How long should it take to get warm air? - PeachParts Mercedes-Benz Forum

hdexpert · #1 11-10-2005, 09:28 AM

This mornings drive to work in my 81 300SD was a cold one for most of the way.Here are the stats,about 30 degrees out, 22 mile drive,temp gauge reads between 80-90, fan blows on all speeds,selector seems to work fine.I didn't get any warm air until about 15 miles into the drive.Is this normal? This is my first Mercedes diesel and have heard most diesel vehicles run cold in the winter.Should a piece of cardboard be put in front of the radiator or not?I did a search on monovalve, read a lot of posts but I don't think that is the problem. Any thoughts?

andmoon · #2 11-10-2005, 09:33 AM

If your temp guage is between 80 and 90 you should be getting warm air. Not sure about 1980 model but my 90 starts pumping warm air as soon as the guage starts moving. If I set my fan to auto setting the fan won't blow until the coolant reaches a temp higher than interior temp.
Vacuum/clean the interior temp sensor. (long shot but easy to do)
Look into mono valve....If you didn't get any heat I would suspect this but you say you eventually got heat????

I wouldn't cover the radiator as your running temp is fine.

yal · #3 11-10-2005, 10:01 AM

There is a monovalve repair kit. The monovalve gets 12v and open and closes the valve to allow coolant into the heater core. www.**************.com has the kit, partshop may have it too.

meltedpanda · #4 11-10-2005, 10:32 AM

its the monovalve, get the repair kit. Make sure engine is cold, unscrew top (4 screws) insert new vavle, replace cover. Caution - do not overtighten screws as they may strip out
Good Luck

hdexpert · #5 11-10-2005, 11:35 AM

Newbie question, where is the monovalve and what does it look like???

meltedpanda · #6 11-10-2005, 01:33 PM

Should be in front of second fire wall several radiator (small diameter) lines into and out. you only wan to replace insert
http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1NP0SZ49Y1NP0SZFNO&year=1983&make=MB&model=300-DT-001&category=All&part=Mono+Valve+Repair+Kit

Should be a two prong connection going to the top or side. 4 small phillips head screws hold it in place.