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?