Reviving a 270K mile Highlander Hybrid
 

Should I install new head gaskets on a lower mileage junkyard engine (90,000 miles) prior to installing it in the car? I already have (felpro) gaskets but I'd need to order new head bolts (~$45) and perhaps send off the heads to be machined ($???).

Long story:
I just bought a smooth running, rust-free 270,000 mile 2007 AWD Highlander Hybrid with a blown head gasket for $3,000 with the initial plan of on replacing the head gaskets myself ($250), along with water pump, timing belt, and the normally hard-to-reach rear bank coils & O2 sensor ($600). My goal is to get another 5 years & 100k miles out of it relatively inexpensively while the crazy car market settles...

But as I was compiling a parts list, I decided to swing by the shop that serviced it for the last decade to see if any of the major items had been replaced recently. There I learned that the head gasket had been blown for ~8,000 miles and the previous owner limped it along with Blue Devil. Well maintained 3MZ-FE engines have been known to go 400K miles, but probably not when coolant has potentially been contaminating oil and scouring bearings (not to mention potential overheating might have warped the aluminum heads & block).

So I bought a ~90,000 mile junkyard engine ($850). From running the VIN of the salvaged car I've learned that it was wrecked (rear ended) in November 2017 so while it does have relatively low mileage, it has been sitting for 4 1/2 years.

I ordered a fel-pro overhaul gasket kit thinking I'd just replace all the external-ish seals & gaskets, but I'm kind of regretting it now that I'm considering preventatively replacing the head gaskets too (having heard mixed reviews on felpro HGs, I've always used Toyota, Mahle, or HKS/GReddy head gaskets in the past). Unless I want to pay dealer prices, it would take a week or more to get better quality gaskets. And I wonder whether age is a bigger factor than mileage in breaking down head gasket coatings. The 3MZ-FE isn't particularly known for blowing head gaskets (unlike the 3rd gen Prius, 80's Supras, & 90's 4runners).

I don't want to get too crazy spending money "while I'm in there" because without a cherry picker & engine stand it already makes more sense to pay a shop to do the 20-hour engine swap ($1,500) bringing my total investment to ~$6,000. And that's with me replacing the gaskets, water pump, tensioner, idler, and timing belt first...

Clean title 150,000 mile 1st gen AWD hihy's are going for $9,000-11,000 here so I still have some room for unseen expenses without getting under water, but it is still on the original:

• hybrid battery ($3,400 to replace with new cells & it almost surely will be going bad in the next 5 years)
• brake actuator/pump ($2,000 to replace with new/updated Toyota parts and there is probably a 50% chance it goes bad in the next 5 years)
• inverter/converter ($750 used, $4,800 rebuilt - probably 20% chance it goes bad in the next 5 years)

$6,000 + $3400 + 50% of $2000 + 20% of $2000 = $10,800. If I sink $11,000 into "capital improvements" over the next 100,000 miles and the car is worth zero at the end, that would essentially be 11 cents per mile depreciation which is still really good. At $5/gal and 25 mpg, gas would cost around 20 cents per mile. At ~$800/year, registration and insurance would be 4 cents. That would leave 23.5 cents per mile for maintenance & repairs to equal the IRS' standard mileage rate - nearly $5,000/year - which I can't imagine spending.

So while I'm wanting to draw the line somewhere to stop the spending, it is still a pretty good gamble that this will be a reasonably economical car - especially for a 7-passenger AWD SUV...

Thoughts? Leave well enough alone? Replace the head gaskets with felpro? Order Mahle head gaskets and use those?

Xist, is that you?

My understanding is that when a head gasket goes, one needs to figure out why. That means figuring out of the head warped and machining accordingly.

I'm far from qualified to answer any of those questions, but in my view one either knows what is entailed and can remedy the issue with reasonable cost/effort, or one is in over their (unmachined) head.

If I understand this, you have an engine with 90k miles that currently runs. If it is showing signs of fluid leakage, replace those gaskets, otherwise you may open a can of worms fiddling with stuff that isn't broken... My wrecking yard guarantees their parts for a while, labor is your dime.

Failure probability is a mix of factors with the long MTBF averaging out the very short early failures. Your stuff could outlive you or be struck by lightening today. That event would be random and definitely unpredictable.

The 270K engine currently runs quite well aside from burning coolant. The previous owner says sometimes it stumbles when first starting or when the engine restarts after being in EV-mode (a common symptom among blown head gasket priuses), but I experienced none of that on my test drive & 25-mile drive home. Coolant temps never exceeded 209 on the scangauge, but it was downhill on a very mild day. Its head gasket likely failed due to a severe misfire that went ignored too long. A new coil solved the misfire 8,000 miles ago, but the damage to the head gasket was already done. Blue Devil head gasket sealant was installed which limited the head gasket symptoms for a while, but coolant loss came back.

The 90K mile junkard engine presumably ran when the donor car was rear ended nearly 5 years ago. Standard practice is to drain all fluids once it gets to a salvage yard to be parted out so I don't know that it doesn't leak today when running. Visually it looks like the valve cover gaskets were weeping a bit, but that's almost universal on high mileage 3MZ engines. A little bit of clean-looking SLL coolant sloshed out on the drive home, so it is unlikely the head gaskets were blown.

The 3MZ-FE engine is an interference engine with timing belts due every ~90K so it'll get replaced. The water pump, tensioner, idler are right there and particularly easy to replace while the engine is out of the car. So are the crank and cam seals - along with the valve cover gaskets. Valve lash is supposed to be checked every ~70K, but with solid cam-over-shims this service is usually ignored. I'll check it while I'm in there but would be surprised if any are out of the generous +/- 0.005 tolerance.

The oil pan is a 2-piece design that I think uses form-in-place gasket from the factory. It and the head gaskets I'd planned on leaving alone, but am now debating replacing just due to age.

It's never just the head gasket on an aluminum engine.
It's usually a warped head and possibly the block too.
Assuming coolant has leaked into those cylinders for thousands of miles they are likely badly tapered. The old engine is a boat anchor.
If you pull the heads off the newer engine you will be able to see how low miles it really is.

I 2nd the vote of "don't fix it if it isn't broke". I'd replace the wear items that are easy to access while out then install the 90k mile engine. Head gaskets though, are not a wear item.

Burning coolant is a matter of concern, but if it's otherwise OK I'd eventually wait before doing something like replacing a head gasket. Unless an engine overhaul is on its way, I'd not mess with the head gasket too...

The AISIN timing belt kit finally arrived today and I'm all excited to swap out the belt. Its after dark so I start shining a light to closely inspect the various existing seals for potential leaks to mentally prepare myself for tomorrow's work when I notice one of the exhaust valves is discolored around its guide. Hmm, that's odd for 90,000 miles...

So I look more closely at things and notice the engine has a VIN plate which I compare against the VIN on my paperwork for the 90,000 mile engine. They're not even close (so not a transcription error). I run this vin and it is also from a 2007 highlander hybrid, but it was auctioned in November 2021 with 168,000 miles. The VIN on the paperwork was from a 2007 highlander hybrid salvaged in November 2017 with 90,000 miles. WTF!!!

When I first called the shop asking if they had a highlander hybrid engine, they offered a 168,000 mile engine for $500. I told them I was looking for under 100,000 miles, did they have anything else? I heard him typing for a bit and he said they had a 90,000 mile engine in "the warehouse" and would need 30 minutes to bring it to the yard. He wanted $830 for it. So they sold me the original 168,000 mile engine for an extra $330 with a lower mile vin on the paperwork...

So now I start looking up reviews of this place (obviously belatedly) and they do have mostly 5 star reviews, but also more than a few 1 star complaints of fraud and bait & switch. It looks like when they are caught lying (er "selling the wrong parts") they offer in store credit. That won't work for me.

Hopefully I'm blowing things out of proportion and they just made an honest mistake and have the correct engine on hand. Or issue a refund. Heck, at this point I'd accept a substitute engine with <120,000 miles. But I'm not going to float them $800+ when I only buy something of that magnitude once a decade from a junkyard...

Go in person with ALL documentation and explain the situation. They'll either understand their mistake and make it right or you'll see their true colors. Possible small claims court suit?

Then again, there is some responsibility on the buyer to verify... not saying I've never made mistakes.

The good news is even a 168k mile engine that has been taken care of should have another 168k miles left in it.

You did more homework than most would. I'm in favor of shops like that being severely penalized for perpetuating their fraud. Go get 'em tiger!

On your original question, engines with aluminum blocks rarely have iron girdles cast into them. The head bolt threads are pulling against aluminum threads in the block. I learned a bunch about this when a friend's Rav4 blew a head gasket, and again when another friend's Cadillac Northstar popped one.

If you're willing, I recommend as a preventative measure to pull the head, use thread inserts in the block (I forget which brand we used, but it was not Helicoil), and put it back together with a Toyota head gasket (not FelPro). I would do this even on a 68k engine, just because statistically it will go eventually otherwise. Easier with the engine out than installed. If you don't use the inserts, I wouldn't bother replacing the head gasket. It isn't the gasket that is the weak link.