Mercedes-Benz Forum banner

1 - 19 of 19 Posts

·
Registered
Joined
·
13 Posts
Discussion Starter #1
Hi guys,

I've now read a variety of posts suggesting different information - the car is a 1991 300E 2.6L engine and I'm attempting to locate and replace the coolant temp sensors as part of a 200K refresh. In various posts I've read that two sensors are located on the thermostat housing (single pin sends data to cluster and multiple pin to the fuel system). What sensor is located at the rear of the head (green top) and is it utilized on all engines?
 

·
W124 Moderator
Joined
·
12,601 Posts
Vic

The rear most sensor on the head is the engine temperature sensor. It to, sends info to the ECU.

Jayare

Sent from my XT1710-02 using Tapatalk
 

·
Registered
Joined
·
13 Posts
Discussion Starter #4
if the sensors aren't broken, don't 'fix' them. those sensors generally last the lifetime of the engine, unless they get physically broken.
I've had recent issues with the car running quite hot (see attached) and intermittent issues with the Coolant Warning light coming on - the coolant levels are perfect, so my concern is that the sensors are playing tricks on the car. While I know these cars are hot blooded, i'm concerned that running this high temp daily may stress the engine. The fans kick on, and California head isn't helping, but still - or is this normal?
 

Attachments

·
W124 Moderator
Joined
·
12,601 Posts
I wouldn't find the temperature in your pic to be alarming. Maybe more importantly, does the car cool down a bit when it's moving?

Miles on the radiator/car? Have you removed the shroud around the aux fans and cleaned the debris collected between the shroud and the condenser?

Jayare

Sent from my XT1710-02 using Tapatalk
 

·
Registered
Joined
·
76 Posts
The lamp is for low level in the tank.
The sensor in the rear of the engine is for the ecu. Sensor for the coolingfan is on the front. 2 or 3 pin.
The sensor for the temp.gauge are also in the front, 1pin or the 1 pin on a 3pin sensor.

Sent fra min H8324 via Tapatalk
 

·
Registered
Joined
·
13 Posts
Discussion Starter #8
I wouldn't find the temperature in your pic to be alarming. Maybe more importantly, does the car cool down a bit when it's moving?

Miles on the radiator/car? Have you removed the shroud around the aux fans and cleaned the debris collected between the shroud and the condenser?

Jayare

Sent from my XT1710-02 using Tapatalk
I'd have to check service records for when the radiator was replaced - the car has 195K miles - I'll also need to search how to remove the aux fan shroud and see if there is debris behind the shroud! All great feedback - really appreciate it!
 

·
Premium Member
Joined
·
6,734 Posts
that low level sensor gets gummed up, especially if funky coolants have been used... its stuck in the bottom of the forward facing side of the coolant overflow tank, and can be removed and cleaned.

hows the centrifugal clutch on the mechanical fan?

as W201 says, the cooling fans are run by one of the front sensors... the rear sensor for ECU will cause lousy gas mileage if its wrong, but not much else... ok, it could make hard starting if it told the ECU that the engine was hot when it wasn't.

reading a hair above the 100 tick on the temp gauge is pretty normal at an extended stoplight in hot weather. it should promptly go down when you're moving.
 

·
Registered
Joined
·
13 Posts
Discussion Starter #10
that low level sensor gets gummed up, especially if funky coolants have been used... its stuck in the bottom of the forward facing side of the coolant overflow tank, and can be removed and cleaned.

hows the centrifugal clutch on the mechanical fan?

as W201 says, the cooling fans are run by one of the front sensors... the rear sensor for ECU will cause lousy gas mileage if its wrong, but not much else... ok, it could make hard starting if it told the ECU that the engine was hot when it wasn't.

reading a hair above the 100 tick on the temp gauge is pretty normal at an extended stoplight in hot weather. it should promptly go down when you're moving.
I appreciate all of the feedback! I will drain the overflow tank and remove the level sensor/replace it as they're fairly cheap, as well as check for any debris on the fan shroud!
 

·
Premium Member
Joined
·
6,734 Posts
I appreciate all of the feedback! I will drain the overflow tank and remove the level sensor/replace it as they're fairly cheap, as well as check for any debris on the fan shroud!
unless the sensor switch is actually broken, you probably just need to rinse the slime off the flippy-end that sticks into the tank, and maybe flush any slime out thats accumulated in the bottom of the overflow tank.
 

·
Registered
Joined
·
13 Posts
Discussion Starter #12
unless the sensor switch is actually broken, you probably just need to rinse the slime off the flippy-end that sticks into the tank, and maybe flush any slime out thats accumulated in the bottom of the overflow tank.
I went out there andchecked it and the switch is actually leaky/the connector is wet, so I think i rather replace it, but i also checked my thermostat housing and I don;t have either of the sensors that sends the temp to the cluster or the fuel module - back to square one. :frown
 

Attachments

·
Registered
Joined
·
13 Posts
Discussion Starter #14
You need to remove the air filter housing to see/test the sensors on an M103 motor.

Sent from my XT1710-02 using Tapatalk
I thought they were on the Thermostat Housing? I come from the VW/Audi world - where can i verify which engine specifically I have? I've seen people post 103.XXX
 

·
Registered
Joined
·
13 Posts
Discussion Starter #17
unless the sensor switch is actually broken, you probably just need to rinse the slime off the flippy-end that sticks into the tank, and maybe flush any slime out thats accumulated in the bottom of the overflow tank.
Ended up checking the sensor and while it was leaking, it certainly was slimy! Due to the leak, I ended up ordering a new one, along with a 87 Degree Thermostat to help cope with California Heat
 

Attachments

1 - 19 of 19 Posts
Top