Are 603-powered cars reliable?
Just what the title says. I've wanted a w124 300D for a long time but what puts me off of them is the potential problems with the 603 engine.
I've read quite a bit about them and while a lot of them reach high miles like 617-powered cars, I've also read about the numerous problems 603 owners encounter, even when they are well maintained. All things considered, is this a reliable engine? |
they are reliable as the 617 provided it is properly taken care of
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Mine has 256k and has been my daily driver for six years without major incident. I can't think of anything engine-related I've had personally other than leaks, which happen on 61x engines, too. New lifters and timing chain at 220k, but that wasn't anything that left me stranded or was catastrophic ... it was 'elective surgery.' I've relied on the car to get back and forth from work, the store, everywhere else on a daily basis. Has always started for me and run great for me in temps from -7 to 107.
You're biggest issue with the 603 would probably be the cracked head possibility ... so don't overheat it. That's generally my approach in any car. I don't think that makes it unreliable. |
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Many of them go 300K without a problem. However, if yours happens to crack a cylinder head or fracture a timing chain cover, you're not going to agree with the "reliable" statement regarding them. It's a statistical issue and we don't have the statistics. Personally, I believe, statistically, that the 617 is going to offer better durability. But, I had one with a cracked cylinder head. Go figure. |
I think the 617 is a little more reliable in the long run, perhaps at a lower maintenance cost. They need valve adjustments and such, but have an iron head that usually never has any issues, and the belt drive system is simple V-belts instead of a serpentine with a tensioner and pulleys etc....less to fail. If properly maintained they probably are about the same. The 603 has more "potentially major" issues that could occur....like cracking a head and such. I'd drive either honestly.
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The OM603 and OM617 engines have similar over-all reliability. Although the 603 is no more prone to overheating than the 617, the aluminum head of 603 is more likely to crack if the engine is seriously overheated. If the temp gauge starts getting up towards the 120C mark, you need to stop and find out why. Trying to "make it home" is risky. So long as you take care of the cooling system (change the coolant at the appropriate intervals, keep the radiator clean, etc.) the 603 should not overheat. To be fair, it's also possible to overheat a 617 but you have a larger chance of getting away with it.
My mechanic commented to me (when I bought my '87 300D) that the OM603 is a more expensive engine to work on. This may be so and if you have to pay someone to do all your work you will want to keep that in mind. If you can do some of your own work (change glow plugs, serpentine belt, oil changes, etc.) you'll save a lot of money. Jeremy |
Changing the serpentine belt on a 603 is a 15minute job including cleaning up, try that on a 617, ... adjusting the valves is a non-existant job on the 603, ...
I think that the 603 is an excellent engine and if not abused, very reliable. I believe that I've read about two timing-cover failures here since I joined years ago, vacuum-pump failures of 61x and 60x engines are about the same, IP failures about the same, seldom see a bottom-end failure or oil-consumption issue either. Get a good one and maintain it reasonably well. |
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Were you thinking of the special tools for removing the fan? Isn't necessary and anyway, you don't need special tools. Jeremy |
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Special tools are made to make jobs easy and on the newer ones(especially 97 and up) special tools are needed otherwise you cannot do the repair. |
I've never removed the fan to do a belt on a 124, just snake it around. The '96-up as you likely know is a different engine and body.
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I always remove the fan when I do the belt. The belt is easier to install with fan removed.
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I've done it both ways on both the OM603 and the OM606NA. Removal of the fan is easier with the special tools, I would imagine, but not having them, I make do without. Changing the belt with the fan removed is so easy we shouldn't be discussing it.
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603 hauls butt
617 hauls my butt around As Jim(from the forum) said to me once.. "not all #14 heads are bad, but all bad heads are #14's" The belt on the 603 is beyond easy. The 617 has more room under the hood to work. |
It occurs to me that the point we perhaps should be making is that a pre-purchase inspection by a trusted mechanic is more important for a car with a 60x engine than one with a 61x engine because of the expensive nature of the things that an unwary buyer (someone like me :o) may miss. Granted that a pre-purchase inspection is a good thing to do on any car, it's critical to 603-engined cars because of the kinds of problems that may be hidden behind the seller's smile.
Given a good bill of health from the mechanic, a 300D Turbo or 300SDL would be a great car. More modern-looking than the older cars, more power yet better fuel economy, more creature comforts. Jeremy |
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I love a 617 because I'm a mechanical simpleton. And I love the looks. If I were looking for a reliable, more comfortable car with money as no object, I'd probably be picking up a 300D turbo in great shape. |
I take what Jeremy says about belt replacement with a grain of salt because he has a 2-piece shroud that comes off without removing the fan. Color me green :)
An alternative to an 87 300D with the 603 is a 90-93 300D 2.5 with the 602 = 603 less one cylinder. Not known for cracking heads but the head is aluminum. Better known for breaking chains but not as common as 603 head cracking. Later 300Ds give you more features/options like passenger side airbag, ASD, more speakers, more wood, etc., and about a 5 mpg bump in fuel economy. Sixto 87 300D |
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removing the belt isnt possible without removing the fan |
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As Sixto says, my 603 has a later-model 2-piece shroud that can be removed with the fan in place. Then it's easy to thread the belt around the fan blades and off. it comes down to (a) the exact makeup of your car, (b) the tools you have available, and (c) what you're used to doing. Where were we? |
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As for the W124, its easy to do the serpentine belt....I left the fan on....I did remove the shroud. Took me about 20-30 minutes, but it was my first time and I was being careful. However, the point of this thread was to determine which engine is better, and obviously that would be the OM617. :D If I was in an off road vehicle (such as a unimog) crossing the desert, I'd want nothing else under the hood than a 617 or 616. |
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Is the original question to determine whether the 603 is more reliable than the 617 or whether the 603 is reliable enough for what alfa 75 has in mind?
I'm curious about "the numerous problems 603 owners encounter, even when they are well maintained." The 603 bottom end is as bulletproof as a 617's. I have to think head cracks are the result of poor maintenance or an inattentive driver. If the repair includes a later head casting, the head shouldn't crack again. Fuel system components are very similar though not interchangeable. The 603 has electronic idle control but who's had a problem with that? I'd say the biggest issues folks have with the 603 are won't start/poor performance caused by either a clogged oxidation catalyst (get a straight pipe) or a stuck open IP return line check valve (replace the check valve). Oops, and Jeremy's lazy #2 fuel delivery :) [edit] I'd say the weak point is the belt tensioner that wears out with catastrophic effect. The 103/104 tensioner can wear out as well but all that leads to is a slipping belt. One thing I read about is forgetting to transfer the thick washer from the old tenioner arm to the replacement. The result is a tensioner pulley out of plane causing the belt to go off track... and wrap around the fan... and cause the engine to overheat. [edit] And the original vacuum pump. So there's more to go wrong with a 603 for sure but there are reasonable preventive measures to give you years of reliable service. Given the number of French cars in alfa 75's fleet, it seems odd to question the reliability of any MB :D Sixto 87 300D |
I keep hearing about a #14 head...I have a 603 in a 86 SDL...how would I check to see if I have this "faulty" head?
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Ive got over 200k miles on a 14 head and no issues
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288k on 603 #14, zero major mtc. last 40k on frybrid 2 tank wvo kit.
603 more expensive, you wont find parts at a junkyard anywhere near as easily as 617 |
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My wife drove our 87 300TD for 13 years, and I never had to remove the fan or fan shroud when I swapped out the serpentine belt..... Jim |
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Its true there are cracked heads on the OM603 and they are primarily #14 but other versions have been known to crack also. You have to account for statistics. The reason that there are cracked #14 is because that was the predominant head produced in the thousands (anyone have the exact sales figures for the '86 and '87 300D turbos?). The real cause however is overheating and the fact that soooo many owners were completely at fault for not performing regular maintenance. And the radiators got plugged, people continued driving with AC on in stop in go traffic while their cooling fans had bad thermo clutches and the electric fans were dead and the stupid thermo sensor switch carries all the fan current and therefore fails prematurely (a separate relay would have prevented that so I consider that a poor design). Generally most people were simply not in tune with their cars, never knowing if the thermo gauge should read 110 or 80 or whatever and neglecting PM. I am running on two #14 heads (different cars :rolleyes:) and never a problem. Of course I will admit that one of the cars, the one shown on my profile - the so called Blue Bomb, was a mechanics lien because it failed on a steep grade and the owner, a CPA, knew nothing about why the engine was running hot, it was out of coolant! so the mechanic who did the analysis removed the head, sent it to be tested and the owner decided to not pay him rather go for a charitable deduction. That never happened because they wanted a running vehicle, so I learned about it, then I got a used head off a wrecked engine that failed because the vacuum pump disintegrated, rebuilt the engine (new rings) and now its a daily driver. Total mileage is over 500K on the two OM603's I own, #14s notwithstanding. Just find a good car, replace your radiators, change coolant regularly and you should be able to get similar life. |
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just don't buy a 606 car that "looks" ok with out a thorough underbody inspection like I did, now after fighting the stuck glow plug issue, I'm having to rebuild the inner fender and shock tower....
I should have bought a southern 123! I should have bought a southern 123! I should have bought a southern 123! I should have bought a southern 123! |
i have nearly 250k miles on a #14 head, about 10k now my own miles. i have changed out the old green coolant, put mercedes orange coolant in. my temp gauge gets a bit over 100C on uphills w/ the AC on, but never really beyond that. i plan to service the thermostat and possibly change out the coolant reservoir itself, maybe upgrade the fan clutch and fan, but for now like others have said, take care of your coolant at the minimum
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nothing wrong with my 603 powered car. 280k miles and still going. Plus its running the proper Mercedes Benz coolant thanks to the previous owners efforts
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Granted the power is not as great as with the turbos, but there are plenty around. If you really want reliability , at less power, admittedly, look at the old diesel MOG OM636 and the OM 621. Those engines worked under true combat conditions and MANY still survive today long after the cars are gone. |
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Lets see, are 603-powered cars reliable? HELL YES!!
If it's properly maintained, yes. If not, like any 61x powered car, (or pretty much anything else on the planet including a Model T and a JD Model B: No. |
I'm sorry, but an owner of any Citroen (maybe the 2CV excepted), Alfas and especially Renaults asking about MB reliability?
Again, no offense intended, but how many of these marques are even seen on American roadways these days? In the 1970s, the highways were chock full of MGs, Triumphs, Sunbeams, Healeys, R4s, 5s (remember "Le Car"?), 10s, 16s, and sometimes even Citroens. All a distant memory now. Not that they weren't loved, they just didn't last. Lloyd, Vespa? The list goes on forever. All lovely cars in their own way. Bring back the SAAB shrike I say.... |
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Having considered and test-driven an '87 300D, I found that car to be a pleasure, especially compared to my first, tired '82 automatic 240D. But as for 603 vs 617, my vote goes for the 617. and not just because of the potential cracked-head/timing cover issues, but because of the generally more complex electrical/electronic systems on the W124 cars. Happy Motoring, Mark |
Well mine has 343000 miles on the original #14 head.
The timing chain has been replaced and is probably due to be replaced again, but the engine has NEVER let me down (like my 617 in the 300SD did twice!) I would never go back to a 5 banger after having the smoothness and power of the 603 |
No question that there are additional systems in the 124 that can fail, the security system is a good example.
However, if you compare a 617-powered 126 to a 603-powered 126, about the only difference is how much overheating it can take before causing head damage, ... isn't there a fairly recent warped/damaged 616 head thread lurking here somewhere BTW? From overheating? Is the 124 heating system more reliable than the automatic CCU in the 123? Probably so. If you want more refinement, power, and efficiency, you need to go newer with the newer technology, and Mercedes didn't give us a cross-flow or multi-valve head in a diesel car, ... in cast iron. It is reliable, as long as it is properly maintained. Some things in the 124 are easier to maintain (ex: front suspension, valve lash), some are not, pretty hard to say either is a better car objectively IMO as they each have their advantages. Being that the newest 603 car other than the W140 is now almost 20-years old, and you're not going to be the original owner (usually the 3rd or 4th), it's not what I'd suggest buying the wife to take the kiddies 40-miles a day or through a bad neighborhood daily, I'd sooner choose a new boring SUV. |
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-Jason |
CCU systems compared
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My '85 300D (W123) and '87 300D (W124) had almost identical CCUs. The differences were: 1. W123 uses a resistor pack and relays to give the blower five (?) speeds while the W124 uses a big transistor on a heatsink to give (they say) "stepless" control. I noticed no significant difference between the two cars in the ability of the CCU to heat or cool and the resulting comfort in the car. 2. The W123 CCU can be fried if something (such as the unfused aux coolant pump) overloads (pulls too much current) whereas the W124 CCU has built-in electronic protection. This alone makes the 124 CCU more reliable. 3. The W124 air conditioner compressor has an RPM sensor that can sense a bearing failure causing the compressor to mechanically freeze. In such a case, the Klima relay disables the electric clutch, thus saving the OM602/3 engine's serpentine belt and all of the accessories it runs. The OM617 engine in the W123 lacks such a feature but has separate belts so compressor failure is less critical. 4. The CCU in the later W124s seem to respond more quickly than either early W124s or the W123. Later versions also had the temperature dial marked in Fahrenheit, while the early W124s, like the W123s, had Celsius markings. 5. The dial lamps in the W124 CCU are built-in while the W123 bulbs are "external" and the lamp holders are slightly fragile. 6. The interior temperature sensor in the W123 is in the dash while the W124 sensor is in the overhead, next to the sunroof switch. The W124 has a separate fan to pull cabin air past the sensor for improved response time while the W123 uses the main blower for this function. The W123 uses a foam air tube that disintegrates while the W124's little fan has no bearings and will die if not oiled every 10 years or so. I didn't notice a significant difference in performance. Late W124 CCUs may have "blink codes" (1995 E300D?). I do not think earlier CCUs have "blink codes" but I would be delighted to be proved wrong. Jeremy |
I like the 60x much more than the 61x.
And I don't have the remove the fan or shroud to change out the serpentine belt. Nor do I have to use a special tool to remove the fan, just a wrench and a hex bit. |
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But, well, there's that Marelli crap to deal with. I sincerely believe Marelli is why FIAT is no longer in the American market. It's the electrics. Especially their pathetic excuse for electronic ignition. (And believe me, I know crappy electrics. Me and Smokin' Joe Lucas go waaaay back.) OK, sorry, I kind of hijacked that one, didn't I? :o |
I put 45k miles on my last 300SDL in the manner of 12 months without one single issue. That is maybe because it was well taken care of by previous owners and myself. Only thing it needed was a new steering box because the replacement in it sprung a leak
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Happy Motoring, Mark |
In europe dual zone semiautomatic HVAC controls were standard on the W124 and W126. Fully automatic controls were optional.
-Jason |
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Happy Motoring, Mark |
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