Okay - this is starting to get on my nerves...

I took the car to Sig's ******** (the only Mercedes shop in Las Vegas that I've seen mentioned on this forum) for some work because I want to get all the bugs worked out before my daughter is born in June. He did a good job on most everything, but when I picked up the car the temp gauge was not working properly. I thought the car was running cool because the temp gauge only read 60-70C, but the car is actually running at proper temperature - it is the gauge that is not reading right. By the next day the temp gauge was completely dead - pegged at the bottom. He just replaced the temp switch (on the manifold between 2nd and 3rd cylinders) but the gauge is still reading low while engine temps are normal.

Any idea what else might be causing this problem? Thanks for the help in advance! I hate having to do research for my mechanic - I just wish I could find someone local who is really knowledgeable.

__________________
Autos:
1991 350SD 276,000 miles
2001 VW Beetle TDI 115,000 miles

Horns:
1955 Selmer Mark VI Alto (55,xxx)
1958 Selmer Mark VI Tenor (85,xxx)
1964 Selmer Mark VI Tenor (125,xxx)
1967 King Super-20 Tenor (430,xxx)
2002 Selmer Series III Soprano

For Jazz Saxophone enthusiasts - check out my website...
www.RustyBlevins.com

I would suggest pulling another gauge from a diesel W126. I don't think the ones from the 85 and older diesel W126s will work, since the newer W126 diesels have little lights that give ABS warnings and low windshield washer fluid level warnings.

__________________
'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.

Obviously I could be wrong, but I am not sure the gauge is at fault. If the gauge is grounded, the needle pegs at 120. It just does not read correctly from the temp sender.

Could it have something to do with low coolant level? When I started the car the evening after I picked it up, the coolant was low because of my greasecar system - all the air pockets filled and the coolant was low. I filled the coolant tank and it seemed to be okay, but I wonder if it could be related...

Any thoughts?

__________________
Autos:
1991 350SD 276,000 miles
2001 VW Beetle TDI 115,000 miles

Horns:
1955 Selmer Mark VI Alto (55,xxx)
1958 Selmer Mark VI Tenor (85,xxx)
1964 Selmer Mark VI Tenor (125,xxx)
1967 King Super-20 Tenor (430,xxx)
2002 Selmer Series III Soprano

For Jazz Saxophone enthusiasts - check out my website...
www.RustyBlevins.com

Try another temp sender....sometimes senders go bad right away. I had a brand new oil pressure sender go completely dead in 2 days.

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

Could it have something to do with low coolant level? (See my previous thread) When I started the car the evening after I picked it up, the coolant was low because of my greasecar system - all the air pockets filled and the coolant was low. I filled the coolant tank and it seemed to be okay, but I wonder if it could be related...

__________________
Autos:
1991 350SD 276,000 miles
2001 VW Beetle TDI 115,000 miles

Horns:
1955 Selmer Mark VI Alto (55,xxx)
1958 Selmer Mark VI Tenor (85,xxx)
1964 Selmer Mark VI Tenor (125,xxx)
1967 King Super-20 Tenor (430,xxx)
2002 Selmer Series III Soprano

For Jazz Saxophone enthusiasts - check out my website...
www.RustyBlevins.com

Any thoughts?

On my 85 617 there are 2 temp sensors on the left side of the engine between the # 1 & #2 glow plug and one between #2 & #3 plug. one is the temp sender & the other is for the temp sender for the glow plugs.
switch the wires, both senders wouldn`t be bad.

Don`t know about the 91 350, so just a guess.

Charlie ☺

__________________
there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works

Anyone else have an idea?

Are you sure the correct sensor was replaced?

__________________
1987 300TD 309, xxx 2.8.2014 10,000 mile OCI


Be careful of the toes you step on today, as they may be connected to the ass you have to kiss tomorrow. anonymous

“Be who you are and say what you feel, because those who mind don’t matter, and those who matter won’t mind.” Dr. Seuss

Yes - when the two contacts on the back of the sensor/sender are grounded, the temp gauge spikes to 120, so I am sure we are working with the correct sensor/sender. Neither the gauge nor the circuit are the problem - the sensor/sender is just not sending the temp to the gauge.

__________________
Autos:
1991 350SD 276,000 miles
2001 VW Beetle TDI 115,000 miles

Horns:
1955 Selmer Mark VI Alto (55,xxx)
1958 Selmer Mark VI Tenor (85,xxx)
1964 Selmer Mark VI Tenor (125,xxx)
1967 King Super-20 Tenor (430,xxx)
2002 Selmer Series III Soprano

For Jazz Saxophone enthusiasts - check out my website...
www.RustyBlevins.com