2000 Sienna PCV / Oil Leak / Check Engine Light

It's been quite a while since I last posted. My 2000 Sienna, with just over 153,000 miles so far, has been very reliable. I do most of
the routine maintenance and minor repairs myself..
My oil change interval always has been 3000-4000 miles (usually in the low 3000's). For the first 15,000 miles, I had used conventional Mobil 5W30. Since then, I've been using Mobil 1 -- most recently the "high mileage" version that is formulated for better seal swelling properties. I also change my pcv valve (using a Toyota OEM part) every 15,000 miles.
When I changed the oil 3000 miles ago, I couldn't get the usual Mobil 1, so ended up buying WalMart's house brand, fully synthetic 5W30. The purpose of this post is not to malign WalMart, because I've read that their full synthetic is a very high quality oil. However, unfortunately, after a few weeks of using this oil, I started noticing that oil was oozing out around the valve cover gasket, and dripping onto the exhaust manifold (and burning) and/or onto my garage floor. I attribute this to the fact that this oil probably doesn't swell the engine seals as effectively as the high-mileage Mobil 1.
After the WalMart synthetic had been in the engine for about 2000 miles, the "check engine light" came on. I noted that the oil still looked nice and clean, and I'd only lost less than 1/2 quart due to seepage during those 2000 miles (and I don't think I'd used or burned any oil). Also, there has never been any smoke coming out of the tailpipe or any other sign of engine sludge. For some reason, I decided to investigate the condition of the pcv valve (which also had only 2000 miles on it). I found that it had a coating of oil on the intake portion of the valve (i.e., the part that is inserted into the rubber grommet in the engine manifold) and, most importantly, it seemed to be clogged. I shook it, but there was no rattle.
So I replaced it with a brand new pcv valve and, lo and behold, after just a few cycles of driving the van, the check engine light went back off and stayed off for about 1000 miles.
Just a few days ago, after about 3100 miles with the WalMart oil, I did another oil change (back to the Mobil 1 high mileage oil). The WalMart oil still looked pretty good. There had been no large loss of oil, and I saw no sign of any sludge or solids in the drained oil. But the next day, after driving around a little with the Mobil 1 in the engine, the check engine light came back on for the first time in about 1000 miles. So I checked the new pcv valve (in use only about 1000 miles), and it once again had a coating of oil on its intake portion, and it also seemed clogged (i.e., would not rattle). So I cleaned it out with a carb cleaner spray, blew it out with a compressor, and it seemed like new again. I reinstalled it and then, today (after just a few cycles of driving with the clean pcv valve), the check engine light went off again, and has stayed off.
I don't have an OBD reader, so I don't know the code for the CEL event that just occurred. I've read that a clogged pcv valve would NOT trigger a check engine light. However, this is what seems to have happened these last two times.
When the van reaches about 180,000 miles, I plan to bring it to my local garage to replace the timing belt and to have the valves adjusted. At that time, I will ask them to look closely to see whether there are any blockages in the engine, and hopefully they'll be able to stop any remaining new leaks when they install new gaskets and seals. Between now and then, I intend to clean or replace the pcv valve at every oil change.
Does anyone have any ideas about what is going on, or any suggestions about this? Thanks for your help.
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You spin an interesting tale, but to no avail. There is nothing to do until you pull the code that turned the check engine light on. Lots of places will pull the codes for free, and for the price of paying the dealer to do it once, and at most twice, you can buy your own code reader and pull codes anytime you want and as often as you want for whomever you want.
You throw good money after bad by changing the oil far too often -- you buy expensive oil that is designed for long life, and then change it as if it is the crap that they put in Grandpa's engine in the decades that followed the invention of the wheel.
You drive a car that is closing in on 15 years old, and are asking why it leaks. Age, my friend. Age. The leak and the light are not likely related, and the oil you use and the light are not related. You are taking steps to fix stuff, but you don't know what to fix.
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I doubt the Wal*Mart oil is a factor. Most likely you eninge is suffering from excessive blow-by, likely related to worng rings. The appearance of oil leaks and the coating on the PCV valve point to this BUT, it is only a guess. Next time the light is on, take your car to the local AutoZone and get them to read the codes for you. Regardless of the codes, a plugged PCV valve can contribute to oil leaks by allowing pressure to build up inside the crankcase and valve cover.
Ed
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Jeff and Ed,
Thanks for your thoughtful replies. I really appreciate that knowledgeable individuals are still taking the time to participate and help others in this forum. A few years ago, at least 90% of the posts here actually had to do with Toyota ownership and maintenance, while fewer than 10% of the posts were by trolls, political zealots, and the lunatic fringe. Unfortunately, that 90/10 ratio now seems to have reversed to 10/90. It is the price and the blessing of living in a free society.
I agree that an OBD reader might be a good investment at some point. Ironically, this Sienna is the first vehicle I've ever owned (in more than 32 years of car ownership and maintenance) where I've had to deal with a check engine light. I get the idea that, even if I'm able to pull the code(s), there sometimes can be quite a bit of additional diagnosis and intuition involved.
So far, each of the CEL incidents has coincided with (if not been caused directly by) a clogged pcv valve. Each time that I cleaned or replaced the valve, the CEL turned off after a few driving cycles. So, even without the benefit of an OBD reader, I think I had reasonable intuition about the condition of the pcv valve (after I saw all the oil seepage from the engine).
I guess I shouldn't be surprised to be seeing increased blow-by after 153,000 miles. The strange thing is that I haven't seen any evidence that the van is burning oil. Since there hasn't been much time/ mileage since the last oil change (to the Mobil 1 High Mileage), it may take a while for me to see whether this oil actually reduces the blow-by, reduces the oil seepage, and allows the pcv valve to stay unclogged. I have to believe that different oils have different properties, and that some would be better than others at reducing blow- by (without simply switching to a higher weight oil). I will post again after I've had a chance to see whether there's been any improvement.
Finally, as for the short oil change intervals with synthetic oil, this was a conscious (if not very economical) decision, based on two factors: (1) 5-quart jugs of the Mobil 1 are relatively inexpensive at Walmart. (2) Normally I would run the Mobil 1 for an oil change interval of at least 5000 miles (as I do in another car that I own), but am deliberately committing "overkill" here since the Sienna's engine seems very sensitive to sludge formation.
I'll post again after I see how the van is doing over the next 1000 miles or so. If the CEL comes on again, I'll definitely buy an OBD reader and will report back with the code(s).
Thanks again for sharing your expertise.
Ron
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Jeff, Ed and NM5K,
I just wanted to report back. After about four months and 3000 miles, the Mobil 1 High Mileage oil seems to be improving the situation. The total oil loss during the last 3000 miles (with total mileage on the van now over 156,000 miles) has been less than a half-pint -- i.e., next to nothing. I also am seeing less evidence of seepage: There are only a few drops of oil on the garage floor after 3000 miles (much less than I was seeing before), and I don't smell nearly as much oil burning (caused by dripping onto the exhaust manifold). The check engine light also has not come back on. I did notice that the pcv valve was a little gunked up. Although it still rattled somewhat, it definitely did not rattle completely freely, and there was a coating of oil on the discharge end of the pcv. So I cleaned it with carb spray. It now rattles freely again. I realize this may be a bandaid approach (i.e., using the "high mileage" version of Mobil 1 and cleaning the pcv valve every 3000 miles) to reduce seepage and keep the pcv valve clean, but I'm hoping that it will continue to minimize the problems until I can have everything taken apart at 180,000 miles.
If the check engine light comes back on, I will pick up an OBD reader and let you know what I see.
Thanks again.
Ron
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