overheating 450SL
 

Hi Folks,
Any one have a suggestion on solving the overheating problem on my 77 450SL?
What I've done so far:
changed the thermostat
had the radiator redone
changes all the hoses
put in new red coolant
tuned up the motor
The radiator doesn't boil over, but the temperature gauge goes up to the 3rd mark, just before hitting the red mark. The heat seems to build after cruising speed is maintained and then the heat builds while stopped.

Re: overheating 450SL
 

I have a 78 450 slc that was overheating. I did the usual, but what fixed it was a new 15 lbs. cap. It still runs a little hot but doesn't loose fluid anymore. I live in Palm Springs and it is 115 outside so most cars run a little hot.

Hope it helps!

What caused you to do all the work initially? Where does the temp run when it is working correctly? What was the "failure mode" ... did it just "happen" one day or did it get slowly worse?

Does it overheat while constant state 60 mph on flat road? If not, and it only overheats after you come to a stop, it could be viscous-clutch fan (don't know if you have one of these or if you have a magnetic clutch fan) ... unless your temps are real high, you may not even get to the temp (around 105C or so) that will kick on the electric fan ... could be a bad tstat (sometimes happens) ... was it mounted correctly (they have been put in upside down ... on the other hand, I don't know if it would run without overheating in this case even on the road at 60 mph level) ...

You are in luck, though ... there have been many overheating stories this year with lots of good information being passed on the various overheating threads.

Worst case is that it is not a cooling issue, but a head gasket issue.

Check the ; cap, auxillary fan and coolant ratio.