92 Pathfinder: Repair head gasket or Replace engine?

[wayneindustries]

I have a '92 Pathfinder with the VG30E engine. Head gasket shot, coolant and oil mixing and leaking out of... somewhere. Compression test showed driver side cylinders were all low. Don't have the exact numbers handy but they were all below 120. And the magic test of dripping some oil in and retesting showed better numbers as expected.

Decision time: replace head gasket, or replace engine? Pretty sure if I replace the gasket I will also need to take the cylinder heads to a machine shop per everything I've read (any idea what that should run me, btw?). Meanwhile, I can find plenty of engines for fairly cheap, 600-800 range. I've never done an engine replacement - obviously an intense job but not one I would necessarily shy away from. And on the same token, if I were to replace the engine - has anyone put a different engine into an old Pathfinder, for better power and/or efficiency?

I love the truck and would like to get it running well again, but not really in a spot to dump many thousands into it.

[QCtech]

A used engine from a yard will have the same probability of being bad without the proper checkups, which will mean disassembly anyway. Unless you want to just hope for the best or that you can actually see and measure the yard engine running before buying. Unless your car overheated, your heads may not need machining at all. There are ways of measuring this with the block in the car. Also if your pistons are good you could measure the cylinders and just lighty hone them and put bigger rings. A different engine will require a different ECU and harness in most cars. It is a manual transmission or auto? I dont know if a 92 used a TCU but if they did, then you also have to factor that in a different engine with a different ECU. And all that involves a lot of money. I have bought a used JDM engine for other type of car, from companies that specialize in bringing them straight from Japan and with a warranty. It was a drop in and is been running for more than 10 years to this day. I think that would be your lowest cost alternative, or you can start by taking out your head and measuring if it is straight and then measure your cylinders, and just change the piston rings and the head gasket.

[Blindaviator]

If it is the original engine and has high mileage you would be better served (if you plan on keeping it) to replace the engine... I just found one on car-part.com with 132k miles for $250 locally with a warranty...

I don't know how different a 92 is over my 2001 but with mine Nissan recommends removing the engine to replace the head gaskets... The book time to replace the head gaskets is 22 hours...
I could replace the head gaskets on my Chevy's 427 in about 3-4 hours while it's still in the car... Hell I could pull the entire engine, replace the head gaskets and reinstall the engine in the car in half the time of the Nissan...

I would rather go out to a salvage yard and pick up a low mileage engine from a reputable salvage yard that gives a warranty (usually 30-90 days)... You can get an idea of the shape of the head gaskets on the replacement engine with a borescope... Look down in the cylinders for the coating of carbon on the piston head... If it is a uniform black over most of the surface then that cylinder is likely in good shape... If you find one that has a very light coating or looks almost new (no carbon) then it likely has a blown head gasket or a crack... When the cylinder starts to burn the water it turns it into a super heated gas that scours all the carbon from the cylinder...

A good rule of thumb on a salvage yard engine is this... If the engine is still in the vehicle then look the vehicle over... If it was in an accident then you found the reason it was salvaged... But if it has no visible damage then it is likely a mechanical failure that brought it there... You will need to determine if it was the engine or something else mechanical that caused the salvage... If it's not in the vehicle then ask what the condition of the vehicle was when it came into the yard... Most reputable salvage yards keep "induction" pictures of every car in their files to help identify them...

You can use all the sensors off the original engine and shouldn't have any issues with the ECU... Not to mention you will have plenty of spare parts just in case...