Thomas2015

During a recent cold spell my wife's R350 started but only ran a few seconds. On the 4th attempt to start the motor the starter engaged but didn't turn the engine over. After a tow to the dealer they informed me the initial problem was probably related to a frozen muffler but now the motor was seized up. The quote for a new motor was $12,700 (parts and labor). Prior to this occurring the engine was running perfect (no ticking, check engine light nothing). Does anyone have any ideas as to why the motor wont turn?

Max Blast

Have you removed all plugs and cranked?

My guess is either it's hydrolocked due to leaking head gasket or
mechanically locked due to timing chain breaking.

If truly broken then find an indy with STAR machine to put in a known good used M272 for waaaay less than $12,700.

Thomas2015

Max, Thanks for the reply....Yes, the dealer pulled the plugs, they had it outside last weekend so I opened the hood and with a huge breaker bar tried to turn the engine both ways (no movement). I would think if a piston was hitting a valve (due to timing chain) that I would be able to back it off. What else would you check? Worst case I will buy and install a used M272.

geniushanbiao

If it can't turn then it's probably the crankshaft shot. Better off get a used one. You can also try to take the engine to a local machine shop who does engine rebuilds for an estimation. My idea is that if the engine works well a quality rebuild is better than installing a used one since you have no idea about the condition of a used one.

leeroytandy

My 1st Mb had the same motor and it had bent all the conrods due to water getting into the chambers.
if you up to it, you could open it up from the bottom and check this, avoid removing the cylinder heads, they need to be locked into position before being removed. Infact your air filters would tell whether water got into it or not.you'd probably need to replace your 6 conrods (+/- $250 each).
also if your catalysts are blocked, that could also be the cause.

my mech is an ex-Mb tech and he strongly feels that the oil pumps on the 272s is the biggest problem (evan though Mb hasnt realised this).

geniushanbiao

I don't think replacing the conrods can restore the motor. It just makes the motor run again.

I agree. M272 is not a well designed motor and it has so many problems. I think MB just wanted to have a V6 with more power so they designed M272 based off M112 but this was so crappy.

Thomas2015

We pulled all of the spark plugs and checked for hydro lock (water in cylinders). The crankshaft wont budge in either direction with a huge breaker bar on the crank pully. Engine was running fine (no noises, or CEL alerts) right before this.