Dave M. wrote:
Hi Chris,
1) Go to the dealer and get it replaced with the straight pipe. You
get a free new exhaust too. They probably won't notice, or care, that
the trap was modified.
2) My text file has the information on the high pressure syndrome...
it's high pressure in the cooling system after the engine has cooled
down (say, overnight). That's not normal. It should have very low
pressure or even a slight vacuum after cooldown.
I have a 190D 2.5 that displays excess pressure in the cooling system
even after it's cooled for several days! Has since I bought it in 1997.
Doesn't have any other symptoms. I also had a 190D 2.2 that sometimes
displayed the same symptoms for 10 years, but not regularly.
Pressure in the cooling system MIGHT mean a cracked head (and I'd
suggest investigating), but that is NOT conclusive. It may mean nothing
but a defective cap - or some other anomaly.
As to the number of cracked heads - no way there are more than about 1
in 5 (20%).
Many of the people that sell their 124.133 and 124.193s sell them
because they have the symptoms of head cracks, but many/most of the
people that have 124.133 and 124.193 without cracked heads tend to NOT
want to sell them. These are VERY desirable cars and there are very few
of them in the US (fewer than 6000 124 sedans and wagons with OM603.960
engines were ever brought to the US)! If 20% had cracked heads that
would be about 1200 124s with cracked heads. Then there were the almost
13,000 1986 & '87 300SDLs. If 5% of the '86s and 20% of the '87s failed,
that would add about 2000 more cracked heads and still fewer than 20% of
the "14" series heads would have cracked!
MOST 603.96 engine heads will not crack and fail unless abused. Most ALL
of the OM60x heads (even "17" series and later) WILL show some signs of
cracking when they are removed after years of service, but MOST of the
cracks are superficial and will seldom result in catastrophic failure.
This is common to almost ALL of the 1st (and many 2nd) generation
aluminum diesel heads. The trick is sort out and separate the fatal and
inconsequential cracks - and that is VERY difficult to do. Even Mercedes
points out that the pressure testing procedure in the engine manual is
NOT 100% reliable and occasionally a head that passes the pressure test
will fail when put back into service.
Marshall
--
Marshall Booth (who doesn't respond to unsigned questions)
"der Dieseling Doktor" [EMAIL PROTECTED]
'87 300TD 181Kmi,'87 190D 2.5 199Kmi, '84 190D 2.2 227Kmi, '85 190D 2.0
159Kmi, '87 190D 2.5 turbo 234kmi
Diesel Technical Advisor MBCA, member GWSection
http://www.dhc.net/~pmhack/mercedes/mbooth1.htm
