Tried Search but to no avail....PLEASE HELP
 

I have been having coolant temp issues with my M103...1990 300E and was hoping for direction...David Lee or Bong36 or someone? they seem to have a lot of expertise in this:

Here is my situation:

My car has been running between 100-118 for a while during most stop and go, I replaced the thermostat today and took it for a test drive..temp here is about 18 degrees celcius ..the car seemed great, not getting hotter than 100 degrees while in stop and go traffic, but then I decide to pull over and let it idle....sure enough it climbed back up :( Checked the fans and the passenger one was spinning but not the driver's side. I touched it lightly and it started going...

People were mentioning fuses and relays, My fuses are good, but for the relays different story: On the forum it was mentioned that if you take out the relays with the car started, the fans should come on, well I took the relays in position C (Aux fan relay) and B (preresistor relay) out and nothing happened. When I put them back in, the fans started turning, the passenger fan was spinning much faster than the driver's side fan. Also what occured above with the driver side not working till touched, occured.

Should I replace both relays? What is wrong with the driver's side fan? I am planning to do a flush and replace the fluid with 50/50 MB and Distilled water...what else??

As for the temp being normal and optimum, I do not believe that is correct...my car is much more sluggish when at that temp..

PLEASE HELP
:confused:

bump! :)

Hi

I've solved cooling issues on my grandads E220 (W124) my kid bro's 190e (W201) and my 190e.

Just for reference, the ambient temp where we are is like 30 deg celcius and all of our cars' running temp are around 82 to 85 deg in stop-go traffic.Never had a report of even reaching 100 deg!!!

My kid brother recently drove to Malaysia for the F1 races and he was stuck in a 1 1/2 hour jam coming back from the races and he reported that his running temp was at 85 deg all the way!!!

Back to your problem...

1 Fan bearings are going south???Source a cheap replacement from the wreckers...

2 I normally test the relays by applying 12V to it and use a multimeter to check the contacts.

From experience, if you are running around 100+ in low ambient temperatures, the electromagnetic clutch fan is not working (the big engine fan).

If it's working (it's electromagnetically locked to the engine somewhere above 100 deg celcius - i forgot the actual value), it will spin with the engine speed.If you are running at above 100 deg, you can rev the engine and get a friend to see if the clutch fan spins faster when you rev.If it consistently spins at the same velocity regardless of engine speed, it's not working.

3 possibilities - Fuse (unlikely), clutch fan temp sensor or electromagnetic clutch.

Of the 3 cars, only mine has 2 aux fans (driver and pass side).And yes, one spins faster than the other. One works off a temp sensor and the other works off both the sensor and the aircon high pressure switch.

Check and let me know if u are unsure. I can post photos if u need 'em.

Cheers.

Azhari
Babybenz 1991 190e 1.8

I also agree with you that if your temp there is 18 deg celcius, running at 100-118 deg celcius is abnormal (from experince with our Mercs here).

Optimum?No.Crappy?Yes.
:D

Oh, by the way, visited your website and your car rocks!

Cheers.

Azhari
Babybenz 1991 190e 1.8

ZorroAmg
 

What do you mean by "passenger side fan"? I have '86 300E . It is equiped with a viscous fan clutch. I am not sure if '90 model is the same, if so check your fan clutch to see if it gets engaged when hot as follows as follows: When the coolant temp gets high, lift the hood while the engine is running, turn off ignition while you watch the main fan. If it stops right away when the engin goes off then it works ok. If it continues to run for few more turns then it might have a problem. Also, if your coolant is old you might want to change it.

Engine fan properly the culprit
 

AZHARI had a very good reply for you there. However I just wanted to add something here for you.
If you can identify the engine fan sensor, while the engine is running you can short the two wires that go to the sensor together to force the electromagnatic clutch to engage.
-If the electromagnetic clutch engaged then your problem is the sensor.
- If the electromagnetic did not engage then the electromagnetic clutch is bad.
Or one other way is to turn on the A/C. When A/C is on, the electromagnetic clutch also engages automatically.
- So if A/C is on then the engine fan should be on. If the engine fan is not on while the A/C is on then most likely your electromagnetic ass'y is bad. Not the sensor, because when the A/C is on, the electrical circuit bypasses the sensor.
Good luck

On my M103 I had one bad fan and it didn't get unusually hot like yours. I expect its the engine fan. The electric fans can't cool an engine by themselves, I've been able to tell right away when the engine fan stops working.

I did fix my aux electric fan. One of the brushes stuck. I just had to take it out and apart and un-stick it. Your's is slow so it just needs cleaning/lubing. On my 190e the front bumper had to come off. If its the same on the 300e, take the temperature sensor off first before you drop the bumper, its in the licence plate frame.

Thanks for the info everyone...keep the posts coming...i need as much info as i can to start the diagnosis...

The engine fan sensor is located where? Is it different from the relay?
Taking off the bumper to diassemble the driver side relay is out of the question, I do not know the procedure and do not want to try it...How much labor/ tiem would the mech charge to replace the fan?

Ho about the Clutch fan...I wont have access to a hoist without taking it to the mech..

TIA...please help me solve this little bugger of an issue...

The engine fan sensor is cylinderical and is screwed into the engine behind the oil cap.

Another way to test it is as 16VAlex mentioned.You pull the connector off the sensor and use a piece of wire to create a short on the connector.

My mech took about 25 minutes to replace the electromagnetic clutch on my car (he's GOOD, FAST and CHEAP).No hoist required.

He worked from the front of the car and had to loosen the serpentine belt.Then he took off the fan shroud, blades, etc before gaining access to the clutch in front of the water pump.

I replaced the aux fan on my kid bro's 190e and it took me about 2 hours.I had to do some modification to the mounting brackets coz the fan came from an earlier model 190e and had slightly different mountings.

I believe a good tech would take about half an hour to do it.

Good luck with the test.

Azhari
Babybenz 1991 190e 1.8

FWIW fan cut in temp must be country dependant. On UK 190's for example the Fans do not cut in until just over 100 deg C, about 104 I think. Normal temp on the move is about 84 deg C. This is with abient temps of 15deg C. My Volvo has exactly the same setup so I guess this is pretty common for the UK at least.