what temp should a '69 280se 6cyl run at?

[rtykw2]

I ask this because this car is new to me. I have not driven it much, however I replaced the water pump, thermostat, and flushed the cooling system with a flushing solution.

It is about 80f outside, and the car runs at the line above 175f, which is the last line before you get to the red 250f. While it is under the 250f mark, I am worried that when it is hot outside and the air is on, it will get too hot.

The thermostat was replaced with a 87c unit. At idle, and the engine hot, the top of the radiator becomes very hot while the bottom is cool. I also swapped fan clutches with one that is locked up hoping that it was due to poor air flow. The fins are clear.

I could drop another themostat in before I have the radiator boiled, but it is a PITA because this car has AC. I started all this because I had to helicoil the AC bracket back to the cyl head. One of the holes was already helicoiled and it is in poor condition. I do not want to remove the bolt unless I have to.

Is this temp normal on a cool day? Could I have a bad thermostat? Or could I have loosened up a bunch of trash and clogged the radiator up when I put in the flushing solution?

Any ideas are appreciated. Thank you.

[300SDog]

MB recommends flushing the radiator, cooling and inside heating system twice each year. Mechanics hate it because it trashes their shop.

I like the 6 hr. valvoline or prestone flush.... saw the guage gradually go down recently on trip using this stuff.

Also got myself one of those cheapo garden hose backflushing kits that hooks up in feeder hose that runs to heater valves. Trick is to *remove thermostat* and backflush after 6 hr. treatment when engine is cold. Also backflushed through several passages including out the radiator top and by disconnecting heater return line, even putting my thumb over heater return hose - letting it shoot out the engine until the water ran clear.

Another trick is to drill small 1/16" hole in lip of thermostat then point the hole at highest point as thermostat fits in housing. This will prevent air chamber from occuring.... some thermostats have this hole already.

Free turning fan clutch is designed to enable fan blades to spin faster than crankshaft when car is travelling at speed, helped by airflow. The device quit grabbing on my 280/8 and it caused rise in temperature at normal slower speeds. Had to get $50 junkyard replacement part..... more than $100 new, i think.

[ctaylor738]

I think you are running hot. I would expect around 180-190, maybe a little more sitting and idling on a hot day. Are you heating up while driving or idling? If while driving, I would suspect the radiator and go with a flush. If while idling, I would check out the fan clutch.

[rmasteller]

87C sounds like a pretty hot thermostat. When ordering for my 230SL last year, the dealer had 79C, 82C, and another hotter one (can't recall). I recommend the coolant flush and a cooler thermostat. I also recommend acquiring an owner's manual as it probably says what your normal operating temp should be. MB Owner's manuals have lots of good information in them.