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65transport · 02-04-2021, **(Subject: 2016 peterbilt 579 )**

Looking at purchasing a peterbilt 579 with 660k miles and has an isx15 motor. It’s specced out how I want it (listing says 600hp 18spd 270”wb disc brakes air ride front) but it hasn’t been overhauled and sounds like it hasn’t needed much motor work aside from a recent head gasket.. What are some things I should be concerned about or questions to ask the seller. He wants 65k for it and that seems high for that many miles.

Thanks!

tree98 · 02-04-2021, **(Subject: 2016 peterbilt 579 )**

Run away very fast!!!!!!

If it needed a head gasket you can be sure it dropped a liner. You can also be sure it wasn't put back together correctly. It will be nothing but problems, trust me. Look for a different truck unless you're ok with sinking about an additional $25k-$30k into the engine alone.

65transport · 02-04-2021, **(Subject: 2016 peterbilt 579 )**

(02-04-2021 )tree98 Wrote: Run away very fast!!!!!!

If it needed a head gasket you can be sure it dropped a liner. You can also be sure it wasn't put back together correctly. It will be nothing but problems, trust me. Look for a different truck unless you're ok with sinking about an additional $25k-$30k into the engine alone.

That’s the kind of response I was looking for thank you! I appreciate it. I would definitely put the money into the motor it if I could get it bought for the right price. I don’t see him backing off 20-25k though.

Rawze · 02-04-2021, **(Subject: 2016 peterbilt 579 )**

head gaskets do not fail without liner issues... that truck needs an inframe and the block counter-bored, liners raised to at least 0.014" .... the whole nine yards. I don't give it 40k miles and that head gasket will blow a second time.

most likely the thing blew the head gasket... owner got the bad news and put a head gasket on it and is trying to unload it on someone before she blows out again.

the truck is worth maybe 12k - 14k on a good day with it in that shape.

you never mentioned the rear axle ratio... how much you want to bet its geared tall and its been lugged to death its whole life ,... and that is what killed the engine. That or its deleted and has a bad delete program in it... or .. perhaps both.

65transport · 02-04-2021, **(Subject: 2016 peterbilt 579 )**

If that’s the case and it does in fact need an inframe what would that truck be worth?

Rawze · 02-04-2021, **(Subject: 2016 peterbilt 579 )**

(02-04-2021 )65transport Wrote: If that’s the case and it does in fact need an inframe what would that truck be worth?

maybe 18k on a good day + dropping it over at Mr.hags for a reliable million-mile+ type custom inframe to the tune of another $25k or so before it is all said and done.

You'll be into it at about 45-48k at that point + the $5k or so to chase all the neglect of the rest of the truck... totalling about $50 - 53k or so by the time you get it 100% road worthy again.

You also did not mention the rear axle ratio... Another $4700~ish to re-gear it if it has anything much taller than about 3.55's so that the engine isn't lugged to death below 1500 rpm's and it happens all over again. The market is flooded with trucks that are geared wrong, lugged to death in the name of forced-company driver fuel mileage savings specs at the cost of the engine life + that 500k - 600k mileage range where they will loose head gaskets and all sorts of ill-fates ... meaning the engine is done for at that point and these fleets who sell em well know it.

65transport · 02-04-2021, **(Subject: 2016 peterbilt 579 )**

(02-04-2021 )Rawze Wrote:
(02-04-2021 )65transport Wrote: If that’s the case and it does in fact need an inframe what would that truck be worth?

maybe 18k on a good day + dropping it over at Mr.hags for a reliable million-mile+ type custom inframe to the tune of another $25k or so before it is all said and done.

You'll be into it at about 45-48k at that point, but it will be reliable again.

you also did not mention the rear axle ratio... Another $4700~ish to re-gear it if it has anything much taller than about 3.55's so that the engine isn't lugged to death below 1500 rpm's and it happens all over again.

3.36 gears, which is what my current truck has and I don’t mind it but I’d prefer something a little taller. Don’t want to be maxed out at 65-70.

Waterloo · 02-04-2021, **(Subject: 2016 peterbilt 579 )**

(02-04-2021 )65transport Wrote: If that’s the case and it does in fact need an inframe what would that truck be worth?

Like Rawze just posted, $12,000 - $14,000, if really nice maybe as high as what, $16,000?

You will be lucky to get a few weeks out of the truck and I bet that head gasket fails again.

Bottom line, the only reason a head gasket fails in an ISX is due to the liner(s) breaking loose from lugging or abusing the motor. And you are at that magic number mileage wise, the truck is more than likely going to need more work than just the in frame. Figure $30,000 for a basic in frame, possibly a six pack of injectors and fuel pump. I am sure it will need a new crankshaft damper, replace all of the mounts, pulleys, the list can get extensive. And while she is in the shop, how is the clutch? These trucks are designed to make it 500,000 miles and than sold off to a sucker. Many of us here can attest to that. Purchase wisely grasshopper.

Rawze · 02-04-2021, **(Subject: 2016 peterbilt 579 )**

(02-04-2021 )65transport Wrote: 3.36 gears, which is what my current truck has and I don’t mind it but I’d prefer something a little taller. Don’t want to be maxed out at 65-70.

I have 3.55's and I can drive 90+ mph if I wanted to. your statement does not make much sense.
ref: http://rawze.com/forums/showthread.php?t...3#pid17353