Boiling Coolant in Reservoir


Happy to be part of Car Talk.

2006 Chrysler Sebring Touring 2.7 L ( 160.000K)

I replace the coolant bleeder housing,which blew up a 1 month ago,it was last replaced 3 years ago, however since then coolant keeps boiling in the reservoir. I took the car to the mechanic and they cant seems to find the problem, Mechanic said its the fan Not Coming as it should automatic, however they can connect the fan to work once the engine starts( but I want to solve the problem the right way)

I have already replace the Radiator cap with the correct one.
Using Prestone green coolant( 50/50 mix)

Test the mechanic done.
1 coolant temp sensor is working properly ( he sees the temp rises when the OB2 connect to the car.) at 250F Coolant starts to boil and fan not coming on.
2 There is no leak in the coolant systems.
3 connect fan directly with 12 v it works
4 the car AC is working
5 The temperature gauge on the car dash board its at 1/4
6 Top rad hose is hot, bottom is warn, i check then after driving.
7 When the car is left park and running both hose are extremely hot

The car only boil coolant when I leave it park for more than (1 hours ) with the engine running ,when driving I don’t have that problem.


  1. I can smell coolant burning when driving, through the heat vent ( scare the car will over heat so I drive will the heat on)

Notice: coolant on my drive way last Thursday, but then is stop leaking, jack up my car to see where the leak is coming from can"t seems to find the leak source, however I notice on the water pump there is a black stain, to what I have read that normal( not sure ) no visible sign of the green coolant .

Drove the car for 3 day with the coolant reservoir on the low mark on the bottle( at the time there was not smelling of burning coolant, however I tap up the coolant Reservoir and now i can see a little coolant on my drive way this morning before leaving home.

Thank you and any help will do


Based on what you say and have done, I would say there is a strong indication you have a head gasket problem. The “boiling” coolant may be combustion gasses finding their way into the cooling system.

The engine you have is known to have these problems.

Get a COMPETENT mechanic or cooling system specialist to determine exactly what the problem is.

The coolant isn’t boiling, it’s bubbling, probably from exhaust gases getting in the cooling system from a blown head gasket. A good shop should be able to diagnose this.

Edit - I agree with @asemaster - until the fans are fixed you’ll have this problem. And if the system has been pressure tested and passed, then it’s not the head gasket.

Well the first problem is that your cooling fans aren’t coming on. That needs to be fixed. Since you say the problem only happens when you leave the car parked and running and doesn’t happen when you drive it I think there may not be a head gasket problem.

Tell your mechanic to fix the fans properly, not by hot-wiring them. If he can’t seem to figure that out then he’s not a competent mechanic. Ask your friends, neighbors, and coworkers for the name of a reliable independent garage.

Thanks Guys
Compression test confirm is not the Head gasket, also the Oil is good no milky stuff, nor tail pipe issues, I don"t have any lost of power to the vehicle( it run great )except for the coolant system.
As for the Fan he said he think its the Pcm, but he not sure( I don’t want to replace the PCM if is not 100 % sure
Coolant is Boiling and Steam is coming out from the little hole on the coolant Reservoir.

For sure I will find another Competent mechanic, just wanting a second opinion.

Thanks for all the Help

On the highway I can drive at 120 kilometre, with no problem.
Since the issue happen I only drive to work and back which is 30 K Daily ( 10 k on the highway )

“… I would say there is a strong indication you have a head gasket problem.”
“The engine you have is known to have these problems.”

Are you sure about that? Please give me your source that indicates this is a known problem with the Chrysler 2.7L.

I learned almost everything about these cars in the many years I owned and operated one.

Earlier versions (prior to say, 2004) of this engine had oil sludge problems. People who did not properly maintain their 2.7L engines developed sludge. I owned a 1999 Dodge Intrepid, purchased at 6,000 miles (rental) and ran to 250,000 + miles with no internal engine repair and no overheating, ever. I changed oil and filter every 5,000 miles using Havoline conventional 5w30.

I would have had overheating problems had I not caught coolant leaks at 2 different heater, coolant pipes that rusted through when they were over 12 years old. Both were a pain in the butt to replace. One was hard to get to off the back of the water pump outlet (pump inside timing chain cover) and the other ran under the upper intake manifold.)

Oh yah, some of these early 2.7s had timing chain guide problems when the coating wore off the guides, but mine never had a problem with guides/chains. These DOHCs had chains all over the place, too!

This was one reliable, extremely smooth, quite engine. This whole car was terrific, a family favorite. It was roomy and fun to drive. We were sad when it was replaced by a newer car in the family fleet.


Sounds to me like it could be a faulty cooling fan relay.

Thanks Jesmed1, I look at that video already

Sorry it not that, I forget to mention the mechanic swap then out, and same issue, that why he thinks its the PCM.He even pull the relay and the fan came on cool the engine down and shut off, as the PCM recognise its a fault, that why I don’t its the Pcm.

I bleed the car twice even jack the front of the car up to make the cooling reservoir the highest point,just in case there were trap air in the system to purge it.

What I read on the internet, is if there is air in the cooling system it will boil, air is getting in the system from somewhere.
The PCM monitor the Coolant Temperature sensor send the signal to the relay to make the fan comes on,( 212 F) but if there is air in the system the fan will not come on, cause air make the coolant boil.

I have just notice under the hood just above the coolant reservoir, that area is wet with coolant, there a few droplets on the top of the reservoir as well, could it be porous Coolant Reservoir Tank or a bad Temperature sensor as this Sensor is built in the part I change.

I not a mechanic but could it be a faulty thermostat, that close and open,when the park is been park and engine running.
I am planning to change the coolant reservoir, water pump, and thermostat 1 at a time to see what will help
First Thermostat
second Water pump
Third coolant reservoir and top rad hose

I will take the car to another Mechanic to hear what he has to say.

There is a fuse and a couple of relays for the fan. I would check or replace them before I bought an ecm.

Car only boil when car parked for more than 1 hour with motor running.

Why would you do that?

The coolant bleeder housing blew up, so I wanted to investigate as to why that happen, from that I found two issues.

  1. The fan not coming on to cool the engine.
  2. Car boil coolant after running in park, 1 hour with motor running ( this test was done during the winter months) - 20 Weather

Thanks for asking

You need to find a mechanic that understands the interaction between the car’s components. The PCM should command the fan on–if the relay is good and there are both power and ground present at the relay cavity, it COULD be the PCM at fault, but a competent mechanic would look at the wiring diagram and check to see if there is output at the PCM connector terminal associated with powering (or grounding as the case may be) this relay. He or she needs to TEST, not just plug in parts. On some cars the body controller module also has a hand in whether the cooling fan runs or not.

Like others have said, the fan needs to be fixed first. With summer coming up, this isn’t going to get any better and you will soon have a head gasket problem if you aren’t paying attention and it overheats.

Hello I jack up the car a few hours ago as the weather was nice
started the car open the reservoir cap and let the engine warm up ,as the engine warm I see coolant leak so I went under the car and found it was comming from the thermostat area it leak a little and then it stop , could it be that its sucking in air from the leak and that was causing the coolant reservoirs to boil
I cant get to see clearly as the alternator is blocking my view.
I will let the car sit overnight and do the same and see what happen
I will change the thermostat next week or tomorrow at the mechnic as I cant handle that job. The alternator
have to be remove first
any help will be appreciated

the Pcm circuit to the fan is good no issuess found by mechnic specialist.

Happy Good Friday

“…I see coolant leak so I went under the car and found it was comming from the thermostat area it leak a little and then it stop , could it be that its sucking in air from the leak and that was causing the coolant reservoirs to boil”


…however I notice on the water pump there is a black stain,…

I don’t know if a 2006 2.7L is similar to my older 2.7L, but the water pump on mine was run by the engine timing chain and is covered by the timing chain cover. Only a small weep hole is exposed to the outside. Be sure the water pump is not leaking. I don’t remember the proximity of the weep hole to the thermostat, but I think it was behind the power steering pump, above the alternator.


I Took A Look. Your 2.7L Water Pump Is Inside The Timing Chain Cover As I Stated Above. Be Sure It’s Not Leaking. A Leaking Pump Can Behave As You Describe. Also, It Could Completely Let Go And You’ll Do Major Engine Damage.

Be sure that a mechanic who is completely familiar with this 2.7L and it’s cooling system checks this out as soon as possible. I can’t advise driving it.


I haven’t change the water pump or nothing in regards to the cooling system, the car still leak coolant, every 2 weeks I have to put approx 1/8 to 1/4 of a coke can of coolant, also there is no issues with the fan is working great, and it not overheating and the leak in not getting worse, it about 6 months now.
If its the water pump leaking, i believe it would have fail by now.
Any idea what the cost is to repair the water pump in Toronto including labor.


I had a similar problem with a 2002 Chrysler v6 that turned out to be a cooling fan control module. I looked at rock auto and they list several fan control modules for your car but they all look like aftermarket products. I suspect but don’t know that your pcm controls the fan and these may be a workaround for a pcm that is no longer controlling the fan.
Check with your Chrysler dealer and see if your car had a fan control module. If it didn’t, one of these may work for you. Or replace the pcm. Know anyone with a similar car you can temporarily swap pcms with?

Thanks for your reply, however the PCM control the fan, and the fan is working great, it comes on and off when needed.

Can you explain a little more if you don’t mine as to why you think it that.

I am not a mechanic, jusst wanting to ensure that i spending my money to fix the correct issue

My suspicion is that if the coolant is boiling without the engine overheating, 1) you’re lucky 2) don’t count on it continuing to happen like that because if it boils long enough you will overheat, and 3) it’s because there’s an opening somewhere in your system that’s allowing it to depressurize, which in turn allows the boiling to happen.

If there’s coolant coming from around your water pump then you need to look at replacing the pump. It might keep going like that, with just enough of a leak to boil the coolant, for awhile, or it might fail catastrophically tomorrow. You don’t know, and boiling the coolant isn’t good for your car at any rate. If the pump is leaking, get it replaced.