2006 Volkswagen GLI



February, 26, 2013 AT 1:37 AM

Could a rod bearing fail due to a hard impact on the engine block?

3 Answers



February, 26, 2013 AT 2:39 AM

Doubtful. I'd want to know a lot more details to correlate those two things.



February, 26, 2013 AT 3:24 AM

About 2 months ago I had a hard impact on my 2006 Volkswagen GLI and after the impact I was forced to carefully drive the vehicle about 20 miles as well. What was repaired from the impact was radiator and radiator support, A/C condenser, intercooler, both electrical cooling fans, lower engine covers, left and right fender liners, and headlamp washer pump. The car never did quite run the same after the impact and recently I was driving about 67mph and my vehicle powered down, smoke arose, the whole signs of engine problems. Took it into the shop and they inspected the engine. The damage is the connecting rod in cylinder number 3 went through the engine block. Now I've done all required maintenance on the vehicle perfectly; could this connecting rod be caused to fail from what happened two months ago or faulty repairs? My initial belief is that the rod bearings were jolted from the impact causing them to loosen over the course of time, could that be a possibility?



February, 26, 2013 AT 4:41 AM

No. I can't say the crash is not a factor in any way, but the last thing that would get damaged in that way is an engine bearing. They take a REAL hard pounding every time the cylinder fires.

To put it in perspective, I helped a friend rebuild a smashed Dodge dually diesel pickup truck two years ago. That's what he specializes in at his body shop. It was hit so hard in the front that the engine was pushed back over a foot right into the firewall, and it wrinkled the floor and bent the frame. The front of the engine had to be disassembled to replace the pulverized power steering pump bracket, but through all that the engine still runs fine to this day.

The point is cars get into crashes every day with no serious engine damage. If your problem were to be related to that crash you would have had some indication right away. Connecting rod bolts don't come loose on their own, and the stress they're under is WAY more severe than anything you can do to the car and live to tell about it.

My only question would be about the engine covers you mentioned. I suppose a piece of debris could have fallen inside but that typically wouldn't cause serious damage even if it got hit by the crankshaft. It would normally just get stuck by the oil pump's pickup screen. If something managed to sneak through, that's what the oil filter is for.

If you have any old parts to look at, inspect the failed connecting rod. If the rod bolts worked loose you would first have seen the oil pressure warning light turn on. The same is true of a "spun" connecting rod bearing. You would have heard a lot of banging too. If you kept on driving like that long enough for a rod cap to come all the way off, the connecting rod and piston would have been shoved up to the top of the cylinder and stayed there. Usually the journal on the crankshaft will hit it and the crank will lock up.

You also have to look at how the block got a hole in it. For the connecting rod to come through the block it is typically because it broke. That is not common. More likely the bearing spun, then the hammering action pounded on the cap until a bolt broke, then the crank journal hit the large end of the rod and cracked the block. In that case there would be a hole but nothing sticking out of it.

You may be able to get an idea of what happened too by looking for scratches on the rod indicating it went through the block. Look at the bearings. If all of them show areas of copper and dull gray, they are worn through the first layer of metal. That would be due to engine oil with the wrong additives, oil that's too thin, excessive engine speed, or engine coolant mixing in from a leaking cylinder head gasket. Oil can also be seriously degraded if a no-start condition or fuel system problem result in raw gas washing down the cylinder walls and diluting the oil. The gas will kill the oil's lubricating properties.

Those are a few educated guesses related to things I've seen. I also blew up two engines on the race track from constant high-speed left-hand turns when they weren't designed for that. The oil runs away from the pickup screen for too long. It only takes one or two seconds without oil pressure to start the damage occurring to the bearings.

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