Hopefully I'll be getting a replacement non-rod-knocking 4.3 Vortec for the Blazer this weekend, and want to do I what I can to ensure that the replacement engine doesn't suffer any premature failures beyond those that were inevitable. So I want to take care of all the normal maintenance items on it before firing it back up for the first time.
Here's what I've come up with so far:
- Drain the coolant completely, flush, and use a flush/cleaner product on it before flushing it out completely and refilling with newer universal coolant
- Drain and flush the oil- what's the best way to do this? Something like Seafoam for a short while before changing the oil & filter again
- Replace thermostat. Not guaranteed to be necessary, but it's cheap and may as well do it while the coolant is drained anyway.
- New spark plugs. If the wires look good, is it really necessary to change them too?
- Any gaskets that are touched- should only be on the exhaust as I intend to keep the donor engine as together as possible, but may also pull the oil pan to inspect the bearings, crank, and rods for visible issues before putting the engine into the car where doing so would be impossible
- New serpentine belt.
- Check air filter- initially it looks like it was replaced not too long ago though
Things I'm not sure of either if they'd really be necessary/smart or of exactly how to do:
- Replace idler pulley and/or tensioner- I just don't know enough about these engines to know if they're a common problem. On the up-side, they're fairly easy to get to so if it sounds like one is having issues I can easily replace it once everything is back together.
- Drain/flush the transmission- again, not sure how crucial this would be
- Seafoam the whole engine- likely to be worth it, or see how it does without it first?
Is there anything I've missed? Are there particular things/fixes I should be looking into specific to this engine? Thanks!
Replace the intake gaskets, they seem to fail more than any other gasket on those. Easier with the engine out. Don't put Dexcool back, just run extended life green coolant.
I would just change the oil and run it, then change it again. Not a big fan of putting cleaners in oil. If you pull the oil pan and intake, you should be able to clean most of any crud out then. Check the oil pickup screen for any debris as well.
Finally remembered the other thing to ask about: Water pump. Should I just replace it, or see how it goes if it spins smoothly and freely?
I'm of two minds on junkyard engines -- either do everything while it's out, or do nothing until you know what you have.
Rear main seal and front seal on the trans. You dont want to find out they leak after its in.
Do those have an engine oil cooler? I know they have a remote mount filter. I would flush that stuff while the engine is out to clean out all the metal the old engine left behind.
I wouldnt bother with the water pump if it feels good. They arent bad to do in the vehicle
oil cooler lines are usually leaking.
the middle spark plug on the drivers side is a huge bastard. replace with something very long lived.
last night after work, i was prepping my junkyard 4.3 to go into my 2wheel drive blazer... i had to swap the oil pan and pump, so i did that... then i got to looking at the intake gaskets because they are known to go bad.. the one corner looked a little "funny", so i popped the intake off and saw this:
3 of the 4 corners looked more or less like this..
yes, Dexcool is awesome...
The radiator has an engine oil cooler, it taps off from the remote mount filter.
I'd leave the oil alone, just change it. Replace any gaskets that are clearly bad or impossible to do with the engine in, e.g. oil pan, rear main, front cover, trans input. If the coolant is nasty you might want to do freeze plugs too. If it has over 100k on it, you may as well toss a timing set on it while the front cover is off. Sounds good otherwise.
On the trans, if the fluid is red and smells ok, just do a pan drop and fill it back up with valvoline maxlife.
How hard is the front trans seal to do with just the engine out and the trans still in the truck?
belteshazzar wrote:
the middle spark plug on the drivers side is a huge bastard. replace with something very long lived.
Go through the wheel well. Easy-peasy. 
In reply to Ashyukun:
Stand in the engine bay, yank the converter out (prepare for atf to spill), then you'll be looking at the seal. Make sure the converter is seated properly on reinstall.
RealMiniParker wrote:
belteshazzar wrote:
the middle spark plug on the drivers side is a huge bastard. replace with something very long lived.
Go through the wheel well. Easy-peasy.
IDK man, that steering shaft is still in the worst possible place.
novaderrik wrote:
last night after work, i was prepping my junkyard 4.3 to go into my 2wheel drive blazer... i had to swap the oil pan and pump, so i did that... then i got to looking at the intake gaskets because they are known to go bad.. the one corner looked a little "funny", so i popped the intake off and saw this:
3 of the 4 corners looked more or less like this..
yes, Dexcool is awesome...
Yikes! I included the intake gasket set in my parts order from Amazon so will be doing them as well.
belteshazzar wrote:
RealMiniParker wrote:
belteshazzar wrote:
the middle spark plug on the drivers side is a huge bastard. replace with something very long lived.
Go through the wheel well. Easy-peasy.
IDK man, that steering shaft is still in the worst possible place.
I should've included "with universal joint and extensions". It beats the hell out of trying to do it from the top. But at long as he's got it sitting in the bed of a truck, it won't get any easier than that! 
81cpcamaro wrote:
Replace the intake gaskets, they seem to fail more than any other gasket on those. Easier with the engine out.
Say what?
It's like a half hour-45 minutes to remove the intake on one of those. The hardest part is getting the fan off after some bozo invariably overtightened it.
Do NOT pass go, go directly to a new quality cap and rotor. Period. And don't use the new screws, use the old ones. The distributor is plastic and the force of putting the new hard-Loctited screws in WILL break the distributor. So use the old screws...
novaderrik wrote:
3 of the 4 corners looked more or less like this..
yes, Dexcool is awesome...
Dexcool had absolutely nothing to do with that... the heads and intake fret against each other and the plastic dies from the heat, the weak plastic and the fretting equal the plastic coming apart. Bozos who overtighten the intake instead of following the correct torque procedure make them die faster. (YES clean the threads on the bolts and the head, YES use blue Loctite, YES when they say 15n-m they really friggin' mean 15n-m, which is 216in-lb IIRC)
Fords don't use Dexcool, and Fords with that style gasket will do the same thing in the same amount of time.
One thing you can blame on Dexcool is turning into mud, when the crappy intake gaskets fail and the vehicle operator ignores it/trains the engine to run a half gallon low on coolant. Then oil and air get sucked in to the cooling system, and this turns into a foul sludge that plugs heater cores and such. I had an Express with a radiator that was pure sludge in the bottom three inches. Intake had been leaky for the previous three years but they kept putting it off, putting it off, putting it off.
Of course, if they would have FIXED the leak when it started, the sludge wouldn't have happened. And they wouldn't have had to have us replace the radiator. And the head gaskets after they overheated it sky-high...
Knurled wrote:
81cpcamaro wrote:
Replace the intake gaskets, they seem to fail more than any other gasket on those. Easier with the engine out.
Say what?
It's like a half hour-45 minutes to remove the intake on one of those. The hardest part is getting the fan off after some bozo invariably overtightened it.
Do NOT pass go, go directly to a new quality cap and rotor. Period. And don't use the new screws, use the old ones. The distributor is plastic and the force of putting the new hard-Loctited screws in WILL break the distributor. So use the old screws...
Never said it was hard to do the intake in the vehicle, but I would do it while it was out before changing parts over from the old engine. I prefer to not lean over vehicles and having had a 4.3L Blazer, they aren't my favorite to work on either.
Oil pressure sensor. Just don't bust it going back in.
Spinout007 wrote:
Oil pressure sensor. Just don't bust it going back in.
Where is the sensor located?
Back behind the distributor.
Hotlinked for your pleasure. #78 on my dad's 96 4x4 Jimmy it was a righteous PITA to get to without pulling the distributor. and the stupid socket sold by Advance/Vatozone is BARELY deep enough to grab just the lip of the sensor. Common fix is to add a tee and relocate it off to the side a bit and pointing vertical.
tuna55
MegaDork
9/10/15 8:53 a.m.
I would pull the water pump. I've seen Dexcool eat impellers where coolants were mixed. It would be easy to check.
Spinout007 wrote:
Back behind the distributor.
Hotlinked for your pleasure. #78 on my dad's 96 4x4 Jimmy it was a righteous PITA to get to without pulling the distributor. and the stupid socket sold by Advance/Vatozone is BARELY deep enough to grab just the lip of the sensor. Common fix is to add a tee and relocate it off to the side a bit and pointing vertical.
Cool, thanks. I'm figuring I'll be pulling the distributor on both the original and replacement engines, so hopefully that will help.
