500E still running hot - PeachParts Mercedes-Benz Forum

aldedmon · #1 06-29-2010, 02:51 PM

New Behr radiator, New Fan Clutch, new thermostat, new coolant, New Rad Cap..........and the Damn thing is still running warm. when all is cool, can ride around the neighborhood and the temp is right at 85. Get out on the highway in houston heat at 80 and the temp climbs to 100+. Get off the freeway and slow down and temp starts heading down but hovers around 90.....Please let me hear all / any suggestions......

Kyle Blackmore · #2 06-29-2010, 02:56 PM

It sounds like you might still have some air in the system. Did you bleed the engine as you 'slowly' filled the overflow tank?

aldedmon · #3 06-29-2010, 06:51 PM

Read in another thread that this motor self bleeds. What's the best way to bleed the system

JamesDean · #4 06-29-2010, 08:07 PM

definitely sounds like air to me. I'm not sure about your specific motor however on my 617's I usually fill up the bottle to the mark, put the defroster on and drive around until it gets hot at the vent. Stopping every now and again to refill the coolant bottle. Eventually it'll stop emptying and the system will be complete.

Rahulio1989300E · #5 06-29-2010, 08:40 PM

On the M103 a trick that people have mentioned using is to squeeze and release (over and over) the radiator hose going from the thermostat housing to the top entry point of the radiator. This is done while the system is being refilled, but maybe some variant of this trick will work for an already filled car.

latief · #6 06-29-2010, 09:08 PM

when was your pump last changed? see my thread about overheating on the main page...all kinds of hints and advice from the great members over here....different car but same symptoms

lsmalley · #7 07-01-2010, 05:10 AM

did you try changing your coolant temp switch?

macdrone · #8 07-02-2010, 06:17 AM

All good ideas here that were mentioned, air is the main one and definatley water pump it it gets hotter at speed when it should be cooler. The thermostat could be bad out of the box , it happens alot.

Big ticket items you did not cover as the 500 is alot like my 400 is the reservoir and cap. Haairline cracks in an old tank will leak pressure cause boiling and a overheat state. So cap and tank are suspect. Also a awesome leak point is the washer reservoir heating coil. It will bubble and siphon winshield washer fluid and coolant back and fourth all day causing issues.

Temp sensor was mentioned but usually not an issue.

Hows your A/C charge? it controls low fan speed. How the aux fans running? check the fuse by the firewall? its just like the blower motor strip fuse.

How abbout your viscous fan clutch? When the oil leaks out of it, it should be spinning fast, if its freespinning then its not doing its job at 2000 rpm.

Lots of things but easy to check.

If you need help you can PM me and ill give you my number.

david s poole · #9 07-03-2010, 02:18 PM

based on your description of faster you drive-hotter it gets,if gauge is acurate,main probability is not enough volume of water through radiator.if you accidentally put thermostat in upside down or it is faulty[won't open but halfway and becomes a restriction to flow]this could cause low volume flow.