gomeybear

My lexus rx 300 2001 w/ 74000 miles is burning oil. Not sure at what rate yet because i just noticed the problem. But when I was driving the other day the low oil pressure light would come on when I was hard braking. After checking it I was 3 qts low. I refilled and thought about it some more and it had been about 5000 miles since the last oil change so about one qt every 1600 miles seems to be the rate. Where do I start to remedy?

gomeybear

In addition the gas mileage isn't great at 17 mpg using 89 octane.

fastnoypi

alot of us have solved the oil consumption problem by using the rx330 rear valve cover. Check out this thread https://www.clublexus.com/forums/rx-...lve-cover.html

Drcoffee

Well, it could be leaking badly from the right side valve cover. Or bad piston rings, which you could do a compression test to find out. Or the pcv valve system is faulty. If you have the 2001 rx you would have the plastic push in pcv valve. Unless the previous owner swapped it out already. If it comes straight out of the valve cover and has a hex base its the newer cover. If the pcv comes out and makes a 90 degree turn, its the old cover. The new cover is actually from a rx330 from 2004 and newer.

Because the engine leans backwards towards the firewall, a leaking gasket can lose a lot of oil. If its leaking and you need to replace the gaskets, you might as well change the rear valve cover to the rx330 version. They can be had on ebay used for around $50. And change the spark plugs too. I just did mine and it wasnt as bad as I was led to believe. If you dont have many tools, it can be frustrating because of a few tight bolts.

i am experimenting with adding a restrictor in the pcv line to lower the volume of air it can flow and stop the pcv valve from acting like a soda straw in the oil.

I wont know for another 1,000 miles ( 3 tanks of gas). I will know if the restriction is too much if I start getting oil coming out of the fresh air port in the plastic intake tube infront of the throttle plate. I cleaned completely when I had it all apart. Too much blow by can blow gaskets out but considering the restriction is no smaller than the pcv valve, I dont anticipate any problems.

Drcoffee

If you wanted to test the pcv system for oil consupmtion, cap the vacuum port on the intake and put breathers on both front and rear valve covers. Run it for 800 miles and see if you lose any oil. There wont be any hard running it this way for a short period, but you may smell it. If the oil is unchanged after 800 miles you know its the pcv. If it still loses oil, then troubleshoot the gasket leaks and piston rings.

gomeybear

Drcoffee,

Thanks for the responses. I noticed I don't have the 90 degree PCV valve its just the straight metallic one with a hex around it. Does this definitely mean that I have the updated rx 330 valve cover? Another member just posted to one of my threads saying that he also has a straight metallic PCV valve with the hex and not the L shaped one on his 2001 rx 300. If that's correct did lexus potentially start changing the cover on later manufactured rx 300s? Or does it mean it was changed by the previous owner? (Wouldn't be able to ask previous owner because I bought it from a dealership out of Florida). It seems that if I have the updated cover that would lessen the probability of sludge being the issue of oil consumption? Recently I had my valve cover gaskets replaced (they were leaking) by some mechanics down by the border of texas and wasn't informed of any sludging (although I am not sure if they would have noticed). I may just end up taking it in to a trusted mechanic as I don't think I have adequate tools or a good garage to check under the valve covers.

fastnoypi

gomeybear, it appears you have the v2 cover that i used to have on my 2002 rx300. The internal baffles of that cover can get sludged up on that version. The upgraded v3 models came on the rx330 models before the 3.5L motor was used. I was able to verify at the time by removing the rear valve cover, and pouring water through the pcv hole noticing a lot of resistance as well as using air pressure. If you were to outsource the work, it would be easier to replace with the v3 unit. Otherwise, soaking the cover in degreaser, cleaner, etc..would "recondition" your old cover good for 90-100k miles till it potentially sludges again.

gomeybear

Fast,

Thanks for the reply. I've been recently doing synthetic oil changes on the rx does that eliminate the chance of engine sludging if I were to clean up the valve cover moving forward? Also, being that I have the V2 as you call it does that also lessen the likelihood of sludging being present on more key components like cam lobes, shaft etc?

Drcoffee

I think you are confusing the two issues. Sludging or Gelling is the thickening of the oil which happens from poor ventilation in the crankcase allowing condensation and heat to thicken the oil and make it less viscous. If you had sludge, your mechanic should have told you. I doubt you have that problem because it is difficult to restore and would need immediate attention. on the other hand, the early valve covers had poor air passages and oil drain back and when oil built up under the baffle it could be sucked up to the pcv valve and ingested by the engine and burnt. So if you are losing oil it could be by ingestion thru the pcv or getting by the piston rings from sludge build up.

Like I said above, put breathers on both valve covers and drive it far and fast enough to reproduce the oil loss you now see. If you continue to see oil loss, its not from the pcv. The alternative is to pay a mechanic to compression test the engine and the rear spark plugs are not easy to reach. You said you are already using synthetic oil, you may have begun leaking oil for gaskets that were sealed by oil crusty oil. You never said if you saw oil leaking from the engine. Grab a flashlight and look around, especially on the rear of the passengers side of the engine.

Stick with synthetic oil. conventional oil will gel and sludge.

gomeybear

I am going to just suck it up and try to replace the valve cover, PCV valve and clean up the lines. Quick question its only the rear that needs to be replaced correct? Also when applying the new gasket do I need a gasket sealer? If so where does the gasket sealer need to be applied?

Drcoffee

you can buy the valve cover gaskets most any parts store or dealer and you will need some oil resistsant RTV silicone for 6 spots on the head where there are seam lines. If you have the new valve cover, besure to degrease the surface of the head so the rtv can seal it.

why replace the valve cover? Save your cash for the next project.



The newest valve cover is no guarantee of no sludging. This one obviously is crusted badly.

Drcoffee

There is an old school way to not only prevent sludge but clean the gelled oil thats there now. MMO Marvel Mystery Oil is a mild solvent that will disovle the old oil slowly. You add it to the oil 20% of total oil capacity. So, 4 qts oil, 1 qt MMO on your next oil change. Keep an eye on the color of the oil on the dipstick. If it darkens, change the oil and do it again. Its less agressive than sea foam when cleaning the engine.

gomeybear

Dr Cofee,

I recently bought the Auto RX sludge oil additive to perform there recommended excessive engine oil consumption/sludge method (wasn't cheap). Do you think this will do the job that the MMO will do?

salimshah

Just my 2c, please have the problem diagnosed before embarking on any or all potential solutions.
Valve conver examinaiton
Spark plug examination
Compression testing
Leak down testing
Drop the oil pan
Catch can in the intake path.

Salim

gomeybear

salimshah,

Any chance do you know of any good mechanics here in Austin that are pretty trustworthy? I would like to try and work on alot of this myself but I am limited mainly by tools so I don't feel confident embarking on some of these tests.