Leak down test

[camalot]

Hi

Would a leak down test give the same results on an open water cooling circuit as it would on a closed water circuit like in a car.
Trying to find if the head gasket has gone before I strip it down, I'm getting water in the oil.

Cheers Paul

 

[dubs283]

Re: Leak down test

Hi

Would a leak down test give the same results on an open water cooling circuit as it would on a closed water circuit like in a car.
Trying to find if the head gasket has gone before I strip it down, I'm getting water in the oil.

Cheers Paul

this is a cooling system leak test??

then yes, but you need to block off the exhaust where the cooling water exits the system to pressure test it

water in the oil??

was the engine properly winterized?? - a cracked block or cracked head will also allow water to enter the oil

 

[Mischief Managed]

Re: Leak down test

Should not matter much, the cylinder pressure is so much higher than the closed cooling system pressure that the difference in leak down percentage will be pretty small. The "radiator cap" on the closed cooling is going to let anything over 15 psi escape as though the system were open. That said, I doubt a leak down test will help isolate your problem.

 

[Stamey]

Re: Leak down test

The way I'd go about this is to check for compression, to see if any cylinders are lower than the others. Gives you a place to start. At the time of this test you will notice if you have a wet cylinder or a really clean spark plug, when compared to the others. These are also clues. But, because cracks and even head gasket issues do not always allow water into the cylinder but do allow it into the oiling system, it is possible none of these may yield a clue.
If the doesn't yield a clue I'd heat the engine up to operating temp and do the compression test again, as things may change with heat expansion.

Chris

 

[milestan]

Re: Leak down test

Definitely do a leak down test if you have the gauges and knowledge on how to do one. It will yield much more information than a compression test, whose results can generally be misleading. And yes, no different than like on a car, other than seeing bubbles in the radiator, pop the thermostat housing and listen for air. Often times, you'll even be able to feel the air escaping the block if you've got a blown head gasket between the water jacket and a cylinder. Make sure you bring each cylinder that you test to TDC. If you've got a blown head gasket, a leak down test usually provides pretty definitive results.

 

[Don S]

Re: Leak down test

What engine, year? How much water in the oil?

I seriously doubt you have a blown head gasket on a raw water cooled engine causing water in the oil. Just don't happen.

Drain the cooling system, block off the exhaust and pressurize the block. That's how you will find a leak for water in the oil.

 

[camalot]

Re: Leak down test

Thanks for the feed back guy's

Paul

 

[camalot]

Re: Leak down test

What engine, year? How much water in the oil?

I seriously doubt you have a blown head gasket on a raw water cooled engine causing water in the oil. Just don't happen.

Drain the cooling system, block off the exhaust and pressurize the block. That's how you will find a leak for water in the oil.

Hi Don

I know nothing about this boat, what I do know is it's a 1988 350. I'm a motorbike tech by trade and help a few local guy's out where I can, I will machine some bungs up and block off the exhaust outlets at the raisers then hook up something to the water inlet and pressurize the system as you have suggested.

Where should I be looking for tell tail signs of a block leakage?

Thanks Paul

 

[Don S]

Re: Leak down test

I will machine some bungs up and block off the exhaust outlets at the raisers then hook up something to the water inlet and pressurize the system as you have suggested.

No, block of the water hoses going TO the exhaust manifolds. You are going to be testing the manifolds too, just the block.

 

[camalot]

Re: Leak down test

No, block of the water hoses going TO the exhaust manifolds. You are going to be testing the manifolds too, just the block.

Roger that............ I can see how my original idea would not have worked lol. Thanks Paul