Steam rising

[paulrfrancisco]

First, Twin MercCruiser 7.4 Bravos 1990... I have steam rising from the space between the head and manifold on one side of one motor. It's slight, but noticable. Its difinately NOT coming from the riser gasket. I am unable to see if it coming from a manifold gasket or the head gasket since I simply am not able to get underneith uit enough to see ... So I'm looking for an over/under on it being the manifold gasket only, vs, the bigger problem of it being a head gasket.

Also, if it end up being only the manifold gasket, do I take the cheap/easy route and only do that one side or should I bite the bullet and do both sides of the motor, or both motors...? Opinions please.

Lastly, If I remove the manifold, am I going to see a "tell tale" that there was a leak in the gasket? Is the water passageways from the head to the manifold?​

 

[Bondo]

Re: Steam rising

Ayuh,...

The Manifold Gaskets, At the heads, Only holds back Exhaust... There's No Water there...

 

[paulrfrancisco]

Re: Steam rising

Thanks Bondo, what then would you look for next then? should I remove the manifold and maybe I'll see where the leakis from without having to start and warm up the motor? (tell tale rust, or "clean" spot)​

 

[mthieme]

Re: Steam rising

Can you feel around for wetness and narrow it down?

 

[paulrfrancisco]

Re: Steam rising

maybe.. but the issue is it seems to "steam" when the engine is hot or warm, and to run the enging, I have to have the batteries installed. this issue is on the side next to the batteries so there is very little room to get in to look even with a mirror and light... To feel in the space, I would have to reach up behind the manifold and that space is quite narrow...​

 

[paulrfrancisco]

Re: Steam rising

Bump....

If there is no water that flows from the head to the ex-manifold, then what would the next place that it would likely come from? Could it be a perferated freeze plug weeping, or should I expect it to be a head gasket? In the next week or so, I'll put the batteries in to get it started and maybe with a mirror and light, I might be able to see more, but your opinions are requested.​

 

[Bondo]

Re: Steam rising

In the next week or so, I'll put the batteries in to get it started and maybe with a mirror and light, I might be able to see more,

Ayuh,...
Have you been to the Adults Only section at the top of this forum,+ downloaded the Manuals for these motors,...
You Should if you haven't...

If you've got Steam rising from Under the exhaust manifold,..
The Manifold to Riser gasket is the 1st suspect....
Next would be a loose fitting under the manifold, or along the side of the block....
After that,.. It's probably a Rotten coreplug, or much more likely a Freeze Cracked manifold or block....

 

[navis]

Re: Steam rising

Have you checked the oil for water? That should help to narrow things down a bit too.

 

[paulrfrancisco]

Re: Steam rising

The steam was there at the end of last seasons, so I doubt its a freeze cracked block or manifold. and at the time, there was no water in the oil... Thanks for the suggestions, though....​

 

[paulrfrancisco]

Re: Steam rising

Well I got the motors running this weekend and its still steaming between the manifold and the head just as I suspected... I have been in there with a light and mirror and examined everthing thats visable while the motor is running. The hoses appear not to be leaking and the head gasket doesn't seem to be the source and the riser gasket is definately not leaking...

Bond-o mentioned a possible crack in the block. Could this be in an area between the manifold and the head, since I can see most of the block under the manifold below the head gasket? Does anyone have a picture/diagram of the water jacket on these 7.4L moters so I can maybe zero in on it a bit more?

The funny thing is last spring, it was also steaming then and I had it pressure tested, and the mechanic replaced the risers... The steam smells like antifreese and I lose a little every couple of weeks, so I'm at a loss... What would you suggest I look for or do next...?​

 

[paulrfrancisco]

Re: Steam rising

Does anyone have a picture/diagram of the water jacket on these 7.4L moters so I can maybe zero in on it a bit more?​

BUMP... Just wondering if anyone has some sort of a picture or diagram of the Water Jacket on the 7.4L block and Heads... Not just the picture of the plumbing... I have that already...thanks​

 

[Bondo]

Re: Steam rising

Just wondering if anyone has some sort of a picture or diagram of the Water Jacket on the 7.4L block and Heads...

Ayuh,... No Pictures... But,.. Both the Block,+ the Head are full of Water where you're having the Problem...
Some heads have a plug or 2 in that area,...

I suggest pulling the exhaust Off so you can See what's Up...

 

[paulrfrancisco]

Re: Steam rising

Thanks Bond-o,

Do you have an opinion of how typically tough the manifolds are to take off? The risers are recently replaced, so they should be easy, but what about the manifold bolts... The boat is a 1990 so I'm sure the mani's are not original... but should I be expecting that the bolts would break?

Also, I'm pretty sure the steam smells like antifreeze. Is there Antifreeze in the manifolds? if not, and it ends up being a crack, I guess it would probably be a head. Have you seen heads crack before or do you think its more likely a failed head gasket? Just in your opinion please.​

 

[Bondo]

Re: Steam rising

Just in your opinion please.

Ayuh,.. The manifold bolts Shouldn't break....
But Anything is Possible...
Ditto on whatever you find the Problem to be,...Anything is Possible....

Quit fartin' around,+ pull the darn thing Apart...
You Know there's a Problem,... Tear into it,+ See what's up...