ep4

Ok, so I have visited this forum many times since we purchased our '02 E320, but could not find any definitive answers to a couple of questions, so decided to join and post them here.
The car always ran at 80C and never moved in traffic or with the ac on. I am in FL, so it's hot and humid here all year round. I noticed in the last year or so that the temperature started to move up over 80, but not quite half way to the next mark, 100. The car felt hotter and even heated up the garage everyday when my wife came home.
I decided to get a thermostat and change the coolant. I used the exact replacement 87c thermostat, and flushed all the old coolant out, then filled with a suitable coolant for European cars. I would say I put approximately 6 quarts of full strength coolant in, along with 2-3 quarts of water. I ran the car for maybe 30-45 min in the driveway and let it heat up with the expansion tank cap off. I drove it and then opened the tank again to check the level as well.
After the job was done, the temp was even higher than before, probably 90+. I did the climate control function and watched the temps in F, vs C. When the ac was on, the temp climbed to 195 sitting still and stayed there. With the ac off, it would get up to 202-204. I drove with the air off and it would come down to around 195.
We drove the car all around today with and without the ac on. Cruising at 55-60mph for extended periods with the air off the temp would get to 188. When stopped it jumps back to 200+. With the air on, it stays around 195 most of the time.
I noticed that the electric fan comes on and turns slowly when the ac is on, but it is not on at all and never comes on, when the ac is off. I have no clutch fan, and it's a single electric fan, that from what I read, has variable speeds. I read that some of these E320's had fans that don't come on under 102c. I can't believe this is the case for a car with no clutch fan. In the past I recall the fan cycling at times. It is not doing that now, just runs slow with the air on.
I used the auto buttons on the climate control to see if the fan would actuate. When the buttons are held with the ignition on and engine off, I could not get it to come on. When the engine was running, the fan would come on if I held the buttons for maybe 30 seconds. I noticed the fan seemed to start slow and then gain speed until it reached a higher speed. When I went to turn it back off the same way, it gradually slowed down in stages, then went off. Of course the engine temperature dropped when the fan was running on high, even when driving 50+ mph.
My thought is that the fan is not working properly. Not necessarily a fan issue, but possibly the controller, or whatever is sending the signal to the controller.
I know that many say 90c+ is fine and not to worry about it, but the bottom line is that the car ran at 80c, and is not hotter, so something is wrong and I would like to correct it.
I will add that my father in law thought the thermostat may have been an issue, so I put the old one back in today with no change. I added water to replace what coolant I lost today, so if the ratio was an issue, it is closer to 50/50 now, and that also made no change.
Sorry for the long post, but I wanted to try and give all the info I could up front. Any help is appreciated.

kajtek1

Let me guess?
"suitable coolant for European cars" is a green in color???
Is the >60% mix what the bottle recommend?
Checking the fan switch would be another issue.
From what I remember on those engines the fan should come on high with engine > 90C.

ep4

Suitable meaning it says it is ok to use on European models, and it was full strength, so I added water to get close to the 50/50 premix dilution recommended for this car, on this forum. I am not sure if it's green or yellow because I am color blind, so I can't really say for certain. It is Prestone Af2000 I believe. The same as the Af 2100 except it's not premixed. I know it's new coolant, approved for this vehicle and has about a 50-60% ratio. Adding more water did not change the temp, so I don't think the coolant mix is the problem.
The fan never comes on without the ac running, and at that point, it's a slow speed, but it is enough to keep the engine temp down almost 10 degrees F, than running without the ac and the fan not moving. By fan switch, do you mean the controller? Is there a way I can check it? From what I have read, it's located above the left front splash shield of the bumper.

kajtek1

What I would STRONGLY recommend >>> buy about 10 gallons of distillate water (89 cents at Walmart) , a gallon of MB coolant and citric acid at MB dealer.
Drain the stuff you have in your cooling system, refill with DW + CA and drive for few miles till at least 80C on engine, while using cabin heater for couple of minutes.
Drain the stuff, refill with DW and repeat 2-3 more times.
Last time refill with 1 gallon of MB coolant and top off with DW.
Then seek in stickies DIY for fan troubleshooting. Those cars had several configurations, so find the right DIY for your model.
Chances are that with good coolant you might not need top fan speed (I drove my diesel for years with engine fan removed), but sounds like you are perfectionist (beside choosing coolant) so you will have your chance to learn car electronics.
Good luck.

fabbrisd1

Solid advice from KJK - to get you back to correct coolant - and system clean to eliminate the "junk" in the system - and no, that Prestone AF2000 might be "approved" on the bottle, it is not "bad" - but it is not the correct coolant - as you say your temp went up more with your coolant change too - that's a clue...

From your symptoms I suggest you check the fan clutch - your problem is general operating temp increase - which can be the sign of a "failing" viscous fan clutch - failing clutch drops off fan resistance/control - in turn reduces general cooling airflow - in turn leads to general temp increase . Do a youtube search for a "safe" method to check/diagnose that fan clutch

Please take the opportunity to check the belt tensioner - you need to check if "old" type tensioner - 2002 was a "split" year some are "old" style and some are "new" style. If "old" style - best bet is for the Conti "kit" which is correct OE "new" tensioner, fresh idler pulley, fresh belt.

Check water pump for sings of recent "weepage" which will appear at bottom of water pump, coming thru weep hole, early weepage can dry on "hot" block and not cause garage/water signs.. weepage is the only early warning sign for pending water pump failure.

Keep the beat !

ep4

I understand many here feel there is no acceptable coolant aside from the MB stuff. The bottom line is the temp had increased with the MB coolant, long before the flush and fill with Prestone, and the new thermostat. I will likely flush the system again and may put Zerex or the MB stuff in there at that point.
It appears my issue is with the fan, and lack of coming on without the ac. I will look for the troubleshooting info regarding that, to see if I can narrow it down. I don't think my fan needs to run at top speed to cool the engine, but it should be running at some kind of speed when the engine is at temp.
Fab, I don't have a clutch fan, so there is nothing to check there. The engine has a pulley on the water pump with no fan at all. I have one electric fan on the engine side of the radiator, and that's all.
This may be a silly question, but how do I search the Stickies?

kajtek1

I drove the similar setup years ago and don't recall the single fan to come on high even when I park it with AC on in 110F weather.
The system has originally huge excess of cooling capacity.
With bad coolants your radiator will develop build ups, what lowers cooling capacity.
Citric acid can restore it to some degree, fan will patch the poorer performance to some degree, but with history of bad coolants new radiator might be in the future.
I replaced enough radiators in the past and it was acceptable when they cost $120 for Volvo, but once I replaced $550 radiator on MB, I am religious about using only MB coolant.
Your car your money.
Coming to fan not going to high speed, I recall it being module controlled, so harder to troubleshoot. You said the fan comes on high with climatronic test, what is good sign, but troubleshooting the module is going be pretty difficult and part swap is often the easiest option.

ep4

The coolant has only been in there a couple of days, and the system looked very clean when I removed the thermostat. No sign of any weeping from the water pump or any other leaks I could see. The coolant I drained was almost clear, so it appeared to be the MB coolant. I have no issue putting that back, if needed. I don't think there is an issue with the radiator being clogged as this car was maintained by the local dealer, prior to being purchased. The temperature does respond to air flow when driven or when the fan is actuated, so the coolant is moving through the system and the thermostat is opening.
I don't recall if the fan ran at high speed with the air on, in the summer, in the past, but I do seem to remember it cycling, and I could hear it. Now it only comes on with the ac, and is slow. It never seemed to speed up with the ac, or without it on, and the engine temp rising. I don't think I would have an overheat issue, so the car is definitely safe to drive as it is, for now.
I agree that the climatronic test tells me the fan works, but does that mean the module is also working, since it runs the fan up the ladder at different speeds? Or can this test work, and there still be a bad module? Is the module controlled by the signal from the temp sender, or by the ecm/ecu?
I have read some vehicles had issues with the fans running full all the time due to bad ecm/ecu's but wondered if there could be the opposite as well.
Is there only one temperature sending unit on this engine? The one to the L side of the RH bank, with the U-shaped clip.
I suppose a new module would be a way to check the old one. $150 test, but it would probably cost that to take it somewhere.