It seems the next step would be to check compression. Thanks, Tom Hargrave www.kegkits.com 256-656-1924
-----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Peter Merle Sent: Saturday, May 10, 2008 1:07 PM To: Mercedes Discussion List Subject: Re: [MBZ] W123 300D losing compression?? Engine was bored to 91.5mm ( Yes it is allowed check EPC and Mercedes OEM piston A6170301917 ) was used. HEad was redone using only OEM parts , including new guides all round . Oil consumption has increased from and initial 0.2 to approx 0.5 l /1000 km. Engineering shop was one that services the local Mercedes Dealership here in Capetown , South Africa so they should know what they are doing. Crank was sized up one repair size. Oil pressure is good ( 1.8 bar idle hot ) Running in used Dino oil initially ( 1000km ) and then switched to M1 . Valve clearances are all in spec. I am using DNOSD240 nozzles ( should really be using DNOSD220 nozzles as car is early 1979 ) . Shoud I do a major hill climb burnout? Add some magic potion to the fuel / oil? Peter 2008/5/10 Peter Frederick <[EMAIL PROTECTED]>: > If you don't have increased oil consuption, it's definitely the > valves, but if the valve guides were not installed and sized > correctly, you now have worn over-size guides, and the valve seats, > especially on the exhaust valves, are shot, causing low compression. > > The only way to tell is to do a proper leak-down test and see where > the compression is leaking out. > > On a Benz, you really MUST rebuild exactly to factory specs -- in the > case of the diesel this usually means new pistons, new liners, and > proper clearance --- 0.001" on the pistons (this is NOT a misprint) > and ZERO to 0.0005" on the valve guides. They are correct size if > you can barely get the valve in the guide by hand, oiled. They won't > go in dry. Any looser, and it will both burn oil and wear out much > faster. > > Also, you MUST use bronze exhaust guides on the 61x engines -- steel > ones wear out unblieveably fast (sometimes in less than 10,000 > miles), causing low compression, hard starts, and ruined exhaust valves. > > Crank can be ground twice before you go through the factory nitride > IF it's done correctly. The shop simply has to be using metric > measuring tools, calculated from SAE results in undersized crank > journals every time. > > Don't know the story of the rebuild -- what was the assembly > clearance on pistons, valve stems, main bearings, crankpin bearings? > New oil pump? > > Properly done, with correctly matched rings and liners (there are > several different materials, some are NOT compatible!) a 61x engine > ought to make 250,000 miles before it needs valves on Mobil 1. Lots > of low speed low load driving can sludge it up and cause the rings to > stick, but that's only a problem on a worn engine usually, and can be > cleared by a nice, hard drive on the interstate. Sadly, stuck rings > usually means worn out cylinder walls. > > Peter > > > _______________________________________ > http://www.okiebenz.com > For new parts see official list sponsor: http://www.buymbparts.com/ > For used parts email [EMAIL PROTECTED] > > To Unsubscribe or change delivery options go to: > http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com > _______________________________________ http://www.okiebenz.com For new parts see official list sponsor: http://www.buymbparts.com/ For used parts email [EMAIL PROTECTED] To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com No virus found in this incoming message. Checked by AVG. Version: 7.5.524 / Virus Database: 269.23.14/1425 - Release Date: 5/9/2008 12:38 PM No virus found in this outgoing message. Checked by AVG. Version: 7.5.524 / Virus Database: 269.23.14/1425 - Release Date: 5/9/2008 12:38 PM _______________________________________ http://www.okiebenz.com For new parts see official list sponsor: http://www.buymbparts.com/ For used parts email [EMAIL PROTECTED] To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
