I have a 1980 300 SD and, since I bought it I have had great difficulty in getting good heat. I have had the original control mechanism replaced with an aluminum unit. I have flushed the radiator. The mechanic that just worked on my car said I probably have a problem with the heater core. Or, there might be little "doors" in side that are not functioning. Maybe there is someone out there that has had that model and that problem. Rev Wallace Schulz

I've got two bad rebuilt servo's in my trunk ready to send back, they are notorious for failures.

I finally gave up and bought the electronic control from Performance Products, all works fine now.

I talked to the inventor of the control and he said he was motovated by putting the 5th servo on his car.

See if your servo is allowing flow and make sure the auxillary pump is functional.

I replaced the servo about five years ago with an aluminum unit with a lifetime guarantee. But even with this replacement I was unable to get the heater going. I also had the help of a veteran Mercedes mechanic. But, we still have not been able to solve the problem. Is it possible that the heater core could be so cacified that the core no longer works as an effective heat exchanger? It does heat some, but only barely. WRSchulz

is the control unit and amplifier behind the glovebox still good?? are the lines going through the firewall hot to touch?

__________________


1980 500SE/AMG Euro
1981 500SEL Euro
1982 380SEL
1983 300TD
1983 500SEC/AMG Euro
1984 500SEC
1984 300TD Euro
1986 190E 2.3-16
1986 190E 2.3
1987 300D
1997 C36 AMG
2003 C320T 4matic

past: 1969 280SE 4.5 | 1978 240D | 1978 300D | 1981 300SD | 1981 300SD | 1982 300CD | 1983 300CD | 1983 300SD | 1983 380SEC | 1984 300D | 1984 300D | 1984 300TD | 1984 500SEL | 1984 300SD | 1985 300D | 1986 300E | 1986 560SEL | 1986 560SEL/Carat | 1987 560SEC | 1991 300D 2.5 | 2006 R350

Are you vertain your aux water pump works?
I bought a few bucks worth of heater hose, and bypassed that stupid thing.
Got heat now.

__________________
Think Alternative Energy!
300CD '80 (now gone but not forgotten...)

Monovalves can be had on eBay for ~$16.

__________________
Michael LaFleur

'05 E320 CDI - 86,000 miles
'86 300SDL - 360,000 miles
'85 300SD - 150,000 miles (sold)
'89 190D - 120,000 miles (sold)
'85 300SD - 317,000 miles (sold)
'98 ML320 - 270,000 miles (sold)
'75 300D - 170,000 miles (sold)
'83 Harley Davidson FLTC (Broken again) :-(
'61 Plymouth Valiant - 60k mikes
2004 Papillon (Oliver)
2005 Tzitzu (Griffon)
2009 Welsh Corgi (Buba)

116's don't use monovalves.