.

 

[Ivycon]

If you had the coolant drained out you'll need to burp the cooling system, remove the cap raise the front up about 6" and start the Jeep. Then as the coolant lowers add some more to it.

Thanks. I thought I burped it correctly. Filled it up, pressed the top hose multiple times to lower the coolant, fill it up more, ran it with the lid off, and then once dropped I added more. I can try this method you mentioned though.

 

[Dirty Dog]

Thanks. I thought I burped it correctly. Filled it up, pressed the top hose multiple times to lower the coolant, fill it up more, ran it with the lid off, and then once dropped I added more. I can try this method you mentioned though.

If you don't elevate the nose, you will never get all the air pockets out.

 

[Ivycon]

If you don't elevate the nose, you will never get all the air pockets out.

One of the issues is, I can’t get it to operating temps due to the sensors or something to be off. So I think it doesn’t get the Jeep the opportunity to burp itself.

 

[BLACKJKU]

One of the issues is, I can’t get it to operating temps due to the sensors or something to be off. So I think it doesn’t get the Jeep the opportunity to burp itself.

The sensors only read the temps don't have anything to do with controlling the temps, the T-Stat controls the temps along with the cooling fan.

 

[Dirty Dog]

One of the issues is, I can’t get it to operating temps due to the sensors or something to be off. So I think it doesn’t get the Jeep the opportunity to burp itself.

The sensor can't read the temp if it's in an air bubble. And the Jeep will never, ever, burp itself.

 

[Anybodyhome]

The easiest way to know if there is air in the system is a fluctuating temp gauge. Regardless if you're moving or not, with no rhyme or reason, the temp gauge is all over the map from where it should be to the higher range.

1. Raise the front end and remove the rad cap. As has been said before, don't be shy about getting the front end off the ground by 6". I use a floor jack and then slide jack-stands underneath. Air travels up, so the higher, the better.
2. Add coolant to the rad, not the reservoir.
3. A little at a time, as you add coolant, it will settle into the rad and force the air out the cap.
4. Each time it burps, add a little more coolant until it's at the cap level and no more burps occur.
5. Make sure the reservoir is filled to either the cold or hot limit line, depending on the engine state when you add coolant. I've always preferred cold, it's just safer.

 

[Ivycon]

The easiest way to know if there is air in the system is a fluctuating temp gauge. Regardless if you're moving or not, with no rhyme or reason, the temp gauge is all over the map from where it should be to the higher range.

1. Raise the front end and remove the rad cap. As has been said before, don't be shy about getting the front end off the ground by 6". I use a floor jack and then slide jack-stands underneath. Air travels up, so the higher, the better.
2. Add coolant to the rad, not the reservoir.
3. A little at a time, as you add coolant, it will settle into the rad and force the air out the cap.
4. Each time it burps, add a little more coolant until it's at the cap level and no more burps occur.
5. Make sure the reservoir is filled to either the cold or hot limit line, depending on the engine state when you add coolant. I've always preferred cold, it's just safer.

The sensors only read the temps don't have anything to do with controlling the temps, the T-Stat controls the temps along with the cooling fan.

The sensor can't read the temp if it's in an air bubble. And the Jeep will never, ever, burp itself.

How long could this process take? I jacked it up this morning, easily more than 6". Had the rad cap off, turned on the engine, had it run for about 35 mins, the temp on the gauge never rose past half way to the middle(the normal opp temp). Fluid never dropped. My issue is the engine isn't A. getting hot enough to burp or B. it's hot enough and the thermostat isn't opening up. But as stated I replace that t stat already.

Thanks everyone! Sorry, I can fixed things, just can't diagnose them sometimes. lol

 

[Anybodyhome]

So, let's walk thru these one at a time.
1. "I jacked it up this morning, easily more than 6". Had the rad cap off, turned on the engine, had it run for about 35 mins, the temp on the gauge never rose past half way to the middle(the normal opp temp)." Okay, good. These are good signs. The gauge didn't fluctuate and stayed where it should. Good. Coolant never dropped in the rad, also good.

2. "My issue is the engine isn't A. getting hot enough to burp." The engine does not have to be hot enough. Matter of fact, the engine doesn't even have to be running to burp. All you are doing is adding coolant to the appropriate level. The engine does not need to be running to burp. You add coolant and the coolant displaces the air out via the open rad cap.

3. "B. it's hot enough and the thermostat isn't opening up." But you said the temp gauge was in the middle, where it's supposed to be. That's a good thing. If the engine temp was indeed "hot enough and the t-stat isn't opening, you'd be overheating, the temp gauge raising above normal (beyond the mid-point).

Sounds to me like everything is normal. If you can run the vehicle up and down the road for 30 minutes, hit some lights or stop signs, drive in traffic and your temp gauge remains consistently in the middle, you're fine. Maybe I'm missing something, but I'm not reading where there's a problem now.

 

[Ivycon]

So, let's walk thru these one at a time.
1. "I jacked it up this morning, easily more than 6". Had the rad cap off, turned on the engine, had it run for about 35 mins, the temp on the gauge never rose past half way to the middle(the normal opp temp)." Okay, good. These are good signs. The gauge didn't fluctuate and stayed where it should. Good. Coolant never dropped in the rad, also good.

2. "My issue is the engine isn't A. getting hot enough to burp." The engine does not have to be hot enough. Matter of fact, the engine doesn't even have to be running to burp. All you are doing is adding coolant to the appropriate level. The engine does not need to be running to burp. You add coolant and the coolant displaces the air out via the open rad cap.

3. "B. it's hot enough and the thermostat isn't opening up." But you said the temp gauge was in the middle, where it's supposed to be. That's a good thing. If the engine temp was indeed "hot enough and the t-stat isn't opening, you'd be overheating, the temp gauge raising above normal (beyond the mid-point).

Sounds to me like everything is normal. If you can run the vehicle up and down the road for 30 minutes, hit some lights or stop signs, drive in traffic and your temp gauge remains consistently in the middle, you're fine. Maybe I'm missing something, but I'm not reading where there's a problem now.

The gauge was halfway to normal operating temp. Not at normal operating temp.

 

[Anybodyhome]

The gauge was halfway to normal operating temp. Not at normal operating temp.

Sorry, misread your statement.

Here's the easiest diagnosis that will eliminate or confirm the t-stat needs to be replaced:
1. Have someone start your vehicle cold while you wrap your hand around the upper radiator hose.
2. If you immediately feel coolant flow thru the hose, the t-stat is stuck open. This means there is coolant flowing thru the engine before it's necessary and is preventing it up from heating up to the proper operating temp.
3. If you do not feel any coolant flow thru the hose, continue to hold onto it until you do feel flow. You need to know what the approximate temp is, or where the temp gauge is when you begin to feel the flow.

If your t-stat is okay, you shouldn't feel any flow thru the upper rad hose until the temp gauge is near the normal temp range (middle of the gauge). The normal operating temp for the 3.8L is 195-220. The information I found for the 2007-2011 3.8L calls for a 190-degree t-stat. This means when the temperature hits around 190, the t-stat should open and allow coolant flow thru the engine.

Remember, the t-stat is a mechanical device that opens due to the temperature of the engine. There is a wax cylinder that expands when the engine heats up. When it expands, it pushes a valve open and coolant begins to flow. Nothing having anything to do with the temp sensor is involved in the function of the t-stat. Your engine may be operating at the correct temp, but a bad temp sensor is giving you a bad look at the temp gauge.

Question:
Is the temp gauge giving the same indication now as it was with the old t-stat? If the answer is yes, I'd be more inclined to think the temp sensor is bad and not the t-stat. And it would further confirm this if you don't feel any coolant flow thru the upper rad hose when you start the engine and it doesn't begin to flow until the engine is warm.

 

[Ivycon]

Sorry, misread your statement.

Here's the easiest diagnosis that will eliminate or confirm the t-stat needs to be replaced:
1. Have someone start your vehicle cold while you wrap your hand around the upper radiator hose.
2. If you immediately feel coolant flow thru the hose, the t-stat is stuck open. This means there is coolant flowing thru the engine before it's necessary and is preventing it up from heating up to the proper operating temp.
3. If you do not feel any coolant flow thru the hose, continue to hold onto it until you do feel flow. You need to know what the approximate temp is, or where the temp gauge is when you begin to feel the flow.

If your t-stat is okay, you shouldn't feel any flow thru the upper rad hose until the temp gauge is near the normal temp range (middle of the gauge). The normal operating temp for the 3.8L is 195-220. The information I found for the 2007-2011 3.8L calls for a 190-degree t-stat. This means when the temperature hits around 190, the t-stat should open and allow coolant flow thru the engine.

Remember, the t-stat is a mechanical device that opens due to the temperature of the engine. There is a wax cylinder that expands when the engine heats up. When it expands, it pushes a valve open and coolant begins to flow. Nothing having anything to do with the temp sensor is involved in the function of the t-stat. Your engine may be operating at the correct temp, but a bad temp sensor is giving you a bad look at the temp gauge.

Question:
Is the temp gauge giving the same indication now as it was with the old t-stat? If the answer is yes, I'd be more inclined to think the temp sensor is bad and not the t-stat. And it would further confirm this if you don't feel any coolant flow thru the upper rad hose when you start the engine and it doesn't begin to flow until the engine is warm.

No worries, thanks for the detailed response and your time!!! We must figure this out.

That all makes plenty sense when explained. Roger that to that process. I will try it when I get home this evening.

Correct, the gauge was acting up previous to the new T-Stat and as mentioned.

--- More detail to the story, during the low temps on the gauge. ---
One day when I was idling at "park" in a parking lot the engine started to overheat. I felt the Jeep getting really rough at idle looked at the gauge and it was past the middle mark. My fan had never kicked on either. Water boiling like crazy. I turned it off for 15 turned it on and it was still rough, but I put it in drive and it the rough ride went away. After that day, there was a couple of times at parked idle the temp would rise again. But as soon I it would be in "Drive" it would drop a lot. So my first attack / friends recommendation after that experience was a new t-stat and at that point (just went ahead and changed the water pump.)

Not sure if this help diagnose the situation. But, I live in GA and we previously went through some cooler weather than usual for us. The wrangler would really struggle to start in the mornings. Now that we are back in the 50s in the mornings, it starts right up first attempt.

After typing this all out and thinking about it, could this be an issue with the radiator? Pressure issues?

This Wrangler has taken us on some amazing adventures and would love for it to take us on even more.

 

[BLACKJKU]

No worries, thanks for the detailed response and your time!!! We must figure this out.

That all makes plenty sense when explained. Roger that to that process. I will try it when I get home this evening.

Correct, the gauge was acting up previous to the new T-Stat and as mentioned.

--- More detail to the story, during the low temps on the gauge. ---
One day when I was idling at "park" in a parking lot the engine started to overheat. I felt the Jeep getting really rough at idle looked at the gauge and it was past the middle mark. My fan had never kicked on either. Water boiling like crazy. I turned it off for 15 turned it on and it was still rough, but I put it in drive and it the rough ride went away. After that day, there was a couple of times at parked idle the temp would rise again. But as soon I it would be in "Drive" it would drop a lot. So my first attack / friends recommendation after that experience was a new t-stat and at that point (just went ahead and changed the water pump.)

Not sure if this help diagnose the situation. But, I live in GA and we previously went through some cooler weather than usual for us. The wrangler would really struggle to start in the mornings. Now that we are back in the 50s in the mornings, it starts right up first attempt.

After typing this all out and thinking about it, could this be an issue with the radiator? Pressure issues?

This Wrangler has taken us on some amazing adventures and would love for it to take us on even more.

Have you tried changing the water temps sensor that the ECM reads, i'm thinking someone else did that and fixed there issue.

 

[Ivycon]

Have you tried changing the water temps sensor that the ECM reads, i'm thinking someone else did that and fixed there issue.

Not yet, was hoping to do that this weekend! Kind of would make sense considering the fan didn't kick on the one day it started to overheat.

 

[Anybodyhome]

Have you tried changing the water temps sensor that the ECM reads, i'm thinking someone else did that and fixed there issue.

Not yet, was hoping to do that this weekend! Kind of would make sense considering the fan didn't kick on the one day it started to overheat.

The temp sensor and the ECM are responsible for switching the radiator fan to high speed when the temps get too high. The fact your fan was not kicking into high speed when the temps went up is another indicator the temp sensor is to blame for the issues.

Add that to the results of your radiator hose flow test and we'll go from there. The fact it cooled off when you drove comes from the fact air is circulating around the radiator, has nothing to do with the radiator or water pump functionally.

Am I correct in understanding that your temp gauge is now steady below normal, with no overheating? Even while stopped at idle? Remember, it only hurts the engine when it gets too hot. You'd be hard-pressed to do any damage when it runs 15-20 degrees below normal.