2010 Prius with 214,000 miles. As of late I've been experiencing some rough starts and a bad exhaust leak at the cat to manifold gasket. A few months ago it was throwing misfire codes but they resolved on their own. I'm in the process of tearing into some long overdue maintenance, including new exhaust gasket, plugs, PCV valve, EGR system cleaning, intake manifold cleaning, and more. When I took off the throttle body I was a bit taken aback by the amount of liquid sitting in the intake. It's very oily in texture, and as you can see is a light opaque color. I was worried about coolant in the oil, but the dipstick looks much better than what's in here. (attaching photos of both). Is this normal or is something out of whack?
It's fairly normal, though yours seems thicker and more soupy than most. Adding an oil catch can in the EGR system can limit the severity of it.
Looks like what the service industry calls a "milkshake." Coolant is getting in the oil. It may be the onset of a blown head gasket.
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Rather common in gen3s, particularly those with excessive blowby feeding the pcv. Flawed pistons and rings start the problem, a low pcv intake aggravates it and overfilling the oil makes it worse. A catch can is a good idea if it is a good one with a sintered bronze strainer and the owner remembers to empty it. Don't waste too much money on the major maintenance until the rattling convinces you to change the head gasket. A rebuild with new pistons and rings is the long term solution if you don't intend to flip the car soon.
That definitely looks like it has coolant in it with that pink cast to it. The oil on the dipstick is harder to judge since it's such a small, thin layer, but it looks a little pinkish, too. I'd rent a borescope and look inside the cylinders for a steam cleaned piston top to be sure, but my guess is that you need a head gasket as well as an EGR system cleaning.
Thanks for the thoughtful feedback folks. I was worried about the head gasket thing being probable, given the age of the car and the symptoms I've been experiencing lately. When I swapped the plugs the old ones didn't look like any were particularly "steam cleaned". They all had obvious carbon/oil residue. So, I very thoroughly cleaned the whole intake and EGR system as well as the PCV/crankcase ventilation and have it all back together. It's running much nicer now, and not throwing any codes, but I'm losing coolant quickly. First thought was head gasket (duh), but I actually have a dripping leak somewhere which I want to sort out before I investigate the head gasket further. When I get to that point would you recommend getting my hands on a borescope over a combustion leak detector? Will either work as a suitable head gasket diagnostic? Finally, if it does turn out that my head gasket is shot, is it worth giving a liquid head gasket product a shot? If I'm being honest I'm very doubtful I'd make the investment to replace the head gasket at this point. With the amount of corrosion this car has seen in Northeast winters over the years I suspect I will be chasing down other issues before long, and I really just want to squeak out another year or two tops with gas/car prices being so high.
Give it a week or so and you will get another cold start shake. Sealer is only for shady car flippers; most will work for a month or two but make the prospect of a plugged radiator and heater core more likely along with another cause for overheating even after the head gasket or engine rebuild.