Quick engine swap question - PeachParts Mercedes-Benz Forum

83mercedes · #1 03-07-2006, 02:33 PM

Just picked up an 81 300sd with a junk body but a very strong engine and transmission.

What I want to know: is the 81 300sd engine a 617.952 turbo as well, in other words, will I be able to swap it and the tranny into my 83 300cdt?

rhodes2010 · #2 03-07-2006, 02:42 PM

It lists the same engine for CDT and your SD.
I think it will work.

Here is a list of body type with engine types:

http://home.hiwaay.net/~gbf/mbmodels.html

But I do not have hands on experience with the CDT model.
Let's see what others have to say on this,

Panzermann · #3 03-07-2006, 03:30 PM

No, you won't be able to swap the engines without modification. I did it about 8 months ago 1983 300SD to 1985 300D. The oil filterhousing on the 300SD uses an electronic transmitter, while the 300D requires a direct connect to the guage on the dashboard. Also, the oil supply line from the 300SD oil filter housing will not fit if you put one from the 300 CD on. Can get a replacement at a junkyard. Also, the manifold hose on the a/c is different between the two and the alternator/water pump belts are 10 x 1000 on the 300SD but 10 x 1035 on the 300CD. Will also need to change the motor mounts from the 300 CD motor to the engine your going to put in. Oil cooler lines are also different. Other than these changes (and renewing as many rubber/plastic bits as possible), should work fine.

sixto · #4 03-07-2006, 04:15 PM

SD uses an inductive drive speedo cable and electronic speedo. D uses a direct drive speedo cable and mechanical speedo.

Sixto

1991 560 SEC · #5 03-08-2006, 04:19 AM

No such thing as a quick engine swap.

83mercedes · #6 03-08-2006, 12:36 PM

Quote:

Originally Posted by Panzermann

No, you won't be able to swap the engines without modification. I did it about 8 months ago 1983 300SD to 1985 300D. The oil filterhousing on the 300SD uses an electronic transmitter, while the 300D requires a direct connect to the guage on the dashboard. Also, the oil supply line from the 300SD oil filter housing will not fit if you put one from the 300 CD on. Can get a replacement at a junkyard. Also, the manifold hose on the a/c is different between the two and the alternator/water pump belts are 10 x 1000 on the 300SD but 10 x 1035 on the 300CD. Will also need to change the motor mounts from the 300 CD motor to the engine your going to put in. Oil cooler lines are also different. Other than these changes (and renewing as many rubber/plastic bits as possible), should work fine.

The SD engine is still in the vehicle, so I have a working oil cooler with lines already attached to that engine. Could I swap in the SD's oil cooler with its engine to avoid these problems? AC is not a concern, I wasn't even planning on hooking up the system...too problematic and expensive a system and sucks up too much engine power, which is unacceptable when these engines are relatively low-powered in the first place. When you say change the motor mounts, you mean just buy the SD mounts and those will fit in the CD? How did you overcome the drivebelt, oil pressure issues, and speedo issues or how would you recommend doing it? Are there any transmission issues?

Quote:

Originally Posted by 1991 560 SEC

No such thing as a quick engine swap.

The quality of being "quick" referred to the brevity of the question, not the engine swap.

83mercedes · #7 03-08-2006, 01:29 PM

I just spent a little more time thinking about this, and I believe I've found ways around all the problems brought up in this swap. Correct me if I'm wrong about any of this.

1. By leaving the belt-driven auxiliary engine components of the SD engine on it (alternator, water pump, etc.), I could not have to mess with the drivebelts at all. I'd just have to remember to buy belt sets for an SD engine in the future when I had to replace them.
2. By removing the oil filter housing from the SD engine and replacing it with the one from the CD, I can solve the oil pressure problem and the oil cooler compatibility problem (if the units are interchangeable).
3. Speedometer shouldn't be an issue at all, as all I'm switching is the engine and components, not anything to do with the instrument cluster or speedo cable.
4. That still leaves motor mounts, which could use some elaboration on the problem there, and any issues that might exist for the tranny swap.

Any help is much appreciated.

Panzermann · #8 03-08-2006, 05:57 PM

1. By leaving the belt-driven auxiliary engine components of the SD engine on it (alternator, water pump, etc.), I could not have to mess with the drivebelts at all. I'd just have to remember to buy belt sets for an SD engine in the future when I had to replace them.

-Works fine as regards the belts. I just spent a bit of time trying to figure out why I couldn't get the belt to fit on the alternator/water pump. As regards the a/c, I live in Arizona, so A/C is an essential, but certainly you could eliminate it and get more power and have less parts, if that is not too important to you.

2. By removing the oil filter housing from the SD engine and replacing it with the one from the CD.

-This is exactly what I did to solve the problem. You just have to obtain an oil filter housing to turbo oil line. They are different in length and not interchangeable. Cost of a new from Mercedes for this line is about $120. I have not been able to find new ones available from other suppliers.

I can solve the oil pressure problem and the oil cooler compatibility problem (if the units are interchangeable).

-I would just get new oil filterhousing to oil cooler lines and replace them with ones intended for the 123 chassis. After they get old, they are one site that leaks. They are also MUCH easier to replace with the engine out of the car. Cost for two new ones from ******** arizona (orderable over the net) is about $100 for the set. This of course relates to the overall philosophy of replacing plastic and rubber doohickeys with wild abandon while the engine is on a stand outside of the car, as you'll never get a chance when it is easier. I say this from my admittedly limited amatuer experience doing exactly what you are doing. It is also a great chance to replace the rubber heater hoses at the firewall, for similar reasons (accessibility).

3. Speedometer shouldn't be an issue at all, as all I'm switching is the engine and components, not anything to do with the instrument cluster or speedo cable.

Can't comment on the speedometer issue. I used a 300sd motor from a car with a trashed transmission, but my 300d transmission was still good and, as I recall, input to the speedometer is from the transmission. That might be an issue for you, or maybe not. The tachometer should hook up fine. The oil line is corrected by using the oil filter housing from the 300cd and putting it on the engine in place of the 300sd housing.

4. That still leaves motor mounts, which could use some elaboration on the problem there.

-You just need to swap the metal motor mount arms from the bad 300cd engine to the 300sd engine. Again, I would also replace the rubber motor mounts themselves and the engine shocks/mountings, in the spirit of replacing everything that is accessible and likely to rot.
and any issues that might exist for the tranny swap.
Here, I didn't have so much success, and managed to damage the front pump on the transmission. If you are moving the transmission around, you have to get the torque converter lined up with the front transmission pump. I screwed it up and had to get "professional help" (a mechanic, not the type my girlfriend and parents think I need). It is possible that you won't have to separate the transmission, especially if you don't worry too much about the speedometer issue noted above. Not switching the transmission would save you a significant amount of work and potential for damaging things.

One other thought: While the engine is out of the car, take off the alternator and starter and have them checked. Auto part stores will do it for free. Again going back to the spirit of doing everything possible while the engine is out of the car. There are also a number of gaskets and minor articles that are easy to change. Ones that come to mind: thermostat (I use the 76 degree thermostat for 450sl, which really does improve cooling here in AZ without impairing performance), water pump, water pump housing, intake/exhaust manifold gaskets, turbocharger mounting gaskets, TURBO OIL SEALS (especially the lower drain seal on the turbo and those leading down to the oil pan, as these are culprits for the high baseline number of chronic oil leaks in these engines and they are difficult to replace with the engine in the car).

A great way to learn the anatomy of these cars. I know I did.

83mercedes · #9 03-09-2006, 09:53 PM

I'd sincerely like to thank you, Panzermann, for giving me one of the most complete and intelligible responses I've ever gotten to one of my automotive issues on this forum.

Although I'd already planned on doing so, thanks for the advice to change all the gaskets, rubber, etc as I know this to be invaluable. Indeed, I've already replaced most of the pieces you've mentioned on my CDT engine (with it in the car

) , and will have to do so again with my SD engine.

It sounds to me like I basically just need some relatively cheap parts for the switch; I feel much more confident now that I have these issues sorted out.

As to the transmission: I could just switch in the SD's speedo (if it's compatible in my CDT instrument cluster) and speedo cable with the tranny to avoid that compatibility issue...

On dropping/damaging the tranny: what would prevent one from just removing the engine and tranny as one unit? This would be easier, no doubt, if the correct angling and lifting could be accomplished. Am I missing something?

Panzermann · #10 03-12-2006, 04:56 PM

[QUOTE=83mercedes]I'd sincerely like to thank you, Panzermann, for giving me one of the most complete and intelligible responses I've ever gotten to one of my automotive issues on this forum.

-It's my pleasure to be able to save someone some time!

Although I'd already planned on doing so, thanks for the advice to change all the gaskets, rubber, etc as I know this to be invaluable. Indeed, I've already replaced most of the pieces you've mentioned on my CDT engine (with it in the car

) , and will have to do so again with my SD engine.

It sounds to me like I basically just need some relatively cheap parts for the switch; I feel much more confident now that I have these issues sorted out.

-I've had luck ordering from ***************. they ship quickly, have good prices, and have a really good online ordering system, much better than Performance Product's and better prices to boot.

As to the transmission: I could just switch in the SD's speedo (if it's compatible in my CDT instrument cluster) and speedo cable with the tranny to avoid that compatibility issue...

-speedo will be an issue. The one from the 300sd cluster (126 chassis) is not compatible with that from the 123 chassis. Mechanical (123) vs electronic (126). This is a point where a visit to the Mercedes dealer part shop might be worth your while, as it may be possible to switch the speed measuring equipment from the 300CD's transmission to that of the 300SD. They have really good parts catalogs at the dealership that can help with the determination, just by looking at the diagrams and comparing the two cars.

On dropping/damaging the tranny: what would prevent one from just removing the engine and tranny as one unit?

-YES!!! This would be a lot easier and would avoid the damage to the transmission that I caused on mine. You alone know how good the transmission on the 300SD is. If it shifted well, then taking the two as a unit would be best approach, leaving you with a spare transmission should the 300sd one go bad. Only downside of this is that you will have trouble using an engine stand, as these mount where the transmission goes, so you will have to keep the unit on a hoist. It is VERY heavy as a unit, more managable when broken up (but also easier to break when broken up!).

This would be easier, no doubt, if the correct angling and lifting could be accomplished. Am I missing something?

-No, this is achievable. Make sure your hoist has a load leveler to alter the angle of the engine and take it slow and easy as you're removing and replacing the engine. And off the engine to be discarded, strip everything you can and save it. I used 1 gallon ziploc freezer bags, which I labeled. you never know when the things you stripped will come in handy. I just recently used the glow plugs that I saved and one of the saved fuel injectors, about $100 in parts! Let me know how it goes!