So my father's '01 Chysler 300m is overheating.

[TheVrolok]

Hey all, my first post in The Garage as I'm not much of an automotive guy but my dad is having a hell of a time with his 300m.

Per him:

I have an '01 300M since new. Has 180k on it. Has been meticulously maintained. I have an overheating problem. It will run perfectly at the usual temperature(slightly below half way) for about 20 miles and then overheats. After letting it cool down it may run fine for a day and then overheat again. T-stat been replaced(twice), water pump replaced, head gaskets checked ok, radiator removed and flow tested, again ok. Radiator Flushed (and has been every 30k).

Figured I'd try to run it by you guys just to see if I could get a bite. He has tried posting on another forum, but it is nearly as busy at AT. Thanks for any advice/thoughts in advance, appreciate it AT.

 

[halik]

Is it losing coolant?

 

[shabby]

I would guess the head gasket but you mentioned its fine, i take it they did a leak down test?
What about the coolant temp sensor?

 

[evident]

like halik said, see if its losing coolant. and also check the oil levels, is it burning through oil?

 

[CurseTheSky]

Does it usually overheat during a certain condition, such as when parked or stopped at a light? Does it overheat regardless of speed (on the highway or on back roads)?

If it never overheats on the highway or almost always overheats when stopped or parked, my guess would be the fan(s) aren't kicking on. It might be an easy fix (fuse), and it's easy to diagnose, so it's worth a look.

 

[drnickriviera]

Are you sure it's actually overheating? I know some clusters these days aren't attached to anything, they just display what the computer tells it to.

 

[Bignate603]

I spent a month trying to figure out why an old jeep was overheating. It was driving me nuts. I finally figured out it was the stupid gauge and not the engine at all.

 

[SparkyJJO]

Try replacing the temp sensor, I'm guessing that is just bad considering all the other stuff has been checked out.

 

[woodie1]

Another vote for the temperature sensor or the gauge itself. Ask him if the fuel gauge goes up at the same time the temp rises. Some clusters use reduced voltages and if the voltage regulator for them fails the the gauges give false readings.

 

[exdeath]

Was the cooling system filled and bled properly after the previous work was done?

Most late model cars need to be filled from a bleed port or cross over tube that is the highest point in the system, not the overflow tank. Then you need to keep an eye on it daily for about a week, topping it off from the bleed port to ensure all the trapped air gets burped out.

Air pockets are worse than general overhearing as the heat occurs in localized areas that aren't receiving any cooling.

If the fans are coming on and you can feel high current flow in the upper hose after it's up to temp, there isn't much else that can go wrong.

 

[boomerang]

Good suggestions and I'll add one. The lower radiator hose may be collapsing. There is usually a wound wire in a lower hose to keep it collapsing from the suction that is created. These springs can get partially sucked up into the engine. They can't get pulled in far enough to interfere with the vanes on the water pump, but they can get go in enough to leave enough radiator hose unprotected that it can snap closed and impede coolant flow.

The temp sensor suggestion should be easy to diagnose with a scan tool connected. There is a coolant temp sensor for the computer and a sender for the dash. The scan tool will show the sensor. Drive the car until it's overheating and compare the temp on the scanner with the gauge on the dash. The temps should be very close to each other. I'm betting the dealer already did this.

 

[bruceb]

Could be the radiator pressure cap is bad. Or possibly the electric cooling fans are not coming on when they should. There is a sensor that tells the engine computer when to turn them on. Usually around 200 deg or so depending on the design.

 

[DivideBYZero]

My Golf V6-4motion overheated because the fan fuse had blown and the electric fans never came on.

 

[Dr. Detroit]

I would suspect the overflow tank is cracked.

Had a '98 Concorde with the 3.2L (same platforma s the 300m) the overflow tank cracked and the radiaotr cracked at 110K miles of use or after 9yrs of age.

Cracked along the seams so it was difficult to see.