So I fairly recently purchased a 81 300D NA. My commute involves a 2000 ft elevation gain on the way home and my car routinely gets to between 90 and 100C on the drive, and summer isn't even in full swing yet. In my area it is above 100 degrees from the end of June to the beginning of September. I'd like to do something to get those temps down now before I end up over heating on the side of the road. The only problem is that I'm on a budget so I need to keep these mods cheap.

So, what's your best bang for the buck cooling mod?

I'm thinking so far of raising the concentration of water in my coolant, maybe adding water wetter. Hood louvers? Oil cooler? Anybody know a source of massive aluminum radiators that fit these cars?

Any and all help is appreciated.

Try to hook up a switch to turn on aux fan. Cheap and effective.

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Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

Wahler 75 degree thermostat from a 77 450SL.

1977 Mercedes-Benz 450SL Base Convertible - Water Pump, Thermostat & Hoses - Page 1

I have used these in 240D and 300D in the Texas summer heat with great success. You will need the proper thermostat gasket for your engine. The one that comes with the 450SL thermostat is not the correct one for your diesel.

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Palangi

2004 C240 Wagon 203.261 Baby Benz
2008 ML320 CDI Highway Cruiser
2006 Toyota Prius, Saving the Planet @ 48 mpg
2000 F-150, Destroying the Planet @ 20 mpg



TRUMP .......... WHITEHOUSE
HILLARY .........JAILHOUSE
BERNIE .......... NUTHOUSE
0BAMA .......... OUTHOUSE

First thing you want to do is make sure everything is working ok. Flush the radiator, install a new thermostat, refill with a fresh mix of coolant and deionized or distilled water. If you still have a problem, here's a trick.

I've not done this on a car of this vintage, but I have done it on my 190DT. On the left side of the head, there should be an extra 22mm bung in the water jacket. Remove the plug and install a fan switch from a porsche or VW. 70's-80's vdubs had switches in various temperature ranges: 92c should do. Wire one side of the switch to ground, and the other side to the low speed fan resistor. That will bring the aux fan into play automatically at lower temperature.

http://www.pelicanparts.com/cgi-bin/smart/more_info.cgi?pn=823-959-481-F-92-M2&catalog_description=&Auxiliary%2520Fan%2520Switch%2520%252D%2520%2539%2532%2520deg%252E%2520C%2520

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What is the current status of your cooling system? Have you flushed the coolant? Checked the thermostat? Cleaned the radiator fins? Made sure your fan clutch is working?

My first reaction is that those temps you are seeing seem pretty high in below 100F weather.

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2009 ML320 Bluetec
1985 300CD
1981 300TD

Past Mercedes
1979 300TD
1982 300TD
2000 E320 4Matic Wagon
1998 E430
1984 300SD
1980 300SD

A long time ago I ran across a thread about engine temps, for our diesels what temp should they run at? I have a similar predicament to ArmchairRacer.

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Nosce Te Ipsum "Know thyself"

Sounds like it's getting a bit warmer than expected, but you can go right up to redline without any issues...just watch it close so you don't go over.

Since you've apparently got limited history on the car, a citric acid flush might be in order. You might have some radiator tubes clogged, blocking or restricting flow.

In addition I'd check the water pump. It's possible the impeller has become compromised reducing flow. The thermostat might be not opening completely...or late.

Of course it's possible that the gauge itself is reading high - maybe the needle has been bumped or the sender has partially failed. An IR thermometer will tell you what the actual temp is.

Make sure you've got an extra ground on the cluster. It could be as simple as a grounding problem.

Next time it hits 90, turn on the heater for a bit and see if the temp drops. This will tell you whether it's a lack of cooling capacity or something else.

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Current Stable

• 380SL (diesel)
• Corvette C5
• Manx
• Baja Bug
• F350 Powerstroke
• Auburn Boattail Speedster replica

One more thing...dirt gets entrapped between the a/c condenser and the radiator and between the fan motor and the radiator. you may want to loosen the bolts and see what's in between.

Around 80C...up to 85C under normal circumstances. With the A/C on idling in traffic on hot days it will climb higher.

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2009 ML320 Bluetec
1985 300CD
1981 300TD

Past Mercedes
1979 300TD
1982 300TD
2000 E320 4Matic Wagon
1998 E430
1984 300SD
1980 300SD

Thanks for the tips guys, I haven't messed with the coolant system at all yet, I only got the car about 2 weeks ago. I got it as part of a pair, this was supposed to be the parts car but it runs better than the other one. I should mention that when driving on level ground it stays right at 80C, it's only extended hill climbs that brings the temp up.

For several years, I ran two different 300Ds on a 5000 foot elevation climb to get home. On both of them, I ripped out the entire cooling system and replaced everything with brand new OEM.

What I found is that 90 - 100 is normal for summer temps on this car. There are some variables here like how quick the elevation gain is (i.e. extremely steep grade vs. gentle grade over many miles) -- mine was steep the whole trip as well as the speed of travel. I found in general that the faster I was able to travel, the more I was able to lower the temperature.

I did turn on the heater if it ever went over 100 deg C, but that's more or less what the car is rated to do when climbing elevation in hot temperature.

When you're climbing elevation, changing to a lower degree thermostat will only delay the inevitable temperature your car reaches. If you're already up to operating temperature, it doesn't do much of anything. I had a collection of thermostats I played with including Behr, non-OEM, thermostats with a few holes, thermostats with lots of holes, etc. There wasn't much difference in any of them and this with a new cooling system on both cars.

Dkr.

go get a fan and clutch from a V8 w126 like a 560sel at a pick n pull. it will bolt right up to your water pump and pulley. if you want even more cooling potential, get a water pump pulley off an 85 om617. it is smaller. of course your radiator should be checked as well as the rest of the stock cooling before throwing parts at it. i have this setup on my 83 300cd and i don't see why it wouldn't work on a non turbo. the thing sounds like a bus when it gets hot out

https://www.youtube.com/watch?v=M5lvHxCVxWg

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83 300CD- sanden, dual p/f condensers, 160a alternator, ect
91 300TD- 722.6, #22 head, 3.5L IP, w140 manifolds, ect

Where are you located?

There a good chance, that your transmission is over heating, thus over heating the car. If you are going up a hill, the trans has to work harder thus creating more heat. If the trans is over filled it will over heat even worse.

In the bottom of the radiator there is the trans cooler, there may also be so much gunk in the bottom....that the radiator is un able to cool the transmission fluid.

I would recommend, check the fluid level in the trans, as soon as the car reaches operating temp, pull over and let the car idle in park, pull the stick and the level should be right in between both mark.

I would also suggest a new radiator and possible a new fan clutch, but the non turbo radiators are NLA the few left are very priecy.

One word of wisdom, if you are on a tight budget and need this car as a daily driver, I recommend not owning one.

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I can't imagine there is much torque converter slip past 2500 rpm unless the trans is in bad shape or you're pulling a trailer. and i don't see the need to buy a brand new radiator either unless the cooling system has been extremely neglected. there is nothing wrong with being on a tight budget while owning one of these cars either as long as you take care of the issues and spend your car money wisely and get quality parts when needed. there is no need to spook people away from their own cars...

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83 300CD- sanden, dual p/f condensers, 160a alternator, ect
91 300TD- 722.6, #22 head, 3.5L IP, w140 manifolds, ect

Diesels build heat under load, that's part of the issue.

The rest of the problem is that Mercedes designed these cars to have a wide variation in temperature, which I think was a poor design choice. Try the electric fan mod I posted, it's the simplest solution.