Car is a 70 L46. All stock carb to pan. Last time out I spun it up to 5500ish and shortly after began smelling coolant and hearing a noise I have not heard before. Once the temp gauge started rising I knew it was time to pull over. Temp was about 210 when I shut it down and was spraying coolant from between the block and water pump. Not leaking mind you, it was spraying out with some good pressure. Once the cap was off the pressure obviously subsided. Likely a blown head gasket but the story does not end here.

The noise I was hearing turned out to be a knock coming from the motor. To me it does not sound like a valvetrain noise but rather something more fundamental. When cold it is not heard too much, but when warm it is heard off idle when spinning the motor up. I pulled each plug wire off the cap one by one and the interesting thing is that I did not find one where the noise went away, but I did find one where the noise got MUCH louder when the wire was pulled. There is no white smoke from the exhaust and the oil looks fine, not milky. Coolant/water also looks fine as it pours out while running.

So the question is, what are the chances that water got into the cylinder, hydro locked and caused internal damage. The decision point now is pull the heads, or pull the motor?

 

Easy answer would be to pull the motor.
if you’re trying to take small steps to find the issue first, I would consider dropping the oil pan and inspecting all the main/rod caps. You can also see a good portion of the cylinder walls, pistons skirts and so on. Inspect the oil pump pickup screen, look for debris in the bottom of the pan. Lots of info can be gained.

If you want to take a look at the valve train, something as simple as removing the valve covers and spinning the motor over will let you see if each valve is actuating, in the same amount, fully seating and so on.

 

spun bearing on louder cyl
did water shoot from where pump mounts?

 

Yes....pull the pan and rocker covers as stated.....you can do this while in the car and inspect everything........

Jebby

 

Yes!

 

Borescope the offending cylinder and see if its been stem cleaned.

But if it is a bearing spun, your pulling the motor, Don't think the pan can come off the bottom. Greater minds than mine will have to answer that.

 

No issues puling the oil pan on a C2/C3, disconnect steering linkage and push it out of the way.

 

I have this and I love it.

Pull the plugs and take a peek.

 

I wouldn’t be 100% on it being a head gasket just yet. If it was blowing coolant in the fashion you’re claiming I would be looking for something along the lines of a blown freeze plug or rotted out rear water pump plate. Before you pull the motor pull your plugs and see what you have. If you get coolant out the plug hole or coolant in the oil then it’s for sure a headgasket or worse but do a simple diagnostic first and figure out for sure the issue.

 

Before pulling the heads or pulling the motor, I would investigate the obvious problem first.
I don't see a spun bearing or a blown head gasket causing a water pump to spew water. Blown head gaskets commonly show up at the radiator. I would buy/rent/borrow a exhaust gas/radiator test kit and check for exhaust gas in the cooling system. Then, I would double check where the coolant was leaking from (water pump, water pump gasket, block behind the water pump, etc.). Replace the pump if needed. Looking in the cylinders with a bore scope would be a good idea also.
Do the easy stuff first.

 

Pull oil filter and dump oil in a clean pan. Look for metal. That noise worries me as much as anything. As mentioned pull plugs and see what you have.


JIM

 

before you drain it start it, use a stethoscope or really log screwdriver with the handle in your ear and listen to the exhaust manifold at each cylinder and see if you can hear which one it is. then do the same at the base of the water pump....could be the pump seized up and you blew a hole in it or its the weep hole spewing water...not haveing steam out the exhaust or water in the oil is a major savior.....you can drain the oil and look at it and cut open the oil filter to see if you hurt a bearing..it will be obvious....maybe you will get lucky....if its a spun bearing just put the block in the corner and buy a crate motor...you might get a 400hp crate for the same or cheaper than rebuilding the original

 

yes the pan can come off. yes bearings can be replaced. no i don't recommend anybody who has to ask how to try replacing bearings while looking up at crank and oil dripping on your nose. but first remove the fan belts and see if noise goes away. then consider replacing the water pump cuz you are gonna anyway.

 

#6 is the hole where the knock is coming from as identified by pulling a plug wire at the cap. As mentioned earlier, the knock actually gets much louder at idle when you pull the plug wire. Seems counter intuitive but that is what it is doing.

Pulled the plug and nothing looks out of norm. No water in the cylinder and plug looks fine. Pulled valve cover and all is fine there too. Every rocker is moving as it should. The source of the coolant leak is the mating surface of water pump to block. The gap is so wide that you can not only see water leaking from it, but you can hear air escaping from it when squeezing the hose. Freeze plugs look fine.

I just pulled the fan and belts are next. Will do as suggested but dont have too much faith due to the nature of the knock and the fact that it changes when pulling a plug wire. Oil filter drain after this last test without belts. Dont have a scope so a look inside the cylinder is not an option right now.

 

thunk changes because no explosion to keep piston rod against journal

 

And this is the reason one shalt not listen to poor advice and pull an engine prematurely. Good grief people jump to conclusions and waste time / money.

Are you saying the W.P. bolts let go? Gap between pump and block? Never seen that.

Inspect the inside of fan shroud. Could that noise you heard be the fan blades hitting?

#6 knock could be as simple as valve lash loosened up. Grab each & every rocker when it's not opening a valve.

 

"#6 is the hole where the knock is coming from as identified by pulling a plug wire at the cap. As mentioned earlier, the knock actually gets much louder at idle when you pull the plug wire. Seems counter intuitive but that is what it is doing."

makes that sound when the exhaust valve does not open. Remove valve cover and look at valve train. Broken rocker arm stud and or rocker arm off pushrod.

 

W.P. bolts are tight. Wont know exactly what the deal is there until the pump comes off.

I had my hand on every rocker with motor running. No evidence of lash issues. Shroud is not it either.

 

keep repeating info, maybe it will be read

 

I know your vote is spun rod bearing on #6. I tend to agree but still trying to rule out all possibilities.