Head Gasket??

[Donny1]

I'm working on a 2000, 3.4l.

Originally pulled the trans to do a rear main seal then decided to do the oil pan gasket/sealant as well while I was right there. When I drained the oil a few ounces of green coolant came out first and there is evidence of some mixing in the pan and on the pickup screen.

I am a retired tech but never had experience repairing anything beyond Timing Belt/Water Pump jobs on these motors. It runs perfectly but has 270k miles so I am leery of doing head gaskets with this high mileage. Also curious if there are any other areas like the timing cover where it can be mixing.

I'm thinking it's motor time, your experience and thoughts are much appreciated!

 

[JWaldz]

I mean, you found the evidence. It's up to you how you want to proceed.
I was in the same boat, but maybe little further along. Running a little hot sometimes, adding some coolant occasionally, intermittent rough morning starts (later on), P30# code, etc..
The damage was already done, and I got another 70k+ hard (offroading, cross state trips, etc) miles out of it.
Did maintenance as normal, knew it's limits, and kept chugging along.
Ran it until it didn't run anymore (literally lost all compression and limped it 5-10mph like 5 miles from home lol).
The 3.4 is resilient and tough.

There's a lot of information out there regarding whether to rebuild or replace, and there are pros and cons of each.
I'd definitely do some research on it and decide what works best for you.

If you're not a stickler with "keeping the same engine my 4Runner came with" and have the up front funds to buy a used engine, I prefer this route.
Get one from a reputable source and have record of it's mileage.
If you can, run tests ahead of time like compression, borescope cylinders, and check other signs of ware.
Once you find one, do all the top end maintenance (that's needed) with the motor out, it's much easier.
Take care of other engine bay maintenance with the engine out.
Drop it in and be done.
(this is what I did nearly 80k miles ago)

Rebuild wise, you may have already caused some harm to internal components. Chasing, replacing, and fixing these during a rebuild can start to add up. Not only in $ but your sanity.
With 270k miles you may start replacing things that make the engine just work. Similar to how they say don't flush a perfectly good transmission, bc it's already built up it's own internal tolerances.
I also feel like rebuilds tend to cost more in the end.

Swapping the engine isn't a hard task, it's a weekends amount of work with a helping set of hands (which I strongly suggest).

Good luck with whatever you decide!

 

[T4R2014]

I installed a JDM, kept the original. No way in hell I was going to get the old engine rebuilt quick enough nor to the standard of the FSM (the only way it'll actually last) within the cost or timeframe I was working with.

 

[Donny1]

I installed a JDM, kept the original. No way in hell I was going to get the old engine rebuilt quick enough nor to the standard of the FSM (the only way it'll actually last) within the cost or timeframe I was working with.

What is the "FSM" standard?

 

[T4R2014]

What is the "FSM" standard?

Factory Service Manual, so no hand torquing all the critical fasteners and verifying clearances. Things that can't be rushed and must be done in a clean environment. It's hard to get away with doing that stuff on a modern engine but the average shop thinks new stuff still goes together like an all cast iron 350 small block. A 5VZ is not as forgiving.

 

[espance]

I'm working on a 2000, 3.4l.

Originally pulled the trans to do a rear main seal then decided to do the oil pan gasket/sealant as well while I was right there. When I drained the oil a few ounces of green coolant came out first and there is evidence of some mixing in the pan and on the pickup screen.

I am a retired tech but never had experience repairing anything beyond Timing Belt/Water Pump jobs on these motors. It runs perfectly but has 270k miles so I am leery of doing head gaskets with this high mileage. Also curious if there are any other areas like the timing cover where it can be mixing.

I'm thinking it's motor time, your experience and thoughts are much appreciated!

For what it's worth: If it's running fine at 270k miles, changing the headgasket might buy you another 100k+ miles out of it, especially if it was well taken care of! 5vfes last forever, as you probably know. My engine has 300k miles on it, and definitely wasn't taken care of the way it should've been before I had it.


I changed the head gaskets on my 4Runner, and it was straightforward. Granted, I have a rust free 4Runner from the desert. The most I had done on a vehicle before this was an oil change. I bought the 4Runner as a project vehicle to teach myself how to work on engines... If you're a retired tech, I doubt you'd have any issues. I followed Timmy the Toolman's video series to help myself feel comfortable doing it.

https://www.youtube.com/watch?si=NMHGNBeZRnbobcvq&v=iSFpwnCuBDk&feature=youtu.be

 

[JohnMc]

When my wife did the HG's on her 96 at jsut a bit over 300K we got a good look at the bores, and by the looks, they've got another 300K in them. They had crosshatching on 95% of the bore, just a little slick area at the top of the bore on the thrust side. Put it back together with the late style MLS gaskets and a new TB/WP and it's been perfect for about 40K since.

Another possibility besides a headgasket is the oil cooler - they can develop internal leaks and mix coolant and oil. Try a little more diagnosing before settling on a bad HG. Pull all 6 plugs and look for signs of coolant on any of them. Try a leakdown test and see if any cylinder is leaking into the cooling system.

IMO it's easier to put HG's on a motor than to swap a motor (and I'm not shy about pulling motors either, I did an LS swap on my old Volvo wagon!). If you know the maintenance history and it's been well maintained most of it's life then it's really not worn out.