My 300sd usually runs about 80* all the time and I have been having the typical no heat problem. I replaced the monovalve which had a missing diaphragm now there is heat, but its weak. I felt the upper radiator hose after a 20 mile trip from work in traffic and it wasnt really hot. I squeezed it a bunch and I could see it was purging some air to the resovoir and it started to get hotter. I had the heat on the whole time and the hottest I could get was 120* out of the vents. I remember the 420sel heater getting so hot it would burn your finger if you stuck it in the vent for too long. I remember something like 150* coming from the heater. I shut it down for a couple hours and then went for a cruise later and the car would stay at 80* while the heater was off but as soon as I turn the heater on the temps drop below 80* and the heater still is around 120* at the vent. Its 45* outside. Since I have seen the temps get a little hotter than 80* but mostly hanging in around there and never overheating during the summer I assume I have a properly working cooling system. I just dont know if I have a bad thermostat or just air bubbles. Ive done some searching but I got distracted by a Dokter Bert/Leathermang thread that was very intresting so I may not have done a good job there. Sorry. Also, I noticed that one of the oil cooler lines is weeping a wee amount of oil. I know those could spell the death of the engine but how long would you say these can weep oil? I just spent quite a bit of cash already so I am trying to let the finances recoup for a few weeks before I drop another couple hundred to get the new lines. What do you guys think?

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1984 300SD Orient Red/ Palomino
1989 560SEC
2016 Mazda 6 6 speed manual
1995 Ford F-150 reg cab 4.9 5speed manual

leaking oil cooler lines should be attacked asap. sorry.
they could last a long time, or fail next time you hit 50mph... no way to know.

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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 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

yeah I pretty much figured that already but had to ask. sigh
This car will be the end of me just like the last one!

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1984 300SD Orient Red/ Palomino
1989 560SEC
2016 Mazda 6 6 speed manual
1995 Ford F-150 reg cab 4.9 5speed manual

That would almost qualify as a Yogi Bera imitation.

Both my w126 diesel and w140 with a 180 thernostat run cool.They have a 160 degree,170 degree and 180 degree for my m104 motor.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran

It sure sounds like the thermostat is stuck open. Easily checked by removing and testing in a pot of water on the stove. (Don't use a cooking pot!)

Also, you may be able to find a hydraulic hose shop that can repair those oil cooler lines. It would be a good idea to search the forum to find out what details you need to know beforehand.

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Sam

84 300SD 350K+ miles ( Blue Belle )

Yeah I searched about the lines and I'm afraid to do em now. Too many problems with em leaking..

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1984 300SD Orient Red/ Palomino
1989 560SEC
2016 Mazda 6 6 speed manual
1995 Ford F-150 reg cab 4.9 5speed manual

Sounds like a bad thermostat.

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2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

Annoy a Liberal, Read the Constitution

Is your aux fan hard wired or stuck on?

actually no i disconnected it as my ac does not work.

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1984 300SD Orient Red/ Palomino
1989 560SEC
2016 Mazda 6 6 speed manual
1995 Ford F-150 reg cab 4.9 5speed manual