350 SDL normal temp range

I have just purchased my second 1991-350, my first was an SD, my recently purchased is an SDL with only 76,000 miles. The car is in mint condition. My first cars temperature during in town driving on hot days (90-95F) ranged
100- 120 C, I was never comfortable with this, I replaced radiator and thermostat and helped this somewhat. My current SDL is up to the same old tricks, the owners manual states than in town severe condition driving can approach the red mark. I would appreciate any feedback on this subject. Thanks in Advance, Frank
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

They do that. Being in the red is ok. STAYING in the red for a while is not. Having an aluminum head you only get to do this once, if it overheats, it's dead, Jim, unlike the 5 cyl motors that can overheat and live.
Flush the cooling system and use redline water wetter. And keep an eye on the temp gauge.
--
Need Mercedes parts? http://parts.mbz.org
Richard Sexton | Mercedes stuff: http://mbz.org
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
-I have had a 91 350 SDL for some years now (from 106k to 182 k). They have numerous clever ways of overheating.
- AC charge low. This seems to cause excessive heat discharge by the ac in front of the radiator. - Use of MB coolant. I think this stuff leaves deposits in the cooling system. Citric acid cleaning helps. - I have heard partial plugging of the mufflers can cause the engine to run hot. - Inoperable aux fans (one comes on when at 110 the other when the ac pressures are high) - check the temp sensor of course - low oil level is not good - fan clutch failure - not as uncommon as some think - fan belt failure - Idler pulley or dampers worn out. (this and the ac charge made the biggest difference for me)
In North Carolina mine will often move up over 100 in city traffic but comes back down to 85 on once traffic flows steadily. One exception is driving in the mountains. Sustained heavy acceleration has caused it to go up to 110 (before some of the fixes mentioned above).
AND BE CERTAIN TO DISABLE THE EGR VALVE. Mine was passing black sludge to the intake. This is not good for pistons.
Chris
As Richard said extreme high temp is sure engine failure.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
ChrisH wrote:

Just to throw in my two cents. It seems that most 350SDLs vary their temp around the operation range. I disagree that operating above the upper white line of the operating range should be considered acceptable. Operating in red zone will not cause immediate failure, but it is best addressed when the temp starts getting above the operation range.
I replaced fan clutch, water pump (water pump was bad though and flowing backwards sometimes), several thermostats all to no real avail. The two things that really messed up our engine was 1) a burned through head gasket probably caused by running in the red zone for too long and 2) a clogged exhaust. A new exhaust system on our car dropped the operational temperature about 25 degrees C right back into the operation zone.
I've had the AC system low and empty and for us it never really affected the operating temp, but I can absolutely believe that it will. I've never understood why that happens but it seems to.
In other words, do what Chris said, and don't discount the exhaust. A clogged exhaust can cause bad heating up and low power.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
How does an exhaust get clogged?
This is not a problem one typically sees on older cars. Keeping them from falling off is a more tyical scenario. :-)
--
Need Mercedes parts? http://parts.mbz.org
Richard Sexton | Mercedes stuff: http://mbz.org
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Richard Sexton wrote:

It's a quirk of this car. Oily crap comes out of the cylinders and builds up in the can in the midpipe causing an obstruction in the pipe and there is a power loss and the engine runs hot. It goes right up there with the bent crank arms, which are also a quirk of this car. Personally, once the burnt through head gasket was replaced, I've pretty much turned up the radio and ignored a great deal of what is going on with the 350SDL.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
What is the best way to diagnose a build up in your muffler? Thanks

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
J. Frank Freeman wrote:

Ummm, I have no good answer for that. We found it out by replacing the exhaust stem from stern because it was cracking, and the side effect was an engine that ran much cooler as well as more powerfully.
Sorry that I can't help. I just know that this is what happened to us, and I have read similar experiences from others over the years who have had the same thing happen. Have you tried searching this groupd on the subject? Something useful might pop out at you. Best of luck - H
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
You mention disabling the EGR valve, how is this accomplished? I thought of replacing it, a new one is $142 at part suppliers on the internet. I have a small accumulation of oil around the cap where oil added to engine, I immediately thought of EGR as suspect. Thanks

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

This is for a W126 but you'll get the point:
    http://articles.mbz.org/engine/diesel/egr /
--
Need Mercedes parts? http://parts.mbz.org
Richard Sexton | Mercedes stuff: http://mbz.org
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

The 1991 350SDL is also a w126. With the same engine they later put into the w140.
cp
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Simply remove the vacuum hose from the EGR and insert something like a golf tee to plug it.
Chris

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Um, it's not exacly legal to block the EGR and a golf tee is a dead giveaway.
A ball bearing in the hose is a but more covert. Of course you'd only do this for off road and racing purposes.
--
Need Mercedes parts? http://parts.mbz.org
Richard Sexton | Mercedes stuff: http://mbz.org
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Yes, the 350SDL is known for its tremendous hill climbing AND racing ability. :)
(Sorry, the picture of it made me laugh).
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
It is possible your aux fan is not working when AC is on... I would first buy a infrared thermometer and aim it at the brass sensor to get an accurate reading.
On older cars, the temperature gauge do go bad and can be off as much as 20 degree.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I am not familiar with the brass sensor, does this reflect temp of the AC system? Where is it located? I guess this is the temp sensor that Chris referred to. Thanks

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
The temperature sensor is easily seen... they all have one or two prongs... one is definitely blue plastic with two prongs... this is for AC. Sometime you will have one prong with read coloring... this also related.
Best bet is go to the dealer and they will tell you which controls which.
The single black one is for temperature gauge... sometime this is replaced by 4 prongs round black sensor.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.