Steam coming from manifold cover

[jlh]

I have a 1986 5.7L 260hp mercruiser. I pulled the black hose off the top of the portside manifold cover and noticed steam coming out of the hole, is this normal or could there be a problem?<br /><br />Thanks for your help.

 

[ed hobbs]

Re: Steam coming from manifold cover

Are you refering to the hoses on the valve covers? They attach to the flame arrestor on top of the carburetor.

 

[jlh]

Re: Steam coming from manifold cover

Thanks for catching my mistake. Yes, I am referring to the hoses on the valve cover that attach to the flame arrestor. And the engine was running when this happened.

 

[elpaso]

Re: Steam coming from manifold cover

The steam is probly water vapor - due to water<br />in engine oil. Look inside valve covers for<br />milky oil. If found - risers or exhaust manifolds<br />are first place to check for water leaks.<br /><br />Water in oil will ruin an engine - in short order.

 

[tylerin]

Re: Steam coming from manifold cover

more than likely its blow-by (oil). Rings are probably the cause. A little is ok. But if its like a chimmeny be prepared for rebuild. Your motor is 17 yrs old I assume

 

[elpaso]

Re: Steam coming from manifold cover

Only thing that makes " steam " is water vapor.

 

[tylerin]

Re: Steam coming from manifold cover

I know that steam is from water. But is it steam you see or is it smoke.

 

[akriverrat]

Re: Steam coming from manifold cover

by products of complete combustion are co2 and h20. lots of it.

 

[jlh]

Re: Steam coming from manifold cover

I had a feeling it could be water. I'm sure its steam and it seems to start out a few little puffs but then becomes a little more steady as the engine runs. Its not a huge amount of steam coming out but its enough that you can see it and I don't want to take any chances. This is a remanufactured engine that was just put in. The manifolds are new, the risers were fine according to the mechanic so we used the old risers.Unfortunately the mechanic is on vacation and I can't ask him about it until he gets back.

 

[Ralph 123]

Re: Steam coming from manifold cover

Maybe I'm just a jerk for saying this but why in the world would anybody put old risers on a brand new engine (unless the risers were like 1 season old) It just makes no sense to me given how many time riser failures account for overheating and engine failure.

 

[magster65]

Re: Steam coming from manifold cover

No doubt. Rotten risers and improper winterizing keep the entire boating industry busy.

 

[akriverrat]

Re: Steam coming from manifold cover

till the rings seat fully you will get some blowby. some less after they seat. crankcases wouldn't need venting if all the seals were perfect...rings,valve guides. how many hours on this engine? is the oil milky?

 

[jlh]

Re: Steam coming from manifold cover

Thanks for all your comments and information. Hopefully I'll be able to check the engine out this weekend.

 

[jimmmy]

Re: Steam coming from manifold cover

How much blow-by is OK? I have a 3.0 L merc that has given me endless low RPM problems at WOT. Had two seperate mechanic look at engine over last 7 weeks -moocho$. Carb rebuilt, head gasket replaced and head machined, checked for exhaust restriction, checked engine alignment, new points, plugs, condensor, timing ok. The last mechanic seemed to think that the blow-by was a little excessive?? Compression check shows 150PSI in all 4 cylinders. Engine in gear runs smooth to 2600RPM about half throttle, then there's no more between half and full (actually bogs slightly to full). Runs smoothly to 4500RPM in neutral. Exhaust not smoking but a lot of blow-by to spark arrestor (mainly air not much smoke).<br />running out of $ and options. Could it be carb still? Could it be weak spark, that still shows as ok timing? Is engine pooched? Running 19 pitch prop.<br />Help anyone?