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 ShopForum > Technical Information and Support > Diesel Discussion

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 05-25-2012, 10:02 AM
Registered User
 
Join Date: Feb 2003
Location: Oklahoma
Posts: 1,016
'78 300D losing coolant

My nephew has been driving this car for the last couple of years and I went over to look at it yesterday - he said that it had leaked some coolant out the little overflow hose that is attached to the neck of the radiator. I added coolant - over a gallon - and started it up. After running for 10-15 minutes or so, the upper radiator hose was hot and the lower hose was cool - not even warm. Then coolant started running out the overflow hose again on to the ground - didn't see any other external leaking. Any ideas? Thermostat, maybe?

Thanks, ryan
__________________
RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE
Reply With Quote
  #2  
Old 05-25-2012, 10:03 AM
Registered User
 
Join Date: Aug 2011
Location: Carolina
Posts: 1,275
The cap
__________________
Current fleet
1992 300D "IceBerg"
1984 300D "Blues Mobile"

1978 300CD "El Toro" Gone on to be born again
Reply With Quote
  #3  
Old 05-25-2012, 10:16 AM
Registered User
 
Join Date: Sep 2004
Posts: 8,492
Quote:
Originally Posted by rgnprof View Post
Any ideas? Thermostat, maybe?
The thermostat would be pretty high on the list of possible culprits. Considering that it is inexpensive and easy to replace, that would be a good place to start.

Quote:
Originally Posted by Phillytwotank View Post
The cap
The coolant should circulate with no cap at all.
__________________
When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.
Reply With Quote
  #4  
Old 05-25-2012, 10:21 AM
Registered User
 
Join Date: Jan 2002
Posts: 18,353
The fact that the top hose is warm and the bottom cold is just an indication that the radiator is working and the coolant circulating. I second the idea that the radiator cap could be bad, especially if the car is not running hot. If the car is running hot, then there are other possibilities.
__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13
Reply With Quote
  #5  
Old 05-25-2012, 10:39 AM
Registered User
 
Join Date: Sep 2004
Posts: 8,492
Quote:
Originally Posted by kerry View Post
The fact that the top hose is warm and the bottom cold is just an indication that the radiator is working and the coolant circulating.
A cold lower hose on a warmed-up engine would certainly mean that the radiator is doing a great job. It is also outside the realm of possibility, given normal function of the system.

Either the thermostat isn't opening, the water pump isn't pumping, or the radiator is hopelessly obstructed. Or some combination thereof.
__________________
When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.
Reply With Quote
  #6  
Old 05-25-2012, 10:44 AM
Registered User
 
Join Date: Feb 2003
Location: Oklahoma
Posts: 1,016
One other item is that the heater is not working...doesn't blow warm air at all...

He did indicate that it got hot - approaching the 120 mark on the car before he shut it off and noticed the coolant leaking out the overflow. But, it hasn't been running hot before this...
__________________
RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE
Reply With Quote
  #7  
Old 05-25-2012, 10:49 AM
Registered User
 
Join Date: Aug 2011
Location: Carolina
Posts: 1,275
10-15 minutes of idle might not open the thermostat
__________________
Current fleet
1992 300D "IceBerg"
1984 300D "Blues Mobile"

1978 300CD "El Toro" Gone on to be born again
Reply With Quote
  #8  
Old 05-25-2012, 10:50 AM
Registered User
 
Join Date: Feb 2003
Location: Oklahoma
Posts: 1,016
Agreed, but I shut it off because it was starting to leak out coolant...

I don't think 'leak' is the right word...coolant was running from the overflow tube on to the ground.
__________________
RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE
Reply With Quote
  #9  
Old 05-25-2012, 10:54 AM
Stevo's Avatar
Registered User
 
Join Date: Apr 2002
Location: NW WA
Posts: 6,285
Sounds like air in the system, Did he have anything apart?
__________________

1985 Euro 300TD 5 spd 220K
1985 Euro 240D 5 spd 130K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"
Reply With Quote
  #10  
Old 05-25-2012, 10:55 AM
Registered User
 
Join Date: Feb 2003
Location: Oklahoma
Posts: 1,016
Nothing apart...but I also thought that might be a possibility, but only because it was so low on coolant. I had to add over a gallon before we even started it up!
__________________
RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE
Reply With Quote
  #11  
Old 05-25-2012, 11:04 AM
Registered User
 
Join Date: Jan 2002
Posts: 18,353
The basic question is why did it get hot to begin with? I'd put the nose uphill, fill the block thru the upper radiator hose, put the heater on full blast and get the air bubble out. I'd then replace the radiator cap and do further diagnosis. It may have gotten hot just because the coolant was low and the radiator cap bad. It may have a coolant leak somewhere.
I'm not sure why Tango thinks there's restricted coolant flow? Has that been determined.? Simply looking into the radiator with the engine running after it's warmed up should answer that question.
__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13
Reply With Quote
  #12  
Old 05-25-2012, 11:27 AM
Registered User
 
Join Date: Jun 2002
Posts: 296
I agree air in the system, he must have run it low.

You must bleed air out of the system thoroughly. Localized boiling in air pockets in the cyl head will blow open a new radiator cap even if coolant in the lower radiator is cold. These engines are particularly quirky in that respect.

1) Get the car facing up a steep incline.

2) Open both heater valves wide.

3) Remove the bleed plug on the thermostat housing and fill the radiator with the engine idling.

4) Keep adding water until no more air comes out of the housing and replace plug.
__________________
Beagle
Reply With Quote
  #13  
Old 05-25-2012, 07:00 PM
Registered User
 
Join Date: Feb 2003
Location: Oklahoma
Posts: 1,016
Well, got most of it fixed. Put it up on ramps and bled the air (although I don't think that was the problem). Put a new cap and thermostat in and drove it around for a while - laser temps were all well within specs and no leaking!

Only problem, is no heat still - since it's summer time in Oklahoma we'll tackle this problem later. I replaced the dreaded servo with an aluminum one several years ago and have had no problems with it.

ryan
__________________
RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE
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 05:00 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