I have new coolant in system.... can i replace Tstat--w/out draining coolant?

any advice?

Is wahler- good tstat replacement part? will it come w/ Sensor?

Yes, Wahler is a good brand and may be the brand originally installed on your vehicle at the factory. It is one unit that includes the housing and sensor. I read, perhaps on this board, that if you siphon some of the coolant out, the T-stat can be changed with little or any loss of coolant.

Here is a link to Whaler at a good price ($51): E320 CDI T-stat by Wahler

If you don't need it fast, here is a Behr (also OEM) one for about $42 shipped from Berlin, Germany!: E320 CDI T-stat by Wahler

I considered changing my T-stat when I changed my coolant at 150k. Since the maintenance records indicated it had been done once before and given how you dion't have to drain the coolant, I decided to just keep a spare T-stat in my trunk for cross country trips.

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-- Chris

'95 E300, 216k miles, Silver Surfer
'05 E320 CDI, 138k miles
'07 S550 4matic, 69k miles

Gone but not forgotten:

'76 300D, 350k miles?, SOLD in 1995
'75 240D, 300k miles, SOLD in 1991

You'll have to drain at least out of the cylinder head or 1/2 off the radiator because the oil filter cap is blocking the bottom bolt and the thermostat housing from been removed, and When you remove the thermostat the coolant will come gushing out of the cylinder head and straight into the oil filter housing.

__________________
Current Garage
2008 Mercedes GL320 CDI 188k mi Repair/Work in progress
1994 S350 160k mi Garage Queen & prepping for repairs
2005 E320 CDI 203k mi Healthy & Daily Driver
1994 S350 357k mi Retried as parts car
1984 300TD 214k mi Blown OM617 Poss OM603 Swap??

Sold
1987 300SDL 200K+
1994 S320 181K mi
2008 E320 Bluetec 127k mi
1999 S420 130K mi
1980 240D 360k mi
15+ Others that has come, stay and gone

GONE, BUT NOT FORGOTTEN
1995 E320 SE 220k mi
1984 300SD 350k mi

Yes...just drain the expansion tank.

Watch this DIY video by Josh8loop.

https://www.youtube.com/watch?v=jiV9uhjwTQQ

__________________
14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

Thanks!