Low Cost RX300 Oil Fix that works
02-12-13, 02:06 PM
#1
Driver School Candidate
Thread Starter
Low Cost RX300 Oil Fix that works
I have a '99 RX300 that I bought 5 months ago with 113k miles on it to do major highway driving. About 600-800 miles per week. Very quickly, I learned that, I too, had an RX300 that consumed HUGE amounts of oil, but it ran excellent! I read the forums. Called the dealer. Same message from everyone. Junk engine: $8k replacement, $3.5k for a long block. However, I was not convinced I had a bad engine. After much research and discussions with engine rebuilders, here is the long and short of it, Baseline data: '99 RX300 with 113k miles that used 1 qt of oil every 250-500 miles depending on engine load. 20 mpg. No smoke. Cyl compression varied from 145psi per cyl to 180psi per cyl. Again, it ran good. THE FIX: I ran 3 cans of Mopar Combustion Chamber Cleaner,MCCC,($8/can) in the intake with 500 miles between cans. Drove the car hard in between cans of cleaner. Once I ran the cleaner through, I took the valve covers off and replaced them with the updated ones at a cost of $400. No sludge. Cleaned out the intake (it was covered in oil) and omitted the PCV-intake hose and ran a hose to an external cone filter. Checked compression: 220psi per cylinder. Put in new plugs. I have 127k miles on it now and it has NOT used oil for the last 7000 miles. As it turns out, sticking piston rings caused excessive blow by which causes crankcase pressure which forces oil through the PCV and into the intake, which runs down into the cylinders and burns it through the combustion chamber. My research indicated that the MCCC is the best upper cylinder cleaner on the market. Local Chrysler dealer said the Ford dealer buys it from them by the case. The fix worked for me. No guarantees, but it makes sense. I did it all for $500. I'm much happier with my RX now.
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Smokie (04-29-18)
02-12-13, 03:06 PM
#2
Excellent! I am sure this information will help many people on here with the dreaded oil burning issues. I think the key is once you start burning, you need to replace the old style valve covers with the updated ones. Never thought some combustion cleaner would fix it all!
02-13-13, 06:07 AM
#3
Pole Position
John,
Great post! Thanks for sharing your experience. This will help a lot of folks save money.
Just one question. If the root cause of the problems you had was stuck piston rings, why did you go ahead and change the valve covers and disconnect the PCV? Eliminating the excessive blowby should have meant that the rest of the parts would work correctly as designed. Thoughts?
Baetke
Great post! Thanks for sharing your experience. This will help a lot of folks save money.
Just one question. If the root cause of the problems you had was stuck piston rings, why did you go ahead and change the valve covers and disconnect the PCV? Eliminating the excessive blowby should have meant that the rest of the parts would work correctly as designed. Thoughts?
Baetke
02-13-13, 08:37 AM
#4
Moderator
I have not reconciled with oil level rising as high to get past the pcv? Assuming it does due to some other malfunction, then how can the new valve cover prevent it from happening?
Granted there has been a change in the cover, and it might provide some advantages, but the oil pass through the pcv in design 1 vs 2 still does not make sense to me. Improvement in vapor recovery, improved PCV would make sense.
But if it works for any one, who am I to question?
Salim
Granted there has been a change in the cover, and it might provide some advantages, but the oil pass through the pcv in design 1 vs 2 still does not make sense to me. Improvement in vapor recovery, improved PCV would make sense.
But if it works for any one, who am I to question?
Salim
02-13-13, 01:00 PM
#5
Driver School Candidate
Thread Starter
Low Cost RX300 Oil Fix that works
I decided to replace the valve covers based on future potential issues with sludge buildup. While there was no sludge on the head, the valve covers had some crusty buildup. Also, I put the external breather on to confirm that oil was not going back into the intake. If it didn't work, oil would have puked out the breather. In theory, I could have cleaned and reused the valve covers and reconnected the hose. It is a big enough job that once I pulled them, I wasn't going to take a chance and have to do it again. Talked with too many Lexus mechanics that swore by the updated valve covers. Also, The new PCV has more flow than the old one. I'm thrilled with the outcome. I did the updated valve covers on my 2002 Sienna van at 75k and now have 147k with no oil consumption at all.
02-13-13, 04:28 PM
#7
Pole Position
John,
One more thought I had about your PCV valve mod. The PCV valve is designed to open based on the pressure differential across it; pressure in the crankcase and vacuum from the intake manifold. If you just disconnect the PCV hose and run it to an external filter, that side of the valve will always see atmospheric pressure, never a vacuum. This means the valve won't open up as it should to vent the crankcase. Its your call, but a lot of really smart engineers figured out how to make that system work and any mods you make may have unintended consequences down the road. (pun intended
)
On my car, I discovered that the dealership had left the PCV valve unplugged from the valve cover grommet. This meant the intake manifold would suck fresh air through the valve and into the engine causing a small lean condition. Additionally, since the blowby gasses weren't being properly vented from the crankcase, they backed up through the breather hose into the intake resonator and leaving an oily deposit there. As far as I know, no harm was done, but you can see how that small change affected other things.
Baetke
One more thought I had about your PCV valve mod. The PCV valve is designed to open based on the pressure differential across it; pressure in the crankcase and vacuum from the intake manifold. If you just disconnect the PCV hose and run it to an external filter, that side of the valve will always see atmospheric pressure, never a vacuum. This means the valve won't open up as it should to vent the crankcase. Its your call, but a lot of really smart engineers figured out how to make that system work and any mods you make may have unintended consequences down the road. (pun intended
)On my car, I discovered that the dealership had left the PCV valve unplugged from the valve cover grommet. This meant the intake manifold would suck fresh air through the valve and into the engine causing a small lean condition. Additionally, since the blowby gasses weren't being properly vented from the crankcase, they backed up through the breather hose into the intake resonator and leaving an oily deposit there. As far as I know, no harm was done, but you can see how that small change affected other things.
Baetke
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02-14-13, 02:10 AM
#8
Super Moderator
I have a '99 RX300 that I bought 5 months ago with 113k miles on it to do major highway driving. About 600-800 miles per week. Very quickly, I learned that, I too, had an RX300 that consumed HUGE amounts of oil, but it ran excellent! I read the forums. Called the dealer. Same message from everyone. Junk engine: $8k replacement, $3.5k for a long block. However, I was not convinced I had a bad engine. After much research and discussions with engine rebuilders, here is the long and short of it, Baseline data: '99 RX300 with 113k miles that used 1 qt of oil every 250-500 miles depending on engine load. 20 mpg. No smoke. Cyl compression varied from 145psi per cyl to 180psi per cyl. Again, it ran good. THE FIX: I ran 3 cans of Mopar Combustion Chamber Cleaner,MCCC,($8/can) in the intake with 500 miles between cans. Drove the car hard in between cans of cleaner. Once I ran the cleaner through, I took the valve covers off and replaced them with the updated ones at a cost of $400. No sludge. Cleaned out the intake (it was covered in oil) and omitted the PCV-intake hose and ran a hose to an external cone filter. Checked compression: 220psi per cylinder. Put in new plugs. I have 127k miles on it now and it has NOT used oil for the last 7000 miles. As it turns out, sticking piston rings caused excessive blow by which causes crankcase pressure which forces oil through the PCV and into the intake, which runs down into the cylinders and burns it through the combustion chamber. My research indicated that the MCCC is the best upper cylinder cleaner on the market. Local Chrysler dealer said the Ford dealer buys it from them by the case. The fix worked for me. No guarantees, but it makes sense. I did it all for $500. I'm much happier with my RX now.
03-07-13, 08:51 AM
#9
Driver School Candidate
What am i missing.
Many people swear by the valve cover replacement. OK - sounds like everyone who has done this has cured their oil consumption issues.
However, by the pics of the valve cover on some other posts it does not look all that difficult to clean.
Why not clean it and then re-assemble?
Thanks
Many people swear by the valve cover replacement. OK - sounds like everyone who has done this has cured their oil consumption issues.
However, by the pics of the valve cover on some other posts it does not look all that difficult to clean.
Why not clean it and then re-assemble?
Thanks
03-07-13, 06:17 PM
#10
What am i missing.
Many people swear by the valve cover replacement. OK - sounds like everyone who has done this has cured their oil consumption issues.
However, by the pics of the valve cover on some other posts it does not look all that difficult to clean.
Why not clean it and then re-assemble?
Thanks
Many people swear by the valve cover replacement. OK - sounds like everyone who has done this has cured their oil consumption issues.
However, by the pics of the valve cover on some other posts it does not look all that difficult to clean.
Why not clean it and then re-assemble?
Thanks
03-07-13, 11:53 PM
#11
Carguy, I'm sure you're right. It has to do with the redesign of the new valve covers, not the old ones being dirty. From what I've read, the sludging problem is a least partially blamed on the improper design of the old style covers not clearing the crankcase well enough of the fumes, but especially the condensation from shorter trips. There are quite a few other cars that suffer from sludging caused by the very same thing, (insufficient ventilation of the crankcase) that has allowed condensation to build up, hense the sludging. You just haven't heard about them in the same way that you have Toyota/Lexus sludging.
03-09-13, 06:46 AM
#13
Moderator
This may sound like a dumb question, but is there a way to tell the difference between the new style covers and the old style valve covers by looking at them? With all the maintenance that my RX received by the previous owner, I wonder if this was preformed. It did have valve cover seals, cam seals, rear main and T-belt all done about 5K ago.
Oh, and one more thing.... Was it a Lexus sanctioned repair or is the new valve cover an after market fix?
Oh, and one more thing.... Was it a Lexus sanctioned repair or is the new valve cover an after market fix?
