I have a 2008 Yaris T3. It's been serviced regularly, and at the last service the brakes (front and hand brake discs) were checked, and skimmed. That was about 4 months ago. About two weeks ago, something started happening when I braked for the first (or sometimes) second time during a trip, but only intermittently. There was a knocking feeling (no sound initially) on the brake pedal, two to four shudders that feel like someone is hitting pedal lightly with a hammer from underneath. My ABS light would come on for a couple of minutes, then turn off. The brakes don't feel different, and the rest of the trip no matter how long, would be fine. It's more common on cooler mornings, but not exclusive to them. From limited testing, it happens during equally on slow/easy stops and fast/hard stops.
I booked the car into a mechanic, but with the pre-holiday queues, I had to wait another week. During that week, whatever was happening started making a noise too. The knocking feeling is accompanied by a knocking sound and the "ping" of a large spring releasing (you that "boing" sound?) The mechanic, inspected the brakes, but he couldn't find anything. The ABS reported some minor issues which he attended to, dirty sensor, loose connection, and he told me my clutch was on the way out, but would last another 6 months or so.
My thoughts are that it could possibly be
- the brakes because it happens when I brake
- The CV joints because of the spring sound
- The shock absorbers/suspension because of the spring sound
Searching initially yielded this possibly similar question: Banging sounds coming in front of my car
Is it possible that a loose torque plate bolt is the problem? I have the car booked in for tomorrow morning again, but I'm struggling to describe the symptoms to the mechanic. I was hoping some of you fine folks might have had a similar problem and could point me (and thence my mechanic) to the cause of the problem.