Sludge or Normal?

[Brique]

So I changed my plugs today and noticed that inside the plug hole it was pretty grimy and nasty-looking. I'm still a novice, but I was wondering if that's a sign of engine sludge or if it's normal for it to look like that. When I was changing the plugs in my wife's mazda 3 a few weeks ago, it looked clean as a whistle in her engine.

Picture below. It's big, so you can see what I'm talking about.

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[02SE]

What you are seeing is the top of the piston, which appears to have typical carbon build up on it. Burning pump gasoline, the tops of the pistons will always have a bit of carbon build up after many years, and tens of thousands of miles.

I see nothing to be too worried about.

One way to minimize the build up, is to use a Top Tier gasoline like Chevron, Shell, etc. A bottle of Chevron Techron Concentrate, (which you put in the gas tank) does a good job of gradually cleaning carbon deposits.


If it gives you peace of mind, I'm a former ASE Master Tech, and still work on racing engines to this day.

 

[Brique]

Awesome, thanks for the reply. I just bought the truck in October and over the past few weeks I've been alternating between running a tank of normal gas and then a tank with a bottle of Techron in preparation for the new plugs. I've also replaced the fuel filter. The engine's been running pretty well, so I would have been a little surprised if there was a problem, but at the same time, these 3rd gen engines are such troopers that I imagine they can put up with a lot of abuse and still run well.

Anyway, thanks for putting my mind at ease.

 

[nissanh]

I've been using Chevron or Shell all the time and it is time to see the condition of the pistons.

Sludge buildup is usually where engine oil is circulated. So open the engine oil cap and inspect inside for sludge.

 

[Bt08231]

It's very common for that seal to leak so ive been told by a toyota tech, that's probably what your seeing

 

[02SE]

It's very common for that seal to leak so ive been told by a toyota tech, that's probably what your seeing

The only thing that could be considered grimy and nasty looking after removing the spark plug, as the OP described, is the top of the piston. In a port injection engine burning pump gasoline, some carbon build up on the piston dome is unavoidable. If it were in fact spotless, then he'd have real problems. As that would indicate coolant getting into the combustion chamber, and effectively steam cleaning the piston dome.

Anyway, in regard to the O-ring seal that seals the valve cover to the spark plug tube. It is not leaking in that pic. There are some signs of very slight seepage past the O-ring over the years, but it's nothing to worry about at this point.

If it were leaking to the point where something needed to be done, the spark plug tube would have motor oil in it, and/or motor oil would be running down the outside of the valve cover. I see no signs of motor oil in the spark plug tube, or running down the outside of the valve cover.

There is some slight motor oil seepage around the visible upper valve cover bolt, but again it's not bad. Very gently snugging down those valve cover bolts, would likely take care of any seepage. At any rate, it is typical for the 5VZ-FE at that age. Even the newest 3rd gen 4Runner is now 12 years old.

 

[Brique]

There was some rust-colored dusty stuff in the tube with the old plug before I pulled the old plug out. I made sure to clear that out before dislodging the old plugs. The plugs had a small amount of the same brown dry crap in the threads but there was no sign of oil getting onto or past the plugs.

With regard to the valve cover seepage, I'm pretty sure the valve cover gaskets need replacement. I'm planning to have that done when I have the timing belt and water pump replaced in another 10-20k miles. I'd love to do it myself, but that's a pretty big job beyond my skill level right now.

Thanks again for your help. This truck is my new hobby and my "learner" vehicle for auto maintenance and repair. When I got the truck in October I knew how to change the oil and that was it. With the help of write-ups on this and similar forums I've been able to do a lot with this truck that I wouldn't have even considered a year ago. That said, I still have a ton to learn, and your input on topics like this are helping me understand things a lot more.

 

[eddiebx]

There was some rust-colored dusty stuff in the tube with the old plug before I pulled the old plug out. I made sure to clear that out before dislodging the old plugs. The plugs had a small amount of the same brown dry crap in the threads but there was no sign of oil getting onto or past the plugs.

With regard to the valve cover seepage, I'm pretty sure the valve cover gaskets need replacement. I'm planning to have that done when I have the timing belt and water pump replaced in another 10-20k miles. I'd love to do it myself, but that's a pretty big job beyond my skill level right now.

Thanks again for your help. This truck is my new hobby and my "learner" vehicle for auto maintenance and repair. When I got the truck in October I knew how to change the oil and that was it. With the help of write-ups on this and similar forums I've been able to do a lot with this truck that I wouldn't have even considered a year ago. That said, I still have a ton to learn, and your input on topics like this are helping me understand things a lot more.

No need to be alarmed at the rusty colored "dust', not exactly sure where it comes from, but I see it all the time on older higher mileage spark plug boots. I think it's just moisture or something in combination with the heat drawing it out of the rubber? No big though IMO. Good sign that there's no oil on the plugs!

In case you're curious, best time to check to see if you have any significant sludge build up is when you have the valve covers off and replacing the gasket. Maybe you can read up and get enough courage to DIY, then you're really get to inspect things thoroughly

We all start somewhere, don't be scared to get down and dirty, it's the best way to learn!

 

[Brique]

Man, it sure would be nice to tackle it myself. The problem i see is the rabbit hole of everything that needs to be done. Timing belt, water pump, valve cover gaskets, drive belts... It's a bit of a leap to go from plugs to a project of that size. Maybe in a year or so when it's due, I'll have the gumption to take that on. Of course, this truck is the daily driver, so any screw ups could really cause some inconvinience...

Hmm...