block pressure testing procedure

[t0mmy91]

good morning all, hope all is well! i have a 1999 searay 185 bowrider. engine is 4.3l merc with alpha one gen 2 outdrive. i just bought the boat and am diagnosing multiple issues at the same time. i want to pressure test the block, but i have never done this procedure before. i was wondering if anyone that has done it before on the same engine i have, could provide some basic insight on how to do it. i am very mechanically inclined and capable with tools, i just have never done this procedure before on anything. On top of the intake, i have a thermostat housing with 4 hoses coming into it. is it as simple as removing the 4 hoses from the t-stat housing, plugging them up, and connecting the pressure pumping device to the t-stat opening in manifold and seeing if it will hold pressure? am i missing any steps? how about what psi should i pump in and see if it holds? thanks in advance for your help

 

[scoflaw]

Take the 2 sensors out of the t-stat housing nd use them for a schrader valve and a gauge. Plug 3 of the 4 hoses. Should easily handle 20 lbs.

 

[t0mmy91]

Take the 2 sensors out of the t-stat housing nd use them for a schrader valve and a gauge. Plug 3 of the 4 hoses. Should easily handle 20 lbs.

awesome, sounds fairly simple, one question though. i currently have the exhaust manifolds, intake manifold and t-stat housing removed. i know i need the intake manifold and t-stat back housing on, but do i need the exhaust manifolds on to test? also, using your method, assuming all 4 hoses are hooked up to the tstat housing, and i have to remove them to plug them, wouldnt i need to plug all 4 t-stat outlets also? my apologies if i am missing something. im guessing the hose that doesnt need to be plugged is the one going to outdrive? and if so, wouldnt i need to block that outlet on t-stat housing where that hose connected to?

so to summarize, i would put the intake manifold and t-stat housing back on, valve and gauge in the 2 sensor ports on t-stat housing, remove and block off 3 of the 4 t-stat housing hoses, but what about the 4 outlets on the actuall t-stat itself, im guessing they would need to be capped also? or am i plugging the hoses in the incorrect area? thanks for your guidance.

 

[scoflaw]

EX. manifolds can be left off. The one that doesn't need to be blocked is the 1 that goes to the circ. pump. You can either cap off the housing or plug the hoses.

 

[t0mmy91]

EX. manifolds can be left off. The one that doesn't need to be blocked is the 1 that goes to the circ. pump. You can either cap off the housing or plug the hoses.

sounds good, thanks for the help. by circ pump, you mean the water pump impeller in the outdrive right? not the engine mounted water pump?

pardon my ignorance, but i still feel like i am missing something. the 3 coolant hoses that go out of the t-stat housing (not including the 4th for circ) go to various connections on the block right? if i remove them at the tstat housing, wouldnt i have to plug both the hoses and also cap the housing ports to build pressure? im not at the boat at the moment so im not positive where the 3 hoses go to out of the t-stat housing, i think this is my issue following your steps. thanks again.

 

[scoflaw]

The 2 small hoses go to the exhaust manifolds. 1 large one comes from the drive. These are the 3 that get capped at the housing

 

[t0mmy91]

The 2 small hoses go to the exhaust manifolds. 1 large one comes from the drive. These are the 3 that get capped at the housing

awesome, thankyou!

the drive is the engine correct? so no need to cap the smaller line coming from the outdrive correct?

 

[t0mmy91]

The 2 small hoses go to the exhaust manifolds. 1 large one comes from the drive. These are the 3 that get capped at the housing

sorry im having an issue understanding this, but if i remove all 4 hoses and block off all 4 outlets at the t-stat housing with caps, wont that leave the engine water pump able to leak air? wouldnt i have to cap that hose also? and if so, why not just leave water pump hose connected to t-stat housing?

 

[scoflaw]

Yes that one stays connected

 

[t0mmy91]

Yes that one stays connected

got it, thanks so much for your help!

 

[t0mmy91]

Take the 2 sensors out of the t-stat housing nd use them for a schrader valve and a gauge. Plug 3 of the 4 hoses. Should easily handle 20 lbs.

hi! today i plan on installing the intake manifold as all of the parts have arrived. i plan to let the silicone sit 24 hours to dry, and sometime tomorrow attempt the pressure test. tomorrow if it holds pressure, how long do you allow it to sit at pressure before you conclude all is well, and no crack? a few minutes, hours?

 

[scoflaw]

Silicone on the china wall? No need to wait that long there is no pressure there. If you have a leak you'll know it right away.

 

[t0mmy91]

Silicone on the china wall? No need to wait that long there is no pressure there. If you have a leak you'll know it right away.

ok gotcha, how long do you let the system sit under pressure before you can conclude there is no leaks? is just a few minutes holding 15-20 psi good, or do you let it sit longer to confirm?