BlackEclipse
01-16-2004, 08:05 PM
What is it?
"Crankwalk" is a problem where the main thrust bearing gets worn causing the crankshaft to slide around more. This sliding around or slop is called "endplay". Normally there is a very tiny amount of "endplay" on a crankshaft. This is necessary to keep things from rubbing and causing more friction in the engine. When you get crankwalk , the "endplay" becomes so great that the crank will have a tendency to move towards the belt side of the engine when you push in the clutch. It's as if it wants to come out that side of the engine. Hence it is "walking" towards the belt side of the engine.
What cars get this?
2nd generation DSM's. These are the 95-99 Mitsubishi Eclipse GST/GSX and the 95-99 Eagle Talon TSi/TSi AWD. It's the turbocharged cars that have the 4G63 engine in them. Note that not all of these cars have gotten crankwalk. The ones that did get it did not necessarily get it to the same degree as others. Sometimes it is a mild case of crankwalk, other times engines get destroyed.
What are the symptoms?
1. A ticking sound coming from the belt side of the engine.
2. The clutch pedal going to the floor on left hand turns.
3. Possibly, the separation of the rubber in the crankshaft pulley dampener.
Will this cause any damage?
Yes. The thrust bearing can only wear so far before it is GONE. Then it is just the metal of the crankshaft rubbing against the block. This in turn wears down and ruins the crankshaft AND the block. I don't think they make wider flanged thrust bearings. Plus, isn't the surface of the crank a "hardened " surface and now that surface is worn through?
As the crankshaft moves further and further out the belt side of the engine, that thin metal plate that runs through the crank angle sensor starts to hit one side of the sensor. This can be heard by an audible "ticking" sound on the belt side of the engine. Eventually this will destroy your crank angle sensor and then I think your engine stops running because the computer no longer knows the position of the crankshaft.
Why did this happen?
It seems to be attributed to a design change in the block that happened between the 94 and 95 model years. Mitsubishi changed the design and location of the "oil squirters" in the block. The old style oil squirters tapped into the main oil passage in the block. The new style oil squirters tap into the main bearings. These new style oil squirters are spring-loaded pressure-sensitive valves.
The oil pressure in the block changes with the rpms due to the oil pump being gear driven by the timing belt. At idle, there is low oil pressure in the block. If any one of these oil squirters stays open at low oil pressure then it causes oil to be stolen from the main bearings at a critical time. Usually at low pressure/low rpms, you are sitting at a stoplight with the clutch pedal pushed to the floor. You are now applying force to the thrust bearing that has very little oil pressure going to it. So, it starts to wear.
What can I do?
This all depends on the severity of the damage. Right now, most, if not all of the cars that have this problem are no longer in warranty.
Some general suggestions of what can be done are:
1) Replace the shortblock with another similar kind
2) Replace the whole block with an older style 6-bolt block that doesn't tend to get the crankwalk problem.
3) Fix the problems in the current shortblock.
"Crankwalk" is a problem where the main thrust bearing gets worn causing the crankshaft to slide around more. This sliding around or slop is called "endplay". Normally there is a very tiny amount of "endplay" on a crankshaft. This is necessary to keep things from rubbing and causing more friction in the engine. When you get crankwalk , the "endplay" becomes so great that the crank will have a tendency to move towards the belt side of the engine when you push in the clutch. It's as if it wants to come out that side of the engine. Hence it is "walking" towards the belt side of the engine.
What cars get this?
2nd generation DSM's. These are the 95-99 Mitsubishi Eclipse GST/GSX and the 95-99 Eagle Talon TSi/TSi AWD. It's the turbocharged cars that have the 4G63 engine in them. Note that not all of these cars have gotten crankwalk. The ones that did get it did not necessarily get it to the same degree as others. Sometimes it is a mild case of crankwalk, other times engines get destroyed.
What are the symptoms?
1. A ticking sound coming from the belt side of the engine.
2. The clutch pedal going to the floor on left hand turns.
3. Possibly, the separation of the rubber in the crankshaft pulley dampener.
Will this cause any damage?
Yes. The thrust bearing can only wear so far before it is GONE. Then it is just the metal of the crankshaft rubbing against the block. This in turn wears down and ruins the crankshaft AND the block. I don't think they make wider flanged thrust bearings. Plus, isn't the surface of the crank a "hardened " surface and now that surface is worn through?
As the crankshaft moves further and further out the belt side of the engine, that thin metal plate that runs through the crank angle sensor starts to hit one side of the sensor. This can be heard by an audible "ticking" sound on the belt side of the engine. Eventually this will destroy your crank angle sensor and then I think your engine stops running because the computer no longer knows the position of the crankshaft.
Why did this happen?
It seems to be attributed to a design change in the block that happened between the 94 and 95 model years. Mitsubishi changed the design and location of the "oil squirters" in the block. The old style oil squirters tapped into the main oil passage in the block. The new style oil squirters tap into the main bearings. These new style oil squirters are spring-loaded pressure-sensitive valves.
The oil pressure in the block changes with the rpms due to the oil pump being gear driven by the timing belt. At idle, there is low oil pressure in the block. If any one of these oil squirters stays open at low oil pressure then it causes oil to be stolen from the main bearings at a critical time. Usually at low pressure/low rpms, you are sitting at a stoplight with the clutch pedal pushed to the floor. You are now applying force to the thrust bearing that has very little oil pressure going to it. So, it starts to wear.
What can I do?
This all depends on the severity of the damage. Right now, most, if not all of the cars that have this problem are no longer in warranty.
Some general suggestions of what can be done are:
1) Replace the shortblock with another similar kind
2) Replace the whole block with an older style 6-bolt block that doesn't tend to get the crankwalk problem.
3) Fix the problems in the current shortblock.