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 04-23-2007, 07:51 PM
Registered User
 
Join Date: May 2006
Location: Fayetteville , NC
Posts: 89
why am I over heating??

car ran good all winter.

three weeks ago started to run hot, 115 C, but never hit 120.

took it to an indy, who pressure checked the system, and installed new theromast, and new radiator cap.

car ran ok for a while, and now is back to over heating.

today, after the radiator cooled down, checked the level and it is right at the top.

water pump is not leaking

no air in the cooling system

this is a used car and I have no maintance records.

coolent is not full of gunk, oil, etc

oil is black, and no water in it

I can only think of two possible things:
-- radiator is clogged and will need new one
-- something in the engine is blocking the flow of the coolent, but what?

suggestions?

Bob
1981 240d

Reply With Quote
  #2  
Old 04-23-2007, 08:00 PM
Larry Delor's Avatar
What, Me Worry?
 
Join Date: Jun 1999
Location: Sarasota, Fl.
Posts: 3,114
To see if it is the radiator, wait until it is quite warm, shut it off, and then feel different areas of the radiator. There shouldn't be any significantly cool spots. It may get a little cooler towards the bottom, but not much.*

Does it have a new water pump? I've heard of some aftermarkets not being close enough in the tolerances, and this causing poor circulation. MB's remans. are good, so you don't need new necessarily.

Once it is hot...the radiator hoses aren't plump(under pressure), are they?

Next time you're at the DIY carwash, grab that want and spray the radiator off (from the inside towards the outside). Probably won't cure anything, but it can't hurt.

* If it is not too badly "clogged", you may be able to get by with a citric acid flush.

Good luck with your hunt!
__________________
It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so. Robert A. Heinlein


09 Jetta TDI
1985 300D
Reply With Quote
  #3  
Old 04-23-2007, 08:00 PM
TheDon's Avatar
Ghost of Diesels Past
 
Join Date: Oct 2005
Posts: 13,285
time to try a citric acid flush to clean out the system
Reply With Quote
  #4  
Old 04-23-2007, 08:24 PM
Ara T.'s Avatar
Registered User
 
Join Date: Sep 2004
Location: Santa Rosa, CA
Posts: 2,075
Your gauge might be the culprit too.
__________________
1985 CA 300D Turbo , 213K mi
Reply With Quote
  #5  
Old 04-23-2007, 08:29 PM
Registered User
 
Join Date: May 2006
Location: Fayetteville , NC
Posts: 89
Quote:
Originally Posted by Ara T. View Post
Your gauge might be the culprit too.
good point, how would test?
Reply With Quote
  #6  
Old 04-23-2007, 08:55 PM
Larry Delor's Avatar
What, Me Worry?
 
Join Date: Jun 1999
Location: Sarasota, Fl.
Posts: 3,114
Quote:
Originally Posted by rkerste219 View Post
good point, how would test?
Somewhere, on this site, is a post/thread that tells you what the resistance at the sensor is, at certain temps. In other words, when cold it should read xxxohms, and when warm xxx ohms, and when hot xxx ohms.

Trouble is, I have no idea where this thread is buried - some good search skills would come in handy. (sorry)

Maybe someone reading this remembers the thread, or some detail of it.
__________________
It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so. Robert A. Heinlein


09 Jetta TDI
1985 300D
Reply With Quote
  #7  
Old 04-23-2007, 09:05 PM
t walgamuth's Avatar
dieselarchitect
 
Join Date: Apr 2005
Location: Lafayette Indiana
Posts: 38,611
water pump impeller could be freewheeling on shaft too.

also could have air in system.

radiator could have plugged fins. washing from back to front with a good blast of water can do a good job of clearing it out.

tom w
__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.
Reply With Quote
  #8  
Old 04-23-2007, 09:09 PM
Banned
 
Join Date: May 2002
Location: Blue Point, NY
Posts: 25,396
Quote:
Originally Posted by t walgamuth View Post
water pump impeller could be freewheeling on shaft too.

also could have air in system.

radiator could have plugged fins. washing from back to front with a good blast of water can do a good job of clearing it out.

tom w
Not the water pump.

Unlikely that air would cause such a rise in temp unless it's a massive amount.

Agreed on the radiator. They get hopelessly clogged with debris over the years causing a massive reduction in airflow.

Washing from back to front in the vehicle is useless. The radiator must be removed from the vehicle and a powerful condenser cleaner must be used on the fins together with compressed air. It's a lengthy procedure because the spaces between these fins are very narrow.

Hold the radiator up to the sun and peer through the fins.........you'll see the problem immediately.
Reply With Quote
  #9  
Old 04-23-2007, 09:18 PM
1985 190d
 
Join Date: Nov 2006
Location: canadian border vermont
Posts: 518
I've been having troubles with my cooling system-- acting just like yours.
I quickly found that the trouble was the gauge and that the cooling system was working perfectly, but the gauge was defective.

I used a laser operated thermometer on the engine and found that water entered the radiator at 80c and left it at 60dc. The guys in the truck garage pointed out to me that if I really was running at 120c there would be no question about it if you lifted the hood.

So for the moment I have a mechanical temp gauge installed.

Check the cheap things first!

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 01:43 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2024 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page