Need your advise on peculiar M104 engine
 

Fellow members, the deal is this:

I would like to acquire another 124T. The problem is that most used Ts here are mostly junk. Except for a fine well cared 1993 300TE-24 (Euro spec) with only 55,000 miles.

The problem is the engine it comes with: M104.980

I am deeply familiar with M103s and late M104s engines, I know all their + and - . The M104.980 was a transition engine between the M103s and proper M104.992, and I am not too familiar with it. In the U.S.A. it was only used on the 300CE from 1990 to 1992.

This is the feedback I am getting from techs here:

1/ M104.980 -> Transition engine in which M.B. did a horrible job. Noisy - Max torque and HP come at very high RPM, hence engine needs to be trashed all the time.

2/ Serious problems with wiring harness and valve seal. Redesigned components did NOT helped as much on this engine as it did on the 104.992

3/ High oil comsumption without clear causes to pinpoint a solution.

4/ One of the few M.B. engines that will definitely require an early major overhaul. Unlike M103s and 104.992s that could go on forever.

Do you agree with all or any of the above mentioned faults on the 104.980?

Anyone has anything "good" to say about this engine or should I just pass on it. Your opinions will be highly appreciated!

The early USA version 104's had an additional idler sprocket for the timing chain. That's why they're noisy compared to later versions. They also used the LH-SFI engine management system. It's not a bad set-up, but IMHO, the HFM-SFI system (with resonance intake manifold) is far superior in terms of performance, reliability, and ease of diagnosis.

Here at the dealership, I don't see many early 104's anymore, but I don't recall them having any major engine issues. The 103's were the last of the oil burning,valve guide wearing,camshaft eating MB engines. Headgaskets of course, are another story.

My experience with M104.980 which uses the CIS-E fuel injection...

Purchased car in 2001 with 92,000 miles. It now has 170,000 miles (just returned from a 3,000 mile road trip).

Before I bought the car the following items were done to the engine: leaking EHA (54k), injectors R&I (69k), head gasket and coolant pump R&I (85k). I have all the records. I do not know if the above work was required or not - a lady owned the car and had all work done a dealer.

Since I have owned the car, the following engine work has been done: R&I injectors and fuel distributor (bad gas 108k), fan bearing support bracket (137k).

I'll address your points with my experiences:

1/ I love the engine, especially its power curve - it has much higher (numerically) gearing than the later M104s and thus the power matches the gearing well. I don't feel that it needs to be "trashed" at all. I do not baby it and as you can see, I have had very few problems. It has a great sound when under full song.

2/ Wiring problems with the CIS-E M104 are much less than the later M104s, with HFM-SFI, which had more wiring (due to fully electronic injection system) very close to the engine heat. To date, no wiring problems have occurred on my engine. Also, no valve problems to date.

3/ Engine has only just started (in last oil change interval) to use a bit of oil - about 1 quart in 5 to 6000 miles. Prior to this, it has never used any oil. I use synthetic - Schaeffers last 40,000 miles, Mobil 1 prior to that. Previous owner used dino. Again, virtually no oil consumption.

4/ I foresee no need for an engine overhaul anywhere in the near future. The engine is running as well now as when I purchased the car. On the other hand, my '90 300E M103, at the same mileage, has oil consumption in the 1 qt per 1000 miles range, and has so for the last 50,000 miles. It needs new guides soon...probably did a long time ago.

So, I give MY M104.980 engine two thumbs up. It is, of course, certainly only a sample of one, but my experience has been very positive. I would take this engine over the M103 any day. Personally, I would not hesitate to get that 300TE-24, if in good condition with records.

BTW, the '90-92 300SL used the M104.981 - this also was an M104 with CIS-E, I believe.

I think the 300CEs from 1990-1992 had the 104.990 engine, and used the same CIS-E as M103 engines.

The LH-SFI was used on the one year only 1992 300SE I believe.

I have never heard of a 104.890, but the 104.990 used on 1990-1992 300CE's in the U.S. have a fine reputation as far as I know. I've never heard of a complaint about them, in fact.

Alon Asherson has one (Ashman), a moderator on the Open Discussion forum.

The M104.980/981 were twins that had VERY few problems. M104.981 was in the 300SL.

The headgasket problem compared to the 104.992/994/995/996 was NON-existent.

I liked those engines as the fuel system was virtually the same as ALL previous 6 cylinders.

CIS-E can be a pain to those NOT familiar with the concept & diagnosis.

Wasn't LH-SFI, only the 1992-93 M104.990 used that fuel system(300SE/S320)

That's what I thought.

Thanks guys, I forgot about the CIS-E version. ;)

300ce M104 put out 217 hp, 300sl/300se M104 put out 228 hp.

104.981/ 980/ 990 CIS-E engines, if I understand correctly, are basically a mechanical injection system with electriconic control, using a distributor with one coil wire and 6 spark plug wires, whereas the M104.992 engine is an HFM-SFI system (hot film mass air flow sensor with sequential fuel injection), combining fuel injection and ignition control in one module.

These 3.0 liter M104 engines might be advantageous because they are simpler. They don't have an expensive throttle actuator which are prone to failure, as well as not having the infamous deteriorating wiring harness problem.

The later 3.2 liter M104 engines have variable valve timing on the intake cam, which gives them much more torque, making the torque curve broader and flatter, developing more hp at a lower rpm, making the power more usable and noticable.

Paul-
I don't believe that the .990 was CIS-E. I think it was LH-SFI (and 3.2 liters), but am not positive.

Your statement about the 3.0 L .980/.981 being simpler is probably the case, but those early M104s with ASR/Cruise Control do have an electronic accelerator pedal. It probably isn't exactly the same as that which is on HFM-SFI engines, but I believe it is pretty expensive, too. (I think I have heard they are not even available now.)

Also, BOTH the M104 3.0 liter and 3.2 liter (as well as the 2.8 liter) engines have variable intake cam timing. I suspect that the lower torque curve of the 3.2 liter is a more a product of the cam grind, duration and lift, plus the increased displacement.

I can't comment on the LH-SFI engines, but I know for sure the 104.990 is a CIS-E engine at this is the engine that was in the 300CE from 1990-1992. I am also certain that this engine does not have a throttle actuator, but the same Idle control valve that M103 engines have.

M104.990 was the 1992-93 300SE engine, LH-SFI fuel system..

M104.980/981 was CIS-E & was the 1990-92 300CE & 1990-93 300SL powerplant.

ALL M104 engines are 24V & have variable intake cam timing.

I do really thank all of you for your impressive advice and comments!!!

I have a table about M.B. 6-cylinder engine data on W124s:

ENGINE - YEARS MANUFACTURED & W124 MODEL FITTED

M103.940 - 1987-1991 206 E, 300E 2.6
M103.983 - 1986-1992 300E, 300TE / 1988-1989 300CE
M103.985 - 1990-1992 300E and 300TE 4matic

M104.980 - 190-1992 300CE
M104.942 - 1993 300E 2.8
M104.992 - 1993 300E/CE/TE / 1994-1995 E320 (sedan/T/C/A -cabriolet-)

ENGINE MANAGEMENT SYSTEM:

All M103s and M104.980 - CSI-E (Contininouos Injection System - Electronic)

M104.942/92 - HFM-SFI (Hot Film Management - Sequential Fuil Injection)


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The 1993 300TE-24 in question does not have ASR nor cruise control. It is well equipped for an euro-spec model (it has power seat, fully automic A/C -which I don't like, I prefer the manual A/C unit, power windows and locks, roof rack and a 4-speed auto transmission).

Is it true that the M104.980 is considerable more of a gas guzzler than the M104.992?

Again, thanks to everyone for your advise.

I've owned my 1991 300CE for 11.5 years and is my daily driver. Now have 217,000 miles on it....not overhauled yet. Overall a very reliable MB. :)

Re: gas guzzling

My 1990 300E M103.983 gets between 24 to 27 MPG. 1:3.07 rear end
My 1992 300CE M104.890 gets between 23 to 26 MPG. 1:3.27 rear end (ASR)

These numbers are for freeway driving under various conditions; usually mountainous and high speed. I suspect that the lower MPG of the M104 CIS-E is primarily due to the rear end gear ratio.

I would also suspect that an M104.992 HFM-SFI would get much better mileage due to the fact that they usually had a 1:2.65 rear end ratio. I seem to recall my friend with this engine gets in the 30 MPG area.