shark13

Hello, I'm a first time user of this forum and would like to thank anyone in advance for their suggestions. I am looking at buying my parents 99 RX300 (AWD). They have informed me that it uses about 1 quart of oil for every 600 miles or so. That obviously concerns me. There is little to no oil leaking out the bottom, and no visible white or blue smoke out the back. So here is my question. In addition to the piston rings, what are some other possible causes of this oil loss and what sort of risk level do they pose to the engine...meaning if the oil is continually replaced are they still a major problem or just an annoyance.

Also, does anyone know what the compression levels ideally should be for each piston. I'm planning on running a compression check and need to know what to compare the readings I get to.

Thanks again for any assistance.

salimshah

Even if you were getting it for free, by the time you pay for the repairs, you will be below market value. Buying for parents may be nice gesture, but be aware of the high repair cost of Lexus vehicles .. not good for parents.

I would say walk away and keep looking.

On the other hand if you ar looking for a project car ... it might be worth the fun ... but getting to cylinder 1, 3, 5 will be a major pain.

Salim

hypervish

I think you are probably looking at a case of sludge in the engine. So the best thing to probably do is just keep looking for another RX.

sktn77a

iTrader: (2)

Is the option for your parents to trade it in on a new car? If so, I would take that option. Potential transmission problems, potential engine problems...............

shark13

I appreciate the advice so far. I started running the compression check on the extremely easy cylinders in the front of the engine. From left to right I got the following PSI's:

Left - 170 psi
Middle - 180 psi
Right - 190 psi

I plan on attempting the extremely difficult back three cylinders today or tomorrow. Does anyone know what the correct psi specification are. I would assume there is an ideal number and or perhaps a range. Just for the sake of argument...let's say all the cylinders are in the normal range...what could be some other causes for oil leakage. The only thing I noticed was an unfamiliar canister looking thing located on the front left (if looking at the front of the car) that is just behind the radiator. It seems to be leaking some oil but not a significant amount. If my parents are correct in their assesment of 1 quart per 600 miles I am at a loss for where the oil would be going. Again...assuming the 3 remaining cylinders perform as well as the first did.

shark13

One other thing. Anyone have any experience with removing the three rear spark plugs in an early RX300? Is this humanly possible without removing the intake manifold? Even with the manifold...is it possible. How and why someone would engineer and engine in such a manner just to get the plugs out is beyond me. Much thanks for any help.

Lexmex

https://www.clublexus.com/forums/rx-...-patience.html

salimshah

Removing and re-installing plugs is quite possible by only removing the top cover (which you need to remove to access the front 3 plugs).

Engineers are not silly and or masochists. Usually there is a reason and if there is a potential problem, they try to address it.

Point in question is the access to odd# plugs. Well it started out by having a transverse mounted engine. Then comes the size (fuel consumption + other factors) ... which meant little gap between the engine and radiator and the firewall. [Incidentally the round object you mentioned is the oil filter ... my best guess based on your description]. Back to plugs ... So for a v6, the banks are say 60degree apart .. meaning both the sets cant be on the top. Then comes the plumping .. radiator needs to be in the front, so the coolant plumping needs to be in the front. Then the air intake has to move to the firewall side. The plugs for that bank are going to be that far back. So how do the engineers solve that problem ... use long life plugs.

To be fair, the access is difficult, but not impossible. Getting a compression tested in there ... that is another story.

By the way the first American car I worked on was my room-mates crown victoria LTD, back in 80's. I remember climbing in the engine compartment .

Salim

shark13

So I was able to get compression readings for all 6 cylinders. I have tried to look for a diagram that indicates which cylinder is which but have been unable so far. Here are the readings I have received with my own descriptions of the cylinder locations (view from looking at the front of the car).

Rear Left - 182
Rear Center - 172
Rear Right - 181
Front Left - 171
Front Center - 180
Front Right - 191

All in all the look pretty good. There may be some buildup on the last cylinder but my real concern is the oil loss. So......any ideas where the oil is going? Considering the psi readings my guess would be little to no oil is escaping through the pistons or valves. There is little to no oil leaking below (just a black canister located below the oil filter), and no obvious smoke out the back. There does seem to be some condensation out the tail pipe. Also, when I removed the "L" shaped black tube to get access to the rear left and center cylinders I noticed some light whispy smoke/condensation coming out of the bottom hole. Not sure if this is normal. Can it for the most part be all turning into sludge? That would seem like a lot of sludge (roughly 1 quart per 600 miles).

salimshah

#1 is closest to the front passenger door.

Cabin
1 3 5
2 4 6
radiator

How did you manage to get the gauge in for 3 and 5 ... curious minds want to know/learn.

Black canister below the filter --> are you talking about the engine mount [this is active mount with electronic compensation to minimize engine vibration]. You need to make sure it remains dry and clean after filter replacement.

Salim

blueridge

People will call me crazy for saying this....But is the oil being used Mobil 1? If so, I've never been able to keep that stuff in higher mileage vehicles. Having said that, 1qt per 600 miles does seem excessive.

shark13

I was pretty surprised I was able to get the meter in cylinders 1, 3 and 5 as well. Number 5 was easier than 3 because I could access it from the right of the intake. The compression tool I bought had a tube that was rapped in a wire mesh and it gave the tube some strength. The trick was to put the tube down the cavity and align in perfectly in the spark plug hole. Once in the right place I would spin the tube and gauge together. Most of the time it would not be aligned correctly and the threads would not bite, but I would keep trying till I got correct and then twist it tight to get the readings. Any thoughts on where the oil may be going?

hypervish

How's the coolant look?

shark13

The level hasn't been low. Is that what you mean...or would there be a difference in the color?

hypervish

If the engine has a blown head gasket, the coolant would mix in with the oil and the color would change, but the engine oil color would also change. There are kits to test if the head gasket is blown, although I haven't heard of many cases in the RX.