I have a 2002 Sebring sedan with a 2.4 litre DOHC engine and about 180,000 KM on it. I use it to go to and from work, which is about 7 KM (4 miles) away. It takes me about 10 minutes each way, so needless to say I go through about a tank of gas a month. Many short trips and very few trips longer than 20 minutes.

Everything was working fine until about a two years ago. Up until that time the temperature guage would never rise up to the middle (normal) part of the gauge although I had plenty of heat in the car when I needed it and no overheating issues. I figured that maybe the gauge was worn but didn't think anything about it at the time.

I started to notice that the coolant level in the resevior was higher than normal, and the coolant level in the radiator was slightly low. I would transfer the fliud around so the rad was topped up and the resevoir was at the proper level. Keeping an eye on it I noticed that even after several short trips everything was fine, but if I took it on a longer trip and checked it the next day when the engine was cool, the resevoir level was high and the radiator level was low. I did notice that when I came back from a longer trip (20 minutes) and turned off the engine, I could hear a bubbling sound.

I replaced the raditor cap - no change
I replaced the thermostat - no change
I replaced the engine temperature sensor - no change
I had to replace the timing belt so I replaced the water pump - no change
I checked cylinder compression - all good and balanced
I presure tested the cooling system - no leaks, no pressure drop
I replaced the rad hoses and heater hoses - no change
I replaced the rad and THOROUGHLY flushed the system - no change
I took it to the dealership - no leaks, collant system pressure test good, rad cap pressure tested good


I am still noticing the same drop in the radiator level and a higher level in the resevior. When I transfer the coolant back to the raditor the level in the resevior is normal so I am not losing any coolant. I am running a water antifreeze mix so I am good to -40 (yes it gets that cold up here in the winter). I still notice that if I go on a slightly longer trip I can hear a bubbling sound when I turn off the engine. Also on the longer trips the temperature guage climbs to mid range and the cooling fans turn on.

So to sum up, I pretty much replaced everything, I am not losing fluid, pressure tests are fine, gauge reads lower than it should. After 20 minutes of driving the gauge is mid range, the fans turn on and when the engine is stopped there is a bubbling sound like the coolant is boiling. Local Chrysler dealership is as confused as I am. About the only thing I haven't done is replace the head gasket. Does anyone else have any ideas?

 

The coolant recovery system on the 2.4 L engine is supposed to allow coolant to expand into the reservoir when it's hot and then return to the radiator as it cools down. It sounds like yours is able to flow one way through the hose but has difficulty returning. That little hose leading from the coolant recovery reservoir may have some obstruction. It's a bit of a pain to get to but you might find that clearing or replacing that tube and making sure there's nothing blocking the pathway might solve the problem.

 

Thank you for the reply. Already checked the hose from the resevior, and I cleaned it and the resevior when I flushed the system. I cracked open the bypass valve and attached a vacuum pump to it. With 1-2 psi of negative pressure the rad cap would open and allow coolant to be drawn from the resevior into the rad system.

BTW I also tried some of that stop leak stuff after I replaced the rad hoses and there was no difference with that. I don't realy care for that stuff which is why I thoroughly flushed the system later.

I think that I first need to find out why the temperature gauge is reading low when the system is running hot. I have a partial wiring diagram showing the power to the radiator fans via the low speed and high speed fan relays, and how the temperature sensor ties into the PCM but I don't have the circuit for the temperature gauge. I looked all over the net but couldn't find that portion of the wiring diagram. If anyone has a copy of that portion of the circuit that they can send me I would appreciate it.

 

I did some more testing on the weekend. I pulled off the connectors to the PCM, cleaned all the contacts and reconnected them - no change.

I measured the collant temperature going through the return line from the heater core. The metal pipe portion of the return line was varying from 72 C to 83C ( 162F - 181F) so it looks like the thermostat is operating correctly in that it is opening and closing. The lines to and from the heater core get equally hot. The upper and lower rad hoses get hot as well.

I did notice that both of the rad fans would be off then both would turn on at the same time. Checking the coil resistance of the low and high speed fan relays, I found that the low speed relay coil had a lower resistance. I checked both relays and the contacts on both relays would close when 12 VDC was applied to the relay coils, so both were working. I purchased a new relay and found that the coil resistance was similar to the coil resistance of the high speed fan relay, so I replaced the low speed fan relay - no change.

I did more checking and I have 12 VDC going into the coil of both the low and high speed fan relays. The other side of the coil goes to the PCM, so a ground from the PCM will turn on the relay, and turn on the rad fans. I also have 12 VDC going to one side of the relay contacts on both relays so no blown fuses. I monitored the voltage on the wire from the output of the low speed relay going to the rad fans and found that it always stayed at 0 VDC. When I monitored the voltage from the high speed relay, it would stay at 0 VDC, then would go to 12 VDC turning on both fans.

So I am now begining to suspect a fault in the PCM. This would explain why my temperature gauge displays a value lower than it should, and why the low speed rad fan relay is not turning on.

Before I replace the PCM, does anyone have any other ideas?

 

I wouldn't be so cocerned about the reading of the gauge. I have owned 2 Sebrings (2001 and 2002) and both read a little below the middle of the gauge. (Both were 2.7 L V-6 engines.) They would eventually come up a little higher but it would take more than 10 minutes of driving.
The fans are controlled by the PCM. They come on at different temperatures and different conditions. The PCM takes into account not only the coolant temp but the A/C operation as well. If you are not overheating and getting good heat out of the heater, you might as well leave it alone.

 

Is the coolant level in the expansion tank definitely above the top of the radiator as this has been an issue i have seen in the past as the air tries to escape to the highest point in the system.
Dan

 

Well, it seems that a bulb in the dashboard blew and I will need to replace it. Since I have to pull out thr instrument cluster I'm going to clean the contacts from the instrument cluster to the wiring harness. Maybe that will get the temperature gauge to read correctly. Will keep you posted.

 

Well after ruling everything else I removed the head gasket. The head and the block were not warped and the head gasket was fine (no cracks or other wear/damage). I did notice though that there was absolutely no gasket sealant on the head, block or gasket. This seemed very wrong to me but it made cleaning everything so much easier. I installed a new gasket (with some sealant), put everything back together and after running the car for a few weeks, all is good now. Temperature gauge reads higher (about normal) and no leaks or air bubbles.

This is the original engine from the factory and was never rebuilt. It seems strange that there was no gasket sealant anywhere in this engine when I pulled it apart (there was no gasket sealant on the valve cover either). I suspect that over time the head gasket became separated from either the head or block and allowed air to enter the cooling system.

I think that if the engine manufacturer applied a bit of sealant when the engine was originally assembled, this problem would not have occurred. Maybe the engine manufacturer decided to save a few dollars by not using any sealant, and just relied on "dry" gaskets.

Has anyone else pulled apart an original engine and found that there was no gasket sealant on the head gasket or valve cover gasket?

 

I've been working on cars for over 40 years and although I've never taken a 2.4L apart in my experience sealant is never used on head gaskets.

John

 

your head is still warped the new head gasket just took up the slack of the old one. by a few thousands of an inch.