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Skyvisions, ASE Certified Technician
Category: Lexus
Satisfied Customers: 14501
Experience:  Lexus Expert
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2000 Lexus RX300: rear main seal is leaking of oil

Customer Question

I have a 2000 Lexus RX300. The rear main seal is leaking some. When I drive in town, it uses a quart of oil every 2500 miles. When I drive on the interstate at 80 mph, I lose a quart of oil every 275 miles. Some spots on the garage floor but nothing compared to the oil I'm using. What could the problem be? I believe I have already changed the PCV valve once.
Submitted: 5 years ago.
Category: Lexus
Expert:  Skyvisions replied 5 years ago.

Thank you for choosing JustAnswer and allowing me to help you resolve your Lexus questions!

Have you removed the front valve cover to check for excessive sludge build up?

Customer: replied 5 years ago.
No, I have not. I've only looked in the oil fill hole which has an older oil color
Expert:  Skyvisions replied 5 years ago.
This engine is notorious for excessive oil consumption and typically is caused by excessive sludge build up. The piston rings get collapsed and clogged and at higher speeds the oil consumption becomes greater. It's not likely that you're losing that much oil out the rear main seal in 275 miles. The valve covers have been redesigned to allow better crankcase ventilation. The ventilation ports in the valve covers especially the rear one where the PCV valve is located gets restricted. More than likely you're probably looking at putting new piston rings in or at the minimum trying new valve covers depending on the amount of sludge build up.
Customer: replied 5 years ago.
I have 158,000 miles on it. I know that Lexus had problems with these engines foaming oil. Is that connected with the sludge issue? Do you think that there is a chance that changing valve covers would correct the problem? If so, do you think Lexus would stand behind the parts? If I were to put in new rings, I might as well put in a new short block, right? Where would you draw the line? The body is fine and inside good. Transmission oil has been changed regularly with flushes and shifts well.
What would you do if it was yours?
Expert:  Skyvisions replied 5 years ago.
Is not so much the foaming of the oil as it was poor air circulation or ventilation from the crankcase system. Over period of time this cause the sludge build up and then when you had people not changing oil on a regular basis it added to the problem. Depending on the sludge build up once you remove the front valve cover which is not that difficult to do there's a good possibility that installing new valve covers will help with the oil consumption problem. The only way to know for sure would be to do a wet and dry compression test to see how bad the rings are not sealing. The dealership has a borescope that they can run down into the front cylinders and take a look at the cylinder walls to see if there's any excessive wear or vertical scoring. It is unlikely that the dealership will do anything for free on this given the mileage and the age. The labor to put new piston rings in typically will be cost prohibitive on this old of a vehicle. If you plan on keeping the truck long term you might want to consider just putting a short block in with new valve covers and have the cylinder heads redone. You draw the line at your threshold of pain financially and how long you're planning on keeping the vehicle. These transmissions also had major issues.
Customer: replied 5 years ago.

Thank you. A couple more questions:

1. Why does it burn oil on longer trips but not burn oil locally even though I go 70mph locally for short distances? Is it a crankcase pressure issue?

2. Do you know approximately how much putting new valve covers on it would cost?


Expert:  Skyvisions replied 5 years ago.
That is correct it is a crankcase pressure issue that on longer trips it builds up vs. on shorter trips. Usually the labor to replace the valve covers will run approximately 3.0 up to 4.0 labor hours depending on the shop. Typically most shops are right around $100 an hour. I don't remember the exact cost of the valve covers but as I recall there about $150 apiece roughly. If you need more exact numbers I can look the part numbers up.
Skyvisions and 6 other Lexus Specialists are ready to help you
Customer: replied 5 years ago.
Can you tell me if you can just take the valve covers off, clean the sludge and put them back on?
Expert:  Skyvisions replied 5 years ago.
This is not recommended. You cannot get inside the baffling of the valve covers. I have tried to hot tank them numbers of times and was never able to get them cleaned inside. The design of the baffles was changed.
Customer: replied 5 years ago.
I checked on new valve covers. They are about $350 on line. i assume that putting used ones on would make no sense even if they were clean, right? I heard they redesigned them, is that correct?
Expert:  Skyvisions replied 5 years ago.
You are correct the valve covers are redesigned. It would not make sense to get used ones with the old design even if they were clean.
Customer: replied 5 years ago.
Thanks, you have been a big help in understanding the problem. I think I get the problem now. By the way, I drive the RX300 because I have a horrible back and the seat and egress fit me very well and it rides fairly smooth. The RX330/350 (2004-2009) rides rougher than an RX300. The new RX 350 is pretty pricey. If you were buying one of those 3, which would you buy (old low mile RX300, 2006-2009 RX350, or 2010 RX350)?
Expert:  Skyvisions replied 5 years ago.
I prefer the newer engine in the RX 350 less maintenance and if it's been maintained well. It is a lot stronger engine. Any time you're dealing with the 3.0 L engine there's always a potential of problems. Not only with the transmission but with the oil consumption issue.
Customer: replied 5 years ago.
It's 2 months later and I'm burning 1 quart every 110 miles on the road and every 900 miles in town. The Lexus dealer pulled the front valve cover and there is no sludge. Lexus Corporate has said there is an assistance program for sludged engines and is reviewing my records. Is it possible that there is sludge on the back side of the engine and not the front (under the valve covers)?
Expert:  Skyvisions replied 5 years ago.
The back valve cover could possibly be plugged up it has the pcv valve in it. If the pcv valve system is restricted due to excessive sludge this could be an issue. hopefully Lexus will make it right for you.