How to Replace a Car's Starter MotorBy Elina | Published on Dec 03,2015
This gear-reduction starter (left) is a lightweight drop-in replacement for the older starter that failed. By spinning the armature faster and reducing its output speed with a planetary gearbox, it's possible to get the same starter power in a smaller, lighter package.
Click. Click. Click. That's the noise your car makes when you twist the key. A few more clicks and now you've got a metallic screeching that makes all the dogs in the neighborhood start to bark. The dash lights are plenty bright, the headlights don't dim much when the key is twisted, but obviously something is wrong. With the clock ticking, you resort to that old standby: a jump-start. A few more screeches grating enough to make you cringe, and the engine finally spins merrily.
After work, it's the same story: Clunking and clicking, a few bars of the "Ballad of the Tortured Ring Gear," and you get to drive home instead of ride in the cab of the tow truck.
You've got a bad starter motor. Time to fix it before you're on the bus.
The Way It Works
Saturday morning you give your battery and charging system a full investigation. Even swapping in the new battery from your other car doesn't help. Nope—the screeching has become the only symptom you can elicit. That banshee wail is the teeth on the starter motor's bendix gear clashing against the ring-gear teeth because it's not completely engaged.
The solenoid, or on some starters, just a threaded part of the armature, pushes the bendix gear forward an inch or so until it meshes with the ring gear, allowing the starter motor to spin the engine over until it starts. When the engine rpm exceeds the cranking speed, the bendix automatically retracts, preventing the engine from spinning the starter too fast.
At least that's how it works in theory. Starter motor failure is rarely caused by a blown or shorted motor itself—usually it's a problem with the bendix mechanism or the solenoid. And frankly, most people will never need to replace a starter motor for the life of their vehicle. Intrepid but underfunded Saturday Mechanics might actually dismantle a malfunctioning starter and repair it themselves. You can still find auto parts stores that can get you new bearings, brushes and bendix assemblies. Generally, I just exchange the old starter for a new or remanufactured one, because repairing one doesn't save much money. On the other hand, if you have a rare or hard-to-find starter it might be necessary to fix what you have. Usually, auto electric shops can rebuild or repair a starter with a bad armature, shorted field windings, bad brushes, a bad commutator, or even a bad solenoid if there is no alternative. Be prepared to wait a few days or more.
1. Yes, there's a starter motor hiding up there. On most front-engine vehicles like this Suburban, it's well and truly buried under and behind the engine and next to the transmission.
2. Prepare to get dirty and uncomfortable getting it out. Front-wheel-drive cars with sideways-mounted engines may have the motor mounted above the trans, where you can reach it from above.
3. If you have ramps, they should provide enough clearance. If you need to jack up the car, use jackstands and chock the wheels. Stuck off-road? Dig a trench under the vehicle to crawl into, which is actually not horrible if it's dry.