Edit: Looks like I figured it out. The crankcase was overfilled. The dipstick in a Prius can be notoriously difficult to read. Finally installed an OCC two months ago, and I now notice a faint oil smell in the cabin. I pulled the belly pan and air intake and saw no signs of oil leakage. Emptied about 1” of brown goop out of the catch can, and I tightened the oil sump bolts, where there’s a tiny bit of oil seepage. They turned about 1/4 turn, so that may help but doesn’t explain an oil smell. Mileage remains the same, car runs great. Cabin filter was replaced back in July. Only possibility I can think of is that I spilled a little oil during the catch can install, and it’s slowly burning off. All around valve cover, it’s dry, as far as I can see. No signs of oil anywhere, except the usually grittiness on the bottom of the engine. Any suggestions?
Usual leak is at the timing chain cover but I would bet its the OCC venting or the wrong hoses connecting it.
I still can’t tell. I drove it about ten miles to warm it up, took a bunch of added measurements, and I’m still not sure if it’s overfilled or not. I hate the dipstick design on this car.
Pull the dipstick, wait 5 minutes (say check tire pressures) then do the check. When you pull the dipstick it draws oil up the tube; the delay gives it time to drain back down. also, check both sides; I find the side towards the front more definitive. FWIW, my refill technique: drain well, button everything up, add 4.2 liters (4.5 qts), and don’t even bother checking dipstick for a few days.
Sometimes you can carefully place the dipstick flat on a paper towel to transfer the level to the paper. I find checking it in the morning before starting is often easier since the oil has drained back on the dipstick. Just pull and check. It has been reported that overfilling will push more oil through the pcv to the intake but normally you would not smell oil. So a vapor leak in the aftermarket OCC, the hoses used are permeable or there is oil leaking (maybe leaked) on the engine.
I don't bother to add 4.2l. Just a 4l bottle and I'm at 75% on dipstick. Good enough for me. Yep, this is what I'm doing.
Which oil catch can did you use, Rebound? The one that I used did not come with an o-ring seal on the integral dip stick. The dipstick was threaded M6x1.0. I added an o-ring to the dipstick in the can before installing it.
I don’t remember the brand. It has a dipstick, and it’s screwed in firmly, but I don’t recall checking for an o-ring.
All four that I have purchased had a dipstick and no o-ring, I found the dipstick useless, because the oil vapors would hit the colder dipstick and give a high reading. Examining the cup of the catch can revealed only a small amount of oil and yellow mixture on the bottom. I replace the dipstick wit an M6x1.0 screw and an o-ring. That made the cup easier to screw off, since I did not need to unscrew and take out the dipstick first. The cup never fills much past the bottom of the cup, anyway, between oil changes.
Your explanation is the best so far. No sign of leak, very faint fumes… if the missing o-ring let’s out just a whiff of vapor, that could be exactly what’s going on. I’ll dig into it when I find the time. The OCC is underneath the car, so I need to jack it up and pull the belly pan. And no point until I get ahold of some o-rings.
If you don't want to get the o-rings, you can get some thread sealant like this. It's non hardening and can be reapplied as needed. I used it on all the fittings in my OCC installation. It's oil and gas resistant. It's available in a smaller tube as well, but the bottle wasn't much more so I bought the larger size. Posted via the PriusChat mobile app.
Just found this thread. I'm having the same problem - fairly strong smell of hot oil coming from under the hood - primarily right side near OCC I recently installed (3 months ago). I never noticed it during the first 2 months of operation after OCC but now it's pretty strong, like I smell it when I walk into the garage. Gonna try the o-ring on the dip stick and I'll post my findings.
Another option for sealing the (tapered) pipe threads is the silicon tape (typical plumbing dept item in hardware stores). One reason I like it is with right-angle fittings on my OCC: I want them angled a certain direction, and multiple turns of the tape create a sort of buffer; if you got the fittings rotated to the correct orientation, but they're kinda loose, you stand a decent chance of being able to muscle them through one more rev with the tape on there.
