Why cylinder leak down test fáil at cold
 

87 xj
4 0
After putting a new stat now at hot the coolant overflows like there was air or combustión.
ustión.in
to diagnose that i did a cylinder leak down test at cold and i was frustrated.
i also did an adapter cause the spark plugs hole are very deep.
so every cylinder gave from 10psi to 45psi at 75psi pressure
What the?
The engines has all the rings busted?
Valve cover had the most air flow . No valve leaks as far i heard.
not onlybthe head is warped .. now.i have to rectify the cylindwrs and put new pistons?

A cold leak down test is useless. The rings aren't sealed.
Your coolant overflow is the real clue. Combustion gas is leaking into the cooling system.
This means a blown head gasket or a warped head. You need to pull the head to fix it.

Or they still have lots of air in the system after replacing the thermostat.

^^^^

And when you do a leak down test correctly it's useful to determine where the air is going; out the intake, out the exhaust, out the crankcase ventilation system, out thru the coolant .

I dont think is 100% useless but imagine to make a compression test only in hot when you have a cold engine at 6am.

As far i can check.. the rings and the cylinders have to be check

I will reach operating temp to confirm the leak in the watwr jacket. Hopefully next weekend

i started the engine without the cap at 1st
At 150f i closed the gap then level.start to rise slowly
when reached the cap . I turned off tyr engine and level dropped.
But i want to confirm it with my tool thats why i bought it
Even the fsm says the cap willmopen atb18psi so bubbles can scape

all 6 cylinders at cold , gave me horrible leak from.70% to 40% leak and from the ccv or oil cap

Last owner overheated and didnt tell me

You can see

https://vt.tiktok.com/ZSy7RX8xj/