Age old question:M103 or the M104 engine?

[lincolnmatthews]

I was looking to Maybe get another CE again, I had a 91 (M104) for a few years but ended up selling it. I had head gasket issues with the car, (replaced it once but started to leak oil again later). They said it had some electrolysis issues on the mating surfaces, because of the wrong anti-freeze being used (before me) & not changing it quick enough.
I read one time (in some Euro rag) that the 24-valve engine was never really a good design in that it had basically to many head studs (or something like that, as I recall) for the given area surface & therefore more suceptable to leaking & having head gasket issues. Kind of made sense to me, based on my experience with my car.
Anyway fast forward a decade, so I have stayed away from the M104 engine & am thinking of getting the M103 with its single OH cam versus the double OH cam for the above reasons. I know the 103 had valve guide & seal issues but read where this had been resolved by 1990? I know about enough on this subject just to get my butt kicked, as I always kinda thought that the old M103 single cam was more like the old standard MB inline 6 that powered the cars from the 60's.
For this reason I wanted to stay with a M103 engine when looking for a 300 CE, (seems like I'd rather deal with valve train issues rather than leaky head gasket issues, that really can't be resolved properly). I know head gaskets have been improved since 91, but they did install the latest & greatest in my 91 when done.
I know this is a long post, but have always wondered about this. Thank you for the opinions!

[97 SL320]

The M103 24 valve was also used in similar year R129 / 300 SL. Engine blocks are basically the same between the 103 / 104 , the 103 24 V has a head all to it's self that other than a distributor and round intake ports looks the same as the 104.

The 103 and 104 both have the same amount of head bolts and the oil leak / gasket issue is overblown. Some make a big deal about the " wrong " ( green ) antifreeze but hundreds of thousands of cars used green with little trouble is changed on schedule.

I'd be less concerned about head gasket issues and more concerned about the CIS / K jet injection system on any variant of the 103. Parts are very old / worn out at this point and $$ .

[porkface]

for the 104, use an oe or elring head gasket. they have reinforcements to avoid the oil leaks, PROVIDED, the block and head are cleaned properly. replaced 2 victors with elrings and no problems since. good luck, chuck.

[Marcel107]

There was no M103 with 24 valves, M103.98, 3 liters, KE
M104 with 24 valves, M104.98, 3 liters, KE, in W124, S124, C124, R129
M104 2800 ccm, HFM
M104 3200 ccm

[sixto]

Originally Posted by 97 SL320

I'd be less concerned about head gasket issues and more concerned about the CIS / K jet injection system on any variant of the 103. Parts are very old / worn out at this point and $$ .

x2. Plus why settle for second gear start and numerically higher diff?

Sixto
83 300SD
98 E320 wagon

[Campbelljj]

Agreed on CIS issues. I have one M103 with CIS issues and two M104 both 3.2 and 2.8. Much simpler injection and gobs more power. Not as refined and smooth as the M103. It's really a toss up. Get the best car you can find regardless of engine IMO.

[dynalow]

Old thread here from 2000. FWIW
http://www.peachparts.com/shopforum/performance-paddock/1330-m103-engine%3B-good-garbage.html

My 88 300CE (m103.098) had the head gasket replaced by the previous owner in 2001 with 41k on the odo as a condition of purchase. Now it has 146,000. Still have the same head gasket. It weeps a bit at the rear of the block. My indy shrugs it off. Oil consumption deteriorated to a qt. per 1000 mi. Had the valve stem seals replaced at 75k. Problem solved. Now it burns less than 1 qt. before I change the oil at 3k interval.
Water pump went at about 100,000. I just replaced the fuel pump relay for the second time. Other than that, I've had no problem with the motor or ignition.

I've always followed the MB dealer in this area and used 5W30 motor oil and MB recommended antifreeze.
Runs and looks great for a 28 yr old car.

Had a '91 190E 2.6 before the CE. No problem with that engine either.

[sixto]

I didn't think MB specified any -30 oil for US spec passenger cars of that (or any?) vintage.

Sixto
83 300SD
98 E320 wagon

[rayhennig]

Originally Posted by 97 SL320

I'd be less concerned about head gasket issues and more concerned about the CIS / K jet injection system on any variant of the 103. Parts are very old / worn out at this point and $$ .

But they are fundamentally reliable if the system's looked after. New injectors/seals, good lambda sensor and leak-free vacuum leads to predictable tune-up.

And if the HT is 100% (probably using MB original parts), the M104.98x can be truly rewarding. Some say the most exciting of all.

RayH

[Ferdman]

dynalow, AFAIK factory fill on that vintage MB automobile was 15W40 oil. I run Mobil 1 15W50 year round in our 124 automobiles.

[w123fanman]

FWIW, I love the M103 but I am not the biggest fan of CIS, so I am converting my car to Megasquirt II. The 3.0L engine I have going into the thing has more than 200K miles but passed a leak down test with flying colors. The 2.6L engine I have in the car currently has 207K miles and doesn't burn or leak a noticeable amount of oil between my 4K mile oil change interval. I did finally get the CIS working pretty well on that engine, replaced the injectors, plugs and wires, distributor and rotor, O2 sensor (which was throwing codes but I don't think was bad), EHA, air flow meter potentiometer, and finally reflowed the solder on the OVP relay which solved the issues that started a couple weeks after the air flow potentiometer replacement.

[sixto]

Sounds like you stopped when there was nothing left to replace Was that more or less work than replacing an M104 harness and ETA?

Sixto
83 300SD
98 E320 wagon

[97 SL320]

Originally Posted by rayhennig

But they are fundamentally reliable if the system's looked after. New injectors/seals, good lambda sensor and leak-free vacuum leads to predictable tune-up.

When newish, yes reliable, however 26 years later, not so much. Fuel distributor diaphragms stiffen up or leak. The EHA leaks, throttle position sensor wears out. All of this leads to $$$.

There really isn't anything one can do to extend the life of these parts.

[Air&Road]

The mechanical pluses and minuses are a wash AFAIAC. What makes the difference is that the 104 does away with the CIS in favor of a much more conventional injection system.

My $.02,

[DieselPaul]

except for the part where 300CEs used an M104 with CIS.