Stressed about potential 03 v6 head gasket issues

I was not aware of the head gasket issue in the 03-late 05 v6 (4th gen) 4runners before I purchased mine a few years ago. It has a little over 250k in mileage.

When I bought it, I noticed the PO had taken it to a shop that put green coolant in it. I am a Toyota guy, so I am aware that is a big no-no (I pressed the PO as to why, and couldn't get a straight answer). PO had pretty good maintenance records, with *most* work being done at the stealership. So, I proceeded to do everything I could to determine if there was a leak (other than a leak down test, because I wasn't as wise as I am now). I was mainly paranoid, because in addition to the wrong coolant being used, there was a coolant leak whose location I couldn't immediately determine. Checked hoses, ran dye, flushed the system, only to find the leak on the top of the radiator UNDER THE TRIM, right in front of my stupid face. My caveman brain was like "wrong coolant + leak = worst possible scenario". Keep in mind, I had just learned, right after purchasing the new vehicle, about the head gasket being an issue in these vehicles, so that didn't help the paranoia. Would have been pulling my hair out if I had any.

Fast forward a few more years, and its been fine as far as I can tell. However, a couple months ago I have noticed a long/rough start, not a noticeably rough idle though. Seems to happen randomly, but more frequently from a cold start. The CEL will kick on and go away sometimes without me doing anything. The code is P0430 - Catalyst System Efficiency Below threshold Bank 2. Don't know if its related to the long/rough start or not. Just bought the corresponding O2 sensor to see if that does the trick. Seems to idle fine in general, but about a year ago it would randomly have a rough idle problem in the middle of driving when pulled up to a stop light even when the car is warm. Thought that was related to some battery wiring, as that's went away for the most part, but literally just noticed today that it was idling a little rough, but this was after the car had been warmed up (this is likely extraneous info). She's due for some new spark plugs as well, so I ordered some though the stealership.

Anywhoozers, I have a little more time/money now, and would like to finally do the upgrades I've been always wanting, but I don't want to put money into her just to have the flimsy head gasket go and warp/crack anything (I'd really rather not go through the whole block repair thing if something goes south). I have always thought it was fine because I haven't noticed any of the common head gasket failure symptoms, but I realized recently that I've only been looking out for symptoms of a *major* head gasket failure, and didn't take into account that a small leak could be occurring without me noticing. (I have a borescope to check for coolant when I do the plugs, just as a precaution).

There is also some foamy gunk under the oil cap almost every time I change the oil, which freaked me out, but after some research I determined its because I'm in Utah and it could just be condensation build up? She also burns oil like a son (daughter?) of a gun, but that's probably the mileage? What symptoms should I be looking for? Coolant level seems to stay fairly steady. I notice a pretty small coolant loss over a few months, haven't quantified that though. Oil isn't milky when changed either. Also haven't noticed white smoke out the tailpipe, besides when its cold out, which I'm sure is just normal condensation.

I'm gonna take it to a trusted shop and have them do some proper testing. That *would* be a leak down test, right? What other tests should I have them perform? Any tests you'd recommend doing just in general to ensure that the vehicle is in the best condition possible, so I don't end up wasting time/money (ie - valve related tests/timing chain/etc.)?

Since I wanna keep her, would I be a knucklehead for just pre-emptively paying for the newer thicker head gasket, whether or not a leak is found?

TF would you guys do? I am a dingus and cant wrap my bald head around this whole thing.

 

I can tell you what I wouldn't do.

Mod a 22 year old 4Runner with 250k+ on it. Especially if you are paranoid about a head gasket just imagine how much aftermarket shit can break.

Take it to the shop make sure shes good to go and keep driving is what I would do.

 

Coolant pressure test should answer the question

 

You have an intermittant missfire and it is cooking your CAT - that's why you are getting the P0430. It is marginal at this point and the code is going in and out. Lots of more likely reasons for this besides a bad head gasket having to do with spark, fuel and air. Troubleshoot those possible issues first.

 

You're burning oil and cooking the cat, hence the P0430. Head gasket is the lesser of your concerns. Don't bother sinking more money into this engine. Drop in a lower mile used engine, newer the better.

 

What concerns are you alluding to that would require an engine swap? Worn rings and seals?

 

^That or cylinder wall scoring. There may be other expenses waiting in the future, like rear main seal leak.

 

Really, I would suggest you try to fix the missfire issue first. It could be relatively cheap and easy then see where you go. No need to rip the engine out yet. One step at a time....