Water leaking from manifold bolt hole....HELP!
 

I'm replacing the stock exhausts on my 1991 Merc 454s. I've had to pull both motors as each outter manifold had badly corroded bolts, some of which i have had to drill the bolt heads off.

One manifold was really bad, i've had to use a lump hammer and chisels to get the thing to slide off what is left of the bolts. I managed to get it off but 3 bolts are corroded into the head. So i have started to drill them out, one of them is leaking water from the manifold bolt hole...could someone explain why this is and if i should be concerned??

Cheers
Steve

If it is leaking now after you drilled it then you drilled too far into the water jacket of the head. or the jacket has cracked behind the bolt hole. I work in a ford dealer and we have had alot of problems with manifold studs. we have had a coupe people drill too far. we have offered 2 options.

1. replace the head
2. seal and thread a plug in behind the stud.

i think everyone has opted for option 2. unless it is a real wild setup you should be ok sealing the hole. just cross your fingers that there is no migrating crack or other damage to the head that may let you down later.

the perfect repair would be replacing the head. but that costs a little $

just my 2c

Thanks for your comments Fixxxer. I made sure i didnt drill too far. there is quite a bit of space behind the remnants of the old bolt and the back of the hole. i'm just worried with all the shocks from hammering the old manifold off has caused a crack in the head?! These are stock 330s so the head is iron and pretty strong...i dont really want to have to take the head off if i can avoid it.

Like Fixxer said or the water jackets on the head are so badly corroded and ate away that it has rusted through into the bolt hole.

Is it possible your manifold is cracked?

No it's definately come from the cylinder head, manifolds were not cracked when i pulled them, they seemed intact. i guess there must be a waterway close to the manifold bolt hole.