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Just to follow up on this issue, I decided to run a can of seafoam through the engine for the hell of it.
After a couple hundred miles, the oil burning has reduced quite drastically. I was actually shocked at how much of a difference it's made. I've gone probably close to 1,000 miles now without having to add any oil - coming from needing to add a quart every 500 or so! And I've noticed about a 2-3mpg increase, which is not insignificant.
I've never been a big fan of additives like these as I've always thought of them as snake oil, but I'm pleasantly surprised in this case. Very surprised.
Anyways, that's my update for now.
I did that but used much less-aggressive Mystery oil and high pressure air gun to shoot air through PCV valve hole(tried to push debris out of baffle plate). Yes, look like my problem is gone for "city driving"(less than 55 mph). Half year later, I got a trip to drive 200 miles at 70 mph, it ate up 1 bottle every 70-100 miles. When I was on my way back, I have to reduce my speed to 55 mph or less(I got fingered a couple of times, hey,I live in NY/NJ metro area). So I went to change my rear cover last summer, I tried a 100 miles trip right after that, no oil lost found. Then, I confirm that rear cover is the culprit.
But your case may not same as mine, you definitely try the cost-less way first, if it's not work, then try some other alternatives. I just try to remind you whenever you start a long highway trip; bring some extra oil to avoid a surprised-stuck at middle of nowhere.
Okay, I've driven the vehicle over 500 miles (probably 2/3 highway miles) now since I changed out the rear valve cover and I think I can say with confidence that the excessive oil consumption issue has been resolved! The oil level is still at the top dot and hasn't moved a bit (it had been using about a quart every 750 miles for the past year or more). I believe it also solved another problem I had with the car smoking on start-up after it would sit all day at work. I started another tread about that when I thought oil was getting through worn valve guides. Now it seems as if both problems have been solved by the redesigned rear valve cover.
A big thanks to the board (and especially tllee) for all of the help in getting this problem solved!! It seems as an added bonus, the RX300 has more power (could also be due to new plugs) and is smoother driving. I would imagine having to burn all that extra blow-by impacted the power to some degree. I can't tell you how happy this has made me!! THANKS
Okay, I've driven the vehicle over 500 miles (probably 2/3 highway miles) now since I changed out the rear valve cover and I think I can say with confidence that the excessive oil consumption issue has been resolved! The oil level is still at the top dot and hasn't moved a bit (it had been using about a quart every 750 miles for the past year or more). I believe it also solved another problem I had with the car smoking on start-up after it would sit all day at work. I started another tread about that when I thought oil was getting through worn valve guides. Now it seems as if both problems have been solved by the redesigned rear valve cover.
A big thanks to the board (and especially tllee) for all of the help in getting this problem solved!! It seems as an added bonus, the RX300 has more power (could also be due to new plugs) and is smoother driving. I would imagine having to burn all that extra blow-by impacted the power to some degree. I can't tell you how happy this has made me!! THANKS
Anytime, as long as I'm able to(still learning and at rookie level). You're right about the power, my car also got a big improvement after that. Not just b/c of the new plugs, those excess oil and blow-by screw up power, the prove is when I saw the old plugs removed from cylinder #2 and #1, a lot of white powder residue on them(too much oil but iridium plug burn it off,so we don't see oil deposit yet). The rest of the plugs look fine but still a little bit of wet(blow-by).
Enjoy your "revived" car!
My 1999 RX300 was smoking blue on every start and intensely burning oil (a quart every 300 miles or so) for over 4 months. Note that it started burning oil within oil changes over a year ago and gradually got worse some months ago.
After reading a lot of long threads on ClubLexus, I started by changing my PCV valve (plastic to another plastic) which only worsened the oil burning and smoking issues (Sidenote: I actually had the lower end of the old valve broken and lost in the baffle - after vacuuming to no effect, I left the broken part there and inserted another PCV valve - with a bit of assurance from an auto mech's answer on https://www.justanswer.com/car/c2ilq...mmet-1999.html). My local mechanic (whom I had not yet shared my clublexus research findings with) kept telling me I may be needing a new engine very soon as repairs/replacement of piston rings and valves were not just expensive but did not have long-term warranty.
However, I strongly felt my engine wasn't gone for good. So, I bought a 3rd gen rear valve cover with the metal pvc and was waiting for gasket and extended hose to get to me so I can send my car over to my local mechanic for valve cover change and other necessary maintenance. Note that around this time, my oil consumption had got so bad that an oil quart was burnt in just 2 days city driving (just over 50 miles total driving) that I had to park the car for a while.
While randomly surfing the net , I found myself on an "oil consumption" thread on "toyotanation.com" forum (https://www.toyotanation.com/threads...ption.1655608/).
Long story short, the thread starter (a toyota highlander user) was also contemplating change of valve cover but ended up doing a PCV reversal hack (with tips from someone who did it a long time ago).
His testimony spurred me to getting hoses and fittings and doing the pcv reversal myself at home and guess what? Since then, with over 300 miles driven (50% highway miles at over 60mph), no smoking and no single shortage of oil on drop-stick.
My sincere appreciation to all the contributors that have made my research worthwhile.
Hoping my attestation helps someone someday just as I had been helped.
Gerald
Last edited by geraldd62; 09-03-22 at 04:29 PM.
Reason: Title added
(Updated for clarification) 2001 RX300 165000 miles consuming 1 quart 5W30 Kirkland Synthetic oil per 200 miles with new PCV valve. Reversed the PVC flow per the pics. This modification connects the rear valve cover to the airbox and the front valve cover to the PVC valve. All evap hoses are connected and the PVC valve flows in the correct direction to the intake. Crankcase pressure venting is maintained, it just vents through the front valve cover instead of the rear where it is sucking oil. You will need 5' of hose for this. Modify at your own risk. Will update with results....
Here's a diagram of the fix...
Last edited by RXRIC; 02-10-23 at 12:38 PM.
Reason: Clarification.
Okay, I've driven the vehicle over 500 miles (probably 2/3 highway miles) now since I changed out the rear valve cover and I think I can say with confidence that the excessive oil consumption issue has been resolved! The oil level is still at the top dot and hasn't moved a bit (it had been using about a quart every 750 miles for the past year or more). I believe it also solved another problem I had with the car smoking on start-up after it would sit all day at work. I started another tread about that when I thought oil was getting through worn valve guides. Now it seems as if both problems have been solved by the redesigned rear valve cover.
Thank you. I have '99 RX300 350K miles with original engine and transmission. My mechanic brushed aside my concern about oil consumption, so I still continue to add about a quart every thousand miles. A while back my 1966 Mustang had similar issue (oil consumption but no sign of oil in exhaust or below parking spot) which was fixed by replacing the rear main seal.
Reversed PVC Flow - Update. I wanted to post a quick update since this appears to have solved my oil consumption. 350 miles at highway speeds. No oil loss or day after smoke from the tailpipe. I'll post future updates. Update: 750 miles, mostly highway, oil reads 3/8" below full on dipstick. No smoke from tailpipe.
Last edited by RXRIC; 10-02-22 at 09:31 AM.
Reason: Update
Reversed PVC Flow - Update. I wanted to post a quick update since this appears to have solved my oil consumption. 350 miles at highway speeds. No oil loss or day after smoke from the tailpipe. I'll post future updates.
You can choose to do what you want to your vehicle, specially to test/diagnose, but keep in mind altering emission related stuff is not kosher. You will increase pressure in the block which may cause oil leaks. A more prudent way is to add a catch can in the passage way and reorient the PCV the right way.
You can choose to do what you want to your vehicle, specially to test/diagnose, but keep in mind altering emission related stuff is not kosher. You will increase pressure in the block which may cause oil leaks. A more prudent way is to add a catch can in the passage way and reorient the PCV the right way.
Salim
As I understand it, the original flow is air in through the front valve cover and out through the rear one via the PCV valve.
Why does reversing the airflow direction to be in through the rear valve cover and out through the front via a PCV valve increase pressure in the block?
As I understand it, the original flow is air in through the front valve cover and out through the rear one via the PCV valve.
Why does reversing the airflow direction to be in through the rear valve cover and out through the front via a PCV valve increase pressure in the block?
Good question.
One bank has what is termed as breather ..as it is higher [vertically higher .. the engine has a tilt]. I am not well versant with the breather's valve action if any. One of the reasons cited for oil leaks through front/rear main is clogged PCV.
The vapor recovery is being sent up by the PCV. There is negative pressure due to throttle body to suck in the vapors. I guess Lexus/Toyota has done their homework and determined that is the right spot.
Technically adding a catch can is tampering with emission control with which the engine was qualified [We are also reaching 25 yrs shortly]. I still think the catch can does not mess with the intent of capturing vapors.
Hi Salim. Thank you for your input. The reversal just swaps which bank is input or output. All evap connections are maintained and the flow through the PCV valve is in the correct direction to the intake. Do you have a picture or part# for the "breather valve" that you mentioned? I can't locate it in a google search.
Reversed PVC Flow - Update. I wanted to post a follow up update since this appears to have solved my oil consumption. 1500 miles at mixed highway speeds. No significant oil loss or day after smoke from the tailpipe. It does seem to run better. Smoother. More acceleration. Fuel mileage seems to have improved from 18 mpg to 19 mpg. Oil continues to read 3/8" below full on dipstick. No smoke from tailpipe.
Reversed PVC Flow - Update. I wanted to post a follow up update since this appears to have solved my oil consumption. 1500 miles at mixed highway speeds. No significant oil loss or day after smoke from the tailpipe. It does seem to run better. Smoother. More acceleration. Fuel mileage seems to have improved from 18 mpg to 19 mpg. Oil continues to read 3/8" below full on dipstick. No smoke from tailpipe.
Well, I'm satisfied that the reversal of the crankcase ventilation by connecting the PVC valve to the front valve cover has solved my excessive oil consumption on my 2001 RX300. I have driven 2000 miles of mixed driving with no significant oil loss. This included a fresh oil change and 350 miles of driving at 80 mph and I averaged 20 mpg. It has changed my perception of being afraid to drive the car to enjoying using the car as intended. Cheers!
04-06-15, 01:37 PM
(I got fingered a couple of times, hey,I live in NY/NJ metro area
). So I went to change my rear cover last summer, I tried a 100 miles trip right after that, no oil lost found. Then, I confirm that rear cover is the culprit.
