That’s the one. The idler. Its bearing’s worn, so it wobbles, and that’s the grind you’d hear.
European servicing, diagnostics and repairs in Mile End. We listen to the car before a spanner comes out, and when the job’s done, you get the old part back.
Start the engine and watch the belt. One of these pulleys isn’t spinning straight.Each pulley on the belt is named on the photograph, with the sound it makes when it’s on its way out.
See whyThis is the one that was going.
A bearing only makes a noise once something is wrong with it. Each time a ball rolls over a pit in its outer race, it knocks. How often depends on the number of balls, the size of the race and how fast the pulley turns: on this one at idle, about ninety times a second. So that note points to one part, and not the one beside it.
The belt, the idler and the tensioner have done the same kilometres, so we change them together, check that every pulley runs true, and listen again before the car goes home.
Start with what you heard, saw, felt or smelt. Pick the one closest to yours and see how one like it went here: what it was like, what we tested, and the part we found.
What it was like. A sharp chirp for the first minute, gone once the engine warmed up, and worse on damp mornings.
What we tested. Belt off, each pulley spun by hand, then the stethoscope on each one with it running.
What we found. A drive belt glazed and cracked across its ribs. New belt, tension checked, listened again.
What it was like. On for a drive, off after a restart, back a week later. The car felt fine the whole time.
What we tested. Live data at idle and on the road: the sensor before the converter was slow to switch.
What we found. An oxygen sensor with a sooted tip. Replaced, and the fuel trims watched back to normal.
What it was like. Waiting at the lights, the wheel and the seat buzzed. It smoothed out in neutral.
What we tested. Mounts checked under load, the engine rocked gently, then a look from underneath on the hoist.
What we found. An engine mount with its rubber torn through. New mount, and the idle was quiet again.
What it was like. A warm, sweet smell through the vents after a longer run, and a haze from under the bonnet when parked.
What we tested. The cooling system pressure-tested cold, then again warm.
What we found. A coolant hose with a hairline split at the clamp. New hose, new clamp, the system bled and topped up.
What it was like. A few spots on the driveway, and the coolant a little lower every week.
What we tested. Everything cleaned, pressure-tested, then a light and a mirror behind the belt.
What we found. A water pump weeping pink crust at its weep hole. New pump, and coolant, the pink kind, mixed right.
A four fires its cylinders in that order. A visit here runs the same way.
We run it, drive it with you if you like, and put the stethoscope on it, part by part. We write down what we heard in plain words.
Then we prove it: live data, a smoke test, a pressure test, the voltage at a connector. The cause, not just the code.
We show you the part, or a photo of it in place, and tell you what we’d do and why before we do it.
We fit it properly, road-test it, listen again, and the old part goes in a bag on your passenger seat.
Four steps, in firing order.
Done to your car’s own schedule, with a note of anything we heard on the way. If something can wait until next time, we tell you, and we leave it.
A shake that comes in at one speed is something turning at that speed. Tell us the speed, the gear and where you feel it, and the lines show what’s turning at the right rate.
At 100 in sixth, a shake in the steering wheel at about 14 times a second is most often a front wheel out of balance, or a tyre that’s lost its shape.
Try these:
Tyre size (225/45 R17), final drive and gear ratios are illustrative. Your car’s own figures move these lines.
On the hoist we spin the wheels, check balance and tyres, and look at the shafts and joints. Then we road-test at your speed.
That line is the charging voltage from an alternator with one diode open: two humps in every six are missing.
Charging and starting faults, batteries that go flat overnight, sensors, misfires, and warning lights that come and go.
We test power and earth at the part, follow the wire to the fault, and only then replace anything. You get it in words, with the evidence.
That’s what a worn idler sounds like.
This line is drawn from what you listened to on this page, and it stays in your browser.
Every part we replace comes back to you, cleaned off, in a bag, with a note of what we heard, what we tested and why it had to go.
Keep it, bin it, or show it to whoever asks.
Describe it the way you’d tell a friend. We’ll ask the rest.
Weekdays, and Saturday mornings. We’ll come back to you with a day, and how long we’ll want it for.