I've been going on the assumption that my motor is trashed for the past month. I've been doing some reading on some threads and I've posted a thread similar to this one. I had a couple of things that are giving me some hope that maybe all isn't lost. I've also formulated some questions.

I got some bad rain about a month ago and I parked my car over a weekend and drove a different one. I parked it on a Friday night and woke up on a Monday morning to a loud tapping coming from the motor. Sounds like ****. In person it's loud. I notice my cowl dripping water on the #6 fuel injector.

Here's what I know and some questions I have:

1. Car starts right up every time
2. Car has 60 psi of cold oil pressure
3. Idle is normal with exception of the noise
4. Spark plugs were kind of dark in cylinder 6 & 7
5. I pulled the coils off and pulled the fuel pump fuse and turned it over several times so see if some water would come out. I also had #6 & 7 spark plugs out.

6. There are no holes in the side of the block I can immediately see.
7. Ther is no oil on the ground.
8. Really hard to pin down where the noise is coming from.


I've heard that if a rod broke, then it'd break the oil pan/block, is that true?

If the rod is bent, should it fire up and idle just fine?

If the bearing was spun, would it still have good oil pressure 50-60 psi?

Really confused and I don't have the funds to fix any large issues. I want to at least know what I need to save for. Bent valve is easier to handle than a new engine. I don't have a place to tear it down just yet but I can do some simple things. Any ideas? Can anyone clear up some confusion?

 

You aren't going to hydrolock a motor externally with a drip. It sounds like rod knock. A valve would not have it idling normally nor would it be very loud unless it was so bad it wouldn't idle well.

 

Well a small drip over 2 days, I thought may do it. It rained hard for a couple days. Is it possible to spin a bearing by just starting it? It was running fine when I parked it that Friday night.

 

Also had a guy on a 4th gen fbody fb page tell me that his car had the same noise and a bent flywheel?!!? That'd be a neat trick bending a LS7 flywheel.

 

I am an experienced beneficiary of a hydro lock. No, the car would not start and idle just fine with good oil pressure.

It is very possible you are describing a collapsed lifter or lower rod knock and the water drip is just a coincidence.

 

I also am an experienced beneficiary of a hydro lock from rain dripping on top of the engine. The water gets into the cylinder through a bad injector o-ring or intake gasket. When trying to start the start motor and engine came to an abrupt stop and the starter would only click if you kept trying to start it. After letting the car set for a few hours I tried to start it again and it started right up, with good oil pressure and idled and ran good. The only problem was a loud knocking noise that sounded high up in the cylinder. After running for 5 or 10 minutes the knocking went away. A few days later I was just cursing down the interstate and kaboom. The engine locked up and smoke was coming out from under the hood and a trail of oil behind the car. A rod had broken and put a big hole in my aluminum block and broke the oil pan.

If your engine locked up while starting and then started later on and is now knocking after a rain. I would tear the engine down and have the rods checked, before one breaks.

 

There has been some discussion about water dripping onto the intake manifold when the car is standing in extended rain. It's said that this water can get into the intake manifold and if just the right intake valves are open, water can fill a cylinder.

Crank the engine and this cylinder hydrolocks-even partially and you'll have a bent connecting rod causing a rod knock. But the engine will otherwise run fine.

Bottom line: You'll need to replace the rod.

 

Ahh gotcha. Well it turned over as normal that morning. Maybe some slight changes but I don't remember. I'll have to check and see what's exactly bad. I'm really upset that GM didn't find that cowl leak during testing. Could've saved a lot of motors.

 

It's a rather rare occurrence. We have one member that says it's common and happens often but I think he's just had some bad luck.

If the intake manifold and injectors are properly seated, bolts and gaskets are good, there's really no reason for water to enter the manifold.

Plus it needs certain valves to be open when shut down and the car level with rain blowing just the right way and the NY Mets getting into the World Series........

 

If you open ANY newer fbody in the rain you will be treated to water dripping onto the top of the engine from about 40 different places.........the rest is self explanatory but goes something like this. Water runs all over the intake and WILL find a way in someplace, it pools in the intake OR pools then runs into any open intake valve. Regardless the next start is going to be eventful and most likely damage something.

The weakest thing in the cylinders are pistons, next is the rods EVEN WITH NY Mets getting into the World Series........ something is going to break or bend. I have personally seen this happen DOZENS of times. Take it for what its worth.

To the poster of this thread it is possible you bend the rod and now the bottom of the piston is hitting crank as it goes up and down. The engine doesn't need to stall as you crank to break or bend a rod. In my case it just started hard, it happens so fast you really don't know what happened UNLESS you have a weak battery and the starter stalls.

Normally with the GM reduction starters IT DOESN"T STALL it just breaks something.

 

It doesn’t take a lot of water and I don’t think an intake valve has to be open. The water can just leak in and set on top of the valve and wait for it to open.

Any way if you didn’t notice anything unusual about the way it started this may not be the cause of your knock.

 

Well in hoping its top end related. I'm not sure what else it could of done it. It was running fine. If I rev the engine from the stedy idle, it revs as if it has a misfire, not very smoothly at all. It's just so loud I'm doubtful that it's too end.

Also could a bent flywheel do it? Someone on fb told me his was a bent flywheel.

 

 

Dude, that IS pretty loud. since it is easier to check, I would pull the valve covers and at least look for a broken spring or rocker, broken/bent push rod, or something on the top end. But you're right, that is much louder than I would expect from a top end noise.

Could be a lot of bent things. I'd say start with the easy stuff and work your way inwards. If you rule out the easy stuff, might be just as cheap and a lot easier to swap out the short block.

PS - I misunderstood your "it was running fine" as meaning "it was running fine this morning and fired right up", not "it was running fine on Friday when I parked it"

 

I stand by what i said in your last thread. But the more you run it thinking its going to fix itself lessens the chance of being able to throw another rod in it and having a running motor. In the month thats its been down your surely had enough time to pull the plugs, unplug coil packs and have someone turn motor over while feeling plug holes to see which rod may be broke. My money is on number 6 possibly 8.

 

"LS1 talking to me"

That noise is clearly saying to pull the motor.

 

With noise like that...I doubt its just a topend issue.That sounds like something has broken or collasped.My old ls1 had a similar sound due to the common rod knock on cold startup but even then it wasnt nearly as loud as that! Sorry to say but at that pint..DO Not continue running the car untill you atleast pull the valve covers off and inspect the easy stuff.

 

Does anyone think this could be clutch or flywheel related? My pedal lost its pressure and someone said it may be a bent flywheel? Not sure but has anyone experienced something similar?

 

I will say this much. Yes it is possible, but very rhythmic for a failed clutch.

I still stand by my previous recommendation. Start with the easy stuff and work your way in.

1. Do a compression test. If one cylinder is absurdly low, you're onto it. At least you know where to look.
2. Pull the valve covers and look for rocker or spring or any top end carnage.
3. Pull the trans and disassemble the clutch. Sometimes the pressure plate hides things, so don't stop at pulling the trans.
4. If you still haven't found it, drop the oil pan or pull the heads. Pick one. Do the other next.
5. If you're still lost, you'll be doing a rebuild anyway, so just swap in a shortblock and all the question marks are done.

I wish we could tell you the "one move checkmate", but it isn't there.

 

Bent Rod