Blown gasket for intake manifold?

[6 shooter]

ive got oil in my coolant and vacuum leak too but pulled my intake manifold off ad the intake gasket looked alright with no cracks or anything except there was that brown stuff on the gasket and looked like it had come through.
But i still cant see any cracks in it. Ive heard about oil in coolant with blown intake gaskets but can work out how it still looks ok and leaks unless it wasnt tightened down properly or something

 

[Claudy]

Could've been loose, my mates was loose and was usin water and missin. Also could be head gaskets maybe...

 

[6 shooter]

ive heard abot a few being loose. is there an art to tightning them up or something? or do they need loctite on the threads?

 

[Dayvo]

Once they are loose the damage is done, thats what happened to mine . Yes you can use loctite

 

[Claudy]

And when u put new ones in, make sure u put a blob of gasket goo on all 4 corners