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
  #16  
Old 01-21-2014, 12:15 PM
funola's Avatar
Registered User
 
Join Date: May 2005
Location: NYC
Posts: 8,090
I just took apart a good monovalve and the spring is quite strong. The range of motion on the plunger is about 1/2 inch. I can't imagine that spring can stretch that much and loose effectiveness. Easy to check. take it out and pull on the plunger and feel how much tension is on that spring.
__________________
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
  #17  
Old 01-21-2014, 12:32 PM
Registered User
 
Join Date: Oct 2007
Location: Greater Metropolitan Beaverdam VA
Posts: 1,793
I had to replace my

monovalve connector to correct that problem. Make sure your connector is gripping the terminals tightly and 12Vdc is present when control is at the cold range.
Reply With Quote
  #18  
Old 01-21-2014, 01:15 PM
Registered User
 
Join Date: Sep 2004
Posts: 8,492
Quote:
Originally Posted by funola View Post
I just took apart a good monovalve and the spring is quite strong.
"Good" is the operative word. It does not apply to some aftermarket models.
__________________
When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.
Reply With Quote
  #19  
Old 01-21-2014, 01:18 PM
Registered User
 
Join Date: Sep 2004
Posts: 8,492
Quote:
Originally Posted by rocky raccoon View Post
monovalve connector to correct that problem. Make sure your connector is gripping the terminals tightly and 12Vdc is present when control is at the cold range.
I would appear that the proper operation in the cold range has already been confirmed.

12 volts should be present anytime the key is on; the monovalve is controlled on the ground side of the circuit.
__________________
When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.
Reply With Quote
  #20  
Old 01-21-2014, 01:24 PM
funola's Avatar
Registered User
 
Join Date: May 2005
Location: NYC
Posts: 8,090
Quote:
Originally Posted by tangofox007 View Post
"Good" is the operative word. It does not apply to some aftermarket models.
You mean the MTC kit the op used? got a pic of that kit?
__________________
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
  #21  
Old 01-21-2014, 01:29 PM
funola's Avatar
Registered User
 
Join Date: May 2005
Location: NYC
Posts: 8,090
Found this MTC kit. Do these have weak springs?

MTC Mono Valve Repair Kit : Amazon.com : Automotive

__________________
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
  #22  
Old 01-21-2014, 01:37 PM
Registered User
 
Join Date: Sep 2004
Posts: 8,492
See post #31 here:

1983 300td No heat at highway speed
__________________
When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.
Reply With Quote
  #23  
Old 01-21-2014, 01:49 PM
funola's Avatar
Registered User
 
Join Date: May 2005
Location: NYC
Posts: 8,090
Quote:
Originally Posted by tangofox007 View Post
Read your link. Last post from ytmtnman:


"Phil sent me a new monovalve. I popped it in last night. My drive to work this morning was warm and cozy even at high rpm. It seems that the problem was that the monovalve that I put in last month was defective. My guess is that the spring was getting sucked down, but the new and the old seem to have the same resistance. Problem solved anyhow."

He said new and old springs seem to have the same resistance.
__________________
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
  #24  
Old 01-21-2014, 01:58 PM
Registered User
 
Join Date: Sep 2004
Posts: 8,492
Quote:
Originally Posted by funola View Post
Read your link. Last post from ytmtnman:


"Phil sent me a new monovalve. I popped it in last night. My drive to work this morning was warm and cozy even at high rpm. It seems that the problem was that the monovalve that I put in last month was defective. My guess is that the spring was getting sucked down, but the new and the old seem to have the same resistance. Problem solved anyhow."

He said new and old springs seem to have the same resistance.
I guess was focused on the part that said "Problem solved...". Whatever the cause of the problem, replacing the part made the problem go away.

Maybe the isssue isn't spring tension itself, but some other failing that allows the increased coolant pressure to defeat the spring. Or maybe the measurement of spring tension lacked objectivity.

This forum contains numerous accounts of "no heat at highway speeds." The overwhelming solution to the problem is a new monovalve or monovalve insert.

There are also reports of new monovalve inserts being defective.
__________________
When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.
Reply With Quote
  #25  
Old 01-21-2014, 02:17 PM
funola's Avatar
Registered User
 
Join Date: May 2005
Location: NYC
Posts: 8,090
This is a pic of my good used OE monovalve.

The rubber plug at the tip is the part that moves (opens or close flow). The second piece of rubber (diaphragm) flexes but the non magnetic metal cylinder visible in the pic does not move (there is another iron core cylinder inside that moves). The diaphragm keeps coolant out of the spring cavity and more importantly, keeps coolant out of the electromagnet windings. There is a copper mesh between the 2 rubbers. Do you know what it's supposed to do?

__________________
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
  #26  
Old 01-21-2014, 02:29 PM
Registered User
 
Join Date: Sep 2004
Posts: 8,492
Quote:
Originally Posted by funola View Post
There is a copper mesh between the 2 rubbers. Do you know what it's supposed to do?
I have not figured that one out.
__________________
When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.
Reply With Quote
  #27  
Old 01-21-2014, 02:34 PM
funola's Avatar
Registered User
 
Join Date: May 2005
Location: NYC
Posts: 8,090
Quote:
Originally Posted by tangofox007 View Post
I have not figured that one out.
Coolant flow is horizontal into the mesh, then makes a 90 degree turn downwards. Maybe the mesh acts as some kind of buffer against side loading the rubber plug?
__________________
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
  #28  
Old 01-21-2014, 02:55 PM
whunter's Avatar
Moderator
 
Join Date: Dec 2003
Location: Metro Detroit, Michigan
Posts: 17,350
FYI

Quote:
Originally Posted by steamboatsykes View Post
The symptoms were, no heat above ~45mph. The original mono valve diaphragm was torn in the center. Replaced it with an MTC kit.

Still about the same, no heat at higher speeds. If anything, the heat at lower speeds seems warmer but the transition to cold seems sharper as speed increases.
If this has not been resolved ?

Verify there is no air trapped in the cooling system (heater core).

I use many of the MTC units, because most owners accept the higher defective unit trade off versus MB cost.

That said, I would not be even slightly surprised if the new MTC unit was defective.


.
__________________
ASE Master Mechanic
asemastermechanic@juno.com

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Prototype Vehicle build.
Prototype Fleet Durability
Prototype vehicle instrumentation.
Technical Quality Auditor.
Automotive Technical Writer

1973 300D
1973 309D - stolen
1978 280SE
1980 240D
1983 300D
1984 190D
Reply With Quote
  #29  
Old 01-21-2014, 03:10 PM
funola's Avatar
Registered User
 
Join Date: May 2005
Location: NYC
Posts: 8,090
An easy way to check if there is air in the heater core or other problems is after a high speed drive with heat on, pull over and feel all the hoses going in and out of the fire wall. If they are cold, there is air or blockage.
__________________
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
  #30  
Old 01-21-2014, 03:11 PM
steamboatsykes's Avatar
Le Marche
 
Join Date: Dec 2010
Location: Johns Creek, GA
Posts: 233
Quote:
Originally Posted by whunter View Post
If this has not been resolved ?

Verify there is no air trapped in the cooling system (heater core).

I use many of the MTC units, because most owners accept the higher defective unit trade off versus MB cost.

That said, I would not be even slightly surprised if the new MTC unit was defective.


.
Not resolved as of yet. What would be the best way to check for trapped air?

What was intersting about the MTC kit is that now the heat at low speed seems better, but transitions sharper to cold as the speed increased -~45mph.

The original diaphram was torn. Thanks.
__________________
1981 300D 92k miles (daily diver)
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 01:08 PM.


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