Mercruiser 3.0 - exhaust escaping below exhaust manifold

[Jay E.]

Replaced the manifold and gasket and still have the problem. Didn't see any cracks. Wondering if it could be the gasket below the cylinder head assembly.

 

[Scott Danforth]

welcome aboard.

did you check both the head and the manifold with a straight edge to make sure the surface was perfectly flat. If not perfectly flat, take the parts to a machine shop and have them surfaced

also, are you using the metalized gasket, or the paper gasket. if using paper, go get a proper metalized gasket.

 

[Bondo]

Replaced the manifold and gasket and still have the problem. Didn't see any cracks. Wondering if it could be the gasket below the cylinder head assembly.

Ayuh,..... Welcome Aboard,...... When ya took it apart, did ya find, 'n Id the problem spot,..??

Before ya put it back together, did ya clean both surfaces to clean Flat cast iron,..??

Which gaskets did ya use,..?? how 'bout sealants,..??

 

[Jay E.]

Did not have an absolute id of the problem. Where it appeared the leak was coming from, the manifold gasket was paper thin. Thinner than other areas. I cleaned the cylinder head with a wire brush and carb cleaner. Thought I got it all clean. Put a new manifold (Sierra) on and used the gasket provided. It was a metallic like material about 1/8" thick. Did not use any sealants.

Did not check flatness of the cylinder head.

If I remove the manifold again, do I need to use all new gaskets or will the new ones I previously installed still work?

 

[Scott Danforth]

You will need new gaskets. Use a ground straight-edge and feeler gauges to check flatness

 

[Jay E.]

Looks like I missed the head gasket being broken (see photo). Is there a way to repair the head gasket (e.g., epoxy)? If not, how difficult is it to replace the gasket?

 

[Bondo]

Ayuh,..... The head has to come off,..... after cleanin', 'n checkin' new gaskets are used goin' back together,....

'n Ya, it's fairly involved,....

Good news is,..... We'll be here to talk ya through it, if ya decide to tackle the task,....

 

[Jay E.]

Thanks for all your help. I have now removed the head and confirm the gasket was blown. I plan on taking the head to a machine shop to have it redone. Other than the gaskets, what should be replaced? Push rods?

The block looks good to me, but I am no expert. What are your thoughts? Is it clean enough?

 

[tschmidty]

Clean is fine, but straight and flat are the concern. Check the top of the block really well with a good straightedge and pay particular attention to where the gasket belw out.

 

[fishrdan]

Looks to me like there is still old gasket material left on the block, black areas. I use razor blades held at 90* to the block surface, to scrape the surface, but you have to be very careful to not scratch the block, just remove the junk to get down to bare metal.

Chase all the head bolt holes with a tap and wire brush the head bolt threads, to clean out all the old sealant. Use Permatex Aviation Sealant on the head bolt threads during assembly.