Salvage engine help


…would love your thoughts on this project. Did an engine swap with a salvaged engine. Tried to turn harmonic balancer to put torque converter bolts on and oh no, would barely move. Instructor 1 suggested removing spark plugs and putting oil in holes for lube; Instructor 2 mentioned WD-40 being sprayed in; Also heard brake fluid (but not from my instructors). Took out spark plugs and squirted some oil in/ letting it sit overnight. Please, any suggestions would be appreciated (and I don’t even want to think engine lock-up). We are hoping for the best. What ideas do you have out there? '94 Jeep Grand Cherokee 4.0L,AT,2WD Thanks so much!!!


Where’d the motor come from? Did it ever turn in your presence?

An engine that’s locked up just from sitting will usually come loose with the motor oil in the cylinders. The WD-40 would have been good as a preventative measure, but for actually knocking it loose a penetrating oil would be your next step, although if that does knock it loose, you’ll want to flush the cylinders out with motor oil and change the oil before you fire the thing up. The brake fluid would be, in my opinion, something to do if nothing else has worked and you don’t have anything to lose.


although i am not a “pro” it would be beneficial if you knew if the timing belt was on too. if this has an interference engine you could be fighting the valve/ head clearance issue


Best not to use WD-40 anywhere in or on an engine. It’s flammable and sticky when dry. Break-free was popular with the mechanical people who had old engines or engines with stuck rings. Motor oil is alright too. Nice project, but when you’re done it’s still a Jeep vehicle. Everything can’t be great.


The best thing I have found for lubricating a long-sitting engine is Marvel Mystery Oil. Put about two teaspoons of MMO into each cylinder. Let set overnight. Try to turn engine after you’ve done the above-mentioned checks for timing belt/chain. Use a breaker bar with the correct socket, preferably an impact socket, on the crankshaft pulley (harmonic balancer) retaining bolt. Carefully rock the the socket on the bolt back and forth JUST A LITTLE. Once you have determined that the engine is now not locked up, turn the crankshaft bolt a couple of 360s but do it slowly. Ensure that you are turning the engine in the right direction. MMO will not harm anything. Most of it should blow out of the spark plug hole if it hasn’t all drained down through the rings into the crankcase. Once you fire up the engine, run it up to operating temperature while you’re doing the rest of your checks with the engine running. Shut 'er down, let it cool down, change the motor oil and filter. While you’re at it, throw in some properly gapped new spark plugs and check the rest of the tune-up. I suspect that if you remove the spark plugs, then try the breaker bar/socket thing, that your engine will pretty easily unstick. But putting in that two teaspoons of MMO won’t hurt. When you pull the old plugs, after you’ve introduced the MMO, very loosely put the plugs back in to keep crap out of the engine while you’re letting it set overnight. (Yeah, I’m an old coot still using a lot of the old tricks. And a little bit, 2 teaspoons of K-2 clean kerosene would be preferable over WD-40 or brake fluid.) Another foot note: When trying to turn an engine ‘by hand’, place the auto trans. in neutral. In fact, this applies to manual trannys as well. Just make sure that the wheels are properly ‘chocked’ and the parking brakes are engaged so the vehicle doesn’t cripple you!


You should always attempt to rotate the engine by hand before the installation. However, that’s water under the bridge now.
I would say that you have one of two problems.

  1. The engine is frozen, or near frozen.
  2. This one is more likely. The vehicle has an automatic transmission and the torque converter must be fully seated on its splines. Often when an engine is removed the torque converter may come forward and become unseated on 1 or more sets of splines. When the engine is installed in a situation like this the converter and flex plate binds together. This means engine back out.

(You can verify this if you can get a finger on the converter. You should be able to rotate the converter with a finger; if not, the converter is off the splines and you have to pull the engine).


Tried to turn harmonic balancer to put torque converter bolts on and oh no, would barely move. Instructor 1 suggested removing spark plugs

The plugs should be out for this kind of work anyway. Much too hard to work against cylinder compression. There’s an $8 tool designed for this purpose. It engages the flex plate and has two distinct advantages; way more leverage than you’ll ever get working with the harmonic balancer and you’re able to rotate the engine while remaining under the car and putting in the TC bolts.

Hopefully, the engine is jammed against the TC or you just aren’t getting enough leverage off the HB bolt or a combination of the two. Be very careful about over stressing the rings if they are rusted to the cylinder sleeves. They’re easy to crack. I use MMO or trans fluid, time, patience and gentle rocking motion to try to break them free.


This engine has a timing chain. And if it did have a belt and the belt broke the engine would be EASIER to turn…not harder.


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The best thing I have found for lubricating a long-sitting engine is Marvel Mystery Oil

Beat me to it. Used it a couple times in freeing up a stuck engine.


You might also try PB Blaster