Thank you for reply. I'm confused.
I thought that block test will rule out head gasket or cracked head. If leak is from combustion chamber then high pressure will push gases into coolant and I would have exhaust gases in my coolant. I did block test several times and it did not detect any exhaust gases in my cooling system.
Head Gasket or Combustion Leak Test Procedure (Gasoline Engines Only)
I have purchased block test kit to see if I have issues in my HG, block, or head. Am I missing something?
Since I have negative block test I thought that coolant getting before combustion chamber which would be intake. Is that possible?
The block test can determine a HG/cracked head if there is presence of exhaust gases in the cooling system, but unfortunately just because you didn't find any exhaust gases doesn't mean that you can rule it out. I had 2 cracked heads and my truck passed a compression test, a block test, a leak down test, and a cooling system pressure test. The reason why was because the leak/crack would seal up after a few seconds after start up and then it was undetectable. It wasn't until several months later when it was missing all the time that it started failing the tests.
A negative block test doesn't confirm that coolant is getting lost before the combustion chamber. The white smoke out your tail pipe on start up on the other hand, does tell you that coolant is being burned up in the combustion chamber. It's nasty, but gulp a mouthful of exhaust and if it tastes sweet at all or smells like coolant, you'll know.
Sorry for the downer news, but that's why I really doubt it's just an intake manifold leak. Chances are if it was, you'd see coolant leaking when it's idling or a puddle under the truck after being parked overnight. Intake manifold gaskets don't usually seal up after 30 seconds, but my cracked heads did that for over a year so I know that's possible. I'd start mine up, it would miss and stumble for 10-30 seconds, I'd rev it up, it would heat up, seal up, and it would smooth out and drive fine until the next time I started it up. I was missing about 1/2 of my coolant reservoir tank every 1-2 weeks. After a while it just never smoothed out anymore, it just continued to miss and at that point I had the engine rebuilt.
Although it's probably not going to help IMO, you can see if it's an intake manifold leak by getting a small bottle of propane and opening it up a little so it's leaking out. Go around the intake and all the vacuum lines with the bottle (while the engine is running) and if it sucks in the propane, the idle will change and you know you got a leak.
Another thing you can do is pull the spark plugs (inspect them in the process) and then leave them out overnight. In the morning, look down the holes with a flashlight and see if there is coolant in any of the cylinders. Then you know it's HG/cracked head(s). If that doesn't help you determine anything, I'd do a compression test and a leak-down if necessary after that. But as a I said earlier, even those test don't always determine anything as mine had 2 cracked heads and no tests were conclusive.
