What are the typical operating temps of your 617 engines (highway travel) during cool/cold weather? Mine doesn't seem to rise much above 60C. The heater doesn't blow very hot air, and I have bypassed the ACC servo. This is my first winter with this car (1980 300SD), so I don't have much firsthand experience with it. I am considering blocking off part of the radiator to try to raise the operating temps (I'm also running the car on a WVO blend).

I suppose there's a chance that the PO removed the thermostat for some reason, does anybody have a suggestion for testing the thermostat operation without removing it from the car? I'll open the thermo housing if necessary, but I don't really want to make that big of a mess today.

Thanks for any input.

Steve.

__________________
'93 190E/D 2.5 Turbodiesel 5-speed (daily driver)
'87 190D 2.5 Turbo rustbucket - parts car
'84 Dodge Rampage diesel - Land Speed Record Holder
'13 Ram 2500 Diesel
'05 Toyota 4Runner

I think you have already tested it haven't you? By your temp reading so low in conjuction with lack of heat indicates to me that stat is either missing or stuck open. Better than stuck shut!! Maybe some other more senior members can offer suggestions for testing w/o removal.

I would change that stat ASAP...

Cheers,

Bill

At this point, you have to open the thermostat housing and determine if you even have a thermostat. If you do, I wouldn't even bother to test it. The symptoms, including a low gauge reading and no heat, indicate that you need to change it.

These engines run 83-90 C. on the highway, even if it is 0 F.

They will drop down to below 80 C. at idle if it is really cold (below 20 F. or so).

temp here is around 5dec C, and around town it wud never get up to 80,, but i hardely ever just drive around town.. on the motorway it stays pretty much dead on 80

Please start by replacing the thermostat! Diesels DON'T generate much heat when not loaded and in below zero (F) temperaturers, blocking off part of the radiator can be desirable, but in ordinary driving the engine is designed to come up to the 80-90 degree (C) operating point in about 3-4 minutes of driving. If it doesn't, the most common problem is a thermostat that's stuck open.

Most people think of the thermostat as a device involved in cooling the engine, but it's PRIMARY function is to PREVENT cooling until the engine reaches the lower limit of proper operating temperature range.

If the temperature runs low, engine wear increases and combustion efficiency declines. I've seen fuel economy drop 20% in a Mercedes diesel that's running 15-20 degrees (C) too cold.

Marshall

I'll see if I can get a T-stat locally this afternoon.

Steve

__________________
'93 190E/D 2.5 Turbodiesel 5-speed (daily driver)
'87 190D 2.5 Turbo rustbucket - parts car
'84 Dodge Rampage diesel - Land Speed Record Holder
'13 Ram 2500 Diesel
'05 Toyota 4Runner