190D 2.2, can it run "too cold"? - PeachParts Mercedes-Benz Forum

volosong · #1 07-09-2009, 10:16 AM

I've only had my '85 190D 2.2 5-spd for about a month now and it has been a long, long time since I had my '80 240D 4-spd, so my memory on the operating temperature of a diesel is a little rusty. That memory is also influenced by my driving a 300CE in between, which runs pretty much at 80° C most of the time, unless under load (pulling a long, steep grade in the heat of the day), or cruising on the open road during the winter.

I've notice that my 190D runs pretty cold, hardly ever getting above 60° C, unless I'm pulling a grade when I have to downshift to fourth or even sometimes, third gear to get over the summit. Then the temperature will rise above 60° C, but still stay below 80° C. On the downhill, the temperature drops pretty quickly back to its sub-60° C range.

The radiator was replaced just before I purchased the car. My question is...are there any adverse effects of a diesel engine running so "cold"? Do I need to worry about this...or is this a good thing?

barry123400 · #2 07-09-2009, 11:29 AM

In my opinion normal operating temperature is better. You should check the accuracy of your temperature reading system before changing the thermostat though.

volosong · #3 07-09-2009, 11:58 AM

What is the normal operating temperature for the low displacement diesels? 80°C?

fruitcakesa · #4 07-09-2009, 12:07 PM

Both my 240's run between 80 - 90 depending.

compress ignite · #5 07-09-2009, 12:36 PM

WAG [humor](Since your Thermostat is an 85 "C" )

Eighty Five degrees "C" ?

BUT,take barry123400's advice and check the accuracy of your Temp Gauge
AND Sender before condemning your Thermostat!

pawoSD · #6 07-09-2009, 02:34 PM

Quote:

Originally Posted by volosong

What is the normal operating temperature for the low displacement diesels? 80°C?

Pretty much all MB's run around 82-85C....my diesel and gasser run about the same temp. The gasser gets a little warmer on a hot day sitting in traffic with the A/C.....around 90-93C.....otherwise they both run around 83C.

Yours is running way too cold, get that thermostat replaced! It is very likely stuck open. My gasser had a stuck thermostat when I got it, it would barely get above 65C.....

moon161 · #7 07-09-2009, 03:19 PM

Ill effects of cold running could be lost efficiency and blowby due to poor ring sealing. Rings are sized to fit at a higher operating temperature- that's why compression & leakdown tests are spec'd at 80C coolant temp. Blowby could contaminate crank oil with diesel fuel. If you are greasing, contaminating the crank oil w/ VO is a bad idea.

volosong · #8 07-09-2009, 03:53 PM

Thanks for the info. I'd always thought, (with gassers at least), that the cooler an engine runs...the longer it will last. Your explanations are informative, and I'll heed them.

In purchasing this diesel, I want to attempt to perform as much maintenance myself as possible instead of paying my mechanic to do it. Is swapping out the thermostat fairly simple? p.s. I have a Haynes manual on the way from Amazon, but won't get it until next week.

compress ignite · #9 07-09-2009, 05:07 PM

The only cautions are:
1.'Get All the old gasket off without scratching the Mating Surfaces.
2.Do Not ,Do Not OverTorque the Thermostat housing (or Water Pump) Bolts.
[you be screwing Steel into Aluminum housings!]
3.Make sure you have the Thermostat properly oriented as to Water Flow.