7.4L just purchased boat , water in oil. How to identify issue ?

Pressure test is to pump pressure into the coolant system and see if it holds. Some call it a leak down test because the result is pressure bleeds off if there is a leak. Pretty self explanatory don't you think?

Whatever you call it, you need to do it before pulling the head.

Now it is possible to have a leak due to a cracked block between an oil port and coolant port at the block deck where the head bolt down. This is rear but I've seen it happen. The crack will be very small and magna flux or dye is about the only way to check it. The crack will open up when hot then shrink shut when cold. Since water is not pouring into the oil pan you can rule out intrusion through the piston AKA bad exhaust manifolds. Your compression test proves that.

Cooler is about the only thing left.

As far as the cooling system. Since the temp is now regulating, either the crap pushed through and the thermostat is working or the thermostat finally freed itself from rust/contamination and popped open.

Just my opinion.
 
Yes, I see the test you are talking about. Pressurize the cylinder and see if PSI is lost over a period of time. I have used Top Dead Center for checking the head and then rotate to Bottom Dead Center to check cylinder wall integrity. We use an old spark plug and braze or weld an air quick coupler to it after it is hollowed out. Keep PSI regulator at 60 PSI. and a pitcock valve before the gauge and coupler.

Pump the cylinder to 60PSI and shut the valve off. Time the decent for each cylinder. They should not be more than 15-20% apart. The max time to zero is irrelevant. Make sure they are even is the key.

SRC , thanks for clarifying the test descriptions.
 
decided to knee down and pull boat to replace head and intake gaskets. only fooling myself with wishful thinking . Any suggestions to get a gasket set at a good price . If all goes well still have aug and sept boating
 
Jeff, you may want to consider taking the heads to a machine shop to ensure no warping UNLESS the head gasket(s) is obviously damaged. It's an inexpensive way to eliminate a possible culprit (unless one or both are warped-then it's a bit more pricey)
 
I just hope the head bolts on your engine are in better shape than mine were. Getting the heads off was one of the biggest time eaters of the process.
 
Jeff, you may want to consider taking the heads to a machine shop to ensure no warping UNLESS the head gasket(s) is obviously damaged. It's an inexpensive way to eliminate a possible culprit (unless one or both are warped-then it's a bit more pricey)

The source of my overheating/milky oil (several boats ago) was a failed head gasket between two cylinders. Had the previous owner replaced it immediately, everything would have been fine. By delaying, it allowed the combustion to leak between cylinders...I.e. Cutting torch in water jacket of block between cylinders.

Remove the heads, have them checked for true (no warping), inspect the block for obvious damage and replace with MARINE head gaskets. If this doesn't solve your problem, you may need to have the engine removed and the block magnafluxed.
Pray for a bad head gasket!
 
Is there any trick to closing off the raw water cooling system to do the pressure test on cooling side
 
Is there any trick to closing off the raw water cooling system to do the pressure test on cooling side

Pressure testing closed cooling is easy....with open, you have a lot of hose outlets to close up. Good luck.
 
Is there any trick to closing off the raw water cooling system to do the pressure test on cooling side

You could replace the pass through gaskets that are between the risers and the elbows with a block off gasket that is meant for a full closed cooling systems. Just remember to change them back to (new) pass through gaskets after the test.
 
Was able to do pressure test and I can hear it whistle. Back cylinder are port side. Pumped up to 20lbs. If I shake boat I can hear it gurgle. What you think Head or Intake
 
At this point, there is no reason to try to guess what's wrong. You have confirmed that there is a problem that requires pulling the heads, so just pull the heads and find out what's really wrong.
 
Bad Bad news... just before I was going to pull heads off I was taking a closer look and the Valley and noticed 3 hair line cracks..... f-me..... Well need to find a new block. Also need to figure out how to get motor out of boat. Not a easy feat because the boa sits 7 feet high at the side ledge
 
Man that sucks. A cracked block was my guess but hoped for a different cause of the problem for you. Best of luck getting the bad boy out. I have no answers than Kevin's for removal.
 
I'm sure you mentioned somewhere earlier in the thread, but where is your boat located? Many marina Travelifts have a crane mounted up high to remove masts from sailboats. Our marina usually uses a forklift to get engines out of boats but they are usually not blocked that high.
 
Just an update ... just got new motor in and did a test run in driveway .... all good except for alarm going off. Oil is good on gauge , Water is good on gauge. Just need to figure this out ?
 

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