Warming A Diesel - Study Hall

[Ex-Calif]

Alan,

Excellent post. I'd like to explore the advice regarding warming up a diesel.

We start our diesel and get undeway with no dealy. We operate at around 1,000 RPM for about 3-5 minutes. Here's my concerns.

Oil Pressure - If you are running anything higher than 30W the oil can be very viscous until it is warm. Oil splashing is generally how the cylinder walls are lubricated and cooled. Operating at a high load with highly viscous oil could cause piston skirt scrubbing leading to engine deterioration, higher oil consumption and blow by. Secondly, bearing clearances are also very tight at start up and open slightly with temps. Tight initial clearances and highly viscous oil could cause bearing scrubbing and in a worst case bearing spinning.

Piston and Cylinder Thermal Stability - At start up the clearances between the piston and the cyclinder are at their greatest. Some cylinders are cut with a taper because the upper end is hotter and will expand more at the top than the lower end. A "cocking" of the piston is possible at low temps making the above cylinder scrubbing problem worse.

Thermal Expansion - Metals expand in proportion to the heat applied over time. If I am applying a lot of heat to the cylinder head right after start up there is a risk of cracking as opposed to a gentler warm up.

I am interested to hear your opinions on these statements in relation to diesel engines. I agree that you dont' want to start and run in idle for 10 minutes but on every internal combustion engine I have owned and operated I have always allowed a period of low power operation until oil and metal temperatures are stabilized, or on the way to being so.