I have a new motor plan for my 1990 350SDL - PeachParts Mercedes-Benz Forum

Lampbum2 · #1 02-07-2008, 12:52 AM

Ok, I want to thank everyone that helps people like me with the 1001 questions about there MB's, You folks are great! You always have such great advice. Now that I have you all buttered up, here I go with my 1001 questions.

My Goal

A.) My car is a 1990 350SDL, My goal is to replace the 3.5 liter short block (244,000 miles still runs fine) with the heaver/stronger built 3.0 liter short block (187,000 miles). I want to build the 3.0 short block to go another 150,000+ miles.

1) I am buying a "87 TD short block ($600.00) it has 187,000 miles on it, I am going to put in new bearings and seals front and rear. I'm not sure about rings, this will depend on the surface area of the cylinders.

2) On the head I will change the valve steam seals, check the guides and check the run out of the head, I will also use all new head bolts. I will be getting a damaged head with this motor, I am wondering if the pre-chambers are the same as the 3.5 liter.

3) I am wondering if I need to rebuild the turbo? (244,000 Miles on it), Are the motor mount arms the same? Is the fuel pump the same?

As always, on a serious note, Thank You all that take the time to help!
Jim

PS
The "87 3.0 liter motor with 147,000 miles that I talked about earlier didn't work out, So I am going this route.

jshadows · #2 02-07-2008, 03:46 AM

For 2) no, and injectors are not interchangeable due to addition of small angle in head where injector is placed.

3) for the turbo, well, depends on your school of thought. If it is "if it aint broke then don't fix it" then don't. If it's "as long as I'm there" then you're looking at about another $60 in rebuild kit. The turbo while much easier to play with when the motor is out of the car, is not that much more difficult when it is in the car. I'd at least change the basic oil entry and return gaskets (though I guess you'd have to do that any way).

t walgamuth · #3 02-07-2008, 07:01 AM

You have an excellent plan. The 3 liter is very well regarded for longivity. If it were mine I would have the machinist examine the bearings and reuse them if they are excellent. If it has had any care at all at that mileage they may be virtually without wear. We have reused them several times in my engines with good results.

The bores and rings are much more likely to need attention in my experience, but again, at that mileage if it has had good care you may not really need much there. I would probably replace rings and hone it as a minimum if I had it apart though.

If your machinist has a lot of chevy expereince (cheap parts that wear fast) the tendency there is to just do everything automatically. With the longivity and parts expense in a benz that is just not the right way to do it.

Be sure to do the cam chain guides and tensioner while it is apart.

Good luck.

Tom W

daw_two · #4 02-07-2008, 07:10 AM

QUOTE:
A.) My car is a 1990 350SDL, My goal is to replace the 3.5 liter short block (244,000 miles still runs fine) with the heaver/stronger built 3.0 liter short block (187,000 miles). I want to build the 3.0 short block to go another 150,000+ miles.

Help me understand something about your car. You say at 244,000 miles the 3.5 liter still runs fine. So, why do you want to change it now? I understand about swapping to a 3.0 liter, but I would not want to be without my SDL while the work was being done ......I'd wait until the 3.5 liter was NOT running fine.

Is your 350SDL bored with the 3.5 liter and wants to become a 300SDL?

nhdoc · #5 02-07-2008, 08:25 AM

Quote:

Originally Posted by daw_two

QUOTE:
A.) My car is a 1990 350SDL, My goal is to replace the 3.5 liter short block (244,000 miles still runs fine) with the heaver/stronger built 3.0 liter short block (187,000 miles). I want to build the 3.0 short block to go another 150,000+ miles.

Help me understand something about your car. You say at 244,000 miles the 3.5 liter still runs fine. So, why do you want to change it now? I understand about swapping to a 3.0 liter, but I would not want to be without my SDL while the work was being done ......I'd wait until the 3.5 liter was NOT running fine.

Is your 350SDL bored with the 3.5 liter and wants to become a 300SDL?

Yeah, this is what puzzled me...sounds like he has a lot of free time on his hands...I'd say keep driving the 3.5L and you may never have to replace it. There have been some that go forever just fine without bending a rod. It's even possible that your car has had the engine replaced once already (unless you are the original owner and know the complete service history). Why in the world would you contemplate replacing an engine that shows no symptoms of having a problem?

Lampbum2 · #6 02-07-2008, 09:05 PM

All your input is great! When I say it is running fine, It is running fine for that motor with 244,000 miles on it.
It uses oil, about 1 quart per 3000 miles and smokes (blue) when I first start it ( I always leave it plugged in ) and I do know the history!
The first,second and third (Me being the third owner, I use synthetic) owner was religious about oil and filter changes, I belive this is why the motor has lasted so long.
I do have a great back up car, 1984 300SD! And no I don't have a lot of time on my hands, I just don't want to end up in New Mexico with a blown motor, I want to get this motor back into shape.
Any more feed back? I thought about rebuilding the bottom end of my 3.5 but the rods are $200.00 each, So I feel I could put that $ into the 3.0 block that is solid as a rock and have more confidence down the road!

t walgamuth · #7 02-07-2008, 09:30 PM

Have you had it long?

Smoke on startup could be glow plug related. If it misses a bit and smokes a bit then smooths out in a minute or so it could just be glow plugs. Also it is a good idea to wait another ten or twenty seconds after the glow light goes off before starting. The glows will continue to glow a bit extra and help with roughness.

Tom W

daw_two · #8 02-07-2008, 09:34 PM

Quote:

Originally Posted by Lampbum2

All your input is great! When I say it is running fine, It is running fine for that motor with 244,000 miles on it.
It uses oil, about 1 quart per 3000 miles and smokes (blue) when I first start it ( I always leave it plugged in ) and I do know the history!
The first,second and third (Me being the third owner, I use synthetic) owner was religious about oil and filter changes, I belive this is why the motor has lasted so long.
I do have a great back up car, 1984 300SD! And no I don't have a lot of time on my hands, I just don't want to end up in New Mexico with a blown motor, I want to get this motor back into shape.
Any more feed back? I thought about rebuilding the bottom end of my 3.5 but the rods are $200.00 each, So I feel I could put that $ into the 3.0 block that is solid as a rock and have more confidence down the road!

Okay, I have a brand new idea. Hook a trailer on the back and haul the 3.0 liter around and when the 3.5 goes out, drop the 3.0 in.

Hatterasguy · #9 02-07-2008, 10:09 PM

Why would you swap the bottom end? It sounds like its fine, some 3.5's run hundreds of thousands of miles and never bend a rod.

Blue smoke on start up is probably valve steam seals.

Seems like a lot of wasted time, money and effort. Its not going to leave you in New Mexico with a blown engine, the oil consumption increases graduly over tens of thousands of miles until it just won't run anymore.

barry123400 · #10 02-07-2008, 10:14 PM

I do not think the typical failure mode of the 3.5 leaves you stranded. More likely the base oil consumption starts to gradually increase over time. At some point it is no longer manageable. You slowly lose effective compression in that cylinder as well.
For what it is worth having a really good or reconditioned lower block ready is not a bad ideal. You would want to use your newer series less trouble prone 3.5 head on the lower end of the 3 litre anyways. I would not do anything headwise with the original 3 litre head. Although you could sell it to offset some of your cost if it is pretty good and not cracked.
If I owned a 3.5 it would be prudent to have a 3 litre block in my posession as well. At some point soon enough they may become very scarce. I also would not even contemplate the change until the 3.5 was becoming symptomatic. A quart every three thousand miles does not really justify it. Also do not worry about a couple of hundred thousand miles if you think the odometer is correct. With the amount of tampering and outright failue of the odometers on mercedes that is probably low milage compared to most examples.

TylerH860 · #11 02-07-2008, 10:21 PM

FRANKENBENZ! Keep it original...

Lampbum2 · #12 02-08-2008, 06:56 AM

To answer your question Tom W. I bought this car in June of 1999, It had 166,000 miles on it then, It used maybe 1/2 a quart of oil in 5,000 miles then, this is when I change my oil at 5,000 miles.
My car is always plugged in and I count to 10 when the glow plug light goes out, then I start the car, It doesn't miss at first start or ever and the glow plugs are all good.
I would think that valve steam seals being bad, the oil should burn off by the time the temp is at 80c, I may be wrong on that judgment, I'm sure they are as hard as a rock and need to be changed.
I have heard that these motors can just let go, I hear when they start using oil is when you want to make a plan to rebuild the 3.5 or go with a 3.0 bottom end. So I am going ahead with my plan, The 3.0 liter motor.
My 84 300SD never burns blue and I keep it outside in the cold (Washington State) and it has no block heater, It does have a bit of smoke, but not blue, more like a light gray.
Thanks again for all your help.
Jim

daw_two · #13 02-08-2008, 07:31 AM

Quote:

Originally Posted by Lampbum2

To answer your question Tom W. I bought this car in June of 1999, It had 166,000 miles on it then, It used maybe 1/2 a quart of oil in 5,000 miles then, this is when I change my oil at 5,000 miles.
My car is always plugged in and I count to 10 when the glow plug light goes out, then I start the car, It doesn't miss at first start or ever and the glow plugs are all good.
I would think that valve steam seals being bad, the oil should burn off by the time the temp is at 80c, I may be wrong on that judgment, I'm sure they are as hard as a rock and need to be changed.
I have heard that these motors can just let go, I hear when they start using oil is when you want to make a plan to rebuild the 3.5 or go with a 3.0 bottom end. So I am going ahead with my plan, The 3.0 liter motor.
My 84 300SD never burns blue and I keep it outside in the cold (Washington State) and it has no block heater, It does have a bit of smoke, but not blue, more like a light gray.
Thanks again for all your help.
Jim

Hi Jim.
I have blue smoke on start up. When I bought my car in March, 2007, the odometer read 84K something. No way is it the original odometer is what I guess (see signature). I use to start when the glow plug light went out (newbie), now I wait until I hear the relay CLUNK. I have less blue smoke now.

My oil pressure light came on ONE time right before an oil change. The oil was about 1 quart low, but I don't think I filled it all the way the full line --- I was just learning then. My car definitely has a little miss at idle. I'm guessing it one injector that doesn't quite have the right spray pattern, but I haven't bothered with it yet.

My plan is to keep on fixing the little things and drive it until I find something nicer. I do REALLY like the color, though. My next BIG expenditure is going to be front seats........at least I HOPE that is my next big expenditure. *crosses fingers* None of us like the unpredicatable things that happen.

And yes....I have that ticking noise. If I press down on the shock absorber on the belt tensioner assembly then the ticking noise stops. So, I have to fix that soon.

So, here's to SDLs that are still on the road racking up miles as daily drivers!!! The first round is on me.

CHEERS!

t walgamuth · #14 02-08-2008, 08:08 AM

Quote:

Originally Posted by Lampbum2

To answer your question Tom W. I bought this car in June of 1999, It had 166,000 miles on it then, It used maybe 1/2 a quart of oil in 5,000 miles then, this is when I change my oil at 5,000 miles.
My car is always plugged in and I count to 10 when the glow plug light goes out, then I start the car, It doesn't miss at first start or ever and the glow plugs are all good.
I would think that valve steam seals being bad, the oil should burn off by the time the temp is at 80c, I may be wrong on that judgment, I'm sure they are as hard as a rock and need to be changed.
I have heard that these motors can just let go, I hear when they start using oil is when you want to make a plan to rebuild the 3.5 or go with a 3.0 bottom end. So I am going ahead with my plan, The 3.0 liter motor.
My 84 300SD never burns blue and I keep it outside in the cold (Washington State) and it has no block heater, It does have a bit of smoke, but not blue, more like a light gray.
Thanks again for all your help.
Jim

It sounds like you are doing the right thing. Best of luck with your project.

Tom W

andmoon · #15 02-08-2008, 08:08 AM

My 90 350 sdl has been burning 1 qt every 2~3000 miles for over 75K miles.

Why don't you do a compression test now to set a baseline. If compression keeps dropping along w/ increase in oilo consumption, you may be ovaling a cylinder.

I've seen 3.4 motors go over 400K so I would run that motor until it actually dies.