2.5 engine - PeachParts Mercedes-Benz Forum

dieselmania · #1 08-06-2017, 03:18 PM

Been driving the 3.0 1987 300D in sig for 20 years now, looking at a 91 300D with a 2.5. Planning to go drive it this afternoon, it's an hour away from me. The car looks beautiful but what should I know about the 1991 as compared to the 1987, and the 2.5 as compared to the 3.0? Will we notice a drastic difference in power? Does the 1991 have spring perch issues? It has 236K on it.

shertex · #2 08-06-2017, 03:30 PM

Quote:

Originally Posted by dieselmania

Been driving the 3.0 1987 300D in sig for 20 years now, looking at a 91 300D with a 2.5. Planning to go drive it this afternoon, it's an hour away from me. The car looks beautiful but what should I know about the 1991 as compared to the 1987, and the 2.5 as compared to the 3.0? Will we notice a drastic difference in power? Does the 1991 have spring perch issues? It has 236K on it.

You will notice a difference but it's not drastic. The OM602 is a great engine. Not known for spring perch issues. Plan on it needing a head gasket at some point with that mileage.

dieselmania · #3 08-06-2017, 04:12 PM

Thanks, I'll see if there are any records. It is an estate sale. I wonder if the climate control will be like on the 87, feast or famine I like to call it.

dieselmania · #4 08-06-2017, 09:59 PM

Didn't make it there today, I might let him sit on it for a few and see if it is still there. Just started looking today as my 87 needs AC, paint and rear deck/headrests from sun damage. His price of $2,950 would be cheaper than fixing up mine although mine has less miles at 180K.

Also I am hopeful that it does not have a sun roof....I could use the extra head room.

sixto · #5 08-06-2017, 10:11 PM

One difference is the 2.5 turbo wastegate is controlled by an ECU using a vacuum actuator vs a simpler pressure actuator that reacts to turbo output pressure in your '87. There's not a lot online about the whys and wherefores of a 2.5 ECU cutting boost but a popular workaround is to retrofit a pressure actuator. In short, don't pass on an otherwise nice car because it feels low on power. It could be a bargaining point.

Sixto
98 E320s sedan and wagon

t walgamuth · #6 08-06-2017, 10:31 PM

I had a 91 300d with the 2.5 turbo. Its a slug off the line but hold your foot to the floor and it just keeps winding up. You can cruise all day at 80 and still probably get over 30 mpg.

dieselmania · #7 08-07-2017, 12:35 AM

I called him again, no sunroof, yay I'll be able to sit up straight without hitting the ceiling! No records either, he is just an estate liquidator so knows nothing about the car. He stressed that it is like new appearance wise. I think I will offer $2,500 cash.

I would appreciate any info on what I should plan on for this car if I buy it. Already learned of the head gasket from Shertex and some searching tells me I should check for chain stretch on the dual chain drive for the cam & IP, what about the oil pump chain? Also will this have the vacuum pump without the caged bearings like my OM603? Also heard about the wastegate mod, thanks Sixto. I need a crash course on the OM602!

Will need FSM for it as well and will probably sell or trade my 1987 300D factory manual set.

shertex · #8 08-07-2017, 05:37 AM

Since it's a 91, it will probably have the old style vacuum pump. You will be able to tell by there not being bolts on the face plate. And at that mileage it would be wise to replace as a preventive measure.

jake12tech · #9 08-07-2017, 09:12 AM

Don't veer away from an om602. Head gaskets aren't that much of a problem as people say. They go bad, but they go bad on every car at a certain point. Vacuum pumps go bad too with age, that's pretty normal too. They aren't fast but will cruise at 70mph and get mid 30s mpg all day long. You won't notice much of a difference between the om603 and om602 powerwise

dieselmania · #10 08-07-2017, 09:19 AM

Thanks guys, one more Q, will the 91 have the same tranny as my 87 (with the OM603) and the dreaded B2 piston issue?

Maxbumpo · #11 08-07-2017, 09:30 AM

The other down-side, if you can call it that, is the radio is (I think) the two-piece Becker, with the "control" unit in the dash, and radio and CD player (if equipped) in the trunk. This means the antenna wire ends in the trunk. I'm not sure about speaker wires, I believe they are at the dash end, but installing an aftermarket radio is a pain because the antenna wire needs to be run from trunk up to dash.

jake12tech · #12 08-07-2017, 09:39 AM

Quote:

Originally Posted by dieselmania

Thanks guys, one more Q, will the 91 have the same tranny as my 87 (with the OM603) and the dreaded B2 piston issue?

It has a smaller 722.4 transmission. They still have the same common failure as a 722.3 like in your 87. They also aren't as stout as the 722.3. Once rebuilt, both transmissions are pretty good and smooth.

alghamedGT · #13 08-07-2017, 09:42 AM

from 7 years of owning my w201 2.5D
i think the om602 is the best engine i owned and also the 2nd best engine ever after the good old om617
its not powerful but very reliable
my engine has +500 000Km and its never opened
the only problem i had is some lifter noise but i think this is common in all engines that use hydrolic lifters

dieselbenz1 · #14 08-07-2017, 10:44 AM

The FSM is available here Model 124 Maintenance Manual Index

These are great cars just do your due diligence when you test drive it and ask for the service history. Make sure it does not have any over heating issues or you'll be doing the head gasket sooner than later.

shertex · #15 08-07-2017, 11:18 AM

I had a check valve fail at under 120k miles...wire got mangled in the governor gear and broke it. $800 repair.