fastnoypi

1st pic are both rear valve covers. 2nd pic are the cams in the rear head. You will cannot see the valves as they are under the buckets.

There is no design flaw in the front valve cover that i am aware of. The breather is plenty big and has less a vacuum acting on the oil mist since it is connected to the airbox assembly.

matts6887

fast; in your honest opinion; do you think since i have a 99 300 which is the first year for the rx300; that it would be worth it to do the valve cover swap; and if so; what are the part numbers for the newer style cover; gasket, pcv valve and hose if you know those off hand which would be great because even though i dont currently have any oil burning issues; I want to sorta kinda take proactive approach to this so to speak and put a stop to something bad BEFORE it even starts(hopefully) which is why i think its worth it to do the swap. What are your thoughts on the whole thing in my situation at this point? Also; going off of the 2 listings they have for valves covers off of parts.com; which one is the rear valve cover; the right or the left?

salimshah

There is preemptive and preventive. With old vehicles the preemptive will make you poor real quick while preventive would be cost effective.

Orient the engine right way in your mind ... Main pulley facing the front. Then imagine yourself sitting in the driver seat ... your right will be the right of the engine. So the cover with pcv is the right valve cover. All this is explained in detail in the sticky threads.

Salim

fastnoypi

while i agree with salim with the valve cover swap being preemptive and preventative, this particular preemptive maintenance is not cost prohibitive and may bring an added value maintenance point should you re-sell your vehicle in good running condition.

In your particular situation, you will have to decide whether roughly $150-200 for the cover will break you. As i mentioned to you in another reply, i paid roughly $180 for the cover AND gaskets (found through ebay vendors)
You say you don't have oil consumption issues, but you are due for spark plug replacement. In my opinion, you have to do your back plugs anyway, and you should be doing the correct way with a torque wrench to ensure proper installation and prevent "spark plug blowout". This will require you to remove your intake manifold to fit a torque wrench. While back there, i suggest to minimally replace the valve cover gasket and spark plug tube seals which are rock hard by now.

If you have any more questions specifically about your RX, feel free to contact me via messaging so we can keep this thread on topic

matts6887

Well no; I dont believe i am due for spark replacement yet as the vehicle runs excellent; but; the doing the valve cover swap i think would be a worthwhile investment in terms of maintaining the vehicle and also come time later on down the line when i decide possibly to upgrade to a newer vehicle of some type. Right now though i dont have 145-160 bucks for the valve cover and the gasket as well as the pcv and the hose which i believe should be replaced as well as long as Ive got everything apart if and when i decide to do it.

fastnoypi

According to Lexus, replacement is at 120k. If you are over that on original plugs, you are overdue.
When spark plug gaps change overtime, it causes stress on the ignition system. You can burn out a coil pack and foul out an expensive catalytic converter. Going past the factory recommendation is just borrowed time and a gamble at the expense of one factor of mpg efficiency.

matts6887

Well; Im just about positive that one of the previous owner(s) had the plugs changed because as i mentioned; the vehicle runs excellent at the present time. But; if you really feel that i should get them changed out asap; then I will get 6 new ones and go to town on it even though getting to the rear ones could pose a bit of a challenge and be a bit time consuming. It does sound like it would be worth it though cause it may also help improve mileage a little(probably not a ton; maybe 1-2mpg Im guessing). Not sure right now though if i can swing the 40 bucks or so for 6 new ones; I mean if i have no choice but to do it then yes i will spend the $ for the 6. Unless you know of somewhere that i can get them the least expensive $. And Im talking about the proper brand(either denso or ngk)

fastnoypi

If you have documentation that the plugs were changed, its not worth it. If you don't, i would change them. I just changed out all my plugs during the valve cover replacement with close to 155k on them. My RX seemed like it was running fine before i started the job. Now that i changed them, it noticeably idles that much smoother.

Again, lets keep this thread on topic.

fastnoypi

Interesting note of causes of oil consumption.


https://www.amsoil.com/techservicesb...onsumption.pdf


with some of these first generation RX's ..im leaning toward stuck piston rings and/or clogged oil passages that are the root causes for the oil consumption.
PCV cleaning or removal and valve cover replacement have slowed down consumption but did not eliminate the issue during long highway drives of more than 1 hour.

matts6887

interesting article there fast. So; you dont really think the big issue related to the oil consumption issues is the rear valve cover even though that has apparently solved the issue for a lot of people?

salimshah

This has been my favorite explanation ,,, At high speeds thee oil pump is delivering lots of oil and gravity is working the oil down .. the restriction in oil channels in preventing the drop down .. thus raising the oil level in the valve cover and making it susceptible to be sucked in.

I do not have positive proof but just one more theory.


Salim

fastnoypi

I can't make a blanket statement for everyone else's cars. There are some on this board who've been able to solve their problem with just a pcv valve, others have found evidence of clogging in their first gen rear valve cover.
Displacement aside, Lexus redesigned the rear valve cover baffle on the RX330 for a reason. They wouldn't go through the tooling or paying a supplier for a new design if the old one worked fine. It would shrink their margins.

I can say the rear valve cover replacement did help some oil consumption in my case.

The toughest part of determining possible areas around the engine for sources of consumption is that the 3 catalytic converters do a pretty good job of cleaning up the smoke. In alot of high milage cars, if everything else is sound,..typically worn valve guides are the cause of burning oil but could be masked by an efficient catalytic by cleaning up majority of the smoke.

I wish i could say certainly in my case for clogged oil passages in the head, but i took both my valve covers off myself and did not see any puddling of oil or evidence of sludge.

When i have time, i plan to do another top end clean but this time soak each cylinder in either BG12 or Seafoam to really break up carbon deposits and rule out sticking piston rings. I'd rather battle the long tedious process of elimination instead of throwing needless cash at a dealership tech who might just throw parts at a problem.

hypervish

We also have to keep in mind that people only come on forums to express their concern regarding an issue with their car, so the few reports on CL that we have seen regarding oil consumption do not mean much. We are a small crowd of people in the grand scheme of things. And, it's important to note that the majority of folk on CL do not have an issue with oil consumption, such as myself.

It's hard to come to a conclusion with the limited data that we have. And, "one size does not fit all".

fastnoypi

Agreed, folks who report oil consumption on CL is a relatively small sample however, if you dig in a bit more on other Toyota forums for other models that used the 1MZFE..you will be quite surprised of the volume of complaints for the high miler.
I haven't yet pinpointed the common theme with these engines that have exhibited these problems. The ones that have sludge problems are obvious, but there are a handful that don't have sludge.

matts6887

interesting observations from the both of ya on this subject. Well; I guess as far as i go; for now im not gonna worry about doing anything to the rear valve cover on mine because mine has been solid as a rock thus far. So hopefully with that in mind i wont encounter any issues for quite awhile yet. If for some reason i do in the short term i guess i will just have to take care of it then.