Cooling Question
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Newbie
Joined: May 2015
Posts: 13
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1983 300D and 2008 ML350
Cooling Question
I currently own a 1983 Mercedes-Benz 300D. I am concerned that the vehicle is running too hot. I have read every article I can find on this forum about this matter – and have read a great deal on other sites as well.
Most of the time, the needle on the temperature gauge runs exactly in the middle between the 80 and 100 degree marks, which is fine. However, if I take the car on the interstate and run it at around 70-75 mph, it often gets up to the 100 degree mark and stays there. A couple of times it has even went a bit beyond the 100 degree mark.
Sometimes when I am driving around town, if I put on the A/C, it will run a bit warmer – and will sometimes hit the 100 degree mark at speeds of 50-60mph.
The car just turned over 170k miles – and I want to do everything in my power to make it last as long as possible. In my mind, that means ensuring the engine runs as cool as possible.
So far, I have had a coolant flush performed and have used the Zerex coolant. I have replaced the thermostat with a new good one from Mercedes Source. I have also had the fan clutch replaced. A couple of weeks ago, I added an entire bottle of Water Wetter. After doing all of that, I only saw a slight improvement in temperature after adding the Water Wetter.
The questions I present to the community are:
1 - If this was your car, would you be concerned about these temperatures under the described conditions?
2 - Is there anything else to be done to help ensure the car is running as cool as possible?
See attached pic.
Helpful comments are greatly appreciated.
Thank you.
Most of the time, the needle on the temperature gauge runs exactly in the middle between the 80 and 100 degree marks, which is fine. However, if I take the car on the interstate and run it at around 70-75 mph, it often gets up to the 100 degree mark and stays there. A couple of times it has even went a bit beyond the 100 degree mark.
Sometimes when I am driving around town, if I put on the A/C, it will run a bit warmer – and will sometimes hit the 100 degree mark at speeds of 50-60mph.
The car just turned over 170k miles – and I want to do everything in my power to make it last as long as possible. In my mind, that means ensuring the engine runs as cool as possible.
So far, I have had a coolant flush performed and have used the Zerex coolant. I have replaced the thermostat with a new good one from Mercedes Source. I have also had the fan clutch replaced. A couple of weeks ago, I added an entire bottle of Water Wetter. After doing all of that, I only saw a slight improvement in temperature after adding the Water Wetter.
The questions I present to the community are:
1 - If this was your car, would you be concerned about these temperatures under the described conditions?
2 - Is there anything else to be done to help ensure the car is running as cool as possible?
See attached pic.
Helpful comments are greatly appreciated.
Thank you.
Junior Member
Joined: Sep 2014
Posts: 45
Likes: 0
200D w123
Hello sharpie1,
I have seen these temperatures before. It really depends on what weather you drive in and of course how heavy you load the engine. As long as you don't go beyond 105°C there should be no problem there is a reason the gauge maxes out at 120°C
If you really want to try and cool you engine open up the air blowers (not airconditioning) and set them to full heat and maximum blowing the temp should go down atleast 5-10°C. (don't forget to put your windows open thou). Good luck and please let us know how it went.
-Greetings mercedes w123-
I have seen these temperatures before. It really depends on what weather you drive in and of course how heavy you load the engine. As long as you don't go beyond 105°C there should be no problem there is a reason the gauge maxes out at 120°C
If you really want to try and cool you engine open up the air blowers (not airconditioning) and set them to full heat and maximum blowing the temp should go down atleast 5-10°C. (don't forget to put your windows open thou). Good luck and please let us know how it went.
-Greetings mercedes w123-
Thread Starter
Newbie
Joined: May 2015
Posts: 13
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1983 300D and 2008 ML350
Ok - I just took the car for a little spin to do a test. It's 90 degrees F outside right now. I just took it on a 6 mile trip - the last 2 or 3 miles of which was uphill on the way back to my house. I had the A/C going and I ran it pretty hard. When I pulled in my driveway, the car was at the 100 degree C mark.
I immediately popped the hood and using an infrared thermometer, I measured the temp in various places.
The thermostat housing read 86C. The area where the injectors going into the engine was at 100C. The area on the front of the engine just above the fan clutch read at around 100C. The temp on different parts of the radiator ranged from 85C to 88C. The oil cooler on the side of the radiator read at 100C to 102C.
Should the oil cooler read that much higher than the radiator? It doesn't have a fan on it and it is much smaller than the radiator (less surface area) so that would seem reasonable.
Does this additional data provide any more clues as to what could be going on? I'm considering getting a Spal 4" 12V fan and mounting it to the inside of the oil cooler.
I immediately popped the hood and using an infrared thermometer, I measured the temp in various places.
The thermostat housing read 86C. The area where the injectors going into the engine was at 100C. The area on the front of the engine just above the fan clutch read at around 100C. The temp on different parts of the radiator ranged from 85C to 88C. The oil cooler on the side of the radiator read at 100C to 102C.
Should the oil cooler read that much higher than the radiator? It doesn't have a fan on it and it is much smaller than the radiator (less surface area) so that would seem reasonable.
Does this additional data provide any more clues as to what could be going on? I'm considering getting a Spal 4" 12V fan and mounting it to the inside of the oil cooler.
Last edited by Sharpie1; Jun 23, 2015 at 08:23 PM.
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Thread Starter
Newbie
Joined: May 2015
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1983 300D and 2008 ML350
The car has had two radiator flushes in the past 6 months and the radiator was replaced with a new BEHR one about 10 years ago.
The coolant I use is the Zerex brand which is recommended - and I understand it does have a corrosion inhibitor in it.
Also - I did see your question about the VIN. I chose not to provide it. Thanks...
The coolant I use is the Zerex brand which is recommended - and I understand it does have a corrosion inhibitor in it.
Also - I did see your question about the VIN. I chose not to provide it. Thanks...
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Thread Starter
Newbie
Joined: May 2015
Posts: 13
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1983 300D and 2008 ML350
I just had the radiator replaced with a new Nissens. There is a noticeable difference with the temp. I ran it hard on the interstate today going about 80 with the A/C on. It stayed around 90C. I'm very happy with that. The old radiator appeared to be full of gunk such as road grime and stuff. I wonder if there is any sort of screen or filter which I could put over the new one to protect it.
Super Member
Joined: Jan 2015
Posts: 920
Likes: 46
From: Worcestershire UK
W124 260E
Pluto i think you should get a life and let us sort things out on the forum .The plastic mesh wont up the temp .My mesh as been in for years it is not fine mesh that will stop the air getting to the radiator. Just there to stop stones not flys
Member
Joined: Apr 2016
Posts: 76
Likes: 3
From: Denver, CO
1982 300D
"1983 Mercedes-Benz 300D" is all the information you need. You do NOT need the VIN to figure out what parts the vehicle has/needs.
No mention of the water pump has been made. How old is it?
Member
Joined: Apr 2016
Posts: 76
Likes: 3
From: Denver, CO
1982 300D
