My 93 500SEL is overheating
 

I have replaced the radiator, thermostat, hoses, radiator cap, water pump, fan relays and my 93 500 SEL still overheats. For about 15 miles the temp holds at about 85 degrees C. Then it starts to climb and will vary between 100 and 110C, sometimes dropping back to 85, sometimes not. Driving or parked does not matter. Air temp does not matter. At some point the temp will raise to 120 and I hear boiling - but do not lose fluid. No foaming in oil. No water in oil. No oil in radiator. HELP!!

Are you sure the fans are engaging at the proper times? 100 degrees is normal, even 110 is considered normal, but anything above that and I'd get a little skeptical.

Good luck.

Agree with David. . .
 

check your fans: let it idle in the driveway with hood down, a/c OFF, etc. When the temp gauge shows around 100C, the fans should come on.

With the A/C on, the fans should start almost immediately if the car is 'warm' (80C or higher). The pressure switch should cause the fans to turn on.

Do a search for related articles on the subject.

500 overheating
 

try replacing the fan clutch. If it is not coming up to a ROAR with 100 degree temp, it's not working.

Lots of overheating this year! Check other threads ... several other folks are having same kind of issues.

My understanding is that fans are not the issue if the car is overheating during normal driving ... i.e. there is air flow over the radiator. Usually, can only be: radiator, pressure, thermostat ...

Chances of a bad radiator are limited ... and costly. Chances of a bad tstat are better and pretty easy to replace at less than $20.

You hit all the normal stuff already ... have it pressure checked, maybe (grasping at straws here)?

Broken neck on overflow tank? Too high ratio of coolant to water (although this would more likely be on the margin, I guess).

Keep this thread going, please.

Let us know what happens and how it gets fixed.

Possible thermostat you installed was bad? Can happen.

Just look at my post... just about identical with my 560 SEL (but I'm betting that its the radiator). I bought a new Nissens radiator a little over a year ago and it LOOKS fine but when I reverse flushed it, I got little white particles coming out of it and although it doesn't run hot as quickly as it did, it still does because I probably didn't get enough of the crap out of the clogged radiator and it is still restricted enough to warrant the higher temps...

Did you feel your radiator for cool spots after you stopped your engine? I'd feel around the radiator (in the direction the fan blows) and would find that it would be cool on one side and while running my hand along the radiator, would get hot as hell itself to where I'd damn near burn myself. Check it and see if the same happens with yours. I've got a new Behr on the way now because my old radiator worked just fine (the neck's just shot so I don't want to chance it like the PO did). Before that I also changed the thermostat,coolant tank, cap, etc but just because the radiator's "new" doesn't mean it can't fail--just like thermostats. Good luck

Alan

Just look at my post... just about identical with my 560 SEL (but I'm betting that its the radiator). I bought a new Nissens radiator a little over a year ago and it LOOKS fine but when I reverse flushed it, I got little white particles coming out of it and although it doesn't run hot as quickly as it did, it still does because I probably didn't get enough of the crap out of the clogged radiator and it is still restricted enough to warrant the higher temps...

Did you feel your radiator for cool spots after you stopped your engine? I'd feel around the radiator (in the direction the fan blows) and would find that it would be cool on one side and while running my hand along the radiator, would get hot as hell itself to where I'd damn near burn myself. Check it and see if the same happens with yours. I've got a new Behr on the way now because my old radiator worked just fine (the neck's just shot so I don't want to chance it like the PO did). Before that I also changed the thermostat,coolant tank, cap, etc but just because the radiator's "new" doesn't mean it can't fail--just like thermostats. Good luck

Alan