So I cold-started my 15 prius and it made a very bad knocking/ticking noise when I turned it on and it went away after a minute after cold start and Im wondering if is it the head gasket already going bad or would I just have to do egr clean. Took it to the dealership for a quote and obviously said it would be 195-220, trying to save the most money for the worst. Car already has around 187k miles on it and I bought it back in March with around 179k miles on it. If there's another thread in the forums that can relate to the situation I'm having send it to me anything helps!!
What you want to do now before everybody gets too carried away is take the wiper tray out pull the spark plugs out and smell each one of the spark plugs individually You're looking for the smell of coolant on your plugs with all folks's chemical reactions that everybody has these days you should be able to smell this a mile away It's a very distinct smell You may even see very tiny water droplets and I mean tiny right on the tips of your plugs if you look at them with magnifying glasses or something like that generally they all won't be this way it'll be cylinder one and four or whatever. If you smell coolant on the tips of a spark plug that generally means water is sneaking into that cylinder trying to put out the fire which is what the spark plug does when it gets electricity The fire being partially put out in one cylinder is causing an imbalance and is causing the engine to run rough and slam the torque plate springs and generally make a racket EGR can cause this imbalance too doesn't matter what's causing it you need to get it sorted. So if you don't smell any coolant on any of the plugs then the next thing to be looking at would be for the clogged up EGR cooler and manifold intake ports clogging. I'm banking on water droplets on one or more of the plugs or the coolant smell that's par for the course for this system.
It is not the egr so save your money. A badly clogged egr will produce a P0401 and the more common sticking open egr will cause engine roughness that is unlikely to go away in a minute. A sticking egr will also produce a P0401. The roughness is not the severe metalic sound you may have heard. A more definitive test is a dual view borescope inspection on a cold engine with a manually pressurized coolant system. The unfortunate reality is many flippers use temporary head gasket sealer to mask the symptoms. With only 8,000 miles since you bought it this could have happened. We have had members here say they would do it to flip cars and more than a few used buyers have had the same experience. Shudder video Car Care Nut HG Borescope at 7:40
^ That. Also: THIS. Like Comment Subscribe! Really! These people are dropping knowledge! So.... You do not need $1000 worth of Snap-On tools to do a leak-down test. A $40 Harbor Freight or Amazon tester will siffice - albeit with the caveat that you will have to lean into it a little more. If all of this is beyond your interests or capability? A GOOD independent shop will charge you about an hour's labour (about $200) to do this test with their $1000 tester, shop air, tools to get to the spark plug hole, etc......etc.... If you think that $200 an hour is a little 'steep' then you can always get a $40 Amazon or Harbour Freight tester and DIY. IF your shop charges more than an hour or their rate is much more than 'about' $200 an hour - then they 'might not' be a good independent shop - or they might be a REALLY GOOD independent shop! If the people who are charging you to test the car profit from selling you a replacement for your car....AND buying your old car ????? .....then a you "might" begin to wonder who they are REALLY working for!! Caveat emptor!! Good Luck!
If the EGR has never been cleaned it’ll be quite carbon-clogged by now, as a consequence engine has been chronically overheating, and unevenly so, with cylinder one end (passenger-side end of engine) the worst, and as a consequence of that: the head gasket is failing, leaking coolant into combustion chamber(s). Most likely leaking on the exhaust side, at the common wall between cylinders one and two. I would do an EGR clean, AFTER dealing with the (failing) head gasket. My 2 cents, considering you just recently purchased: the head gasket was likely failing when you bought it; that was why it was for sale. Seller may have added stop-leak product to engine coolant, to mask symptoms, and it’s wearing off. There’s some relevant links in my signature (on a phone turn it landscape to see signatures).
