They symptoms are temp gauge approaches 120. Coolant level light comes on even though tank is full and the switch is new. Granted ambient temps are high 90’s here in Atl but I still don’t think it should ever get that hot. Aux fans are running, plus I’ve got the resistor mod so they kick in early. Even with all that, it’s still getting to almost 120.

After searching around, I’ve noticed many threads talking about a couple things.

First off is an expansion cap change. I pull the cap off and it was in need of replacement, rubber broke apart in my hands. I used the cap off my E420 and its still exhibiting the same behavior. In any case I’ve got a new cap on order.

Secondly; the thermostat. Not sure how to check these, but they are cheap enough and easy to get to so why not. Do I try to get a fastlane part or just go to Autozone/Pepboys. If I go the domestic route, what part do I get?

Thirdly, I’ve come across many threads dealing with flushing the system. Draining it all, flushing with H2O (distilled only?), then adding Shout (pour right into expansion tank?) to degrease it all, then flush with water and then a citrus acid solution. I’m not sure where to get citrus acid locally. I guess I can try drug stores (walgreen’s eckerds, CVS, walmart even?)

I’m going to replace all the fluid with G05, which is what’s in there right now anyways.

I suppose I need to run though all that first before I keep bugging you guys with questions.

my guess is thermostat and it's also cheapest fix. My water pump just went yesterday (100* ambient here too), so I'm doing new G05 and a thermostat since it is original and also, according to the dealer svc dept, "a $10 part." I saw them on fastlane a little higher than $10, but either way, it's a cheap fix. Is yours original? If you've gotten a decade out of it, it's cheap insurance to keep you from being stranded with an overheat situation. Any leaks anywhere at all?

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former: 83 300D, 97 C230, 93 400E

current: 08 C300 Luxury , 92 500SL

How many miles on the car? Is radiator original? Is there any evidence of engine oil in the expansion tank? Have you verified correct operation of viscous fan clutch?

Just some things you should check:

Expansion cap.
Thermostat (for the M104 is rated at 87C)
Aux fans (high speed), starting at about 105C
Fan Clutch (you can test it, do a search on that).
Cooland leeks (do you have to add coolant frequently?)
Water pump.
Last thing is a cloged radiator.

System flush is recomended every 3 years.

Regards,

Juan

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Juan
1995 E320 Sedan
2008 Ford Escape
RC Helicopter

car has 122XXX miles
no evidence of oil in exp tank.
no leaks anywhere.
Like I said aux fans run, and I've got resistor mod.

Not sure why coolant sensors reads low when the tank if full and switch is brand new.

gonna go look at fan clutch.

There is a resistor,, I think thats what it is called,, behind the drivers headlight that controls low speed on the fans. Make sure you have good connections on it. Ours was badly corroded on our 400E and splicing a new wire in cured the problem. Have you done a search ?

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95 SL500 Smoke Silver, Parchment 64K
07 E350 4matic Station Wagon White 34K
02 E320 4Matic Silver/grey 80K
05 F150 Silver 44K

AtlBenz, a new Behr thermostat in our 1995 E320 resolved the high temperatures you're experiencing with your car. Drain some coolant from the radiator before removing the old thermostat and use a new gasket too. Think back to this past winter ... your engine was probably slow to reach operating temperature.

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Fred Hoelzle

I'm gonna try that new thermostat. I also had the walgreens order me citric acid so I'm going to go though the flushing procedure that other threads talk about just for good measure. all fans look to be working.

After the CA flush I'd run a 30/70 (water/coolant) mix w/ Zerex G05 (pep boys carries it) along w/ a bottle or two of Redline Water Wetter.

Make sure you have your heat on defrost while doing the flush.

Jonathan

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Blue Ridge Mercedes
Jonathan Hodgman
http://www.blueridgemb.com/
Enthusiast Service, Restoration & Tuning.
Follow Us on Facebook!
Located in the Atlanta area
Specializing in all pre and post merger AMG's including Hammers and DOHC M117 engines.
Mercedes Repair Atlanta

I put NGK plugs in and the heat crept up like crazy. Bosch Copper cores solved all this... Odd but true. Ran much better. I was reaching 110c in NYC traffic now it stays closer to 80c. The water Wetter is good I hear too. Most likely thermostat, get a fail open thermo.

UPDATE

System didn’t do what I expected. So first I fully drained the system. I pulled the plug on the radiator and opened the block. After everything stopped flowing, I plugged the radiator, but left the block open. I filled with fresh water and started the car. Should I see water coming out of the block? I didn’t, but I guess I was expecting to. Does it take a few min? I would think not since I’m assuming the block is empty and if the car is running, that’s a bad combo. The water pump should immediately pull the water and push it into the block right? If that’s the case, why was it not leaking out the open drain?

Ultimately this is what I need to know. If I drain the radiator (and reservoir obviously), and the block, and then close everything back up, what’s the procedure for refilling it all. Just fill via reservoir and start the car? Does the cap need to be on the reservoir or should it be left open to bleed out the air?


BTW, I replaced the coolant level sensor and thermostat while I was opening everything up. I also didn't mess with the deoil and citric acid procedure since I couldn't get the the flush procedure to do what I expected. On top of it all, I was stopped late in the day by a geyser. yep, maybe it was a contributor to my issues, but the radiator fitting (that little elbow that goes back to the tank totally failed and flew up about 8 feet in the air. it was quite a sight. Upon inspection it was totally soft and brittle. New one goes in after I post this. at this point I just want to have the car filled and drivable.

Did you flush it w/ the t-stat out or in? A proper flush is w/ it removed..ideally, gut your old one and install the remnants as a restrictor plate.

Jonathan

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Blue Ridge Mercedes
Jonathan Hodgman
http://www.blueridgemb.com/
Enthusiast Service, Restoration & Tuning.
Follow Us on Facebook!
Located in the Atlanta area
Specializing in all pre and post merger AMG's including Hammers and DOHC M117 engines.
Mercedes Repair Atlanta

Did you flush it w/ the t-stat out or in? A proper flush is w/ it removed..ideally, gut your old one and install the remnants as a restrictor plate.

Jonathan

__________________
Blue Ridge Mercedes
Jonathan Hodgman
http://www.blueridgemb.com/
Enthusiast Service, Restoration & Tuning.
Follow Us on Facebook!
Located in the Atlanta area
Specializing in all pre and post merger AMG's including Hammers and DOHC M117 engines.
Mercedes Repair Atlanta

initially I pulled out the old one and installed the new one. once I noticed that water was not pouring out of the block, as i was expecting, i thought well maybe the thermostat is stopping the flow. so I just pulled it out all together and ran it sans thermostat for a min. water still didn't come out of the block so I am throughly confused.

With the thermostat removed, water should be pumped inside the block. Maybe shomething wrong with the pump?

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Juan
1995 E320 Sedan
2008 Ford Escape
RC Helicopter