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4jb1 but I keep breaking it

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4jb1 but I keep breaking it

Postby SanchoNZ » Wed Aug 26, 2020 9:08 pm

long time reader, first time poster hopefully I'll get some ideas before going back to it.

I've got a 91 Bighorn w/ 4jb1-tc and the usual things.

It's got a VF10 with a welded waste-gate, 2.5" turbo back exhaust(no mufflers), injectors flowed/cleaned and I replaced the head gasket after it began to over pressurize, it actually made 88kW at the wheels, blistering I know.
I also changed heads, had it skimmed and crack tested/cleaned valves all checked and adjusted etc, usual stuff you do when doing head work.
However it's begun to over-pressurize again. I wasn't running as much boost the first time as I welded the gate shut after I did the HG, so I'm unsure if 28-30psi of boost is actually the issue.

Before I just buy another head gasket and slap it on, perhaps I need to look at something else? could the liners move/fail perhaps and it's causing it to fail relatively early? It worked extremely well for about 2 months before starting to over pressurize again, and it slowly gets worse just like the first time the gasket went though.

perhaps i just need a 12mm pump and jerry rig a big turbo.
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Re: 4jb1 but I keep breaking it

Postby handymanny01 » Wed Aug 26, 2020 9:13 pm

When you say "over pressurise" do you mean the cooling system? Or the boost got out of control? Are you running intercooler?
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Re: 4jb1 but I keep breaking it

Postby SanchoNZ » Wed Aug 26, 2020 9:37 pm

sorry, yes over pressurizing the cooling system, blows water out of the overflow.

Yes, intercooler. EGT's don't go past 500. doesn't get used for towing or carrying loads.
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Re: 4jb1 but I keep breaking it

Postby handymanny01 » Wed Aug 26, 2020 10:27 pm

All sounds fine then,,, I'd be looking at quality of gasket, care of assembly, and (new) quality, torque to yield head bolts as possible causes.. you used new bolts yeah?
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Re: 4jb1 but I keep breaking it

Postby isuzurob » Thu Aug 27, 2020 8:57 am

check the radiator isnt blocked and it has the right thermostat in it, have had the same issue with 2 4jb1t engines
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Re: 4jb1 but I keep breaking it

Postby geeves » Thu Aug 27, 2020 9:06 am

The abuse my old 4jb1 took without complaining was amazing. Has it ever been overheated is always a good question but then again the only time I played with an electric fan I wired it to only work when the alternator was charging. Then killed the alternator in a river just before a 400 meter climb at walking pace. Temp gauge disappeared off the dial no harm. Cracked blocks have happened with these engines but rare. New head bolts and torqued to spec as per Robs suggestion is where I would start but check head and block are flat
Sanding your knuckles before starting work can help. That way you cant skin them
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Re: 4jb1 but I keep breaking it

Postby SanchoNZ » Thu Aug 27, 2020 1:55 pm

Yeah, this is why I didn't think the boost would be the issue.

When I did the head gasket 2-3months ago I

had a spare cylinder head crack tested and planed. however the block was not decked, brand new bolts used at the time from STAParts.

It was just a gasket set that came with the truck as it was supposed to have a blown head gasket but I did 10,000km before that happened lol.

It also has a brand new radiator and thermostat and just running the mech fan, usually runs super cool at like 1/4 on the temp gauge. only ever starts climbing when it pushes enough water out.

It's possible that the block could need looked at next, as who knows what happened to it before I got it.
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Re: 4jb1 but I keep breaking it

Postby geeves » Thu Aug 27, 2020 5:22 pm

"It was just a gasket set that came with the truck as it was supposed to have a blown head gasket but I did 10,000km before that happened lol."
MMMMMMM
I wonder Did it get a ironite or liquid copper type treatment to put off the gasket replacement?
What was the coolant like when you bought it?
Are any of the heater or other hoses brand new?
About the only way you can kill these engines is to run them out of water and the hoses that go from the oil cooler around the back of the engine often get forgotten about until they split wide open
Sanding your knuckles before starting work can help. That way you cant skin them
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Re: 4jb1 but I keep breaking it

Postby SanchoNZ » Thu Aug 27, 2020 6:56 pm

Coolant was absoluuutely disqusting, it had a blown turbo coolant line when i picked it up, and the radiator was incredibly blocked up, like you could look in the cap and see the tubes with rust in them, being the cheap bastard I am i literally filled the engine with simple green and drove it around the block a few... or 50 times until it was at operating temperature on simple green, flushed it out and it didn't seem to overheat again. That's part of the reason I got a new radiator when I put the new head on, it was pretty sad, and now basically everything cooling system wise has been renewed.

Every single hose has subsequently been replaced, inc the heater core because all of that was roooooted.
the oil cooler hoses did split so I had to go tow it from 100km away... luckily before it's ever overheated on me the heater goes stone cold instantly, being winter it's really obvious so whoever's been driving it's stopped.
I could possibly get the block checked, but it's more effort to remove, would almost be better just to get another motor and be ready to pop that in.

as you can tell i paid $1000 for it and it shows. I have changed so many things, all the steering components are new, wheel bearings, bushes, ball joints, knuckle bearing/seals/cv's so I'll probably work this motor out or another one.

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