1990 B2600i engine problem

Hi everyone,
I recently had a problem with my 1990 B2600i 4x4 (208K miles).  Was driving on highway at about 60 mph and heard a strange sound coming from the engine, like it was missing. After I slowed down the oil presure light came on within 8-10 seconds.  I stopped the vehicle and noticed the front of the engine bay was completely covered in oil ( all 5 quarts).  The oil and filter was recently changed and the oil filler cap was on.  I added some oil (4 quarts) to the motor and noticed it was leaking out of the bottom front end, above the oil pan at the timing chain cover.  Was wondering if the timing chain went out?  Threw a rod?  Oil pump failure?  I have never had the timing chain serviced. What is the interval for service on a timing chain for a b2600i, every 100K miles?  Any help on the problem would be greatly appreciated.  I am having the motor and clutch replaced. 

Hugh - sounds exactly like what I recently went through with my '92 B2600i.  Blew out the crankshaft pulley seal.  It's a press-in seal that isn't too bad to replace but mine did it again a few months later.  Can't figure out why but the last time we replaced it we took extra pains to be sure the seal was in properly and we tried very carefully peening over the metal around the seal to prevent it from blowing out again but the aluminum wanted to chip instead of peen so we (honestly this is true) very carefully drilled 3 small holes at 3 points around the seal and drove in 3 stainless steel pins just long enough to rest against the seal and prevent it from blowing out.  So far it's holding just fine. 
 
Rolomac

Rolomac,
Thanks for the quick reply and really appreciate the help!  Sounds like the motor could be rebiult.  I think you are right about the crank shaft seal. 
 
Hugh

after you change it make sure your pcv valve and your valve cover vents are clear and flowing. if its holding pressure it will push your crank seal out.