Rod knocking after pulling trailer up steep hill

While the engine is out, you might consider swapping out any plastic pieces on it that carry coolant. If Toyota has issued a replacement metal version: spring for them.

I'll be interested to hear/see how things look under the valve covers. Should be only a nice golden color and no sludge given the history of the oil changes you mentioned of using synthetic and OEM filters.

 

Take extra care with the valve covers when putting it back together. If they leak, the motor has to come back out to fix

 

Valve covers have a rubber gasket. However, Timing chain cover needs to be sealed with RTV.
Also, need to run a bead of RTV between the head and the cam shafts cradle.

 

This. Coolant pipe between the heads that is known to leak.

 

Pull the hood off! Doing so makes the removal and installation so much easier and better lighting.

 

Curious to see the oil photo you mentioned.

 

Whatever intervals Toyota recommends <shrug>, theoretically they know more about this truck than I do.

 

the engineers definitely do, but the dealership might apply the 10k oil change to everyone despite the fact that regular towing and your usage definitely constitutes the severe oil change interval of 5K.

 

Here's the engine compartment with the motor pulled. The book says to pull the transmission first, but got it out.

 

Now you can see the beginnings of the black crusty oil residue:


Look at the black crusty stuff I scraped off with my fingernail above the main bearing cap:



zoomed in.



up by piston:



gummed up by the oil level sensor:



Under the splash thing under the crank you can see how crusty the oil has become:



This stuff is pretty gross. No idea why it looks burnt though, this engine has never been hot or run wide open since it was new:



Next stop is to pull the bearing caps and look for galling, scarring, discoloration, etc.

So why does regularly changed, not hammered Mobil 1 0-30W do this? Not super cold or hot operating temperatures. pulled trailers with it from time to time, but not super heavy ones.

 

I’m going to let more knowledgable people than me comment on the internals of that engine, but I am curious what makes you think (or how you know) it’s getting mobile one 0W 30 from the dealer yet you aren’t sure what the maintenance intervals were. Because it should be 0W 20, and the dealer is probably using the recommended weight and doesn’t necessarily use mobile one.

 

Should have used Valvoline 0w-20, JK. High heat and moisture = sludge.

 

That didn't happen all at once.
Something has been wrong for a while.
What does the oil pick up look like? Is it plugged up with back particulate?

My following question is not at all to place blame.
How often was the oil changed?

 

Will post pictures as we continue the dissasembly

 

Interesting thread. Might consider a different shop to service your vehicles in the future.

A number of things could have happened. Could have run low on oil. Too long OCI. Some folks have had dealers completely forget to install an oil filter.

Sorry your engine failed at what is a low mileage for Toyota. As others have stated, if you are towing often, definitely need to change oil at 5k miles max.

There's a reason the 4.0 motor has been in the 4runner since 2003. It's a proven motor. I think we will see many more 3rd gen failures as they get higher up in mileage.

 

The only engines that I have seen that looked like that didn't have regular oil changes if ever! And I have pulled down a few engines.

 

Looks like she's been through a few 15,000 mile oil change intervals with some good old fashioned quaker state. And some heat.Thanks for posting the pictures of the engine tear down. Very interested in what you find.

 

Sure you didn’t blow a head gasket going up that hill under load or already had a head leak started? I had that happen on a car years ago, steep hill in the mountains and it was making a sound like a bad spark knock, not a rod knock.

 

Hmmm, almost looks like you were paying for scheduled oil changes and they just simply skipped a few or more and said your all good.

 

op, thanks for posting this. don't forget to replace the PCV valve when putting it back together.

i had one oil change done by the dealer. they told me they use mobil 1. i was really surprised how dark the color was after only 1000 miles. the oil i use is not nearly as dark even at 5000 miles.

i have posted about this before and those that are more knowledgeable mentioned the color of the oil does not matter and is not an indication of the condition or effectiveness of the oil. seems odd to me especially when there is such a noticeable difference in color between two oils, .