Some oil on spark plug threads

james250 · August 11, 2017

I changed my IS250 spark plugs today. It was last done by Lexus and when I went to unscrew them they came seemed rather loose. didnt require much force to unscrew them. The spark plugs were generally in good condition except I noticed that there is some residue of oil on a few of them. Mainly on the thread of the spark plugs some had quite a bit some didnt have much. Some had smear of the oil on the coil too so i cleaned the coils up.

Question is, how comes there is oil there could it be because the spark plugs were not tight enough? The new spark plugs I tightened to about 19nm and the new plugs also come with new metal crush washers. Is there any other gaskets or seals in there responsible for sealing the oil from entering the spark plugs area?

chr15gb · August 11, 2017

Are you sure it is oil and not residue from some tired old thread grease?

If the tips of the plugs, the actual element part, is clean, there isn't anything to worry about, if the elements are oily, then there is a problem.

I put copper grease on my threads when fitting me new plugs.
The coils on mine were dirty, I also thought they looked oily but the only way out of the cylinder is via the crush washers.
The top of the coil has an orange seal

james250 · August 11, 2017

Thanks for your reply Chris. There is no oil on the actual tip/element part. Most of the spark plugs have oil residue just on the threads. One has a bit more and seems to have gone over to the white part too but also no oil whatsoever on the tip. I am hoping it's just a case of lexus not tightening the spark plug correctly. I am tightening them to approx 19nm, lexus said the spec to tighten them to is 18nm so just to be safe i've done 19nm. I've attached a few pics of some of the plugs

ColinBarber · August 11, 2017

highly unlikely to be oil coming up from the cylinders otherwise you would have poor engine compression as air would find its way out easier than oil.

Either water/oil/engine cleaner has made its way passed the coil packs or you have poor seals on the inside of the cam covers allowing oil to drop down the plug tubes to sit on top of the plugs.

johnatg · August 11, 2017

The cam cover gaskets may be leaking, which leads to oil in the plug recesses and it gets on the threads as you extract the plugs.

Lexus spec for plug tightening is 25 nm or 18 ftlbs.

james250 · August 12, 2017

Thanks. I tightened to 25nm now. I just did the second part of the sparks which is the passenger side involving removing the inlet manifold. Last time Lexus changed the sparks it seems the left out the bolt right at the back and also broke a tab on the connector. I used cable tie to just keep it in place and prevent accidentally coming out.

When I removed the inlet manifold there was a bit of old oil gunk which I cleaned up and replaced the gaskets. But most worryingly I noticed quite a it of oil gunk in the small recesses. It's almost like there a perfect recesses for oil to sit in. But question is where is this oil coming from. The inlet part of the v engine seems to be rather greasy and has oil residue. I don't have any oil under the car or anything. I've attached a pic of that side to show where I found oil. I cleaned most of it off before remembering to take a pic.

Have I got a major leak to worry about?

jackcramerr · August 12, 2017

I have seen oil on plugs of another car. I thought it is rocker cover gasket and replaced it twice with no joy. Still oil on threads.

Do this, start the car, carefully undo the oil fill hole with a rag. Does air come out of it?

james250 · February 21, 2020

Sorry to revive this thread. It's been over two years since I did my spark plug change and when I noticed the oil on the top of the spark plugs. I also noticed oil residue around the cover like I mentioned then. I cleaned it off back then but it's dirty again now. But it's not losing a lot of oil but the oil is making the engine block rather greasy and oily. And seems to be on both sides. I've watched a few videos on the cam cover and it seems that the came cover has one big gasket around it's parameter and there is also some sort of seal that seals the cover from the spark plug tube. I assume this gasket prevents oil from inside the cam cover from making it's way up into the spark plug tube. But if it's not sealed then oil makes it's way up into the tube. Can this oil end up on the tip of the spark plug or does the metal gasket on the spark plug prevent this? The oil I was seeing on my old plugs was all on the rear side and it seemed like oil that i was getting on the plug as I extracted the spark plug.

Watching the videos on replacing these cam cover gaskets seems like hours and hours of work. I did the spark plug and removed the intake manifold which was a lot of work and this is more than that. Are there risks of running the car like this without fixing this? If it has to be fixed, can it wait? considering it's probably been like this for a good 4 or 5 years now.

jackcramerr · February 23, 2020

If you can perform the test I suggest please I might be able to give a hint then.

james250 · February 23, 2020

9 hours ago, jackcramerr said:

If you can perform the test I suggest please I might be able to give a hint then.

So you mean start the car and unscrew the oil filling cap? Isn't that going to cause oil to squirt out and make a mess? Is it safe to open the oil cap when car is running?

Beamish · February 23, 2020

With ref to the torque figure given earlier in this thread.

The diagram below refers to my 2009 IS250 and shows a figure of 18Nm. for the spark plugs.

Dec.

jackcramerr · February 23, 2020

3 hours ago, james250 said:

So you mean start the car and unscrew the oil filling cap? Isn't that going to cause oil to squirt out and make a mess? Is it safe to open the oil cap when car is running?

It should not. If it does that then it will make sense why gasket had failed.

In fact, it should be sucking in air. Have a rag at hand if things becomes messy and obeserve common sense.

johnatg · February 23, 2020

I don't think there's anything to worry about in the medium term. The oil will be coming from the rocker cover gasket - fix it when you can but not really urgent. The oil on the plugs comes from there - as you unscrew the plugs they effectively pass through an oil bath and it will seep down the block and into the Vee.

I can tell you that if you remove the oil cap, oil will come out if the engine is running - I once accidentally left the cap off on another car - it was years ago. After a short drive there was a hell of a mess in the engine room! A little bit of oil goes a long way.

Don't overtighten spark plugs - 18ft lbs is perfectly adequate.

Beamish · February 23, 2020

1 hour ago, johnatg said:

Don't overtighten spark plugs - 18ft lbs is perfectly adequate.

As per my post above it would appear that the correct torque figure is 18Nm or 13ft-lbs. 18ft-lbs may risk pulling the threads on the aluminium head.

From Alldata.com:

4GR-FSE ENGINE CONTROL: IGNITION COIL AND SPARK PLUG: INSTALLATION

INSTALL SPARK PLUG

(a)

Using a spark plug wrench, install the 6 spark plugs.

Torque : 18 Nm (184 kgf-cm, 13 ft-lbf)

Dec.

ColinBarber · February 23, 2020

Alldata is wrong. The official torque specification from Toyota for the plugs is 25 Nm (18 ft lbf).

johnatg · February 23, 2020

Well there's a thing. So I looked in my workshop manual. Would you believe - somewhere in the Workshop manual, I found the diagram as posted by Declan above (can't just find it again) showing the torque as 18Nm, 13ft lbs. But everywhere else in the manual, eg under Engine Reassembly and Ignition System on-vehicle Inspection, it says 25Nm, 18ftlbs.

Can't help thinking that someone, somewhere has done a bit of double take.

See screenshot of one bit here:

:

13ft lbs just isn't tight enough - I doubt it would even crush the sealing washer enough.- hell, you can easily get to 15ftlbs just by gripping a socket drive extension and turning it by hand, not with a ratchet or breaker bar. Even 18ftlbs doesn't feel very tight.

The correct figure is 18ft lbs - it's pretty universal figure for 16mm spark plugs in ally cylinder heads.

jackcramerr · February 23, 2020

Guys on idle there should be no air blowing out of the oil fill cap. If you accelerate then that is a differernt story. But on idle there should be vaccum.

If air is blowing out then there is engine issue. This is the first quick check mechanics do.

james250 · February 23, 2020

@jackcramerr so you are suggesting I start the car and immediately while having a rag covering the oil filler lid, remove the lid and see if i can feel pressure coming up? but surely if something feels like air coming out it will be pressure which isnt that normal for pressure to build up inside? isn't that the purpose of the PCV to release crankcase pressure? What exactly am I looking for here? The main thing I see is seeping oil on the passenger side around the edges of the cam cover. I visually inspected from underneath the car and when I look through the passenger side gap between the transmission bell housing I can see oil staining just above the Air Fuel Ratio sensor on the engine block. The other side is super clean, the silver metal on the block looks like brand new silver colour still. So i'm thinking maybe it's weeping oil down the cam cover seal and it's making it's way down. But it isn't enough for oil to drip down and make any marks on the ground.

jackcramerr · February 23, 2020

James250

It takes 30 seconds to do the test. What harm is there?

Ok so let me tell you my experince with a non lexus car. I noticed the car was consuming oil. So I took the plugs out to do compression test. I noticed oil one one or maybe two plus. Clean golden oil. On threads. So I continued with compression test and results were good. So I thought it can be oil from rocker cover gasket so I replaced that. A month later I noticed oil dropping again so I pulled the plugs. Oil again there. I bought oe gaskets this time and made sure I follow specs and torques. 2 months later, oil again. So I started the car and remove the oil fill cap when car was idle rpm. Air was blowing out from the hole.

I didn't gave up there. I removed the cover and used sealant and over tightented the bolts. Still no joy.

So I thought of replacing PCV. I stripped down header, injectors , a lof of stuff to get to PCV. Spent some money for oe gaskets etc. PCV was fine to my disappointment but I still replaced it. Needless to say, the isssue was not resolved.

I then thought it could be valves or maybe oil scrappers. But that means engine overhaul. I left it there.

I took it to a mechanic and told him my efforts. He opened the oil fill cap and said, scrap the car when it dies. Your catalistc convertor will go out next. He was right. Cat took a hit as emissions grew. Car's been scrapped. They end.

jackcramerr · February 23, 2020

Btw I did comparison test with is250. And is250 instead of blowing air out, it sucks it in.

johnatg · February 24, 2020

Let's not get too carried away here.

Any engine with worn bores/pistons/rings will pressurize the crankcase and blow oil out of the most well sealed cam cover. But a reasonably well maintained (frequent enough oil changes) Lexus will not do that, at least until starship-type mileages have passed. Oil on the plug threads is just from oil sitting in the spark plug recesses and arrives on the threads as you withdraw the plugs - there is no way that oil can come from the combustion chambers.

Most modern engines use a neoprene cam cover gasket which fits in to a groove in the cam cover. Although nice and soft when new these gaskets harden and become brittle with heat and age - it's quite instructive to compare a new gasket with one that has done 50K miles or so. Eventually oil will seep out and end up in the plug recesses, in the vee and down the sides of the block.

James - you need a new cam cover gaskets, plug tube gaskets and various other seals - see attached pic (just right hand side shown) - oh, and you need to tighten your spark plugs to 25Nm/18ftlbs.- see the pic.