sdl v. sd - PeachParts Mercedes-Benz Forum

Hogweed · #1 11-27-2006, 10:09 PM

quick question. how does the 6 cyl in the 300sdl comapre with the 5 cyl in the 300sd? i've been running a 300 sd for about 5 years w/ few issues and was thinking of buying an sdl locally. thanks for your input in advance.
gregg

TheDon · #2 11-27-2006, 10:37 PM

SDL has the 603 with the problematic head.. but more power compared to the good ole 617

Hogweed · #3 11-27-2006, 10:50 PM

is there anything to look for to determine if the head is going or gone? i read an older thred comparing the 5 and 6 cly diesels...seems to be mixed opinions

Brian Carlton · #4 11-27-2006, 10:59 PM

Quote:

Originally Posted by Hogweed

is there anything to look for to determine if the head is going or gone? i read an older thred comparing the 5 and 6 cly diesels...seems to be mixed opinions

The 603 has considerably more power than the 617 powered SD. It's quite noticeable at 70-80 mph.

There are several ways to check for a cracked head or a bad head gasket:

1) After the vehicle has been run and sits overnight, squeeze the upper radiator hose. If it feels very hard, open the expansion tank. If it now feels soft, it's got head issues.

2) If any oil appears in the expansion tank.

3) If any coolant appears in the crankcase (usually an oil analysis is required).

4) If it exhibits heavy white smoke on startup........and it smells like coolant.

5) If it consumes coolant at a noticeable rate.

Clearly, some of these items are not possible when evaluating a potential purchase, which always makes a 603 somewhat risky.

mj_sid · #5 11-27-2006, 10:59 PM

Quote:

Originally Posted by Hogweed

is there anything to look for to determine if the head is going or gone? i read an older thred comparing the 5 and 6 cly diesels...seems to be mixed opinions

I've had both and think that they are both good engines. When in the 617 (5 Cyl) you hear a bit more of the diesel clunk and have less power. In the 603 (6 cyl) you don't hear as much of the clunk (it took a long while to get used to it but now I'm used to the 603's clunking and like it). IMHO both are great choices and I think that the problems with the 603 tend to get overblown. The problem was/is with the early heads (#14-16or18 as I recall) where they would crack if they were overheated. Newer heads do not seem to have this problem.

One thing to note which nobody has done yet. There are two different types of 603 engines pertaining to the SDL. The early ones used in the 86-87 300SDL had the head problems. They then in 1991 made the 350 SD and SDL which have issues with the lower end of the engine. Not 100% sure what the issues are but be aware that they are there.

This topic has been discussed many times before. The general consensus I get is that owners of the 603 love their engines and could never go back. Owners of the 617 consider owners of the 603 traitors and focus on any and all of the engines pitfalls

.

Hope I made some sense,
Matt

pawoSD · #6 11-27-2006, 11:00 PM

overall the 6cyl models are a little more maintenance needy, they will last just as long or longer than a 617 if properly maintained and never overheated. Overheating is what kills the heads (cracks them) on those engines....otherwise they are pretty much bulletproof

amosfella · #7 11-27-2006, 11:00 PM

The head gasket on a 300 sdl is more likely to give trouble then a cracked head. That being said, I own a 300 sdl, and wouldn't trade it for anything. I like it too much. The ride is greatly improved. If the head is cracked, usually it used antifreze from what I have heard. The sd's have their own problems anyways. I think in the end it comes down to personal preference. Probably like a ford and chev thing. both drive down the road (althought chevs do it better

).

dieseldiehard · #8 11-27-2006, 11:14 PM

Quote:

Originally Posted by pawoSD

overall the 6cyl models are a little more maintenance needy, they will last just as long or longer than a 617 if properly maintained and never overheated. Overheating is what kills the heads (cracks them) on those engines....otherwise they are pretty much bulletproof

I attribute most of the overheated engines to lack of coolant maintenance and plugged up radiators. I've seen too many running with engines on the hot side of 110 degrees C with AC on all the time and it takes its toll eventually on an incline on a hot day in Summer. I have two #14 heads in use at about 260K on each so proof that they aren't all bad! its the owners maintenance (er, lack of same) that is a big factor.

One thing I believe no one mentioned with respect to 603's is the fact the early vacuum pumps can self destruct after a while, usually taking the engine out when they dump bearings into the timing gear.

A big plus with the 6 cyl engines is the hydraulic lifters, that eliminates the need for a valve adjustment every 15K as with other MB diesels made before then. And they are quieter and more fuel efficient. And seem to use less oil than the 617's in my experience. I like both the 617 and 603's (I guess I like all diesels basically) and own several of each, the wife's nephew uses another. I use the wagon to haul stuff but the '87 300D turbo is king of the road.

sixto · #9 11-27-2006, 11:40 PM

If you're thinking of the SDL to replace the SD, keep reading. If you're thinking of adding an SDL to the fleet, stop reading and buy one!

Sixto
93 300SD

greasybenz · #10 11-28-2006, 02:02 AM

i have a W124 with a 603 and love it. It lets me do this: http://i20.photobucket.com/albums/b205/greasybenz/IMAGE_00136.jpg on a slight uphill.

The 617 in my SD wouldnt let me do that. But it will cruise at 80mph without much trouble, i cant push it farther unless im going downhill but its still good for cruising.

the 617 vs 603, id go by what sixto recommends. The cracked head problem seems likes its a rare occurance as long as you glance at your temp meter every 50miles or so. But from my prefrence, driving the 617 is ok for getting me to work or for my back up car. But if i want to drive to say sacramento or anywhere on the highway id stick with my W124 with the 603. Its lets me pass up other cars quickly when needed and is much faster off the line when im in a hurry.

My SD with the 617 is like a tug boat, slow....slow....slow.....getting there...almost....cruisin

Test drive a SDL with the 603 and see how you like it then make your own decision.

pawoSD · #11 11-28-2006, 02:08 AM

Wow...your 617 must be out of tune or just getting weak....mine has 249k and it can still break 100mph UPhill (slight grades)....and easily max's to 113mph on level ground. It pulls pretty hard between 70 and 95....after that it builds to 100+ for about 25 seconds. I've buried my speedo down beyond the 90 mark and gone up a significant grade before, I could feel it slightly slow...but the speedo never came unpegged. So 90+ on hills!

All factors aside, I'd not mind having an SDL, I've ridden in one, and they are amazingly powerful and quiet.

Still love the SD though.

greasybenz · #12 11-28-2006, 02:18 AM

well my SD isnt in perfect tune, but my friends 81 is as it has a new MB engine put in by the PO. But he still maxes out at 100mph going downhill. And the engine is screeming! with your foot to the floor.

with my 603, the pedal was half way when i was at 100mph and it was quiet, silky smooth, and efficient.

Not saying that it isnt possible to do 100+mph in a 617, even my dad has done 90mph in his 78 non-tubro going downhill. But it just doenst feel as good as it does in a 603 nor does it get to 100mph as easily. I guess im just more biased towards the 603 because i love its smoothness.

And as dieseldiehard said, its the king of the road!

Ara T. · #13 11-28-2006, 03:44 AM

300SDLs are great. The handling also seems a lot stiffer than a W123 ( i haven't driven a 300SD). If you have the money go for the 300SDL, its a lot more enjoyable than the OM617. That it as long as you do a lot of highway driving. The 617 feels torquier and peppier around town. The 603 really shines when you can take it out and open it up.

Diesel Giant · #14 11-28-2006, 05:34 AM

I definately like the 617 better. All cast iron, easy to fix, reliable as a door stop, cheap parts, better diesel sound etc. I will give up a little power to have a more reliable engine.

mplafleur · #15 11-28-2006, 08:14 AM

I love my SD, but I can't wait until I get my SDL restored.