Coolant level sensor question

[500Espot]

Postby slk55r on Mon May 11, 2009 4:28 am

Hello,

I was just wondering if the coolant sensor is a weak link in the car. I've look at the extensive history of a couple 500e and both of the have had the coolant light come on with plenty of coolant. Seems like they had the sensors replace several times.

Is this something that I should expect on most 500e?

Regards,

Jesse
Renntech SLK55
Renntech Supercharger, Renntech ECU, Supersprint Long Tube Headers, Supersprint 100cell Cats, Supersprint X-pipe, KWv3 coilovers, Stoptech steel brake lines, 19in Carlsson Uls 1/16, 18in Renntech Monolites Matte Black

===============================

Postby gerryvz on Mon May 11, 2009 5:37 am

Yes, the coolant sensor is a common part that needs to be replaced. Mine had its first one done while still under warranty (i.e. nearly new), according to the dealer records.

Cheers,
Gerry

 

[Unavita]

Old- Gerry- but will this cause a stall or non start when warm?

 

[gsxr]

Old- Gerry- but will this cause a stall or non start when warm?

Nope. The coolant level sensor will only trigger a warning light in the instrument cluster. It has no connection to the powertrain computer systems.

 

[Unavita]

Nope. The coolant level sensor will only trigger a warning light in the instrument cluster. It has no connection to the powertrain computer systems.

Okay then. I made the mistake of shutting her off before warm then. Next time she runs I will allow her to reachoperating temp and then test the CPS again (CPK).

 

[Unavita]

Waiting for an SDS...

 

[Unavita]

It started all day today. I drove it several times. Then, at about 5pm, I went to start it again. All the dashboard lights came on but then they go dim, the fuel gauge goes to empty and there is a clicking sound in the glove box area- DID NOT RESTART this time.

 

[gsxr]

It started all day today. I drove it several times. Then, at about 5pm, I went to start it again. All the dashboard lights came on but then they go dim, the fuel gauge goes to empty and there is a clicking sound in the glove box area- DID NOT RESTART this time.

Do the lights go dim with clicking sound in glove box area, when you were turning the key to engage the starter?

If so, this sounds like a weak or dead battery. Put a volt meter on the battery and watch the readings while someone else turns the key. If the voltage drops from normal (~12.6v) to very low (below 12v, possibly much lower) when you turn the key... the battery has a shorted cell.

If the battery reads low (around 12.0v) with no load, it is badly discharged and needs to be recharged before testing.

 

[Unavita]

CPK warm is .990 Ohms.

 

[Unavita]

Battery reading when attempted start does go below 12v. Will use "restore" on charger and go from there.

 

[emerydc8]

@Unavita--You may already know this, but there was a service bulletin that discussed installing a washer/spacer on the crank position sensor to move it further away from the magnet. It's discussed somewhere on the forum.

 

[Unavita]

@Unavita--You may already know this, but there was a service bulletin that discussed installing a washer/spacer on the crank position sensor to move it further away from the magnet. It's discussed somewhere on the forum.

No I has no idea. Thank you very much. That is very good to know. I will search the forum for specs on the washer- because I am sure there are specs! After all, this is Mercedes-Benz we are talking about!

 

[emerydc8]

There is definitely a spec size. I remember having trouble finding a washer thin enough so I went with one over spec. It made no difference to my existing idle problem one way or another so being lazy I just left the washer in there.

Here it is.
Thread 'Crank Position Sensor: Adding Shim'
Crank Position Sensor: Adding Shim | M119 Engine

 

[Oldcar]

Okay then. I made the mistake of shutting her off before warm then. Next time she runs I will allow her to reachoperating temp and then test the CPS again (CPK).

Tested the 3 sensors on intake manifold
Black ones were whithin specs.
blue 2 pin was not.

Have replaced blue 2 pin coolant sensor about 4 times over last 15 yrs.

Symptom hesitation rough running prior to replacement then gone after replacement...

 

[gsxr]

The 2-pin sensor only connects to the HVAC system (climate control PBU). This should not affect engine operation.

The 4-pin sensor is for the ECU and EZL (fuel & ignition computers).

 

[Oldcar]

The 2-pin sensor only connects to the HVAC system (climate control PBU). This should not affect engine operation.

The 4-pin sensor is for the ECU and EZL (fuel

Wonder why it goes out so often and seems to be always be a fix? Mercedes mechanic turned me on to switching it out 20 yrs ago?