1976 300 engine replacement - Mercedes-Benz Forum

 
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post #1 of 8 (permalink) Old 05-06-2007, 06:13 AM Thread Starter
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1976 300 engine replacement

Brand new to the forum, hope to become a longtime member. But first, I have to buy a Mercedes.

A older gentleman that attends our church is trying to sell a 1976 300 D, or at least that's the model he says it is. The car has been parked in his shop for at least 20 years, clean and dry. The previous owner had a major engine problem and that's how it came into the current owner's possession. The bad engine has been removed and a replacement is setting beside the car.

How hard is an engine installation? I've done it on other cars and the seller has a hoist and shop space. What should I look for that may cause problems? I expect that I'll have to prep the engine since it's been unused for so long. Any ideas?

The car is in very good shape overall, based on my experience, definitely worth saving. Under 100,000 miles on the body and chassis and the replacement engine reportedly has similar mileage.

Thanks in advance for any input.

Matt
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post #2 of 8 (permalink) Old 05-06-2007, 12:51 PM
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A 300D as you know is a diesel, a rather slow vehicle, but very dependable! swapping engines is very straightforward like any gas engine. There is less to hook up but more vacuum hoses. And because its a diesel, you have to bleed the fuel system to draw fuel to the engine unlike a gas car with a fuel pump. its bled much like brakes. Loosen a line, crank engine till air is expelled. They require a very fresh strong battery because of the ultra high compression to crank fast enough to fire. You can verify the replacement engine is free by removing injectors and using a breaker bar on the crank bolt to rotate it. Spray some oil in the injector holes prior to rotation. Might be a good idea to replace the water pump based on age and seals drying up. Drain the fuel tank because diesel gathers water and allows alge to grow within the tank! Less likely if it was stored empty.
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post #3 of 8 (permalink) Old 05-06-2007, 02:47 PM
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Quote:
Originally Posted by carnut1
A 300D as you know is a diesel, a rather slow vehicle, but very dependable! swapping engines is very straightforward like any gas engine. There is less to hook up but more vacuum hoses. And because its a diesel, you have to bleed the fuel system to draw fuel to the engine unlike a gas car with a fuel pump. its bled much like brakes. Loosen a line, crank engine till air is expelled. They require a very fresh strong battery because of the ultra high compression to crank fast enough to fire. You can verify the replacement engine is free by removing injectors and using a breaker bar on the crank bolt to rotate it. Spray some oil in the injector holes prior to rotation. Might be a good idea to replace the water pump based on age and seals drying up. Drain the fuel tank because diesel gathers water and allows alge to grow within the tank! Less likely if it was stored empty.
What else one can say to posts like this: BRAVO!
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post #4 of 8 (permalink) Old 05-06-2007, 04:29 PM
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great car ,, I want one , ,

The injector pump has a hand primer on it , (round knob) that you unscrew , pump like mad till all bubbles are out of fuel . Check flow by loosening bolt on top of fuel filter , this is a little messy but Doing this will save your battery.

'76 - 300D
'72 - 240D (noddy)
'40 Chev pickup
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post #5 of 8 (permalink) Old 05-06-2007, 04:49 PM
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The degree of difficulty depends in large part on what engine is resting next to the vehicle. The further it moves away from the the exact engine the car came with, the more difficult the replacement. If you provide an engine number, we can see what you have there.

"If spending money you don't have is the height of stupidity, borrowing money to give it away is the height of insanity." -- anon
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post #6 of 8 (permalink) Old 05-06-2007, 08:40 PM Thread Starter
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Thanks for all the information! I'll have to check the numbers on the engine but was told that it came from the same model car. Good advice on bleeding the fuel system too, went through that with a diesel tractor last week and don't want to do it again.

Hopefully I'll have an opportunity to buy this thing and get it running.

Thanks again everybody.

Matt
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post #7 of 8 (permalink) Old 06-13-2007, 01:20 PM
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Quote:
Originally Posted by carnut1
... They require a very fresh strong battery because of the ultra high compression to crank fast enough to fire. ...
21 to 1 compression ratio, isn't it? That's 2 to 3 times the compression of most gassers, plus you sometimes need to keep a diesel cranking until it's firing on all cylinders depending on the engine and environmental conditions. You'll notice that the car has a longer battery tray... should be able to find extra long (large capacity) batteries for diesels. I think the part # for an International DieHard is #33349, but you'll want to check to be sure.

Also, the 5 cyl diesel engine (3.0 L) is a bit more cramped in the engine compartment than the 4 cyl (2.4 L) and might use different engine mounts and shock. Hopefully it's a replacement rather than a swap. If it's the same engine as the car originally had, it should be fairly straightforward. Take LOTS of pictures, put everything in labeled bags, and keep a detailed journal of every nut and bolt

You can find links to online/CD service guides somewhere on these forums. I have a copy on my hard drive and double check everything before I pick up any tools.
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post #8 of 8 (permalink) Old 06-13-2007, 03:09 PM
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You'll have to check on the block. It would have to be a OM617.910 not a OM617.912 or other variant since the oil filter will interfere with the brake booster. If that is the case the engine will drop right in, definitely squirt some MMO or ATF into he cylinders to let the rings reabsorb oil before cranking the engine dry.

1977 - W116 - 6.9
1974 - W115 - 240D /8 - 4(M) OM617.910 + Turbo + 300D FW - Completed 7/8/10
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