Over cranking diesels with waterlift mufflers-Potential Prob

[Don Metznik]

Viewing the recent post on bleeding a diesel (I have the MD7A in my CD30) reminds me of a caution I learned at a diesel seminar. According to my instructor, if you crank a diesel with a waterlift muffler for over 30 seconds you risk filling the muffler with water and forcing the water back into the cylinders, with disasterous results. This occurs because the water is not being exhausted, as the engine is not running. I was told that this is a possibility even with vented hoses.

The solution is to close off the cooling water supply during extended cranking.

I recently bled the engine and I cranked it at least for a couple of minutes until she was free of air and caught on. Then I opened the seacock and everything was fine.

You can also open the drain screw in the muffler to check if it is filled. I did this at one point after cranking for about 30 seconds and found very little water in it.

I was not very comfortable with the idea of closing the intake, but it seemed to work.

I welcome comments and corrections.



don@metznik.com

[Randy Bates]

That's EXACTLY how I've been taught. If for ANY reason you need to crank for an extended period of time, close the seacock and then open it once the engine fires. This includes excessive cranking needed to bleed the fuel lines or simply a motor that is taking too long to fire.

Viewing the recent post on bleeding a diesel (I have the MD7A in my CD30) reminds me of a caution I learned at a diesel seminar. According to my instructor, if you crank a diesel with a waterlift muffler for over 30 seconds you risk filling the muffler with water and forcing the water back into the cylinders, with disasterous results. This occurs because the water is not being exhausted, as the engine is not running. I was told that this is a possibility even with vented hoses.

The solution is to close off the cooling water supply during extended cranking.

I recently bled the engine and I cranked it at least for a couple of minutes until she was free of air and caught on. Then I opened the seacock and everything was fine.

You can also open the drain screw in the muffler to check if it is filled. I did this at one point after cranking for about 30 seconds and found very little water in it.

I was not very comfortable with the idea of closing the intake, but it seemed to work.

I welcome comments and corrections.

randy.bates@baesystems.com

[Chris Scheck]

Do you mean 30 seconds total, or 30 seconds continuous cranking? I'm sure I've cranked for 30 seconds total plenty of times.

Chris Scheck
CD33 #117
Ragtime



cscheck@aol.com