hgpreston

Had the intake mainfold gaskets and valve cover gaskets on my 1991 Vette replaced. Car has 107k miles on it. Mechanic, who I've known a long time and have faith in, calls me tonight and said when he reassembled everything and started the car it is knocking.
He said that he is thinking that too much coolant ran out of the intake and it possibly filled a cylinder...and when he started the motor it bent a rod. Mechanic is assuming all responsibility on his end.
I spoke to another mechanic and he said he doesn't think it would have started, with a cylinder full of coolant, but if it did he said it would have bent a valve.
Car, all stock, ran like a top before this and all he did was replace gaskets. Any ideas would be appreciated.
Bought an L98 car for the simplicity of it..and now this.

oldalaskaman

if the mechanic's taking responsibility, let him, seems a 'lame' mistake, whatever it is

hgpreston

I'm just curious if anyone has ever encountered this problem..and what the actual problem is.

Cutter1

It could bend a rod its called hydolock but normally it needs to be spinning pretty good to do that.If cylinder was full it should have just not spun over but always a chance You would think that he would have drained the coolant before removing intake.More likely dropped something in intake runners.Is it missing as it would smash plug to.
I would pull 1 plug wire at a time while running and if noise goes away you found the cylinder.Reinstall each wire before next cylinder.

hgpreston

Someone else told me it would be hard for it to hydrolock on start up too..
He did drain the coolant but there was still some coolant in the intake runners when he removed it.
He is going to pull the intake and valve covers back off and try to figure out what it is.
Any ideas are still welcome and I'll post what he finds out..

hooked073

Dont realy know how water would have gotten into cyl doing what he did. When you pull the intake what ever cooleant is there runs into the valley, you throw a couple of shop rags down soak it up and change the oil cause it is going right back to the pan from there not the cyl. Sounds more likely to me he dropped something down a intake port and messed something up. Hey but that is just me thinking. At least he is covering it..

Keystring

Coolant in the cylinder wouldn't do it.

If the valves were closed, it just wouldn't spin. (at least not much)

If the intake was open, then it would have found it's way to the pan through the manifold.

If the exhaust valve was open, it would have just blown out the tail pipe.

Bet something fell in. Bolt, wrench, screw driver?

Happened to me on my 67 firebird. Bolt fell down the intake and bent a valve when I started
it up. Pulled the plug and hit the starter and it 'fired' up and broke the valve off and shattered the piston. Cracked the block too.

Not fun.

Glad he's covering the problem.

Sounds like an honest guy.

joe paco

anybody ever lose a check ball for the carb accellerator pump while replacing one on the engine?

if valve covers were removed, it's possible something is changed in valve train. not sure what removing intake would tell you. before I tore it down again, I would isolate the noise as much as possible. I'm sure the mechanic has thought of that.

it does not take much material on top of a piston to make a horrible noise. if it is the piston...

joe

1963SS

Absolutely! The good news is that it will usually just blow out the exhaust valve after some really scary initial knocking. I never had the opportunity to look at the head and piston after that but it ran fine.

MyFirst90coupe

If he routed the plug wires wrong after putting everything back together it doesn't sound so good, I know from experience and yes, it almost sounded like a knock to me.

HlhnEast

This is a possibility If the wires are crossed and you are getting a premature firing of a cylinder it will make a helluva racket.as well. I agree with Keystring when one hydrolocks that means the cylinder is full and there isnt any room for the piston to go anywhere. I dunno about just one tho. If the cylinder was worn the water may escape when compressed but thats just a guess. You might check and see if there is water in the oil pan.

As long as he will fix it dont worry. Hopefully he is good enough for a complete overhaul. Maybe he will just pull one head and get whatever is rattling around. Make him keep and show you the parts that are messed up so you will have some idea if a similar problem crops up later.

Good luck!

GREGGPENN

Vette mechanics may not be aware of the need to remove the esp (brown) wire by the fuel pump. Maybe. I know the ignition system is a bit unique (dizzy used only on one/two other vehicles). Maybe he didn't know or forgot to unhook that wire to retime it? Can't remember for sure, it may also be called the reference wire? (I know I've posted about it last fall.)

Obviously, he removed the dizzy to pull the intake. The wires could be incorrect (PITA to route and get right), or the timing could be off. Either could cause severe detonation/knock.

Hard to imagine they bent a rod unless doing something stupid...but ya never know.

GREGGPENN

That's the other possibility. And, it wouldn't be the first foreign object to end up in the lifter valley of a SBC.

One guy here found a pint can of sealer (empty). (Possibly from the factory?)

Another dropped a bolt inside during a SR swap.

GREGGPENN

If it turns out to be a block issue, figure out how to barter for a 383!!!

coupeguy2001

When did owning an L98 ever stay simple???

Cliff Harris

The engine wouldn't start if a cylinder was full of water. It wouldn't get far enough in the cranking cycle. When I had a head gasket leak I had this happen to me. It only turned a fraction of a revolution and jammed. When I tried to start it again it did start but ran rough until all the water was blown out.

The best test for water in the cylinders is to pull the plugs and crank it. In my case water blew out of cylinder #7.