Hydrolock...still won't fire.

Stock 98 4.0 ax15 165k

Before I get flamed, I've been crawling every thread I could find and yes.. I'm a retard for pulling this cap on my poor DD. Correct me if I'm wrong, but it looks to me like hydrolock is a case by case issue, depending on whatever else was damaged by the water, the amount of water, etc.

Last Saturday night I sucked some water through the intake while crossing what looked like a shallow enough canal. Had too much speed, caused a wave to hit the other bank and upon exiting, the water sloshed back against the front of the jeep. Got out of the water and engine died. Tried to crank (no bueno, i know now) thinking I had just suffocated the engine, and nothing. Realized what I did, called a buddy for a ride, left a note and headed home to figure out a game plan. Returned the next morning and tried to get the water out via removing the plugs, she didn't have enough juice to crank, so another buddy was called to flat bed her back to the house.

Back home. Plugs out, fuel fuse pulled, battery charged, she cranked and water was evacuated. I let it dry out and sit and even used a syringe and hose to pull out what was left in the #6 cyl. After that, I couldn't get the engine to fire at all. Figured the distributor has water or condensation in it, and I was right, so I pulled that, dried it out and reinstalled the next morning.

Now I sit here, where two days ago I could get the starter to engage the flywheel, there's nothing. First crank it sounded and felt like I may have been in luck, but after that, no movement. The starter clunks as if it's trying to engage, but no motion in the flywheel whatsoever.

I want to believe the starter is still good, seeing as it partially engaged about an hour ago and engaged fully two days ago. My battery is fine and fully charged. The no spark is irrelevant at this point; I've tried with the plugs out as well. While there could still be a fried distributor, I'm more concerned with the starters inability to turn the motor, both with and without plugs. Hand turning the engine is proving futile- but how is this so? Can an engine seize this quickly? Is it done for? I'm reluctant to bump the motor, but have the means to do so.

Any water in the oil?

Pull the plugs and bump it. Once you get it turning over, I would do a compression check.

If the starter doesn't get hot when you try to turn the motor, the starter is most likely having an issue.

It wouldn't be a bad idea to pull the valve cover and make sure the valves cycle as you turn over the motor. You could have bent a valve or possibly broken a timing chain.

Many vehicles expire shortly after dunking because they bent a rod. Pulling the pan and taking a look isn't a bad idea either. If you find a bent rod, you might get away with replacing it and limit any damage.

There was water in the oil, upon returning the next morning, I cycled the oil once, waiting to get the engine started to continue cycling a few more times.

@old_man - bumping this thing while it's apparently locked up isn't going to snap anything will it? I've got to assume that if it's locked, there's something that's preventing the flywheel or the pistons from moving. Would a broken timing chain prevent the starter from engaging the flywheel? Sorry for the onslaught of probably basic engine questions, this is the first time I've had to explore this deep into the mechanical bits of an engine beyond a valve cover gasket and various bolt on replacements.

I'm very obviously in damage control mode at this point and if I have the chance to replace a few things or rebuild *this* engine, I'd like to save as much time and money as possible.

Most likely the water in the oil/intake allowed the rings to rust to the cylinder walls. This is not an uncommon occurrence in this situation. You will have to pop them loose one way or another. Squirting a small amount of oil in each cylinder and letting it sit would be a good idea. If nothing else put a cheater bar on the harmonic balancer and try to pop it loose. That way you have more control. Once they pop loose, they will most likely be OK unless you break a ring.

I would also replace the spark plugs. They can get fouled and make it hard to start.

Thanks, that's pretty much what I was looking for- I didn't know if for some reason my case was much worse or if this was just something that could happen. I was afraid that if it was seized up it was toast right off the bat, but what you just told me was a little bit reassuring.

BTW, new to this forum, I was on Jeepforum for a while, but have constantly found myself coming to naxja for better info. Thanks for the quick replies and help.

Not bash JeepForum - but they're a bunch of amateurs... :roflmao: LOL. Tom's giving good advice - follow it.

This board is far more concise and I'm grateful to not see 10,000 posts on wheel size and lift height. I'm definitely appreciative of Tom's advice and I'm following it closely. I'll be sure to update here once I get the pistons freed up.

A little bit of oil in the cylinders for half a day did free them up, so thanks a bunch for that tip. Running to Napa for some new plugs and hopefully I can get her to fire before dark.

in the future, my mix for freeing stuck rings is 50/50 acetone/ATF.

works fawesome as a do all penetrant.

good luck.
Don't forget to check the trans for water intrusion as well. Its vent isn't that high.

Diesel works too. Did that with my uncle's scout he bought.

87manche said:

in the future, my mix for freeing stuck rings is 50/50 acetone/ATF.

works fawesome as a do all penetrant.

Click to expand...

I agree 100% on that mixture. I've been using it for about 40 years and there is none better. Too bad you can't buy it over the counter.

Short update on my progress, if you want to call it progress:

Oil seemed to free the cylinders up enough to get the flywheel turning via the starter with the plugs out and fuel pump fuse removed.

Next step, create combustion... which I haven't really achieved yet. I picked up new plugs so I wouldn't be dealing with the old ones that may or may not be fouled and despite some valiant attempts by the old 4.0 to start, all I could manage were some chugs. It sounded and felt like some cylinders would fire a few times, but it didn't ever really start the engine. After trying a few turns of the key with this result (it really felt close) the engine locked up again. Couldn't turn it by hand as I was able to before and so I'm here looking for next steps.

I definitely smell fuel when I pull the plugs after trying to start the engine and judging by the sounds/movement I'm going to go ahead and assume the plugs (new) and distributor are in working order. This leaves me with air and/or some kind of internal resistance being the issue at the moment. Additionally, why/how would it lock up again? Seeing as the lube in the cylinders was able to free it up yesterday, would the lock up today be something different?

If it locked up, I would be worried about a busted rod. Squirt some more in the cylinders. Leave out all the plugs and do a compression reading. Things are not sounding promising. If you can get it to turn over and get compression, you have a chance. Once you do that, I would put pulling the pan next on the list.

did the water happen to get in your gas tank, if so could be part of starting issue

@old_man, I agree that things aren't looking good. I have a ZJ that will soon find itself off of non-op reg if it turns out a rod is busted. I should be able to verify this visually after removing the oil pan? Follow up to that, will I be able to see whether the engine is in condition to rebuild without pulling it completely? I am already contimplating the next steps for the 4.0...whether that includes swapping for a donor 4.0, rebuilding the existing engine or something different. I am at the point where I am pretty happy with my 98 5-speed and actually have money put away to repair it properly. That being said, I don't want to spend everything on a crate motor as I have several other plans, but what direction would you go given the circumstances? A budget stroker build sounded enticing at first, especially if I had to pull the engine anyways, but reliability is my main priority given where I take the jeep.

@randomguy310, @old_man, my girlfriends father suggested water in the fuel early on (while we were waiting for a ride the first night, before the extent of anything was known), but since the xj was never submerged and certainly didn't even sit in the water longer than it was splashed up front, I had dismissed this possibility. Is there a breather for the fuel tank somewhere in the engine bay? How does water enter the fuel tank and why doesn't it happen more frequently? Is there a way to test for this besides draining my half a tank? Does this seem likely given the lock up status?

Sorry for the slow progress, have guests staying at the house to ski all weekend and I'm not getting as much work done as I'd like to while trying to entertain, plus I have a week long mission in the backcountry starting Monday that's been planned for months.

Open up the throttle body and look in the intake, it sounds like the intake is full of water and its getting sucked into the motor when you try and start it again.

I opened up the tb initially and saw trace amounts of water-nothing standing. Would there be another point in the intake in which it would be able to reservoir up?

x1n54n3x said:

I opened up the tb initially and saw trace amounts of water-nothing standing. Would there be another point in the intake in which it would be able to reservoir up?

Click to expand...

Grab a papertowel and roll it up and stick it trough the TB and back towards #6, if it comes out soaked keep doing that till it comes out mostly dry. I had to do that for a jeep that sank his jeep in a mud hole and hydrolocked the motor. We kept cleaning the plugs and every time he'd try and start it it would foul the plugs with mud. After cleaning out the intake we finally got it running again.

Hey all, sorry for the radio silence. Got out of the backcountry on friday, competed on Saturday and proceeded to sleep all of Sunday.

I was in the process of yanking the intake and noticed this. Probably why I'm having trouble at this stage of the game. Should buff out I assume.



Anyhoo, I found a guy on Craigslist selling stroker parts for a really good price...block, crank, head, accessories and all. My next question is, what is salvageable from my motor? Exactly what happens when one throws a rod? I think I'll have to pull the head to inspect that, but not a ton of hope for the valves, timing chain, etc.

It would be much quicker to find a complete donor 4.0 from the yard, but what are opinions on the stroker build? What questions should I ask the seller of the parts? He mentioned in the ad that it was setup for long rods. I'd like to have the xj running by June at the latest, but preferable to complete the build or swap by the end of April.