Guys I'm at a total loss here. I'll start from the top & try to be as descriptive as possible. 6+ months ago, I replaced my valve cover gaskets on my 3rd gen since they were leaking (shocker). In the past couple of weeks, I've noticed that upon initial cranking for the there was oil that was burning. I located the source, the drivers side valve cover was leaking on the crossover pipe & causing some significant smoke bellowing out from under the hood. So I checked a few of the easily accessible bolts & most weren't very snug. I pulled the top 2 pieces of the intake manifold so that I could access all of the bolts. Got everything taken off & sure enough the back 2 bolts were not even finger tight. I presume they just backed out through expansion/contraction due to not getting them tight enough when I replaced the seal.
Here's where the trouble starts, I button everything back together & somehow I forgot both of the lines to the rear of the throttle body. Somehow I'd gotten the coolant line connected to the vacuum line & left the vacuum line undone. Just coincidentally, I removed the radiator cap to ck my coolant level before I realized what I'd done. When I removed the cap, coolant started pouring out of the coolant line on the rear of the TB that wasn't connected. I immediately connected the vacuum line to it & it felt a little loose, so I started switching the 2 lines to correct the mistake. I'd gotten some coolant in my vacuum line, but not enough for me to really be that concerned over it. I topped the radiator off & had everything back together, both sensors on the TB were connected, intake ground wires were connected, intake plumbing in place. I attempt to start the 4Runner & I get a "dead battery-esque" type click. No starter engagement on multiple turns of the key. I'm thinking ok, this cheap battery from Autozone bit the dust a yr after I bought it. Had the battery tested & it was fine. I tried battery from my 4th Gen & I get the click. Then suddenly it sounded like the starter gear was barely engaging. I bumped the key a few more times, & I get a really unnerving binding sound. It almost sounded like the starter gear was engaging & having the teeth ground off. The truck won't crank. The starter was replaced earlier this year, & it cranked fine before I pulled the intake.

I'm fairly mechanically inclined, but short of tearing it back down, I don't know what else to look at. I'm pretty sure I'll be tearing into it tomorrow night to see what I can find. If anyone has any insight, I'd greatly appreciate it.

Can you turn the engine by hand? If you can't, try turning it backward (counterclockwise).

If you can only turn the engine by hand a little, (like a third of a turn) backward then forward, you won't like the answer of what it is. But I'll hold out until I hear back.

I'll step in and tell you what @stir_fry_boy didn't, you most likely need another motor. Coolant went into places it should have. Relatively speaking a good used 5vz shouldn't be more than $600 these days.

More than one member on Yotatech has done the same thing.

^^^ This. When the engine has coolant inside the cylinder, it doesn't compress like air does. On the compression stroke, the valves are closed and when the piston goes up with water/coolant inside instead of air; Your connecting rod hates you.

I'm praying y'all are wrong. However, the way my luck has been the past few years, it's totally plausible. However, like I said in my initial post, there was not even the slightest budge when I hit the key. So at this point, I wouldn't be surprised by any outcome. I'm working til 7 tonight & once I get my girls to bed, I'll be burning the midnight oil trying to hand turn &/or correct my attempt to fix a problem while creating another.

Take all of the spark plugs out and then try cranking it over. If coolant comes spraying out, your motor was hyrdo locked and is probably toast. You can also inspect the oil and see if there is coolant in it.

I'd start looking for a low mileage used motor to swap in.

I hydrolocked my Bonneville years ago. I didn't know it but I tried cranking it over so many times it broke the starter off. I tried saving that motor by fixing the cause of the hydrolock (failed upper intake manifold) and doing several oil changes. The motor lasted maybe another 500 miles before the rear main bearing wen't on it.

Sorry for the bad news..

I'm at least 90% certain you hydrolocked the engine and the connecting rod is broken. I've diagnosed this issue on Hondas and Toyotas. The Toyota was a 4Runner with 200k miles, someone didn't tighten the crank bolt properly. The crank would only turn about 30-40 degrees and stop both ways. Did the same thing you described. Just would turn 30-40 degrees one way and back.

I think you hydro locked the engine BUT nothing is broken because the engine was not running. The starter is not strong enough to bent a connecting rod.

Yes, just take off all the plugs out and inspect the cylidners. Remove any liquid in the cylinders. Now spin the engine by cranking the crank bolt by hand.

I think you should be fine.

Pull the plugs and crank it. From what I'm reading I don't think it's damaged permanently.

IF coolant got in the oil, the engine is probably shot because it washes the bearings out. It may be fine for awhile, but eventually they will fail.

If it just hyrdolocked but no coolant in the oil, it *may be ok.

I also highly doubt the connecting rods got bent from the starter but you never know.

Reading through this thread has scared the bejabers out of me


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It's really easy when you put things back together to do something - let the hoses go where they want to go. Don't force them onto something else. If they are untangled, and you are putting it back together, they will nearly put themselves on.

If there are two hoses together, I will disconnect the near end of one and the far end of the other. That way I know they will go back where they are supposed to. This worked well on fuel and other connections on my recent frame swap.

Just a quick update. Per y'alls estimation, hydralocked she was!










I spoke w/ a master mechanic(25+ yrs of experience) & ran everything by him. He said that since the motor never turned over, the likelihood of damage is very slim. I pulled the sparkplugs & spun it over & coolant shot out. I spun it over until I couldn't see anymore significant vapor. I put the plugs back in & got everything tentatively put back together so I could burn off any excess in the combustion chambers. She smoked for a while, but cleared up after a drive around the neighborhood. My neighbors loved it. So I drained the oil, which was not really milky at all. Filter was changed. I'll be changing the sparkplugs tonight.


Generally anything I take apart, I label. I didn't this time & it bit my ass. We'll see how she does on down the road, I really don't think there will be any long-term issues. She ran really smooth & didn't miss once the smoke cleared.


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Good to hear your engine seems to be ok. I bet it was a serious relief when it cranked over and ran.