[JAP/UK] Slight knock/rattle and medium shake on low rpm
So i have a bit of a odd scenario i wanted to share and get some ideas from the community before I message the dealer with my concern. Sorry for the ramble, my brain is kinda scattered right now! Thank you in advance!
I bought a gen 3 Prius Alpha 2013, 190k miles, originally imported from Japan. When I drive, i can feel a slight rhythmic ticking/knocking sound coming from the front passenger side (left side of car). Cabin fan is off. This sound does not come on cold starts. The engine turns on and sounds okay. The sound/shake starts after Ive been driving (on battery and engine) for 10-15 mins and is most prominent at low RPM. Imagine that you're waiting at a traffic light and need to go, or while driving the hybrid battery drops low and the engine turns on so you only press the accelerator enough to maintain the speed. Steering wheel doesnt shake but i can feel the car shake a bit when this happens.
Another thing to mention the sound/shake doesnt happen instantly after the engine switches on, it happens maybe a couple of seconds after.
We noticed this on our way back after driving for about 200 kms after coming off the motorway. Driving on the highway it wasnt noticeable as it is on low RPM. (maybe due to sound/vibration from the outside?) But i think we got less mileage tho - with 25 liters (the cheap UK petrol) we got approx 285 miles? is that okay? Should I put higher quality petrol?
Anyway I looked far and wide on google and the 2 most common issues reported in forums and reddit were EGR and Head gasket (rip). The dealer said they got the EGR service done (no receipts) recently. But i'd still like a way to test it if possible. Ill confirm when them when exactly they got it done.
I thought that the rattle sound might be a fan hitting something (doesnt explain the shake) but i turned on maintenance mode and sat in the car for about 2 hours. No rattling sound whatsoever. I even went out front and waited for the radiator fan to cycle twice and no sound from it. At the same time I turned on the cabin heaters to HI with the hopes the hybrid battery fan might kick in but turns out the fan is under the drivers seat - not where the sound is coming from (glove box side passenger). After our long highway drive, I even put the car in maintenance mode and had someone press the accelerator to check for white smoke. I took a 30 second video, the first half without the flash you cant really see much smoke and with the flash you can see a very small amount of smoke however i dont know if white colour is the flash or smoke. It's not cloudy. I will do this again in day time, but honestly there wasn't much smoke. At the end of the 30 second video a small water drop fell from the exhaust. Maybe thats why there not much smoke? if there is a gasket issue maybe its super early stages so only a small leak? Note the engine was already hot after a long drive so no condensation (maybe). We also checked the coolant level and will check at a later date to compare. Today after letting the car idle for 2 hours, i checked under the exhaust, no water droplets, i might let it idle again and literally sit there and watch.
Ive ordered a head gasket leak test kit so will try that tomorrow when it arrives. Btw this is probably a seperate issue but the AC doesnt work, might need a re-gas. Only sharing this JUST INCASE they maybe linked but doubt it?
Is there anything else I can test? Any ideas on what I should look for or do/test/inspect before messaging the dealer to get this checkout.
Thank you in advance. If i missed something I will edit this.