OM642 Water pump impeller failure - PeachParts Mercedes-Benz Forum

markg612 · #1 05-03-2016, 11:43 PM

REVISED--pump didn't fail after all , a screw lost for 4 months came out of its hidy-hole and locked up the pump pulley from behind!

This was the original post:

Might be a rhetorical question given the slim number of 642/648 participants here, but any one out there had an impeller break apart and jam the shaft and subsequently shred the belt as well as melt off one of the shelve pulleys?

117,809 original pump, no leaks, bearing still perfect, impeller imploded.

t walgamuth · #2 05-04-2016, 07:16 AM

I've never heard of such a failure before...but there is a first time for everything! Was it a cast impeller or stamped sheet metal?

jcyuhn · #3 05-04-2016, 07:32 AM

Never heard of a failure like that, and I collect om642 stories as a hobby.

markg612 · #4 05-04-2016, 09:29 AM

Cast, MBs used the conical turbine style for years.

Photos to follow.

Shop buddies have seen this a couple of times and it's ugly.

From MB. . .

The mainstay of the water cooling system is a belt-driven pump on the crankcase. This is a double-helix pump which forces the coolant into the cylinder banks within the crankcase from the front, where it mainly flows to the exhaust side via special holes bored in the cylinder head gasket.

Diesel911 · #5 05-04-2016, 05:29 PM

Have never read or seen that type of failure on any Water Pump in 18 years of being a Diesel Mechanic or on my own or others vehicles.

I have personally had an Impeller that when the Coolant got hot would not turn/pump because the hot impeller expanded enough it was loose on the shaft. Can't remember if was a kit I used to rebuild it or was a rebuilt from the Auto Parts store.

Seen lots of corroded impellers as in the 1960s and early 1970s here in CA people only used Water in their cooling systems on their Cars.

Dan Stokes · #6 05-04-2016, 05:54 PM

I once had a Chebby Impeller - fine car.

(sorry, I got nothin')

Dan

markg612 · #7 05-08-2016, 11:49 AM

Quote:

Originally Posted by Diesel911

Have never read or seen that type of failure on any Water Pump in 18 years of being a Diesel Mechanic or on my own or others vehicles.

Well, as it turns out, neither have I!

I changed the glow controller in January, which resides directly above the pump. One of the bracket screws was lost to the gods during the repair. I spent about 45 minutes searching to no avail.

Needless to say one should never give up on a lost screw in an area with rotating components. UGH. After nearly 4 months, the fastener dislodged from its hidy-hole and made it's way behind the pump and stopped all motion.

Strangely enough, my friends from the local independent MB shop in Minneapolis were doing an oil change on a OM642 E class fresh from an oil cooler seal replacement at the dealership a week or two earlier. The customer drove away after the oil change and about a mile away, the same thing happened. The Dealership tech had lost a fastener that did the same thing and made its way behind the pump and locked it up, resulting in the same damage. The dealer made it right.

KrustyKustom · #8 05-08-2016, 11:33 PM

Wow, that's just crazy. I have two vehicles with OM642 engines so I follow several forums that have a lot of discussions on them. I do not recall any waterpump issues, had to be the missing bolt!

I know that the 642 seems to not be very forgiving when ever something steps out of line....just briefly. They like plenty of Preventative Maintenance.

Sent from my SM-G920V using Tapatalk

Frank Reiner · #9 05-09-2016, 12:00 AM

Quote:

Originally Posted by markg612

Well, as it turns out, neither have I!

I changed the glow controller in January, which resides directly above the pump. One of the bracket screws was lost to the gods during the repair. I spent about 45 minutes searching to no avail.

Needless to say one should never give up on a lost screw in an area with rotating components. UGH. After nearly 4 months, the fastener dislodged from its hidy-hole and made it's way behind the pump and stopped all motion.

Strangely enough, my friends from the local independent MB shop in Minneapolis were doing an oil change on a OM642 E class fresh from an oil cooler seal replacement at the dealership a week or two earlier. The customer drove away after the oil change and about a mile away, the same thing happened. The Dealership tech had lost a fastener that did the same thing and made its way behind the pump and locked it up, resulting in the same damage. The dealer made it right.

I'm confused; how did the screw get into the cooling system to damage the impeller? Or did the screw remain outside the pump, so that damage was restricted to the pump drive components, with the impeller itself remaining undamaged?

I ask, because the thread heading indicates impeller failure.

markg612 · #10 05-09-2016, 10:05 AM

Frank, It started out believing it was the pump--I didn't have visual access to the area along side of the road, I was only able to touch the components and the water pump was turning but would clinckle and lock up when I turned it one way, but not the other. Once I began the repair in my shop, I removed all the dry items and oil separator to have the most room to work on the pump. I gave it one more look, not really enjoying the idea of draining coolant and making a big nasty mess before I started removing the water pump only to feel the screw in the pulley bell and then see it poke out from behind.

I'll change the title for future readers. . .

PS, I see you're out in the valley, we'd driven into SF off castro in-between the 101 and 280 from antioch, it took the tow driver 2:20 minutes to go 55 miles in traffic that afternoon. Poor guy.

markg612 · #11 05-09-2016, 10:14 AM

Quote:

Originally Posted by KrustyKustom

Wow, that's just crazy. I have two vehicles with OM642 engines so I follow several forums that have a lot of discussions on them. I do not recall any waterpump issues, had to be the missing bolt!

I know that the 642 seems to not be very forgiving when ever something steps out of line....just briefly. They like plenty of Preventative Maintenance.

Sent from my SM-G920V using Tapatalk

So get this though--all the sheave pulleys and the water pump it self on my OM648 failed around 100K miles. the pulleys went first and about 2 months later the pump started leaking. this 642 is way past that mileage and neither of the bearings in the sheaves or the tensioner show any signs of wear and the pump is still snug and dry as new. . .

BillGrissom · #12 05-09-2016, 02:27 PM

Quote:

Originally Posted by markg612

Needless to say one should never give up on a lost screw in an area with rotating components. ...

I 2nd that. Long ago when we were young, my younger brother was in college and into cars, so changed the points in the distributor of my 69 Dodge Dart. He didn't mention that he dropped the little screw inside and didn't retrieve it. A week later, it jammed the shaft and broke the nylon drive gear (good they used plastic there). Took a while to figure that one out. My father shook the distributor and out came the screw, while my brother looked on sheepishly.