2003 300m special overheat
 

Having a problem.. 300m special overheating. Takes about 5 minutes to get to normal temp. If idling, stays at normal temp, idle up between 1500 and 2000, starts to climb after about two minutes, turn heater on, drops down to normal. even with idle speed up, takes a little bit to climb. Turn heater off, wait, temp starts back up again, no more than 3/4. turn heater back on temp drops back to normal. Shop advised bad head gasket and to repair, I could by new engine. No leaks anywhere, fans are working as they should. Oil remains clean. Recently replaced: spark plugs, cam sensor,crank sensor and one O2 sensor, just about 700 miles ago. current mileage 131800. Water flow in reservoir is good.

ecently replaced: spark plugs, cam sensor,crank sensor and one O2 sensor,

have nothing to do with the car over heating.

when the temps gets to about 210 thats when the heads are so hot the head gasket is what really takes the pressure. If the heads are warped enough the gas will escape out in the coolant or oil or something.

if you have the ac on all the time will it over heat then?

sorry for the delay... work schedule.. No the A/C is not on while overheating. Thought maybe bad thermostat, took the cap off the reservoir and ran car. Once it started getting warm, appears that thermostat is working fine. Going to get back to the car this weekend.. thinking, bleed the system first, then go from there. I had though for sure the shop I took the car to would have done that, but after some of the commits I have seen on here, maybe they didn't. As for the overheat, gauge never did hit red, so don't think any head damage happened. Just trying to avoid having to tear into it and start replacing parts.

I have a 2002 300m that is having the same overheating problem as long as I run my heater and don't go too far I don't have a problem red lining I have been told to check the coolant switch or the coolant sender. I was also told it might be a water pump malfunction due to a bad belt. I haven't had a chance to check these options out yet but hopefully one will work for you.

ok a little few things First if you see the coolant temp in the red and car is over heating the coolant sender,or switch or what ever some one wants to call it is doing its job. possibly a water pump yes it usually will make it over heart real quick even when sitting still.