Other Diesel Engine Manufacturers

CURRENT POSTS:	0 from past 7 Days
TOTAL POSTS:	783 posts [Members]

BOATDIESEL FORUMS

POWERTRAIN

Marine Diesel Engines

Ford Lehman

TOPIC DETAIL

Topic: Cracked Engine Block!

				
         Originator: John
        
			Level 2 Member 
			    									
        Date: 
				
           17 October, 2009 - 09:04 PM

I think I have a cracked block!
Equipment: Lehman 2715 E (120 HP) 1981 with approx 1100 hrs reading on hour meter. This engine is the port counterpart in a twin engine 42 GB Classic that I have owned since 10/2007. There have never been any major problems and I have been compulsive with maintenance. I have contributed 400 hrs plus to the total hours on the meter. I have NEVER overheated my engines.

I now have persistent contamination of my crankcase oil with coolant (and visa versa). This problem started in early August, and I went thru the litany of possible causes. I changed the head gasket and took the head to a very reputable machinist. It was magnafluxed and deemed in good shape. I had it reconditioned. After completing this project, the problem has recurred.

For the sake of thoroughness, I will outline below my initial observations (August) for your consideration. Please note I am compulsive about checking my fluid levels. My engines NEVER are started without the proper checks. NEVER. Further, my crankcase oil was less than 20 hours old, changed only a few weeks prior.

Saturday morning (8/1) I checked my engines prior to a quick run to the fuel dock. All levels (oil, coolant in expansion tanks, transmission fluid) were a GO. The engines perhaps were running for thirty minutes, TOPS. I ran to the fuel dock, shut down, fueled, started up, returned to my slip and shut down again. There was nothing unusual, there were no new "knocks", there was no trailing oil slick, certainly no overheating or precipitous drop in oil pressure, and both engines shut down normally.

Sunday morning (8/2) I was preparing for a day trip. I scurried down below for my normal checks. At once, I noted the port side expansion tank was VERY low, and there was an oily residue that was apparent on the bottom of the expansion tank cap.

Trembling, I withdrew the port dip stick and as expected, the once clean oil was now the muddy brown color indicating emulsification. Further, the level was well over the fill line reflecting the new volume rendered from an encroaching source.

I tasted the oil, it was NOT salty. I tasted it once more, definitely not salty. I would not expect it to be given my empty expansion tank. Were it salty, then TWO simultaneous catastrophic events would have necessarily occurred. Though not impossible, this would be far less likely. Occam´s razor would prompt one to consider all observations or symptoms related to one another.

So, here were the considerations as I saw them:
1. Cracked Cylinder head Gasket
2. Cracked cylinder Head
3. Cracked block
4. Broken manifold

As indicated above, I essentially eliminated numbers 1 and 2 by replacing the head gasket and ruling out cracks within the cylinder head. I was fully expecting resolution. After I had reassembled the motor, twice I ran it (no load) for 15 minutes or more. No problems. Further, I had understood that it is exceptionally rare for a Lehman 120 (2715 E) to have a cracked block.
I thought I was golden.

However, a few days later I ran the engine again but for about 30 minutes. No load was applied. When I checked my expansion tank, it was down about ½ gallon! I said “Oh sh#@! under my breath but hoped it was simply a matter of under filling after all the flushing earlier. However, when I pulled the dipstick my worst fears were realized. The oil had the dreaded muddy emulsified look and was up about ¼ inch over the “FULL” line.

Clearly the mixing of the oil and coolant was not a result of a blown head gasket after all. I spoke with Bob Smith at American Diesel for some time over the phone. We went through everything starting from the very beginning. He and Brian have been exceptionally helpful in walking me through this and other problems in the past.

According to Bob, although a busted manifold could lead to this type of oil contamination, generally one would note a very distinct bubbling in the expansion tank while the engine was running. I did not see this sign.

Therefore, it appears that the block is cracked somewhere. Oh boy! Now the real fun begins!

It appears that the motor must now come out of the boat. My machinist is interested in looking at it to see what the problem is and if it can be fixed. Bob Smith did mention that often times this problem can be solved by boring out the offending cylinder and placing a liner. So it sounds plausible.

The alternative is going with a new (rebuilt) motor.

So, before I actually start tearing down the motor and make arrangements for a dockside crane/forklift, etc, etc, I would really appreciate any thoughts/insights you guys might have.

Is there anything I might be missing?

Is fixing a broken block wise? Or should I go for the “new” engine?

Thanks,

John

				
         Response #1 from: Ray D
        
			Level 1 Member 
			    									
        Date: 
				
           17 October, 2009 - 11:54 PM