This is for a 1990 300e - I noticed a small crack in my upper rad hose, and want to know what is required to replace it so that I don't get air in the system. I have the replacement part ready to go, by want to do this correctly.

Also how do I test my aux fans, both are free to move by hand but car is running hot in traffic, no problem when moving. I am in Toronto Canada and it's not even summer yet.

Hi there,

It is possible that your rad plastic tube that the hose connects to is cracked or broken.

I am assuming you mean the large rad hose - correct?

When the engine is cold, remove the air temp sensor and the air snorkle connected to your air filter housing. Now you can hold a clean plastic container under the hose at the rad as you loosen the clamp.

Carefully remove the hose allowing the coolant to drain into the plastic container.

you will see clearly if the plastic is cracked or broken or not. You will likely need a new rad. I replaced mine two weeks ago, also 1990 w124.

I'm in Richmond Hill, feel free to send me a PM and I can advise better.

Thanks, Got it done, looks like the housing is okay, didn't see any cracks.

I now need to address the aux fans, which aren't working on the high setting (since my A/C doesn't work). Disconnected the sensor recommended by others, and that didn't get it working. So I am guessing either relay or motors themselves. Any way to test either?

Did you pull off the connector to the sensor forward of the temp sensor on the cyl head? Or you can jump the wires that connect to the temp switch on the AC dryer. the switch has wires directly attached that are about 5" long, jumper the wires that attach to those on the switch.

Either of these should get the fans to come on.

I assume you have checked/replaced the fuses?
Acky

These are the wires (tails) that are jumped to activate the aux fans at low speed.


The fans operate at low speed when the sensor in the A/C dryer determines that extra cooling air is required to flow across the condenser in front of the radiator. If you are low on AC gas then the sensor will not operate correctly and the fans will not engage when required.

There is a sensor on the engine block that engages the aux fans to high speed. The fans should come in when the temperature reaches around 120 degrees and then shut off again when the temperature is reduced to 100 degrees.

There is a controlling relay near the fuse array that activates from the sensors to engage the fans. If shorting the AC sensor tails does not cause the fans to operate I would be looking at the relay.

Fuses okay, I have checked the fans by removing the connection to the sensor on the Cylinder head but no luck.

Thanks for the drawing that helps me understand a bit more. But which wires do I connect exactly. And if that gets the fans going, then I am assuming it's not the fan motors but the relay. Which relays control the fans, I believe B and C, but which one works the high speed portion, since I won't be fixing my A/C anytime soon.

addbhp,

Dude,

If you did not already, carefully check fuse 7, and fuse D. They power the two relays involved.

Make sure you disconnected the correct sensor, forward of the 4 pin temp sensor at rear of cyl head....do this with the engine running. This activates relay in possition C. of relay box at rear of fuse box.

To sumulate high AC temp jumper the wires that connect to the wires attached to the switch in the photo...see arrows. Note do this also with the engine running. Also note that If the fans do not come on here don't worry because they will never come on until you repair the AC system anyway.

If the fans do come on here, everything is in order, they will not come on untill the sensor senses hi temp at the dryer (only possible with a charged and working AC system)

Good luck with it,
Acky