300CD Running hot on highway

Page 1 of 2  
I'm currently on a road trip with my '82 300CD-T, and I'm having problems with it running hot. It's not overheating, but only because I'm able to mitigate the problem by turning on the heat in the car. It
looks to me that my coolant is pretty dirty, so that may be the simple answer, but I'll run down the other symptoms in case someone thinks it could be something else.
1. Only runs hot at highway speeds. Doesn't overheat immediately, but over a period of time driving at highway speed. I haven't sat in much stopped traffic, so I don't know if it would overheat then as well.
2. Running A/C makes the car overheat.
3. When it begins to get hot, all I have to do is turn on the heat and temp drops IMMEDIATELY to a safe temp. Will stay that way all day long if heater is on. Air coming from vent is so hot that I can't keep my hand next to it for more than 20 seconds.
4. Temp gauge sometimes spikes up and down very quickly, as if something were bumping into it. I would blame this on a faulty gauge, except that it always stays within a certain temp range when it does it (i.e. It doesn't just randomly flop all over the dial.)
Is it just in need of a radiator flush? I just got a new thermostat last week.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Radiator is dirty. Have a shop clean it, inside and out. Or, buy a new one.
--
2007 T.G.Lambach. Publication in any form requires prior written
permission.
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I'm in Fort Stockton, Texas right now. Is it something that any old shop can manage? Everybody drives trucks here.
On May 23, 1:31 pm, "-->> T.G. Lambach <<--" <"T.G. Lambach at NoHamorSpamcomcast.net"> wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Just went out and answered my own question. Nobody here has a power flush machine, so I guess I'm SOL.

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

Nah, you can do it yourself. Flushing a rad in a Mercedes is not unlike flushing the rad in any other car. Get any book about cars from the library.
Use liquid Tide first to dissolve any oil. FLush with water.
Mercedes sells a pretty plastic container of rad flush. It's just citric acid also called sour salt. That'll dissolve any rust in the rad. Flush well with water, add new coolant. The proepr coolant, not the evil green stuff.
Some people in warmer climates use redline water wetter - it helps.
--
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
No need for power flush... It is not likely the internals od radiator is plugged... more likely external fins are clogged... so use water or air to flush it clean.
I would double check the thermostat to see if it is good and then I'd check the radiator cap... alot of time, they do go bad and temp rises because system cannot pressurize.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I always buy a coupoe of thermostate at a time. EVen the proper and new ones are sometimes faulty right out of the box. I always test them with a candy thermometer to see if they open when they should.
--
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 would change the thermostat and flush out the coolant. Clean the radiator from engine outward to dislodge any bugs or dirt. Any shop can do this for you.
As for AC, make sure your aux fan is on when AC is on... remove and replace the fuse to see if it solves the problem. Otherwise, at the drier, jump the factory wires together at the green or red sensor... if fan comes on while AC is running then i'd keep it jumped until you reach your destination to fix it. It should turn off when car is off.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Yes.
Call around and see what the best price is on a rad. It may not actually me much more than having it cleaned.
--
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'm in Fort Stockton, Texas right now. Is it something that any old shop can manage? Everybody drives trucks here.
On May 23, 1:31 pm, "-->> T.G. Lambach <<--" <"T.G. Lambach at NoHamorSpamcomcast.net"> wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I'm in Fort Stockton, Texas right now. Is it something that any old shop can manage? Everybody drives trucks here.
On May 23, 1:31 pm, "-->> T.G. Lambach <<--" <"T.G. Lambach at NoHamorSpamcomcast.net"> wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I'm in Fort Stockton, Texas right now. Is it something that any old shop can manage? Everybody drives trucks here.
On May 23, 1:31 pm, "-->> T.G. Lambach <<--" <"T.G. Lambach at NoHamorSpamcomcast.net"> wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I'm in Fort Stockton, Texas right now. Is it something that any old shop can manage? Everybody drives trucks here.
On May 23, 1:31 pm, "-->> T.G. Lambach <<--" <"T.G. Lambach at NoHamorSpamcomcast.net"> wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 23.05.2007 20:16, eyeball kid wrote:

Does the radiator fan work? You should be able to hear it when you park the car and let the engine run for a few minutes.
Kind regards
    robert
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
ONLY if the A/C is on!
The aux fan in front of the condensor on a 123 body diesel is ONLY connected to the temp sensor on the A/C receiver/drier. It is ONLY a temp sensor, NOT a red or green pressure sensor.
The cooling system is NOT and NEVER has been integrated with the aux fan on a 123 diesel.
If turning the heater fan on cools the engine temp, the radiator is clogged inside. You can blow out the bugs til you are blue in the face but you will not help the 'no water flow' problem. Either get the radiator professionally flushed or replace it. Quit wasting time and do it right.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 24.05.2007 16:27, Karl wrote:

Just to make sure I understand you properly: if you are stuck in a traffic jam and do not shut down the engine and have no AC switched on, no fan will blow air towards the condenser / radiator in a W123?
Kind regards
    robert
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
The viscous fan clutch should lock up [IF the radiator gets hot in front of it!!!] and the fan should pull air thru the radiator.
No fan will blow air thru the condensor/radiator with the A/C off on a 123 body diesel. The 212 degree switch most people think about are on the gas engine MB's and the 126 body 6 cyl diesels.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Alright... I reread all your post. My question is...
How high of temperature do you mean by overheating? With and without AC?
I finally saw you said you changed the thermostat.
Overheats only on highway but still... what temp are you talking about?
If I were you, I'd get a infrared thermometer and measure the actual temp at the thermostat housing. The problem with older gauge is the temp gauge become inaccurate. It is hard to get a non-digital thermometer to measure high temp... toward 200 degree.
When I changed my thermostat on older MB... 84... the temp immediately rises higher and I freaked out... I changed out everything from radiator to fan clutch... no difference... turns out, it was the temp gauge freaky thing... I even changed out the thermostat to 2 other new one... same damn thing.
My temp problem is local... not highway... highway should never be a problem unless you put in absolutely wrong thermostat.... MB thermostat is very specific... two stage type... where did you get your thermostat?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I was looking on ebay for cheap radiator...
http://cgi.ebay.com/ebaymotors/81-85-MERCEDES-BENZ-300-TD-RADIATOR-DIESEL-AUTO-CAR_W0QQcmdZViewItemQQcategoryZ33602QQihZ014QQitemZ330122428910QQrdZ1
It might fit on your car... but you gotta double check. It is most lkely made in China... but at that price I wouldn't care... Good price and all brass radiator is pretty reliable. I have bought from this seller before on body parts... it is good.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I just looked it up on Carparts.com... they list it $455 where as on ebay is 1/4 of the price... These radiator is made by Modine... and backs by lifetime warranty.
I looked up your 82 300CD and also 82 300D... they both use same radiator so they will fit.
In any case, I wouldn't hesitate to buy this radiator if I have to.
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.