View Full Version : Steaming exhaust

Ray Daoust
06-30-2002, 04:45 PM
" I have a CC 283 ci chev engine that steams just alittle at 1500 rpm but alot at 2500 rpm,engine is not overheating.What could be the problem?


06-30-2002, 11:46 PM
" I assume that the steam you speak of is coming out the exhaust as opposed to steam in the engine compartment. Steam in the exhaust means that you have water coming in contact with very hot metal. This is probably either in the combustion chamber or in the exhaust pieces attached to the engine. Since you have a V8 you could have a nearly plugged riser on one side so that side's exhaust manifold and riser are getting very hot which won't register on the engine temp gauge. With enough water going through the other side the engine itself could cool normally. The first thing I would do is to check the manifolds and risers. Manifolds and risers which have sea water going through them that are 5 years or older should be suspected of leaks or blockage. Check them and replace as necessary.

Water flashing to steam in a combustion chamber is normally caused by a blown head gasket. Is you engine freshwater cooled? If so check for loss of coolant as you may have a blown head gasket and what you're seeing is the result of water and antifreeze leaking into one of the cylinders. If your loosing coolant, see my post to the "Chrysler 318" question for additional diagnosis ideas. A blown head gasket could be the problem with a raw water cooled engine also, but you'll probably have to do a compression test to diagnose it. "

07-01-2002, 05:29 PM
"Just one thought to add....depending on air temperature & humidity, steaming as you describe from a wet exhaust system may be perfectly normal.

On a cool, damp morning my Catalina's exhausts produce clouds of steam, but on a hot, dry day it's barely visible. However, if you see steam just a few seconds after a cold start, be suspicious of all the stuff Bilgeguy mentioned.


ray daoust
07-02-2002, 02:01 PM
" I don't think it's due to humidity as the other motor is clean.All spark plugs look good ,iplan on doing a compression check on weds. "

07-02-2002, 02:54 PM
" Sounding more and more like manifold or risers. Be carefull, water in exhaust manifold can get back into cylinders and cause hydraulic lock and ruin the engine. I recommend that until you diagnose the problem you hand crank (wrench on vib damper bolt) through two complete turns before attempting to start it. If engine locks during hand crank, remove sparks and hand crank to expel water. Fix immediately! Let me know how you make out.

Watch for any water which might be expelled during compression test. Most likely cylinders if bad riser or manifold are 7 & 8 since they are the lowest. "

ray daoust
07-06-2002, 08:19 PM
" compression check showed 140/150 in all cylinders.i removed all conections and plugs to the risers and rodded every nook and cranny i could reach with a stiff wire,now it doesn't steam until i reach 2600rpm.tempoary fix seem to help. "

07-08-2002, 06:02 PM
Sounds to me that your unto your problem. Remember these thing rust out as well as scale up. It's usually good advice to replace them once they start to plug.

ed bishop
07-09-2002, 09:40 AM
" to bilgeguy,
you mentioned water getting the cylinders causing hydraulic lock-up and ruining the engine, could you please expand on that..thanks
Ed Bishop "

07-09-2002, 10:28 AM
" Ed,

Liquid water is incompressible, so if there is sufficient amount in a cylinder when the piston comes up during the compression stroke, it will stop the piston, crank and all causing extreme stress on the piston, rod, crank, head, valves, and block. Normally this isn't a problem during cranking as the motor isn't moving fast enough for the momentum to cause damaging stress. However if it fires and then experiences hydraulic lock, most likely something will break.

Another effect is that even small amounts of water in the cylinder during the power stroke will cause additional stress. Water in the cylinder flashes to steam during the ignition. Steam expands much more than a similar amount of heated air causing additional stress on the engine parts. This fact was used at one time in aircraft engines to increase power during take-off and combat. Small amounts of water were injected into the intake air when increased power was needed.

Chuck "

ed bishop
07-09-2002, 05:20 PM
" Chuck,
If the water in fact entered the cylinders when the engine was running, could it have bent a connecting rod...I pulled all the plugs, turned it over several minutes to clear the water, replaced the plugs and have the same symptom...sounds like a dead battery...errrrr-errrr---errr, and when I pulled the plugs again, it still turns over very slowly.
Ed "

07-10-2002, 09:42 AM
" Ed,

I assume that you know the battery is in good shape? A dead cell in the battery may cause it to look like it is charges normally, but it will bog down as soon as there is a load like cranking the engine. How about the starter? Battery wires? Connections? Is the transmission disengaged?

With the plugs out the engine should turn easily. Have you tried turning it manually with the plugs out, a wrench on any of the bolts on the front of the crank should work. Loosen the belts for this so that you eliminate the accessories as the source of the problem.

A very stiff engine means you have some internal problems (ugh!).

How did the problems start? Did you hear any knocking in the engine? Did it start occuring after the winter layup? Anything unusual the last time you used the boat?

From the info in your last append, I would first make sure that the battery and starting system is in good shape.

BTW when you cranked it with the plugs out did anything come out of the plug holes? Were the plugs wet, rusty, or fouled? "

ray daoust
07-10-2002, 02:56 PM

have you removed the battery terminals and cleaned them [shiny] if there is a black oxide not enough current will pass and give the same indication as alow battery

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