Post by enigmas on Apr 29, 2023 3:10:17 GMT
Mitsubishi Starter Failure.
I thought I'd post this comment here as a notification to those owners of a "modern" who have experienced a similar component failure virtually just after the car's manufacturer warranty has expired.
This starter motor looks fine but isn't. One component failure condemns it to trash.
The vehicle in question is a Mitsubishi ASX (CVT automatic), purchased new on the 21/11/2017.
Apart from this one component with regular scheduled servicing, the car has been perfectly reliable, a comfortable long distance traveller and very fuel efficient todate. The car has currently recorded 60,000 kms.
The issue in question is a total and unforeseen failure of the starter motor. Working perfectly...and then nothing. It simply failed to engage one day during a trip to the Mornington peninsula.
Fortunately we are long time members of the RACV and so a service vehicle and then a flatbed truck was organised to pick the vehicle up and move it to a holding station and then on to an RACV nominated repairer/service garage.
The assessment by the mechanic who repaired the vehicle initially was that the starter motor drive gear was not connecting to and/or driving the engine's ring-gear/flexplate to crank the engine over. The starter could be heard to spin when the key was turned to the cranking position but it failed to engage and turn over the engine.
The starter motor was replaced with a new unit. The loose spinning drive gear on the failed starter was shown to me. The apparent conclusion was that the mechanism that allows the drive cog of the starter to engage in one direction and run free in the other (the usual mechanical practise of any starter motor) was broken.
The starter motor is physically quite small, it looks like something you'd find fitted to a ride on mower or quad bike. It incorporates an internal planetary gear reduction system, the outer gear and the solenoid throwout lever being made of plastic.
Here is the starter motor beside a can of WD40 for size comparison.
This is the planetary set minus the 3 small internal gears. Note the outer annulus gear is plastic.
Most of the components that could be disassembled.
View of the gear reduction planetary gears and solenoid.
This is motor and tiny drive spindle. The ratchet is a quarter inch set.
This is the starter motor drive gear that engages with the engine ring gear. Note there is no wear apparent with the gear.
This is the sprag assembly.
This is the Sprag and Gear separated
This is the sprag close up. Look at the rollers carefully and note the pitting on the surfaces.
This is the drive gear.
Note carefully the surface of the journal. It is both rough and eroded by friction with evidence of slippage slowly chewing away the surface of the gear's journal. These are meant to be precision parts.
Sprags function due to carefully set tolerances. Once the journal size was reduced due to friction slippage, followed by surface erosion in it's lockup function, wear escalated to a point where the component failed completely.
The Causes of failure:
Sub standard metallurgy of components combined with inadequate lubrication.
I took the old starter motor home as I was interested to know what internal component had actually failed. Upon disassembly (some components of these starters are not designed to be disassembled) I found that the one way clutch or "sprag" had failed due to poor metallurgy and perhaps inappropriate long term lubricant within.
The sprag was not designed to be disassembled as it has a shrink fit pressed steel retainer cover plate. I removed the retainer cover plate with an appropriate cutting tool which then gave me access to view the internal components.
Once these were cleaned of the dried internal grease the reason for the failure was obvious.
For those that don't understand how a sprag (one way clutch device) works, it allows free rotation in one direction and locks in the other direction. Sprags are used in many automatic transmissions with perfect reliability for hundreds of thousands of kilometres or miles as the case maybe.
The other components of the starter motor showed little wear. The failed sprag condemns the remainder of the starter motor to the bin as it is a non-serviceable component due to the manner of its construction. If it had a threaded cap rather than an interference pressed steel cap it could be repaired and serviced. Also, several other components have spring steel snap rings that allow for fast assembly but not disassembly.
I predict more starter motors on these vehicles will expire and need replacing every 60,000 kilometers or equivalent usage, 5 years or just as the Factory warranty expires.
I thought I'd post this comment here as a notification to those owners of a "modern" who have experienced a similar component failure virtually just after the car's manufacturer warranty has expired.
This starter motor looks fine but isn't. One component failure condemns it to trash.
The vehicle in question is a Mitsubishi ASX (CVT automatic), purchased new on the 21/11/2017.
Apart from this one component with regular scheduled servicing, the car has been perfectly reliable, a comfortable long distance traveller and very fuel efficient todate. The car has currently recorded 60,000 kms.
The issue in question is a total and unforeseen failure of the starter motor. Working perfectly...and then nothing. It simply failed to engage one day during a trip to the Mornington peninsula.
Fortunately we are long time members of the RACV and so a service vehicle and then a flatbed truck was organised to pick the vehicle up and move it to a holding station and then on to an RACV nominated repairer/service garage.
The assessment by the mechanic who repaired the vehicle initially was that the starter motor drive gear was not connecting to and/or driving the engine's ring-gear/flexplate to crank the engine over. The starter could be heard to spin when the key was turned to the cranking position but it failed to engage and turn over the engine.
The starter motor was replaced with a new unit. The loose spinning drive gear on the failed starter was shown to me. The apparent conclusion was that the mechanism that allows the drive cog of the starter to engage in one direction and run free in the other (the usual mechanical practise of any starter motor) was broken.
The starter motor is physically quite small, it looks like something you'd find fitted to a ride on mower or quad bike. It incorporates an internal planetary gear reduction system, the outer gear and the solenoid throwout lever being made of plastic.
Here is the starter motor beside a can of WD40 for size comparison.
This is the planetary set minus the 3 small internal gears. Note the outer annulus gear is plastic.
Most of the components that could be disassembled.
View of the gear reduction planetary gears and solenoid.
This is motor and tiny drive spindle. The ratchet is a quarter inch set.
This is the starter motor drive gear that engages with the engine ring gear. Note there is no wear apparent with the gear.
This is the sprag assembly.
This is the Sprag and Gear separated
This is the sprag close up. Look at the rollers carefully and note the pitting on the surfaces.
This is the drive gear.
Note carefully the surface of the journal. It is both rough and eroded by friction with evidence of slippage slowly chewing away the surface of the gear's journal. These are meant to be precision parts.
Sprags function due to carefully set tolerances. Once the journal size was reduced due to friction slippage, followed by surface erosion in it's lockup function, wear escalated to a point where the component failed completely.
The Causes of failure:
Sub standard metallurgy of components combined with inadequate lubrication.
I took the old starter motor home as I was interested to know what internal component had actually failed. Upon disassembly (some components of these starters are not designed to be disassembled) I found that the one way clutch or "sprag" had failed due to poor metallurgy and perhaps inappropriate long term lubricant within.
The sprag was not designed to be disassembled as it has a shrink fit pressed steel retainer cover plate. I removed the retainer cover plate with an appropriate cutting tool which then gave me access to view the internal components.
Once these were cleaned of the dried internal grease the reason for the failure was obvious.
For those that don't understand how a sprag (one way clutch device) works, it allows free rotation in one direction and locks in the other direction. Sprags are used in many automatic transmissions with perfect reliability for hundreds of thousands of kilometres or miles as the case maybe.
The other components of the starter motor showed little wear. The failed sprag condemns the remainder of the starter motor to the bin as it is a non-serviceable component due to the manner of its construction. If it had a threaded cap rather than an interference pressed steel cap it could be repaired and serviced. Also, several other components have spring steel snap rings that allow for fast assembly but not disassembly.
I predict more starter motors on these vehicles will expire and need replacing every 60,000 kilometers or equivalent usage, 5 years or just as the Factory warranty expires.