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2001 Mercedes E430 & 1993 Mercedes 300TE 4MATIC Wagon
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Discussion Starter #1
Ok, so we finally decided to get our drivers side catalytic converter fixed tomorrow as well as the oxygen sensors. (Car is at 107k miles)...so Im wondering if fixing this would fix some rough idle, lower gas mileage and performance issues??? Does a rattling cat converter really influence all of this or is fixing it a waste??? What does fixing the converter fix specifically???
 

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Discussion Starter #2
Oh yea, does it affect the temperature? The gauge goes up REALLY high when we sit in traffic...and the idle gets kind of rough and the car gets loud...after driving a while, no matter how fast, the temp goes down a little, but its scary to me when its high. Could this be because of the rattling converter???
 

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1994 E320 Wagon,1999 E320 Wagon,2000 E 320 Wagon, MGB Track/Rally, ,1988 300E ,more....
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What do

you consider high temp?
Clogged cat will cause timing issues which can lead to high coolant temp and if retarded to far timing can melt a piston.:(
MPG is greatly affected by the cats and the o2 sensors.
Lazy o2 sensors relay the wrong info for A/F ratio and bad cats can block off a whole exhaust bank and cause more misfires than a cat has lives.It is the proverbial catch 22 cat creates misfire,misfire creates unburned fuel,causes more cat problems ,ad infinitum.
You can get an oe universal o2 and have it spliced in for far less than the whole side.
:bowdown:
 

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2001 E320 - Brilliant Silver/Ash: 107,000+
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Bad O2 sensors will affect gas mileage by telling the car to run a richer fuel/air mixture than is necessary. How high is really high with the temperature? (mine runs about 80 C regardless of the conditions). If the rattling cat is plugged, that could explain at least one of your symptoms, specifically the rough running. The loudness sounds like broken bits of the cat might have worked their way into the muffler.
 

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Discussion Starter #5
The temperature goes right below the mark that is between the 80 and 120...its only when we're sitting in traffic for a few mintues or cruising around a parking lot for a few. When the temperature outside is cold, like it has been for the past week, it will stay right above the 80. But today, we got 78 degree weather which caused the engine to go way up!
 

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2001 E320 - Brilliant Silver/Ash: 107,000+
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It has been unseasonably warm in West Virginia too, but I don't think your car should run near 100 C unless it's about 90 F outside, your'e driving as you described, and running the A/C. Replacing your thermostat might be an inexpensive and quick fix. MB recommends changing the coolant every 3 years, and maybe that's a possibility as well.
 

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Discussion Starter #7
Yep its crazy...we're not running the a/c...i figured this was happening b/c of the clogged cat converter...i think of it as the car breathing through one nostril...i hope it fixes the roughness and noises...what exactly does getting the cat converter/oxygen sensors fixed do for the car besides helping w/ mpg and performance?
 

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2001 E320 - Brilliant Silver/Ash: 107,000+
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All I can say that is your car will thank you for replacing all of those at this mileage. There are a few experts here that will hopefully answer you with some specifics. Good luck.
 

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How many different ways can I say NO! as to part of the responses re temp?

While cats and O2 sensors can affect operating temp, what you are describing sounds like a fan issue, either the fan is not coming on because it is shot (or only one is coming on because the belt is shot) or the coolant temp sensor isn't sending the right signal, or there is a bad connection in all of that. The car is getting hot at idle because there is not sufficient air moving through the radiator, when you are driving air naturally moves through the core to cool it.

O2 sensors are 100K spec items, simple DIY saves you lots of money, especially if you splice in Bosch universals (not from E-bay).

Cats should be changed when plugged or noisy; Magnaflow 53005 is a great replacement for the rear cats outside of CA, about $60 from allexhaust.com, great company, have an exhaust shop weld them in for $30-$50 ea.

Take care and enjoy the ride,
Greg
 

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Discussion Starter #10
Are you kidding me? There is always something going on with this car...i think we're going to get the cat converter and O2 sensors done and see what happens! We have a long trip coming up next weekend and we have to haul people around so we want to get this done...but if something else is wrong with it, its just something else to fix haha
 

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Are you kidding me? There is always something going on with this car...i think we're going to get the cat converter and O2 sensors done and see what happens! We have a long trip coming up next weekend and we have to haul people around so we want to get this done...but if something else is wrong with it, its just something else to fix haha
I'm not kidding, and personally I'd be sure that the cooling system is working properly before heading out on a trip. If there is a problem with it -- and it sure sounds like there is -- and you end up stuck in traffic, I can promise you that overheating and costly emergency repairs will not add great memories to the trip.

To me that is far more important than the O2 sensors (which are probably still working fne) and noisy cats. Take it in and get the cooling issue resolved, order the magnaflows from allexhaust.com and you can have them welded in when you get back from the trip.
 

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2001 E320 - Brilliant Silver/Ash: 107,000+
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Ditto to Greg regarding the cooling system components. Those aren't hard to diagnose (in person) and shouldn't cost very much to fix.
 

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Discussion Starter #14
ok...we arent leaving until next thursday for pennsylvania (300 mi. trip) so I have some time...how exactly to do diagnose this by myself? What signs do I look for?
 

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2001 E320 - Brilliant Silver/Ash: 107,000+
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Better wait for Greg's response since he started you down this path. But in the meantime, you can check to see if the radiator fan is turning. That won't narrow down the several reasons he gave for overheating but it is a pretty safe diagnosis that the cooling system is to blame. If it is not running, it could still be the fan, it's fan belt, the coolant sensor, or a connection within that system. Good Luck!
 

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Has your thermostat ever been changed? If not then I would just go ahead and do this item today anyways. DIY is on this site for this. Greg will tell you how to check your fans. Checking the cooling system is a priority. The cats won't do any more damage so don't even worry about those and this can wait until your next inspection conceivably.
 

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ok...we arent leaving until next thursday for pennsylvania (300 mi. trip) so I have some time...how exactly to do diagnose this by myself? What signs do I look for?
I'm not sure of your MY arrangement, either you have a mechanical clutch on the front of your water pump that turns the fan (which is attached to it) or you have an electric fan that is mounted to the radiator. If you don't see anything bolted to the front of your water pump pulley, then you have the electric one. If you do have a clutch and fan assembly, then it is most probable that the clutch has failed, just replace it.

If you have the electric one, turn on the AC (with the engine running) and it should engage and turn (or after driving you can pop the hood and let it idle and wait for it to come on as the coolant heats up). If the fan fails to come on for both tests, then disconnect it (with the ignition off!) and run 12V to the fan motor, if it doesn't turn you can probably conclude it needs to be replaced, if it comes on for either test or with the bypass then you have to start working backwards, either wiring, the resistor/controller or a temp sensor (or dirty/corroded connections somewhere).

With cool weather and constant movement, you'd really have nothing to worry about, but if you got caught in a traffic jam it could overheat, and that isn't pleasant by anyone's book.

Take care and enjoy the ride,
Greg
 

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Has your thermostat ever been changed? If not then I would just go ahead and do this item today anyways. DIY is on this site for this. Greg will tell you how to check your fans. Checking the cooling system is a priority. The cats won't do any more damage so don't even worry about those and this can wait until your next inspection conceivably.
FWIW, personally I'd ignore the thermostat. If that was the problem it would not cool down once you're driving (and in fact would run hotter). Thermostats in these cars rarely seem to give trouble, I can recall only two threads discussing it and they were both about an engine that was running too cool.

There are two components to the cooling system, the coolant recirculation system and the heat exchanger system (that removes the heat from the coolant). The coolant passages, water pump, thermostat, hoses and overflow bottle are all part of the former, the radiator and fan arrangement comprise the latter. The latter only requires air to move through the radiator to effect the heat exchange, which is accomplished by the vehicle moving forward or via the fan pulling air through the radiator at slow speeds.

Take care and enjoy the ride,
Greg
 
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