That logic would invalidate 90 percent of the posts on this forum.

Do it. $1000 for the car. If it craps out you can always find another. The Mercedes engineers don't put anything in the car unless they think it's necessary---BUT--- My C141 manual had procedures for removing the Aircraft batteries if the overnight temp was going to go below -44F. Never had to do this thank God. The oil cooler may have been installed for the Sahara Dessert operation that the car may have seen. Now which is hotter. The Sahara in the middle of the day or a HOT and HUMID Georgia summer day. I go for the Georgia day.:D :D

Dave

The only engines that I have operated that had an oil temp limitation specified 245F as the maximum temp.

The complete story on the W123 oil cooler thermostat is that it begins to open at 110C and does not fully open until 125C.

Now if only they had a procedure for when the C-141 wing spars fracture Dave, ...

Oil coolers are likely not necessary for low-speed operation and general driving. Yes Mercedes did it for a reason, I've seen 130C on the oil temp gauge on my quattro driving hard for extended periods, have gotten my manual transmission hot enough to burn my arm from same driving. I am pretty sure that the M-B will get hot too if run hard enough long enough, but most of us will never see / do it. Personally, I'll keep it operational on a car because it's good insurance for the oil temp.

My 300TE 4matic had a heat exchanger where the fuel was cooled by the A/C system on its way back to the fuel tank also. Again, I believe that up until recent years, Engineering at M-B came up with a good idea to make something more robust for a 1% application, and it went on all cars. That's what made a Mercedes a Mercedes.

I got a fuel cooler of that exact description from a 60's MG.

A '60s MG with Air Conditioning was rare enough.

One with AC that worked was even rarer.

N/A 240Ds have oil coolers. I would guess this is for wide open autobahn driving. The 300D Turbos have them as well. For a turbo car, I would keep it because a big hill in the summer will put a big load on the engine. For a N/A diesel that will not see any hard running you may be OK. I would reccomend synthetic oil in that case. I'd be nervous if you have to take on large highway hills, especially with the A/C on though.

Euro 240D's do not have oil coolers.

It seems the one thing this thread lacks is actual oil temps under various load and environmental conditions. I'll put a gauge on my list of things to think about; it does sound interesting. Lemme think about where I might mount it. Anyone know where to stick the sensor on a 617 motor?

The only experience I've had with removing oil coolers was on my 1988 BMW R100RS (air-cooled twin) motorcycle. The bike came with an oil cooler; I asked the dealer (an experienced rider himself, his opinion meant a lot to me). He said that the cooler was needed only for high-speed riding in hot weather, i.e., 80 MPH+ continuous in 90+ weather. Since I didn't plan to do any of that, I took the oil cooler off, along with the smog stuff, and had no problems. With the cylinders sticking out in the airstream, the twins are very difficult to overheat -- in 200,000 miles of riding I've never had a problem. Maximum oil temp I ever saw was about 250F (120C) on my 1973 R75/5.

If I were to think about bypassing the oil cooler on either of my Benzes, I'd put an oil temp gauge on first, get to "know" the temperatures that the engine sees, then repeat with the cooler bypassed. If the temps stay reasonable (whatever that means) without the cooler, then sure, leave it off. But don't do it blind.

FWIW:
I was doing some towing (sled dragging up a 45% incline, repeatedly, then off to the dump with a full load and trailer) with my Chevy truck and noticed that my engine didn't sound happy after a few hours of that, burnt the trans fluid and oil :( (regular ATF and castrol 5-50 synthetic). Changed the oil right then and had the ATF purged at a quickie place.

Installed both an inter cooler on the trans and an oil cooler on the front (damn thing was stubbed out for one but it seems to be a factory option that no one buys...). Anyway, next time I abused the heck outa the thing everything was roses. When not punishing the truck I notice that the oil stays "nice" far longer than it did before. I know it's not your situation, but IMHO I'd keep the oil cooler.

Heck do a cost/benifit analysis. ~$100 to fix Vs. how much to bypass + shorter oil intervals?
-nB

The oil cooler combined with oil squirter pistons are meant to take heat away from regions inside the engine where normal coolant won't be able to do so, also it supplements the radiator and keeps the oil from heating up excessively, even the best oil heated up beyond a point would tend to thin out and be subject to thermal breakdown, oil cooler is the life of your turbo engine along with the radiator, take either of them out of the equation and your engine goes KAPUT.

everybody seems to have good ideas on this.

i think maybe craig summed it up best. i suspect rigging it to run without them will take as much or more time than fixing them.

imo, they are there for our extended drives in hot weather on the interstate. there is noplace in europe where you can drive 1000 miles without doing much stopping like you can for instance in texas.

they provide nearly an extra quart of oil too to make it all last longer and run cooler as well.

i wouldn't take it off.

and buying a used benz with it taken off would give me pause.

tom w

I knew this was going to be controversial! :P

I do appreciate all the input, but up to this point, it's all been speculation about why it's necessary. The only hard data that's been presented is the temperature that the thermostat operates at.

Yes, I understand it contains an "extra" quart of oil. No, that will not help with refreshing the oil if it doesn't get changed out, nor will it provide extra cooling if all it does is sit there lounging in the tubes 'cause the thermostat hasn't opened.

Yes, I understand turbo engines run hotter and have turbo bearings to cool and piston squirters that increase the oil temperature. No, that will not matter if the temperature doesn't get high enough in my driving to open the thermostat -- the presence of, or lack thereof, the oil cooler will be irrelevant.

Yes, I understand that oil that has gotten too hot will damage an engine and harm the oil's properties. Again, no, that will not matter if the temperature doesn't get high enough in my driving to open the thermostat.

Yes, I understand that not having the oil cooler would give some buyers second thoughts. No, I am not doing this with any consideration of resale. In any case, I have already mentioned that this will be a reversible mod.

Folks, as I have said multiple times, I am not going to remove it blindly! I was already planning to install an oil temperature gauge (IMO, all vehicles should have a full complement of gauges) and will be able to determine once and for all what the temperatures really are. It's beginning to look as if I'll be the only person to have actually done so!

I have an '82 300D. I can say for certain that my oil cooler thermostat opens during "around town" driving, as evidenced by the cooler return line being hot to the touch.