1982 300D Running Too Cold - PeachParts Mercedes-Benz Forum

DetroitFlyer · #1 01-23-2011, 11:55 AM

My 1982 300D struggles to get much past 40 degrees C. Sometimes, sitting at idle or with lots of gas pedal such as driving uphill, it might approach 60 degrees C. My heat is blowing cold on these frigid days, (0 to 15 degrees F), here in Metro-Detroit. My heat is only blowing out of the side vents as well, no floor vents. Makes for some cold toes on longer drives.... From searching the forums, I am thinking that maybe a new thermostat and some vacuum work for the floor vents? I think my temperature gauge is working as I recently lost the fan belt and the gauge went up right away. With no fan belt I actually had warm heat, LOL! Since my heat is so poor currently, I'm not certain about the monovalve, but from what I can tell, that seems to be working OK. It sure is fun keeping a 30 year old car as a daily driver....

pj67coll · #2 01-23-2011, 12:03 PM

Quote:

Originally Posted by DetroitFlyer

My 1982 300D struggles to get much past 40 degrees C. Sometimes, sitting at idle or with lots of gas pedal such as driving uphill, it might approach 60 degrees C. My heat is blowing cold on these frigid days, (0 to 15 degrees F), here in Metro-Detroit. My heat is only blowing out of the side vents as well, no floor vents. Makes for some cold toes on longer drives.... From searching the forums, I am thinking that maybe a new thermostat and some vacuum work for the floor vents? I think my temperature gauge is working as I recently lost the fan belt and the gauge went up right away. With no fan belt I actually had warm heat, LOL! Since my heat is so poor currently, I'm not certain about the monovalve, but from what I can tell, that seems to be working OK. It sure is fun keeping a 30 year old car as a daily driver....

Sounds like my 240D used to be. I replaced the thermostat and it's temperature went up to normal right away and it behaved perfectly after that. Can't comment on your HVAC issues though.

- Peter.

toomany MBZ · #3 01-23-2011, 01:00 PM

^ Agreed, a t'stat issue.

leathermang · #4 01-23-2011, 01:06 PM

I agree with the Tstat and the vacuum AC flaps deal..
but while you are down there...
if you can do a thorough flush of just the isolated heater core ( both directions, multi times) ...on cars this old.... sludge ' precipitates out' at the low spots in the stream.... and you can have a 30 year old car which had few proper engine flushes and no actual heater core flushes... something to think about when you are down there anyway....

Biodiesel300TD · #5 01-23-2011, 01:20 PM

I 4th the thermostat!

Stevo · #6 01-23-2011, 04:28 PM

I'll take the 5th

Jeff B · #7 01-23-2011, 04:55 PM

Ha, ha Me thinks you should change the thermostat...

layback40 · #8 01-23-2011, 06:17 PM

X6 on the thermostat.
You probably killed it completely with the over heat when the fan belt broke.

thayer · #9 01-23-2011, 07:06 PM

Temp sender?

HA!

leathermang · #10 01-23-2011, 07:36 PM

Would a/the temp sender affect the opening of the valve to let hot water into the cabin heater core ?

Biodiesel300TD · #11 01-23-2011, 11:56 PM

Quote:

Originally Posted by leathermang

Would a/the temp sender affect the opening of the valve to let hot water into the cabin heater core ?

No, I think thayer just wanted to say something other than t-stat.

josha37 · #12 01-24-2011, 12:00 AM

um... upper radiator hose!

leathermang · #13 01-24-2011, 12:02 AM

UM

Quote:

Originally Posted by josha37

um... upper radiator hose!

WHAT ?

josha37 · #14 01-24-2011, 12:13 AM

im sorry it must be the lower how silly of me

leathermang · #15 01-24-2011, 12:21 AM

I have heard of the lower hose losing its metal spring brace to rust...and thus... under suction...which it is... collapsing...and causing hard to diagnose overheating... because it only does it when the engine is not at idle... but have never heard of a way for it to cause cold engine problems.....?