Which Motor Should I Swap Into My 300SDL?
 

First off, i'd like to say I REFUSE to send this car to the crusher. With that out the way what are my best choices?

Obviously the first and foremost choice would be an OM603 or OM606, they are as straightforward was it gets but those seem to be pretty rare and hard to find in the scrapyard honestly. I would like to have a whole car beside me if possible. If I do find an OM603 I will jump on it.

However, if I have no luck finding one OR find a really good deal on another engine. which motor would you recommend?

Engines I have on mind are anything that went into the W126 chassis in stock form, and the M104 inline 6. So that's a lot of options.

I would appreciate the help.

I'd stick with something very close to your original motor. Same year if possible, same model. I'd avoid the 91+ 3.5 liter diesel though because of the rod bending issue. Just look and run want to buy ads, you'll find the right car/motor.;)

with a gasser you'd be changing trany, electrics, exhaust just to name a few. All you may need is a head.

You can put anything you want in it if you have the dollars. With that said why not rebuild you engine (or have it rebuilt). If it doesn't have something sticking through the side of it, they are more affordably rebuilt.

It DOES cost less to rebuild the head than too swap the motor?
Rough estimate how much would it cost to rebuild the head?

Aren't heads expensive? I see them on ebay for $1000- $800 all day long.

Good idea. I might as well stick with the OM603 then.


I hope it stays there. Just don't know how i'll get it back, probably a vehicle moving company

That's a studebaker truck behind it.....dig it.;)

Step one is to do a cylinder leak down to determine in what cylinder the combustion to coolant leak is occurring.

Next pull the head and determine if just the head gasket has failed or the head is cracked.

Does cooling system pressure build moments after a cold start? Does the upper radiator hose get too stiff to pinch within a couple of minutes of a cold start? If so, is there a hiss of air when you remove the reservoir pressure cap 12 or more hours later? Any of those symptoms suggests the head is already cracked.

Drive it until oil consumption is intolerable, exhaust smoke is intolerable or it overheats again. Best case, it survived your uncle. Otherwise, replace at least the head. I wouldn’t bother having it checked. It might check out fine on the bench but the next torquing cycle will cause cracks in the embrittled (is that a word?) material around the #4 and #5 combustion chambers.

You could do a 617 swap so it survives the next negligent relative.

Sixto
98 E320s sedan and wagon

Instead of starting a bunch of threads and panicking over the situation, why not pull the head like you were planning anyway to fix the low compression issues and move on from there? Freaking out and running to the worst-case-scenario isn't going to solve the problem and may cost you way more in the long run.

After you get the car going again, ban the uncle from driving it. Clearly he's not smart enough to drive a car. If he were my uncle, he'd be paying a shop for the repairs, but I'm a harda** like that.

Your uncle isn't allowed to drive a mercedes again, cause I said so. :D

Jokes aside, make him pay for the cylinder head. I wouldn't pay for someone else's idiocy.

Do a compression and leakdown test before jumping to conclusions. If the car didn't shutoff it's probably fine.

Wish I could make him pay, but it would take forever since he works minimum wage, basically he lives in poverty. I REALLY REALLY REALLY wish he could pay for it. :mad:

With that aside, he'll never, nor will anyone else get behind the wheel of this car other than my brother and I. He's literally banned for life.

Once the radiator comes once, I'm going to buy a combustion leak tester and start there.

I'll do a compression test this morning, but like I said earlier I can never grasp the concept of a leak down test. How in the world can I tell if i'm at TDC?

How do I look at the camshaft and tell?

You gave your uncle permission to drive the car, it is your fault and no one else. I never let anyone drive my old bangers, I drive them. What was done was done. Life moves on.

Pull your valve cover and crank the engine over to TDC on 1 like you would for timing chain stretch. (Crank pointer on 0T and the cam mark lined up with the index mark on the 1st camshaft bearing tower).

Look at the lobes for the I & E lobes for Cylinder #1. When you're at TDC for each cylinder, they will look like that. Basically crank the engine until you arrive at TDC for the next cylinder (firing order - 1-5-3-6-2-4) and leak-down each cylinder until you've done all 6.

I've posted a bunch on leak down, do a search for my screen name and leakdown / leak down.

Don't bother with the " test fluid changes color" kits, you already know that there is a combustion leak to coolant. These kits are for a quick test and not that accurate.

A leak down is where air ( around 80 to 110 PSI ) is pumped into a cylinder and you determine where is is leaking out. If you use a compression gauge set, be sure to remove the check valve in the hose end, it is usually a tire valve type with a very soft spring.

Start with cyl 1. With a hose inserted in the spark plug / injector / glow plug hole then engine turned until air stops coming out, this is near TDC. Look at the damper marks and turn engine to TDC / 0.

Apply a quick puff of air and see if the engine turns, if so, turn it back a bit farther than the first time and try again. When the engine won't spin with air pressure and both valves closed, you are at TDC. Look / listen for air coming out of exhaust, intake oil filler and radiator.

Also, you can mark the damper at intervals ( 180* for a 4 cyl , 120* for a 6 cyl ) then pick the next cylinder in the firing order making it easier to find TDC.

To do this by can lobe location, both lobes for a given cylinder need to be up, this is the compression stroke but you still need to find exact TDC.