Will a '84 300D engine fit into a '79 300SD? - PeachParts Mercedes-Benz Forum

beaulieub · #1 07-28-2014, 08:42 PM

My 79 300SD engine (OM617) has some internal damage and I've found a 1984 300D (OM617) for $500. I believe the '79 is a 617.950 while the '84 is a OM617.953.

Anyone know is they can be swapped?

If so, how do I determine if the donor engine is any good (ie. not beat!).

Thanks is advance

NH_Bert

t walgamuth · #2 07-28-2014, 09:12 PM

Check location of oil filter, power steering pump and ac compressor....basic engine is pretty much identical but there may be some ancillaries in different and hard to change locations.

mach4 · #3 07-28-2014, 09:20 PM

Quote:

Originally Posted by beaulieub

My 79 300SD engine (OM617) has some internal damage and I've found a 1984 300D (OM617) for $500. I believe the '79 is a 617.950 while the '84 is a OM617.953.

Anyone know is they can be swapped?

If so, how do I determine if the donor engine is any good (ie. not beat!).

They can be swapped. You'll need to keep your oil filter canister to clear the steering box.

You really can't determine if the engine is any good, but you can come close. I'd insist that you hear the engine run before purchasing it. It's easy to do, just hook up a jug of diesel to the supply and return lines. Check to make sure there's oil in it, and crank it. You can use a battery and jumper cables to run the starter. Get a couple of lengths of heavy gauge wire to hot wire the glow plugs. You should be able to just leave the oil lines be as they shouldn't open until the oil gets hot. 30 seconds to a minute won't hurt anything running without coolant.

If you can't hear it run before purchase, try to make the purchase contingent on the engine running.

If you can't do that, at least turn the engine over by hand and make sure nothing is binding.

If it runs and you own it then do the following to see how good it is before putting it in the car

1. Set the valves
2. Do a compression test
3. Pop test the injectors
4. Check the turbo
5. Check the chain stretch

If everything is looking good swap it in. There's a bunch of things you should do while the engine is out, but that's another thread.

vstech · #4 07-28-2014, 09:35 PM

I think you will need to swap the oil filter, the upper oil pan and the air filter intake manifod, and exhaust manifold/turbo... the last few are not strictly necessary, but the 79 did not have EGR I think... and that's a good thing.

vstech · #5 07-28-2014, 09:36 PM

also, your 300D motor should be a .952 I don't think there was a .953

Zacharias · #6 07-28-2014, 11:16 PM

If you retain the original transmission, you will need to swap over the existing linkages as the later motor is set up for a Bowden cable, while your older trans uses a throttle position rod running from the linkages to the transmission instead.

As vstech mentioned, you have to swap the top oil pan or it will be resting against the crossmember.

AC will need some work to hook up, if that is desired.

You will need to check if you need to swap over your current intake an turbo in order for the front exhaust (flex) pipe to fit. I put a 617.952 into my '79 300sd, but shop had the complete '83 w126 donor car so I do not recall which front pipe was used in the end.

Were you aware that there is another forum member who just gave up trying to find a transmission for his w116 300sd and is parting it? He may still have his motor for sale. I think his forum handle is Assault. Check out the used parts for sale and wanted subforum. Just a suggestion.

Junkman · #7 07-29-2014, 10:08 AM

I would also pull the parts off down to a long block and replace the gaskets. Include the oil filter housing, the manifolds on the passenger side, oil pan, turbo drain etc. Fix any leaks in the trans also while it is out. There is a discussion here of a "leak free engine". Look it up.

t walgamuth · #8 07-29-2014, 10:15 AM

Quote:

Originally Posted by Zacharias

If you retain the original transmission, you will need to swap over the existing linkages as the later motor is set up for a Bowden cable, while your older trans uses a throttle position rod running from the linkages to the transmission instead.

As vstech mentioned, you have to swap the top oil pan or it will be resting against the crossmember.

AC will need some work to hook up, if that is desired.

You will need to check if you need to swap over your current intake an turbo in order for the front exhaust (flex) pipe to fit. I put a 617.952 into my '79 300sd, but shop had the complete '83 w126 donor car so I do not recall which front pipe was used in the end.

Were you aware that there is another forum member who just gave up trying to find a transmission for his w116 300sd and is parting it? He may still have his motor for sale. I think his forum handle is Assault. Check out the used parts for sale and wanted subforum. Just a suggestion.

What about the mounts for the ac compressor?

Zacharias · #9 07-29-2014, 11:38 AM

Quote:

Originally Posted by t walgamuth

What about the mounts for the ac compressor?

Good question. It was about 10 years ago, and I don't recall that.

The OP will do well to have the two motors side by side before the works starts, and look closely for any differences.

clacker · #10 07-30-2014, 10:22 AM

There are lots of differences, the engine mount brackets might be different, the intake manifold is different, the turbo might be different (KKK vs Ta03XX series), the vacuum pump is different (one line vs two line), the air intake tube to the turbo, the air filter assembly, the vacuum system lines, the black box on the valve cover, the transmission control/vacuum source might be different, injectors might be different (they flip flopped part numbers around those years),
It will be a night mare for a non diesel Mercedes shop to swap the engine, a HUGE learning experience and get really expensive. Some parts you cannot eyeball the differences and only find out that it will not clearance or thread or line up and then have to pull the engine out again...you need someone with experience for a job like this. Getting the right vacuum signal for the transmission will be a challenge to set up and time consuming as stuff is always removed and never installed exactly or it was not correct to begin with!

t walgamuth · #11 07-30-2014, 11:45 AM

Quote:

Originally Posted by clacker

There are lots of differences, the engine mount brackets might be different, the intake manifold is different, the turbo might be different (KKK vs Ta03XX series), the vacuum pump is different (one line vs two line), the air intake tube to the turbo, the air filter assembly, the vacuum system lines, the black box on the valve cover, the transmission control/vacuum source might be different, injectors might be different (they flip flopped part numbers around those years),
It will be a night mare for a non diesel Mercedes shop to swap the engine, a HUGE learning experience and get really expensive. Some parts you cannot eyeball the differences and only find out that it will not clearance or thread or line up and then have to pull the engine out again...you need someone with experience for a job like this. Getting the right vacuum signal for the transmission will be a challenge to set up and time consuming as stuff is always removed and never installed exactly or it was not correct to begin with!

What about the ac compressor?