Rod knock on '79 240D, pull the pan? - PeachParts Mercedes-Benz Forum

New2MB · #1 07-31-2006, 03:25 PM

My sister has a 1979 240D that got low on oil over time.

She was driving it to San Fran and the valves started clicking so she immediately pulled over (go figure). Checked the dipstick and then proceeded to beat her fiance as he was the one that supposedly checked the oil before they left, not a drop on the stick. It took 4 qt's to get it back to the right level. They then drove the rod knocker home (didn't lose any oil on the way home) and took it to a local shop.

The shop she took it to verified that it does have a rod knocking and thinks that a new engine is the answer. I called and talked to the shop to see if anything else was wrong. The shop says that as far as they can tell the only problem is the rod knock. Why replace an engine because of a rod knock? They want $3500 to fix a $2500 car.

So my question is, can I jack the engine up, pull the pan from below, and spoon in new bearings? I'm hoping that just the bearings need to be replaced, not the crank.

Any other comments and suggestions are welcome.

Endust · #2 07-31-2006, 03:52 PM

I dont believe the crossmember will allow you the room to pull the upper pan to do the work your talking about. Even if you could, I wouldn't waste the cash. If its eaten 1 bearing bad enough to knock, the others can't be that far behind and the top end was prolly starved real good. Junk yard motor would be the direction I would want to go. I know if the engine in my 240 went, it would become an instant parts car. Motors for these are just too expensive rebuilt or new.

300SDog · #3 07-31-2006, 04:34 PM

Meanwhile replacement engine might not be easy to find, low mileage 240D engines are becoming uncommon. Also the '79 has different components from '80/81+ models, different throttle linkage, manifolds, vacuum lines and electrics. I'd start searching for good used longblock immediately and dont pull the existing engine until you've got a replacement right next to it.

New2MB · #4 08-01-2006, 09:16 AM

Is there some reason I can't pull the engine and rebuild it? Or at least pull the engine and determine what it needs? Maybe inspect the bores/pistons, connecting rod bearings, crank journals, cam lobes, valves, etc.. Or is the general assumption that being 4qt's low is reason enough to replace the engine due to all the damage?

Endust · #5 08-01-2006, 09:43 AM

You could pull it and rebuild it. However, I highly doubt you ahve the tools or specs for checking all the bearings and such that would have been damaged by oil starving it. If you pull the motor and find the rod bearing and replace that bearin gonly it may or may not fix it. It could last 1 year or a day before something else starts to let go. Its really up to you and skills/tools/budget. If its a car you plan on keeping for a long time and you can afford it, by all means take it out and have it rebuilt. If this is a beater car or a daily driver I would try to find a decent engine and just drop it in. There are a few 240's for sale on Ebay for cheap right now that could be good parts cars. One with a blown trans that was quite low in the bidding.

P.E.Haiges · #6 08-01-2006, 10:01 AM

New,

I don't know about if U can remove the oil pan in the car on a 240D. But I do know I removed one from a 190D even though the manual said the engine had to be removed. I even removed the crankshaft with out removing the engine.

U won't know until U try. U will have to loosen the engine mounts and jack up the engine as high as possible and turn the crankshaft so the oil pan clears the rod journals.

If the crankshaft is not scored, new rod and main bearings should fix it.

P E H

jrgslg · #7 08-01-2006, 04:41 PM

Quote:

Originally Posted by P.E.Haiges

New,

I don't know about if U can remove the oil pan in the car on a 240D. But I do know I removed one from a 190D even though the manual said the engine had to be removed. I even removed the crankshaft with out removing the engine.

U won't know until U try. U will have to loosen the engine mounts and jack up the engine as high as possible and turn the crankshaft so the oil pan clears the rod journals.

If the crankshaft is not scored, new rod and main bearings should fix it.

P E H

If you are able to get the pan off and remove the rod,you should be able to give it a good visual inspection and if that looks good,get a micrometer and check if the crank is still round.Hope you can save her,Johnny

t walgamuth · #8 08-01-2006, 09:36 PM

it might be worth while to get a second opinion about the rod knocking.

if it was four quarts low that means it had at least three in it. i would not think three quarts would cause a rod bearing to be trashed.

unless there were extenuating circumstances

tom w

New2MB · #9 08-01-2006, 10:32 PM

Thanks for all of the suggestions. I am going to California to visit her and I will have a chance to check it out for myself. I guess I'll take a stethescope with me to see if I can figure out where the knocking noise is coming from. Are there any other ways I can tell if it is definately a rod knock without disassembling much?

unkl300d · #10 08-01-2006, 11:21 PM

Well, how did it lose 4 qts over time?? That's alot before anybody noticed and it seems that your sister is in the know about checking oil level.

How many miles on the engine? If the car body/interior is perfect, it may be worth fixing.
I am sure you can find a crashed car with a decent engine. Is the car in San Diego??

bgkast · #11 08-01-2006, 11:26 PM

Just post a wanted ad on craigslist. I had a guy offer me a 240 engine (with car attached) for $200 in Oregon, but I couldn't take the whole car.

New2MB · #12 08-02-2006, 08:32 AM

Quote:

Originally Posted by unkl300d

Well, how did it lose 4 qts over time?? That's alot before anybody noticed and it seems that your sister is in the know about checking oil level.

How many miles on the engine? If the car body/interior is perfect, it may be worth fixing.
I am sure you can find a crashed car with a decent engine. Is the car in San Diego??

That's a very good question, I'm not sure how it lost the oil. My sister said she checked it alot when she first got the car but it was never losing any so she stopped checking it as often. The guy at the shop that she took it to said that after 3000 miles the oil starts getting burned up faster. The only thing I can figure is that it becomes more viscous due to breakdown and can then make it's way out of the engine easier.

I think the engine has about 160k on it.

The car is in Sacramento, I don't think the interior and exterior are perfect, it was $2500 and it's almost 30 years old. For me in Michigan the body is like a dream (no rust) but in Cali that is just expected.

barry123400 · #13 08-02-2006, 12:48 PM

To establish the affected cylinder just loosen each injector nut. The knock should lessen or dissapear when you hit the right cylinder. Most problems on the 240d have been the #1 cylinder. If that turns out to be the case you can drop the small forward oil pan. This will allow you to remove the rod cap and see if the crank is damaged. If it is not tore up perhaps the expendature for a pair of bearing shells is worth the risk. Since the engine was not truly out of oil although dropping to three quarts is not particularily good. It might have been somewhat co-incidental. Did your sister observe no oil pressure at any point? Do mark the rod and rod cap before removal. Nothing much to loose. I would not drive or rev the engine as quite a few 240ds have put the number one rod through the block. With my luck it would not be the number one cylinder but there have been so many reports of that particular cylinder causing difficulties the odds might be with you. I believe number two is also workable through the small oil pan as well. I agree this is not the absolute best approach but might give you some more time on that engine. You could plastic gauge number two as well to see if it is very worn or damaged if #1 were the problem for example before buying even the bearing shells.

New2MB · #14 08-02-2006, 01:38 PM

Quote:

Originally Posted by barry123400

To establish the affected cylinder just loosen each injector nut. The knock should lessen or dissapear when you hit the right cylinder. Most problems on the 240d have been the #1 cylinder. If that turns out to be the case you can drop the small forward oil pan. This will allow you to remove the rod cap and see if the crank is damaged. If it is not tore up perhaps the expendature for a pair of bearing shells is worth the risk. Since the engine was not truly out of oil although dropping to three quarts is not particularily good. It might have been somewhat co-incidental. Did your sister observe no oil pressure at any point? Do mark the rod and rod cap before removal. Nothing much to loose. I would not drive or rev the engine as quite a few 240ds have put the number one rod through the block. With my luck it would not be the number one cylinder but there have been so many reports of that particular cylinder causing difficulties the odds might be with you. I believe number two is also workable through the small oil pan as well. I agree this is not the absolute best approach but might give you some more time on that engine. You could plastic gauge number two as well to see if it is very worn or damaged if #1 were the problem for example before buying even the bearing shells.

Thank you very much, that's what I was looking for. I will make sure to try this when I get to see the car. She did not observe zero oil pressure but I doubt that she would have noticed if it went to zero.

diametricalbenz · #15 08-02-2006, 03:37 PM

Hopefully the engine is fixable but in the event that it's not you might be stuck in the same rut I was last year which took 8 months to sort out. The 79 is a split year for engines with loop or pin glow plugs as well as york or R4 compressors which was hard to find. I gave up after finding a nice low mile motor and just changed the car to a fast glow relay. There were also issues with the throttle linkages since the newer engines have the rotary throttle instead of the older firewall "pull" linkages, the exhaust manifold, and air filter due to the air conditioning hose.

But let's hope that's not the solution in this case.