Blown OEM602 - is it worth digging into it?! - PeachParts Mercedes-Benz Forum

MercFan · #1 10-28-2010, 04:05 PM

My buddy is having a new engine put into his '91 300D (602) - he's had some overheating issues he's been fighting and one day the engine started making high pitch noises like something was seized - we thought maybe the vacuum pump, but the noise persisted even when the serpentine belt was off...

We've learned from this forum that some of these engines have [edit] timing chain issues, but if the timing chain was busted I bet it'd sound a lot worse AND it probably would never start again... but this one does - it just sounds like it has a seized bearing (or something) - what do I know... The mechanic that's replacing the engine diagnosed it as a broken rod... I don't know any better but I'm having my doubts just based on the way it sounds - it's not a knocking sound, it's a screaming sound. Sounds like the oil in it was Rotella 5W-30 synthetic - probably not the best choice for the summer heat... thought I'm sure that would cause the catastrophic failure... .maybe?!

Anyway, the reason I'm writing this note is because I was thinking about buying it from my friend and tearing into it to do a little 'post-mortum' analysis on it just so I can learn something from it - and with a bit of luck fix it and bring it back to life again for a bit of money. I bet I can get it from him for around $200.

Is it even worth the effort?! What do y'all think?

James

shertex · #2 10-28-2010, 04:28 PM

Quote:

Originally Posted by MercFan

We've learned from this forum that these engines have timing belt issues, but if the timing belt was busted I bet it'd sound a lot worse AND it probably would never start againJames

The 602 has a timing chain, not a belt. And if it's a 1991, I don't think it's in the production range that had the problems....those were later, more toward 1993.

How many miles on the engine?

MercFan · #3 10-28-2010, 04:42 PM

Quote:

Originally Posted by shertex

The 602 has a timing chain, not a belt. How many miles on the engine?

Sorry, I meant a timing chain (not sure why I typed belt). The engine only had around 153K miles on it...

shertex · #4 10-28-2010, 04:55 PM

Quote:

Originally Posted by MercFan

Sorry, I meant a timing chain (not sure why I typed belt). The engine only had around 153K miles on it...

How well does your friend know the oil history of the car? With proper oil and change intervals, it's hard to believe the chain would be bad with that kind of (low) mileage.

MercFan · #5 10-28-2010, 05:00 PM

Quote:

Originally Posted by shertex

How well does your friend know the oil history of the car? With proper oil and change intervals, it's hard to believe the chain would be bad with that kind of (low) mileage.

Would you even suspect a timing chain failure with these symptoms?! Again, the engine starts and runs... but it sounds awful and it smokes a lot... (black smoke).

04 Diesel · #6 10-28-2010, 05:03 PM

I would buy it, the head alone is worth more than that.

aaa · #7 10-28-2010, 05:31 PM

The vacuum pump is chain driven. Well kinda, it's easy to remove and then run the engine without it.

It's not the chain itself. Could be a chain guide or something. Again wouldn't be hard to just pull the valve cover and see (and maybe run it, if you don't mind oil being flecked out).

MercFan · #8 10-28-2010, 05:55 PM

Quote:

Originally Posted by aaa

The vacuum pump is chain driven. Well kinda, it's easy to remove and then run the engine without it.

My bad... I thought it was driven by the serpentine belt - I guess it's not... my guess is that it's the vacuum pump... would there be other clues?!

layback40 · #9 10-28-2010, 06:34 PM

smoking & noise are probably unrelated.
Has it ever been run on WVO ?
Have you run the motor while its been out of the car?
Seized motors dont normally make a high pitched noise.
I could be a guide rubbing on the timing chain.
Is there a lot of blow by?

MercFan · #10 10-28-2010, 07:21 PM

Quote:

Originally Posted by layback40

smoking & noise are probably unrelated.
Has it ever been run on WVO ?
Have you run the motor while its been out of the car?
Seized motors dont normally make a high pitched noise.
I could be a guide rubbing on the timing chain.
Is there a lot of blow by?

I don't believe WVO has ever been involved with that car. I have not run it while out of the car yet. I have yet to check blowby on it once I fire it up. Is it ok to run the engine briefly without the proper coolant hoses attached?!

Since the donor had a broken oil pan they will be sourcing the pan from the 'seized' motor so I'll need to either weld the old one or get one from the junk yard....

Can't wait to take the cover off and try to start it up to see what I find. I make take a short video of it when I do.

layback40 · #11 10-28-2010, 08:36 PM

If you only run it for a minute or so it wont be a problem. An old towel soaked in water placed around the exhaust manifold outlet is good for getting rid of exhaust noise. Try it.

MercFan · #12 10-28-2010, 11:17 PM

If I were to do this, I'd put the engine on the stand, make sure the oil is in it, connect fuel supply and return lines to a container with fresh diesel, and just hook up a battery directly accross the starter to crank?! I'd have to figure out how to glow the plugs...

compress ignite · #13 10-29-2010, 01:23 AM

I'm gonna prognosticate that the "Sound" (Un-Bearably High Pitched Screeching)
(Metallic) you're hearing is a Spun Bearing...Um, Rod type most likely.Look very
closely at the Two drive chains (Timing/Camshaft and Oil Pump) and their sprockets.

If it's "Spun One" there'll be metal fragments everywhere.You must make sure
that all the fragments are GONE.Do not forget the Oil Cooler,it's on the Pre-Filter side of the Lubrication circuit.

MercFan · #14 10-29-2010, 04:32 PM

Quote:

Originally Posted by compress ignite

I'm gonna prognosticate that the "Sound" (Un-Bearably High Pitched Screeching)
(Metallic) you're hearing is a Spun Bearing...Um, Rod type most likely.Look very
closely at the Two drive chains (Timing/Camshaft and Oil Pump) and their sprockets.

If it's "Spun One" there'll be metal fragments everywhere.You must make sure
that all the fragments are GONE.Do not forget the Oil Cooler,it's on the Pre-Filter side of the Lubrication circuit.

I phone my friend and immediately instructed him to tell his mechanic to make SURE he doesn't use the old oil cooler and lines from his old car.... thanks for that tip!

MercFan · #15 11-06-2010, 06:23 PM

I saw that engine in person today - my friend and his mechanic were busy swapping it for a good used one (at least we hope so). The seized one was on the engine lift with the oil pan off - it looks like it lost the oil pump chain - got some photos of it. See below.

So that kind of makes sense... the oil chain broke which lead to oil starvation which killed the main bearings....