Blue smoke

[Full Moon]

4 or 5 months ago we over heated both engines at the same time for different reasons. We corrected the proplems and everything was fine. We took a trip to Vieques and no problems, no smoke on the old 8v53s. It sat for 3 or 4 weeks and I finally got back to check everything out. Both engines started right up but were blowing blue smoke. The starboard engine finally settled down, but the port side just about smoked the marina out. The smoke reduced a little bit but still really bad. These engines have never smoked at all, even after setting a while. My old mechanic is off the island but he said to change fuel filters and we just cleaned the Raycors, but i never thought to check for water. I know this could be fried rings or something major, but it is strange that everything was fine for our trip but suddenly went bad just setting in the slip. Any ideas? Bad fuel? Boat is a 1970 41 Conv. with 850 and 150 hrs. since overhaul.

 

[Genesis]

Blue smoke = lube oil. Blower seal? If so be careful.... that seal fails entirely and you get a runaway. Got working airdoors on those engines, yes?

 

[Full Moon]

No blower on an 8v53 but the air doors need to be checked, I haven't done that in a while.

 

[piripucha]

All Detroit have blowers. Check your oil level, you are burning oil!

 

[Pascal]

I ve never had 8v53s but I also thought most if not all 2 cycle DDs had blowers...

If the smoke is really blue, and not grey, it's definitely oil. Also, smell the oil on the dipstick and compare to the other engine. Does it smell burnt?

 

[RT46]

I agree with Pascal,

I am pretty sure the Detroit Diesel 2 Stroke requires a blower to push out combustion gases.

It is possible for the DD 53 series not to have a turbo charger.

 

[Full Moon]

I'll do the sniff check tomorrow. They have never burned oil but you have to run them below the full mark because if you top them off to that mark it will blow out to an "operating level" anyway. Once it reaches that point it is stable.

Blower is the same as Turbo? These are naturally aspirated not turbo charged. They may have some kind of mechanical blower but I don't think they are that complex.

 

[Pascal]

The blower on a DD is more like a supercharger, except that it s gear driven, not belt driven. Even naturals have them... Turbos on the other hand are turbines driven by exhaust gases.

 

[Genesis]

All DD 2-strokes have a blower (they will not run without it as there is no second piston stroke to remove the combustion products and introduce a fresh air charge for the next power stroke.) Some (commonly called "naturals") do not have turbocharger(s).

The blower is lubricated by engine oil and has seals on the shafts. If these seals fail oil will leak into the intake path and be blown into the engine, then burned. If the leak is modest you get blue smoke. If the leak is serious (and it can be) the engine can get enough oil through this path to run on, and will run away.

If it's blue (and not gray) smoke it's engine oil that is being consumed and the most-common way for it to get into the engine where it can be burned for a non-turbo engine is through the blower seal. It is also possible for severely-damaged oil control rings to permit engine oil to pass north of the that point in volume; this ring does not reach the exhaust ports during engine operation. In a circumstance where oil control at the piston has been lost the carried-up oil is then ejected into the airbox and, when the piston descends, blown into the cylinder and burned.

Obviously it's a hell of a lot harder to fix that (this problem typically requires new cylinder kits as the damage that leads to this problem usually includes scored cylinder walls) than the blower seal.

Checking the blower seal is pretty easy although controversial among some. Remove the airhorn and start the engine (WARNING -- make damn sure nothing can get sucked into the open blower!) then shine a bright flashlight on the end plates. With the rotors spinning you can see the entire end plate and, if there's oil leaking from the seals, you'll see it. Just be very, very careful doing this as the open blower will "eat" anything that gets close to it, including parts of you.

How is your crankcase blow-by? If normal the odds of the problem being at the blower go up a lot although you can have an oil control problem with good compression rings (not common, but possible.)

 

[krush]

Kinda strange that overheating would cause both engines to have blower seal problems, don't ya think?

Considering the original poster said he overheated both engines (how badly, we don't know), and the smoking began AFTER these events, it would be diligent to consider this event as a possibly for causing the smoke.

1) Now, common sense for engine experts, especially "diesel gods", would first go with the fact that quite often when an engine is overheated severely, it is not abnormal for the oil rings to get messed up and the thing burns oil. So now we have ONE possibility.

2) Another thing that any "diesel god" DD expert should probably mention is that 53 series engines are wet liner engines. And as nearly all that read the wonderful words of wisdom plagiarized--I mean posted--on this forum, we know that overheating a wet liner DD creates a situation that has a strong possibility for O-ring fail in the liners, liner cracking, head cracking, distortion, or other similar problems that would cause fluids to go places they are not designed to be.

It is possible that the original post is seeing white smoke or white smoke tinted by blue as well.

Regardless, the events leading up to the failure may have a contributing cause of the smoke. Or maybe not. But two engines needing blower seals at the same time may be possible, but seems less likely to me.

 

[krush]

Or what about leaking water in to the cylinders while sitting? Starting up the engine, bending a rod or scoring the cylinder.

Was the coolant level low?

Quite a few possibilities.

 

[Genesis]

All of those are far more difficult (expensive) to fix than the blower is, which is why you check the simpler ones first.

Cooked liner seals usually (but not always) results in coolant in the oil. Cracked heads can result in all sorts of fun events including the symptoms involved, but both of those are expensive to fix and it's wise to eliminate the less-expensive-to-fix and easy-to-verify possibilities before ripping the engine apart.

Carry-up due to oil control problems (possibly caused by overheating) can usually be seen through the inspection covers on the airbox but the presence of excessive amounts of oil there doesn't tell you how it got there, which is why you want to check the blower seals first. If they're dry you know where it didn't come from and you can check the blowers (both engines) in an hour or so, assuming reasonable access.

 

[Boatnut]

Here is a good place to mention where the loss of respected knowledgeable proffessional would be great. It's sad that the people who type what they read in books, or google, will argue and make them hesitant to post. Unless you know someone with proven experience and works in the business, beware the guiy who tells you to jump in and take things apart,

Unless you are experienced in Diesel Engine repair, consider getting a reputable mechanic to diagnose the problem, it will save you much confusion, and probably some money in the long run.

 

[Boatsb]

Here is a good place to mention where the loss of respected knowledgeable proffessional would be great. It's sad that the people who type what they read in books, or google, will argue and make them hesitant to post. Unless you know someone with proven experience and works in the business, beware the guiy who tells you to jump in and take things apart,

Unless you are experienced in Diesel Engine repair, consider getting a reputable mechanic to diagnose the problem, it will save you much confusion, and probably some money in the long run.

And it might also save some fingers too.

 

[Full Moon]

Boatnut. Good advise. I've got a professional mechanic checking it now. They started it up and felt all of the cylinders and #4 cool. They did a compression test and it was 300psi. Next step is to check the valves and hope that's it, but i would bet it is rings. We didn't see or smell anything in the oil so hopefully no cracked head or something like that. Just one of those things with a boat that you start digging a hole it's hard to find a place to stop.