Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help




Go Back   PeachParts Mercedes-Benz Forum > Mercedes-Benz Tech Information and Support > Diesel Discussion

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 12-29-2015, 01:11 PM
ivandrocco's Avatar
Registered User
 
Join Date: Mar 2010
Location: Amherst, MA
Posts: 243
w123 lukewarm heat

Seems like my heat isn't as hot as usual. It's just lukewarm.

Coolant is good, hoses at monovalve hot, 12v when set to MAX cold, Monovalve seems to be working.

I do have intermittent clicking from the CCU, i cleaned the contacts and it clicks less often.

Most threads on heat are about a failed monovalve and no heat, what's up with luke warm heat?
__________________
1984 300CD
Reply With Quote
  #2  
Old 12-29-2015, 09:39 PM
Control Freak
 
Join Date: Oct 2011
Location: Columbia, SC
Posts: 3,180
What is your engine temperature? Should be right around the 80C/175F marker after driving a few miles.

If it is significantly below that, your thermostat is probably stuck open and the engine can't heat up to optimal operating temperature - this is bad both for you and for the engine.

Feeling the hoses won't tell you anything, the difference between 130 F and 175 F is hard to tell since both are painfully hot to a human.
__________________
2014 ML350 Bluetec (wife's DD)
2008 E320 Bluetec (my DD)
2008 ML320 CDI (Older son's college DD)
1998 E300DT (Younger son's college DD)
1987 300TD sold to vstech
----------
gone but living on
1983 240D (body to greazzer, engine to t walgamuth)
Reply With Quote
  #3  
Old 12-29-2015, 10:08 PM
mannys9130's Avatar
Ignorance is a disease
 
Join Date: Aug 2013
Location: Tucson, AZ
Posts: 1,244
Back flush the heater core and thoroughly bleed the cooling system with the front of the car raised above the rear and the heat on full blast. Run the engine at 2000 rpm until it settles at operating temp and the lower rad hose gets hot. Once that is done let the engine cool down, and check the coolant level.
__________________
'84 190D 2.2 5MT (Red/Palomino) Current car. Love it!
'85 190D 2.2 Auto *Cali* (Blue/Blue) *sold*
http://badges.fuelly.com/images/sig-us/302601.png
http://i959.photobucket.com/albums/a...0/sideview.png
Reply With Quote
  #4  
Old 12-29-2015, 10:54 PM
Registered User
 
Join Date: Aug 2010
Location: Sacramento, CA
Posts: 2,460
In my experience, when the coolant is low you won't feel much heat. It doesn't take much. My son was complaining, "heat doesn't work" in my 1985 300D when he came home last week. I had told him to check the coolant when he left a month ago since I had drawn it down to check the upper hose and knew it would drop a bit as air worked its way out, but he doesn't listen. I only needed to add ~1 cup to hit the full mark (using Evans Waterless) and the heat was much hotter then.

I have also seen the temperature read too high when there is an air pocket. I have used a HF IR gun to measure next to the temperature sensor in the head (goes to dash gage) and the reading agrees quite close w/ the gage. You can get one on sale for <$30 and they prove very useful.
__________________
1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans
Reply With Quote
  #5  
Old 12-30-2015, 12:19 AM
Registered User
 
Join Date: Apr 2003
Location: Phoenix Arizona. Ex Durban R.S.A.
Posts: 3,206
Maybe nothing to do with the coolant. Could it be that some flap in the heater box is not operating correctly. Maybe the recirculate flap is not closing all the way? This time of year that would allow cold air into the mix would it not?

- Peter.
__________________
81 240D stick. 316000 miles at purchase. 340000 now
2000 GMC Sonoma
Formerly...
2002 Kia Rio. Worst crap on four wheels
1981 240D 4spd stick. 389000 miles. Deceased Jan 08
1984 123 200
1979 116 280S
1972 Cadillac Sedan DeVille
1971 108 280S
Reply With Quote
  #6  
Old 12-30-2015, 04:13 AM
mannys9130's Avatar
Ignorance is a disease
 
Join Date: Aug 2013
Location: Tucson, AZ
Posts: 1,244
It could be a flap issue, but the worst case scenario failure is FULL heat and full defrost. It's a safety thing.
__________________
'84 190D 2.2 5MT (Red/Palomino) Current car. Love it!
'85 190D 2.2 Auto *Cali* (Blue/Blue) *sold*
http://badges.fuelly.com/images/sig-us/302601.png
http://i959.photobucket.com/albums/a...0/sideview.png
Reply With Quote
  #7  
Old 01-04-2016, 01:08 PM
ivandrocco's Avatar
Registered User
 
Join Date: Mar 2010
Location: Amherst, MA
Posts: 243
Car runs at 100C... always has, runs fine. At one point I replaced the thermostat, same running temp.

Coolant is topped off, added a "cup" just so you couldn't say I told you so. Still luke warm!
__________________
1984 300CD
Reply With Quote
  #8  
Old 01-04-2016, 03:02 PM
dude99's Avatar
Registered User
 
Join Date: Nov 2009
Location: Vancouver, BC
Posts: 1,350
Is your auxiliary water pump working?
__________________
2003 Volvo V70 5 Speed
1997 E290 Turbo Diesel Wagon -traded for above, an amazingly comfortable car to drive, great drivetrain, but the rust, oh my god the rust
1992 BMW 525i -traded in
1990 Silver 300TE -Sold Loved the wagon, hated the M103
1985 Grey 380SE Diesel Conversion, 2.47 rear end, ABS -Sold, really should have kept this one
1979 Silver 300D "The Silver Slug" -Sold
Reply With Quote
  #9  
Old 01-04-2016, 04:05 PM
ivandrocco's Avatar
Registered User
 
Join Date: Mar 2010
Location: Amherst, MA
Posts: 243
Quote:
Originally Posted by dude99 View Post
Is your auxiliary water pump working?
I was going to ask, "how do I tell?",

Here's a thread on it, I'll report back: Auxiliary Water Pump - Mercedes-Benz Forum.


HOWEVER, the pump is to provide heat at idle speed, and I'm not getting significant heat at ANY speed. It's warm, but not retina blasting hot like it should be at max heat.
__________________
1984 300CD
Reply With Quote
  #10  
Old 01-04-2016, 05:28 PM
mannys9130's Avatar
Ignorance is a disease
 
Join Date: Aug 2013
Location: Tucson, AZ
Posts: 1,244
You need to backflush the heater core like I said.
__________________
'84 190D 2.2 5MT (Red/Palomino) Current car. Love it!
'85 190D 2.2 Auto *Cali* (Blue/Blue) *sold*
http://badges.fuelly.com/images/sig-us/302601.png
http://i959.photobucket.com/albums/a...0/sideview.png
Reply With Quote
  #11  
Old 01-04-2016, 05:56 PM
dude99's Avatar
Registered User
 
Join Date: Nov 2009
Location: Vancouver, BC
Posts: 1,350
Quote:
HOWEVER, the pump is to provide heat at idle speed, and I'm not getting significant heat at ANY speed. It's warm, but not retina blasting hot like it should be at max heat.
True, My 79 had a bad one and I had very poor heat at idle and acceptable heat when moving. However, my heat got noticeably hotter at all speeds after I replaced it.
__________________
2003 Volvo V70 5 Speed
1997 E290 Turbo Diesel Wagon -traded for above, an amazingly comfortable car to drive, great drivetrain, but the rust, oh my god the rust
1992 BMW 525i -traded in
1990 Silver 300TE -Sold Loved the wagon, hated the M103
1985 Grey 380SE Diesel Conversion, 2.47 rear end, ABS -Sold, really should have kept this one
1979 Silver 300D "The Silver Slug" -Sold
Reply With Quote
  #12  
Old 01-04-2016, 08:02 PM
funola's Avatar
Registered User
 
Join Date: May 2005
Location: NYC
Posts: 8,110
Feel your hoses, it can tell you a lot. Quick touch, let go, then slightly longer touch, let go, before it gets uncomfortable. You will not be able to measure temperature accurately by touch, but you can tell if one hose is hotter than another by how long you can your keep hand on them.

Feel the in/ out hose on the monovalve as well as the hoses into the firewall to/from the heater core. They should be similar in temperature. If not, monovalve may be blocked or heater core may be blocked. At full heat, monovalve/ heater core hoses should be less hot than the upper radiator hose (because it is further away from it), but not by a lot. If it is very cool in comparison, you may have some coolant flow issues.

I find it very useful to start the engine cold and feel all coolant hoses as the engine warms up, which shows you the flow path.
__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked
Reply With Quote
  #13  
Old 01-04-2016, 09:05 PM
fahrvergnugen's Avatar
Yeah, THAT guy...
 
Join Date: Jul 2014
Location: Olathe, CO
Posts: 649
After I reconnected the plug on my aux heater, I noticed a small increase in heat. Seems to come to temp a little faster. Not a huge amount, but measurable.

I'm due for a coolant flush; I think I'll back flush the core as well as do the MB flush as recommended, something about citric acid?


EDIT To add, I found this link after posting this... http://dieselgiant.com/mercedes_citrus_flush.htm

He mentions that his engine temp dropped about 10* after doing the flush, whereas mine normally runs a bit above 90*, not at 100* like others have mentioned. That makes it seem like mine doesn't have much corrosion in it... I'd be interested in thoughts on that, especially if the OP doesn't mine the sideline.
__________________
---------------------------------------------------------------

1983 300TD, 215K

Pics here... http://s86.photobucket.com/user/diutley/library/
Reply With Quote
  #14  
Old 01-05-2016, 06:27 AM
Registered User
 
Join Date: Apr 2009
Posts: 58
I had this problem this fall on a 1983 300TD and checked the usual suspects--turned out to be a loose connector on the box of electronics that lives behind the glove box, not sure if that is the CCU you refer to or not,--the connector fell out in my hand as soon as I touched it. Easy to check if you haven't.

Peter
Reply With Quote
  #15  
Old 01-05-2016, 10:39 AM
ivandrocco's Avatar
Registered User
 
Join Date: Mar 2010
Location: Amherst, MA
Posts: 243
Quote:
Originally Posted by mannys9130 View Post
You need to backflush the heater core like I said.
Are you saying flush the whole system with a hose, or just blast the heat with the front of the car raised above the rear?
__________________
1984 300CD
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -4. The time now is 06:57 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page