Knock/tap after engine was covered with snow

[__CHI__]

So a few months ago I was driving to work with 6-8in of snow on the ground. Got stuck in a drift and waited to get pulled out,so I popped my hood to see how buried it was around the frame. The engine was caked in snow,like even the intake was covered. I got pulled out and the truck ran fine until I was almost home then it started knocking. Haven’t taken the engine out yet to look because I’m too mad at the truck,anyone have an idea what could be wrong? I still have full coolant and oil,they haven’t mixed. I wasn’t over 2700rpm trying to get unstuck either. It’s not my y pipe either,I figured that was the noise but it’s definitely an internal thump/:

 

[Lanny]

Well i've never heard of anything like that. My first thought would be the heat change. If you take a hot engine block and immerse it in cold snow I could see some things happening that might not be too great. Cracked block or something like that.
But thats just a guess and honestly I don't think that could happen as the temps are not that extreme.

 

[__CHI__]

Well i've never heard of anything like that. My first thought would be the heat change. If you take a hot engine block and immerse it in cold snow I could see some things happening that might not be too great. Cracked block or something like that.
But thats just a guess and honestly I don't think that could happen as the temps are not that extreme.

I’ve never had this problem before and I drive it every winter. That was what I was thinking too..I had to replace the intake on the engine before I put it in because the intake was cracked on the bottom from a “freeze out” plug. The only thing keeping me from the cracked block possibility is none of the fluids are mixed,it never got hotter than operating temp,and it still fires right up with no issues. How devastating would it be for the engine if it sucked in snow?

 

[mr_josh]

You sure it’s not one of the front accessories (alternator, fan / water pump, power steering, A/C, idlers and tensioner)? Having all of the snow packed in there could have messed with that. Maybe start it with the drive belt off?

 

[Lanny]

Snow is mostly air with very little water. But if it managed to get enough I guess it could hydro lock but that probably wouldn't cause a knock.
I like the idea of starting with no accessories. Could have easily bent the fan or similar.

 

[kenh]

Cracked exhaust manifold, or do you have headers? Still exhaust leaks can make weird noises. I had a bone stock Colorado that had a cold knock. It was an exhaust noise. No leak. Just a weird thing until it ran for a couple minutes

Ken

 

[__CHI__]

You sure it’s not one of the front accessories (alternator, fan / water pump, power steering, A/C, idlers and tensioner)? Having all of the snow packed in there could have messed with that. Maybe start it with the drive belt off?

I’ll have to give it a shot later and see if it still knocks

 

[__CHI__]

Cracked exhaust manifold, or do you have headers? Still exhaust leaks can make weird noises. I had a bone stock Colorado that had a cold knock. It was an exhaust noise. No leak. Just a weird thing until it ran for a couple minutes

Ken

That was my first thought,so I put it on jack stands and let it run while I was under it feeling for leaks. Didn’t find any leaks or visible cracks

 

[kenh]

Just a thought. I ran over something and it bent the converter cover. The pan was hitting the converter.

Ken

 

[thinger2]

I would be shocked as hell if that turned out to be a cracked block from the snow.
I highly doubt it.
And I dont think you could hydro lock it unless you shoveled snow and packed it into the intake while it was running.
We have been involved with hydroplane racing since the late 60s and at one time or another every one of the boats have flipped and dropped a red hot engine into the lake.
Ive never seen one thermal shock so bad that it cracked.
Not even the aluminum Buick/Olds 215s
As long as the deadman switch worked, and it wasnt running they didnt even hydrolock either.
And some of those boats sank and stayed on the bottom for a week.
I think you have a "coincidental"
In other words a problem that has nothing to do with the snow bank but you associate it with the snow bank because of vehicular trauma.
Take the serp belt off and run it.
Make sure you dont have a broken motor mount or trans mount.
Look for exhaust and heat shield banging.
Look for suspension parts especially shocks mounts banging.
Make sure the ring gear didnt get packed full of **** and has a little damn rock flying around inside the bellhousing.
Yep, that can happen and it will make you nuts trying to find it.
And, the one everybody misses
Pull the starter and make sure the throwout fork for the bendix hasnt failed and the noise you are hearing isnt the starter gear skipping off of the ring gear.
If all of that fails, I would start looking at a cracked flex plate way way before I thought about it being an internal problem.