Blown Head Gasket - Please confirm...

[mciaio]

Merc 260/5.7/350

Running full throttle on our way back from Lloyds Creek last Saturday. Engine got hot. Up to 220*. Pull back the throttle to about 1/2. Engine cools off. Little bit of a miss fire and no engine oil pressure. Get back to the ramp and pull the boat. I just got a chance to look at it today. Engine had very low oil in it because of a leak. Filled and ran, oil pressure came up but still has a miss. I start pulling plugs and find #4 clyinder full of clean hot water from my hose. Run it with the plug out and water still coming out. The oil is still clean.

I suspect a head gasket leaking water into the cylinder but would like other opinions on this. I am unsure if the running hot caused the head to crack. What are the chances of that? Also, what else can cause water in one cylinder? Nothing that I can think of, but I gravitate towards car engines, so I may be missing something. Keep in mind the water is not in the oil.

 

[zbnutcase]

Re: Blown Head Gasket - Please confirm...

It can be the head gasket or an exhaust manifold issue, not likely cracked at only 220 deg. Water will be in oil soon enough if not corrected in a timely fashion! Blow water out with compressed air and oil the crap out of it to prevent rusting until it can be repaired.

 

[chaparall villain 2]

Re: Blown Head Gasket - Please confirm...

low on oil i wouldnt think head gasket .. could be blowin oil but hard to check compression if you have a blown gasket .. i would probably pull manifold riser first and look for signs of leak at gasket since you would have to remove that anyway ... and if no signs of rust trails i would probably do compression check on that cylinder after you pull plug and turn over to get the water out of it then pull head if compression is off from other banks ... is there any oil in your bilge to suggest leak externally ... good luck

 

[mciaio]

Re: Blown Head Gasket - Please confirm...

Thanks, That is a good idea. The oil leak is an external leak and I know about it. These are two different problems.

I am going to pull off the exhaust elbow and hose from thermostat. Plug the hose and fill manifold with water. If it leaks down, I know it's in the manifold. If not, I will do a compression test to already confirm what I know, that it is in the head or gasket. Then pull the head.

 

[Alpheus]

Re: Blown Head Gasket - Please confirm...

Just perform a leak down test. That will show you where you waters coming from pretty quick...

 

[hawkf250]

Re: Blown Head Gasket - Please confirm...

9 times out of ten it is the manifold gasket, id check that first

 

[franktrav]

Re: Blown Head Gasket - Please confirm...

sound like an single cylinder specific problem, if there are no signs of water in the other cylinders on that bank (2,6,8)
i lean towards the head gasket. because with as much water as you describe leaking from the exhaust manifold/riser gasket- i think you would surely have some sign of water in another cylinder on same side. why would the water only enter the number four cylinder ? it could just as easily go int any of the cylinders on same bank

 

[mciaio]

Re: Blown Head Gasket - Please confirm...

I agree Frank. There is nothing in any of the other cylinders. I am really think it's a head gasket; which sucks because they were put on in the spring of 2009 season. Oh well.

 

[Mohawkmtrs]

Re: Blown Head Gasket - Please confirm...

I agree with Alpheus. A compression test will only tell you how much compression a cylinder is making. A leak down test will tell you if/where the cylinder is leaking.

 

[TilliamWe]

Re: Blown Head Gasket - Please confirm...

Hawk is right on the money. Exhaust manifolds/riser are the #1 source of water in the cylinders of marine engines.
Sure it could be a headgasket, but sometimes you have to not think like an automotive mechanic and understand how the cooling system works in a marine engine.

 

[mciaio]

Re: Blown Head Gasket - Please confirm...

I took the exhaust elbow off and the manifold still had water in the jacket. That indicates to me that the manifold is intact. The manifold-elbow gasket was good and no visible signs of leaking past. At this point I feel confident enough that the head needs to come off.

I guess I can run it with the water to the starboard side elbow turned off to confirm further.

 

[TilliamWe]

Re: Blown Head Gasket - Please confirm...

Well, the manifold might not be empty if it's cracked. When you go to take the head off, you'll remove that manifold first. When you do, look inside the exhaust passages for any signs of rust, a crack, or water intrusion. If you find it, voila, you need a manifold, and you don't have to take the cylinder head off.
It's also possible that when you cut the throttle back, you got water reversion. What did your exhaust shutter on that side look like when you removed the riser?

 

[franktrav]

Re: Blown Head Gasket - Please confirm...

if the exhaust manifold is leaking, it must be very nearby to the #4 cylinder exhaust passage, considering the other 3 cylinders on same side have no water intrusion at all...good luck with it

 

[Aloysius]

Re: Blown Head Gasket - Please confirm...

Don't forget the intake manifold has water in it. The intake manifold gasket is the major culprit on water leaks on vortec Chebbies.

analyze this issue. WHAT caused the overheating? WHY were the head gaskets replaced previously?

When an engine is running, water doesn't get INTO the cylinder from a leaking head gasket. However, pressure will leak OUT of the cylinder and into the cooling system. This can cause overheating, because the leak displaces a huge volume of the coolant in the area of the leak, in addition to simply overpressurizing the entire cooling system.

 

[mciaio]

Re: Blown Head Gasket - Please confirm...

Head gaskets were replaced previously because the engine wasn't winterized properly and cracked the block. The engine is misfiring on that cylinder when running. Which leads me to believe the head gasket.

 

[MPII]

Re: Blown Head Gasket - Please confirm...

Anytime you get water in a cylinder the first thing you should do is a leak down. If you get good results, it is most likely either a intake issue or can be a exhaust manifold gasket. You can get water from the exhaust manifold that sits on top of valves and then drops in. But, with that you'll get your milkshake. Good Luck!

 

[Aloysius]

Re: Blown Head Gasket - Please confirm...

A cracked cast iron block is not really repairable, especially if the crack is around the cylinder.