4.3 Head Gasket Issue

3

300sflyer

Chief Petty Officer
Joined
Jan 1, 2009
Messages
610
I'm in the process of replacing the Merc 4.3L engine out of a 1994 19' Sea Ray. The previous owner did not winterize properly, and you guessed it... a cracked block. I found a truck engine that seemed to be in good condition, and have swapped everything needed from the original engine. I installed new felpro head and intake gaskets, brass frost plugs, and had the engine running on a skid for about 45 minutes. All was really good, until I checked the fresh oil I put in it, and it was slightly milky... I pressure tested the cooling system with 12 -14 PSI, and I can hear a very slight hissing air sound coming from the spark plug hole on cylinder #3.

I did not use any sealer on the head gaskets, as I believe they are ment to go on dry. The surfaces were well cleaned before it was assembled. I then pulled the head back off, and checked to make sure the surfaces are flat with a straight edge, and they seem to be good.

Is there any type of sealer I can apply to the gasket to fix this small leak?

Thanks for your help!
 
Howard Sterndrive

Howard Sterndrive

Rear Admiral
Joined
Nov 5, 2008
Messages
4,603
Re: 4.3 Head Gasket Issue

Fel-pro composite head gaskets are very forgiving and self sealing. If the head and block are not warped, that gasket won't leak.

Did you use sealer on the head bolts?
 
Howard Sterndrive

Howard Sterndrive

Rear Admiral
Joined
Nov 5, 2008
Messages
4,603
Re: 4.3 Head Gasket Issue

lots of good visual inspecting... magnifying glass and good light - look for cracks around #3- especially around valve seats and bolt holes
 
888

888

Petty Officer 1st Class
Joined
Jan 7, 2012
Messages
358
Re: 4.3 Head Gasket Issue

300sflyer said:
I'm in the process of replacing the Merc 4.3L engine out of a 1994 19' Sea Ray. The previous owner did not winterize properly, and you guessed it... a cracked block. I found a truck engine that seemed to be in good condition, and have swapped everything needed from the original engine. I installed new felpro head and intake gaskets, brass frost plugs, and had the engine running on a skid for about 45 minutes. All was really good, until I checked the fresh oil I put in it, and it was slightly milky... I pressure tested the cooling system with 12 -14 PSI, and I can hear a very slight hissing air sound coming from the spark plug hole on cylinder #3.

I did not use any sealer on the head gaskets, as I believe they are ment to go on dry. The surfaces were well cleaned before it was assembled. I then pulled the head back off, and checked to make sure the surfaces are flat with a straight edge, and they seem to be good.

Is there any type of sealer I can apply to the gasket to fix this small leak?

Thanks for your help!
Click to expand...
Pressure test the head of the engine. If the block cracked,why not a head too.
 
3

300sflyer

Chief Petty Officer
Joined
Jan 1, 2009
Messages
610
Re: 4.3 Head Gasket Issue

888 said:
Pressure test the head of the engine. If the block cracked,why not a head too.
Click to expand...

The heads used are from the truck engine, not the ones from the cracked block.
 
3

300sflyer

Chief Petty Officer
Joined
Jan 1, 2009
Messages
610
Re: 4.3 Head Gasket Issue

Turns out the block surface is not flat... :( Time to find another one.
 
G

gear79

Cadet
Joined
Oct 8, 2012
Messages
18
Re: 4.3 Head Gasket Issue

300sflyer said:
Turns out the block surface is not flat... :( Time to find another one.
Click to expand...
If you are going that far and have the deck blocked true, be sure to take your intake and have that deck matched, this is depending on how far the deck (block) is warped, it had to have gotten hot to warp a block. Pressure test the heads, may be cheaper to find a complete long block.
 
W

wca_tim

Lieutenant Commander
Joined
May 28, 2007
Messages
1,708
Re: 4.3 Head Gasket Issue

are you using the exhaust off the previously frozen engine?

I bought a bot from a guy once that had rebuilt the top of the engine three times. couldn't for the life of him figure out why he kept blowing head gaskets... He'd cracked one of the exhaust manifolds and it was leaking on the inside... Just a thought.
 
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