To warm up or not to warm up? - Page 4 - PeachParts Mercedes-Benz Forum

wildest · #46 02-15-2014, 11:44 PM

Quote:

Originally Posted by whunter

This is not a 1908 Oldsmobile...

This is a MODERN vehicle.

Do not waste time attempting to warm up.

Once the engine is running stable, oil pressure has come up, it is ready to drive.

I DON"T baby my vehicles, hammer the throttle and ignore the sluggish response (typically gone within 2-400 feet).
This is a prechamber diesel = it is always happiest under LOAD, especially in the cold.

Putter and baby the engine in cold weather, and you build excess coke in the prechamber - piston chamber..

If everything is stock; You can not damage the engine in any manner by instantly driving to the limit (as designed) in cold weather.
I have Never lost or had a customer lose a Mercedes diesel by instantly driving on winter cold start.

Typical cold weather engine failures:
* Water pump belt failed, and continued driving.
* Little or no Antifreeze protection = slush or frozen cooling system.
* Engine oil below critical level, and continued driving.
* Road ice breaking radiator or oil pan.
* Engine temperature falling while driving (extreme arctic cold), partially block the radiator with cardboard so you don't freeze to death.

I have heat within one mile, unless ambient temperature is below -20° F, then it takes 1.5 miles.

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My experience in a much warmer climate with 2 very different 123's.

NZScott · #47 02-16-2014, 01:04 AM

Very interesting thread.

I always warm my car up for 5-10 minutes before I drive it regardless of temperature (and I do live in a rather warm area where it rarely gets below freezing). It's 20C/68F at 7pm right now.

I always use the high idle knob. I take off when the temp gauge says 40 (my temp gauge is horrendously inaccurate though, it says around 60 when hot). I just don't have the heart to drive off when the injectors are nailing away and smoke is wafting across the front lawn...

I realise idling and driving a diesel like a granny is bad for it, so I have a lead foot - I even broke the accelerator cable once!

whunter · #48 02-16-2014, 01:26 AM

Quote:

Originally Posted by Jnormous

Alright so we have the following post:
and then we have this post:
So I'm left with the conclusion that I should drive immediately in old weather (0-30 degrees) yet keep it under 2500 rpm until the engines reaches 80 degrees C.

This sounds about right, although I do have one last question.

My SD struggles to shift right off the bat in cold weather.
Feel like she shifts very late.
She is fine once she reached optimum temperature and operates as expected.
Is this normal?
Anything I can do to alleviate this?

As I noted:
I DON"T baby my vehicles, hammer the throttle and ignore the "cold NORMAL" sluggish response.
This is a prechamber diesel = it is always happiest under LOAD, especially in the cold.

Note: When I use more throttle throttle in drive after a sub-zero cold start:
* Sluggish is a generous description of engine response 32° F is OK, -10° to -20° F is 2-2.5k RPM for the first mile, -25° to -40° F is 1.2-2k RPM for the first mile, then I can back off as it warms up.
* Automatic transmission response time is directly related to ambient temperature, 32° F is not to bad, -20° F is poor, -30° to -40° F is horrible until the engine reaches 40° C.

BASIC PHYSICS / thermodynamics:
From experience, the safety is designed / built into these engines, COLD cylinders = seriously poor combustion = self limiting energy available = the transmission wants more power/energy than is available = using more throttle under load has little or no effect "UNTIL" the cylinder combustion improves (warms up).
Please consider the cylinder temperature gradient
http://www.peachparts.com/shopforum/diesel-discussion/134359-never-touch-hot-diesel-glow-plugs.html

Common sense should tell you how rapidly to back off the throttle as it warms up.

As long as the engine has the correct SAE weight oil for the ambient temperature and is under load, there is no risk of engine damage.

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