are you certain the fan blades are oriented the correct direction? of course it spins the correct direction, it's attached to the serpentine belt, it has no choice but to spin that direction, but if the blades are oriented the wrong way, you could be blowing instead of sucking.
just something to check.
sounds like you are searching for ANY reason for the heat.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

I had the same problem with my 1987 300SDL, I replaced both hoses, thermostat (drilled three holes), Radiator, citric flush multi times new water pump. Then I checked the fan clutch and it was bad. I ordered one from Phil, and replaced it. Know I can have my A/C on in stop and go traffic, and she sets just a hair above 80 C.

But they are right, the cooling system on these MB aren’t the best. I would expect a larger more powerful electric fan upfront.

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Professional greasecar installer
Austin TX


98 Jetta TDI with grease car kit + veg-therm (totaled)
87 MB 300SDL running on B99 / greasecar kit + 30 fphe
www.austingreaseguys.com

Just to update on this issue...

Thanks everyone for your help and ideas. The problem ended up being cracks in the original #14 head.. at first I thought about replacing it with a used one, but decided to just go with a new #22 and eliminate it as a concern going forward. The car is in such good condition otherwise that it would have been wasteful to junk it, and I figure it should now last roughly till my kids are in college, lol. The repair will be right around $4k.

Anyway thanks again. Hopefully some of your suggestions end up being the fix for someone else having similar symptoms.

Glad to hear the problem was solved. The important thing for others to remember. Is that I believe there were no other indications of a cracked head other than the operational temperature was generally too high to be comforatable with.

Tough call to pull the head if there is nothing else indicating the fault. On the other hand you pretty well had already covered probably all other possible external faults.

It is a real shame mercedes did not get a good reliable head casting in production with the 603 type initially. The result has been a lot of grief for a lot of people.