heater- themostat question

[edge]

My 1984 300D's heater doesn't get very warm. The heater does not seem to warm when I am at a stop. When I start moving again, it begins to warm but not hot enough...and I have it turned up to the max. Do I need a new thermostat? Is this relatively inexpensive? Thanks, guys.

[Capt Kirk]

whats the temperature on the temp gauge?

Hi all. I was just about to post a similar question. I recently purchased my first benz a 83 300d and while driving around town in 40 F weather the temp gauge stays between 40 and 80, a few minutes after getting on the highway the gauge reads at 80, then promptly returns to between 40 and eighty after slowing down. heat seems to be the same in town or on the highway, there is heat but never the blasting dry out the eyeballs kind.
thanks,
Gregg

If the coolant temp guage is not going up to a little over 80, you need to replace the thermostat. Not only will this effect your comfort, it's not at all healthy for your engine.

If your coolant temp is coming up okay, but the heater is not making warm air, you have blockage in the heater core or hoses, or the climate control/monovalve are at fault. The mono valve typically fails open, so that is probably not the cause of such a problem.

Good luck,

[edge]

My car operates around 76-80 degrees. Would this still be a thermostat problem? This is my first winter with this car. During the summer the air conditioning didn't get very cold but was adequate. In Sept, the heat would get too warm then had to be set cooler, then hotter, it needed constant manipulation. Now with the cold weather, the heater is inadequate and I leave it at the max! Thanks for your help.

[be459]

76-80 degree is low. As Larry said, it should a little over 80, at least. You need a new T-stat.

Happy Holidays.

David

[savagetom]

You may need a new thermostat but at 75 deg C (167 def F) you should be getting plenty of heat from the heater. Often the monovalve diaphragm fails allowing coolant pressure on both sides. It then opens irregularly or not at all. It is a cheap fix and you can get the part at Fastlane. Good luck.

[edge]

Thanks, guys....sounds like I need both, t-stat and monovalve

[300CE]

My 85 300cd has intermittant heat ; and blows cold very well as I haave changed out the compressor to the new type a year ago. I am also getting a moisture smell when the a/c isn't turned on. Tye temp gage stays above 80c. Any ideas?

[mplafleur]

Is there an electric circulation pump in this car as well? Make sure it is operating. It helps circulate the coolant at idle because the vane pump is insufficient.

[savagetom]

I don't have any direct experience on a 300D but I can tell you that on a 190D the auxiliary circulating pump is not needed. In fact, cars delivered in Europe didn't have one. Mine was leaking so instead of replacing it I installed a by bypass. I used a brass hose barb from Lowe's. I believe the size is 5/8".

The replacement pump is about $130 IIRC. Good luck.

Hey guys! How much does that circulation pump actually move the coolant? My '76 didn't come with one ,but I'm thinking up trying to put some type of pump inline, just curious about the "flow"?

Tom ( warm air when moving but not when sitting!, and when I'm moving I have at least one if not two windows open!)

ok now this has me really boggled. my thermostat is fine reading just over 80c. got a new temp dial,new blower motor even a new switching block or whatever you call it but check it out, I can get heat from the car sometimes really hot, sometimes luke warm however if my rpm's go over 4g on the tach the heat shuts off completely and will not come back on until I turn off the car and restart it which now; cause its cold consists of pulling over popping the hood and pushing the stop button. obviously a vacume problem there. but would the vac have any effect on the heat? I would love to hear some analysts on this one. it's getting pretty cold to drive 60 miles a day with out heat.
thank's for any ideas

j

[engatwork]

You need to fix the vacuum leak if you are having to pull over and pop the hood to shut it down. The underdash actuators are vacuum controlled and can cause problems similar to what you are talking about. Fix the leaks and I suspect you will resolve some of your heating issues.

thanks at least that gives me an idea on why the heat is so quarky.
man is there any thing on a diesel thats not run on vacume
headlights perhaps
guess i'm gonna be in for a long summer. if i'm gonna trace might as well replace all the vac lines ugh