Car: 2001 E430

How do I replace the coolant temp sensor on my E430? I can see it in plain view but suspect it clips into place, as there is no bolt hole on the new sensor's housing.

I just don't want any nasty surprises, as I will have limited time to do the job and need to be back on the road quickly.

__________________
2008 E350 4matic / Black/Anthracite

------------------------------------
Gone but not Forgotten:
2001 E430 4matic, 206,xxx miles, Black/Charcoal
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black

Got a pic? Coolant sensors need to be wetted with coolant in order to give an accurate reading. I've never seen a clip on external sensor, they should thread in.

Or do you mean that the sensor has an o ring and it slides into the housing? In that case the retainer bracket is to be reused.

Yeah, in these end times it’s held by a clip. There’ll be something like a staple sticking up where the sensor meets the engine. Pull up to remove the clip then wiggle the sensor out. Nothing to it.

Sixto
98 E320s sedan and wagon

Yes, I see it -- an inverted U-clip that I will pry up using a long screwdriver. As I will almost certainly drop the clip, I hope it is magnetic.

Thanks, to both of you.

New question: Will replacing this sensor likely "wake up" my aux fans, which I noticed were not spinning yesterday -- neither when engine is hot or when A/C is on. (A/C works but feels only about half as cold. R134 pressure is at max/full.)

Some background:
I an focused on the coolant sensor because, since last Fall and into the winter, I was getting frequent Check Engine lights with P0115 codes (along with camshaft position sensor error, which has already been replaced). Interesting how they are right next to each other and crapped out at the same time. More interesting is that I did not get a P0115 when I checked codes yesterday (but if the sensor was faulty in the winter it is still faulty now.)

Additionally, I have replaced the number 20 fuse for the fans but still nothing. If the coolant sensor is not the solution, I will shift focus to the fan control module.

__________________
2008 E350 4matic / Black/Anthracite

------------------------------------
Gone but not Forgotten:
2001 E430 4matic, 206,xxx miles, Black/Charcoal
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black

There’s one coolant temp sensor for everything. Is the temp gauge accurate?

Does at least the driver side fan spin freely by hand?

IIRC the ACC module triggers the fan even when ACC is off.

The fan controller is under the driver side headlight. [edit - I said passenger originally]

Sixto
98 E320s sedan and wagon

I believe the gauge is accurate. It is behaving as it has for years, except now it reaches 100+, something it has never done before.

Both fans spin freely by hand -- turning one turns both. I also tried a climate control test I saw online -- holding both "auto" buttons down for 5+ seconds to kick on the fans but that did not work, or may not apply to my car.

Thanks for the scoop on the location of the fan control unit! An online source said it was on the left side, which to me is driver's side; but the source was obviously speaking from a mechanic's POV, where left is passenger side.

Regarding the ACC (which I assume means automatic climate control), and which may or may not be relevant, is that I threw the serpentine belt in January when the idler pulley shattered. After repairing it, and replacing the belt, the climate control EC light would not go off. Resetting the ACC, using that method where you add 16 to the number displayed next to "P2", resolved it. (When I backtracked to the previous setting the EC problem resumed. Resetting it cleared it again.)

__________________
2008 E350 4matic / Black/Anthracite

------------------------------------
Gone but not Forgotten:
2001 E430 4matic, 206,xxx miles, Black/Charcoal
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black

>>>>a mechanic's POV, where left is passenger side. <<<<

L/R are orientated from the OPERATORS seated position.
Left is always Operators left , and Right is always right.

The only time Passengers side is Left is on a RHD car.

__________________
A Dalton

I edited the statement on the location of the fan controller. It’s under the driver side headlight.

Sixto
98 E320s sedan and wagon

OK.

Also as Sixto noted, the control unit is indeed on the drivers side -- in a very inaccessible place under the headlight between the bumper and wheel well. (Requires an inspection mirror to locate.) I suppose it could be reached more easily, if necessary, by removing the front fender liner.

__________________
2008 E350 4matic / Black/Anthracite

------------------------------------
Gone but not Forgotten:
2001 E430 4matic, 206,xxx miles, Black/Charcoal
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black

Im not familiar with facelift 210s but it should be accessible if you remove the panel under the bumper. Then it’s above the fog light.

Sixto
98 E320w sedan and wagon

You mean the panel that I open to change the fog light bulbs? Never considered that -- thanks!

I am just hoping it does not come to that.

__________________
2008 E350 4matic / Black/Anthracite

------------------------------------
Gone but not Forgotten:
2001 E430 4matic, 206,xxx miles, Black/Charcoal
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black

I'm pretty sure this still has the older heater control that goes back to 95 or so. ( long thin display, buttons all around )

With the key on or engine running, turn the fan to low. Press and hold the " REST " button and wait. The display will go to a data screen flashing a 01 then another number. Use the fan - and + buttons to scroll through the screens ( 02 , 03 , 04 ) Engine coolant temp is somewhere in the 05 to 09 range.

If the coolant temp is showing a believable temp, changing the sensor won't fix your problem. There is only one coolant temp sensor, it is connected to the engine computer then data sent over CAN bus to trans . HVAC , dash.

You can also get diagnostic info with other buttons. The type of control was used on most all MB from 95 to 01 or so. They do not directly interchange as the E and S had split temp and the C / SL single temp.

Ran the tests and I assume 1 to 4 refer to these:

B1226 - In-car temperature sensor (B10/4)
B1227 - Outside temperature indicator temperature sensor (B14)
B1228 - Heater core temperature (B10/1)
B1229 - Heater core temperature (B10/1)

And 5 to 9 refer to these:

B1230 - Evaporator temperature sensor (B10/6)
B1231 - ECT sensor (B11/4)
B1232 - Refrigerant pressure sensor (B12)
B1233 - Refrigerant temperature sensor (B12/1)
B1234 - Sun sensor (B32)

The values for 1-4 made sense and seemed accurate, relative to ambient temperature (80-90 degrees). Values for 5-9 were off -- by EDIT: 12-70 degrees -- relative to ambient. (I had not started the car since yesterday, so all should have been at or near ambient.)

The sensor replacement, as expected, had the nasty surprise I was wary of: The old sensor melted/fused into the socket, which itself crumbled. So I will be replacing that also -- and I would advise anyone who does this job to spend the few extra dollars on that, in case you need it.

Overall, the job itself is straightforward -- IF you know to remove the secondary air pump first (and how easy it is to do it). I did not, at least not for the first hour... Getting the sensor clip off without removing the air pump is easy; getting it back on without doing so is impossible.

With sensor not present, I have a new CEL but still no aux fans, which I assumed would kick on like they did in my W124's, when said sensor was disconnected. Or are the 210s somehow different?

__________________
2008 E350 4matic / Black/Anthracite

------------------------------------
Gone but not Forgotten:
2001 E430 4matic, 206,xxx miles, Black/Charcoal
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black

*** UPDATE ****

Fans are running intermittently.

I read that banging them could bring them to life. I used the climate control to to start them, lightly pounded the left one (with the motor) with the heel of my hand, and got some slow movement.

Started engine with A/C on and, after spinning the left fan, got slow movement with a with loud squeal from the bearing, then it stopped, Spun it again and it resumed (with squeal), then stopped. Spun it yet again, then it accelerated to its high-speed roar; slowed; accelerated; slowed; accelerated, etc.

I am guessing the latter behavior is related to the absence of the coolant sensor, thus the fan has no idea what speed to stay at(?) I will know for sure tomorrow when the new coolant sensor is in. For now, it seems the (left) fan is the problem.

Can these be serviced, i.e, new bearings -- or is it best to replace?

__________________
2008 E350 4matic / Black/Anthracite

------------------------------------
Gone but not Forgotten:
2001 E430 4matic, 206,xxx miles, Black/Charcoal
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black

The second nasty surprise: You must assemble the sensor socket!

There are three components: The plastic socket housing; 2 metal plugs (for the sensor prongs); and 2 rubber grommets.

The presumption is that a user will slide the grommets over the live and ground wires; one end of the wires into the metal plugs; crimp the grommet to the plug; slide the plugs into the plastic housing’s respective holes, with grommets sealing the holes against water intrusion. Simple, right? WRONG!! The plugs and grommets are TINY, like grains of rice.

If I was the size of a squirrel, with squirrel-sized hands, that would not have been a problem. So what I had to do instead was:

* Recover the plugs, wires and grommets intact, from the old socket, cutting about 2 inches down the harness
* Strip insulation from ends of old wires;
* Splice one end of old wire to a section of new wire;
* Crimp inline wire connector to other end of new wire;
* Wrap one metal plug with friction tape (to prevent shorting);
* Push the plugs onto the new sensor’s pins;
* Pack the new grommets into the sensor’s cavity (to minimize any plug movement);
* Wrap friction tape around the new wires and part of the sensor housing (effectively immobilizing them);
* Wrap a layer of self-fusing silicone tape (for water resistance);
* Strip insulation from two wires in sensor harness;
* Crimp inline connectors from new wires to harness;
* Slide new sensor into engine and clip into place.

Works just fine.

Using climate control unit data, I observed my fans come on at 218 degrees (F). Running at low speed, they maintain 206 at idle and 184 to 211 in normal city driving. Dashboard needle sat at the top of the “8”on the 80 degree mark, as it has ever since I had the car, so all is normal.

Because the fans came on right as I tapped them with my hand (at 218F) I worried that after shutting the car down they would not start again. However, after running an errand and parking for a bit, they did come on at low speed. Nonetheless, I know they are sticky and may still need replacement.

Finally, I could hear some evaporator hissing, suggesting my refrigerant pressure is low. While adding a small can, I heard/saw the aux fans surge once or twice, so I think the high speed is more specific to the A/C than the engine.

__________________
2008 E350 4matic / Black/Anthracite

------------------------------------
Gone but not Forgotten:
2001 E430 4matic, 206,xxx miles, Black/Charcoal
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black