Oil additives for blowby problem?

[skipjack27]

I'd much appreciate opinions and experience re the use of oil additives to ameliorate blowby problems in my Volvo Penta AQAD41A (1987 model). I've previously recounted on this forum my problem with oil squirting out of the crankcase breather at high revs, and received a great deal of very helpful advice. A compression test and borescope revealed a very worn engine, with compression way below the bottom limit on all cylinders. Obviously, it is the blowby gases that are forcing the oil out of the crankcase breather - starts as the occasional drop at 2700rpm, and rises to quite a fast trickle into the bilge at around 3400rpm.

Curiously, the engine otherwise runs extremely well - starts faultlessly in the coldest weather, doesn't smoke or overheat unduly, has reasonable power, etc. But I have yet to decide whether I want to keep this boat - it has been disappointing in some respects, but needs to be further explored. The engine obviously needs to be rebuilt, but how comprehensive this rebuilding will be depends entirely on whether I see a future for the boat, or whether I just want to make sure it's saleable. I've already spent a great deal of money (in my humble terms) on this boat, and I'm not prepared to spend a lot more fixing it up for another owner.

Pardon my longwindedness: but I'm looking for workarounds - bandaids - for the oil discharge problem. A cure would be far too much to ask, but anything that helps to reduce the oil flow into the bilge would make the boat more useable and help me to explore the potential of the boat and thus make a decision about the nature of the rebuild.

What I really want to know is whether the various oil additives (Lucas, etc) that are advertised for blowby problems are likely to be useful in ameliorating this oil discharge problem. Do they work at all? And are they suitable for use in marine engines? Do they cause problems themselves?

Jeff

 

[DJ]

Re: Oil additives for blowby problem?

Skipjack,

I assume diesel? I'm not that familiar with older Volvo's but all diesel engines have similar characteristics.

There are NO miracle cures. I would NOT want you to put in a temporary Band Aid to try and pawn that worn out engine off on another unsupecting buyer.

If the compression is that low, you are close to having a MAJOR failure by having a piston ring go awry and ruin the engine or, at least, a cylinder.

Diesels will run with lower compression and oil control. But, not well. If the oil blow by is that bad, you run the risk of a "run away". A run away is where the engine starts to ingest and burn it's crankcase oil as a fuel. If it happens, you have NO control. It will run (at wide open) until it either blows up or seizes due to no more lube oil. SCARY! If the engine blows, you have a distinct possibility of an an engine part "holing" your boat-read SINK.

If you don't like the boat, sell it and disclose what is wrong with it.

Those engine are VERY rebuildable with great success. THe key is to do the rebuild before something catastrophic happens.

 

[Luhrs28]

Re: Oil additives for blowby problem?

Skip: In my opinion your only hope is to modify the valve covers to fit much bigger crankcase vent filters. You now have a lot more CFM of air to vent out than the engine designers ever anticipated. If you install big vent filters on the valve covers you'll reduce the crankcase pressure and the oil will be back under control.

I would remove the valve covers, figure out what the biggest pipe coupling is that can fit on there, then cut out the valve covers and weld on the pipe couplings. Then get some tank breather vent filters from McMaster-Carr supply and attach them. (or if you're real clever you might even be able to find some shop-vac filters at Home Depot that will work.)

Good luck.

 

[infideltarget]

Re: Oil additives for blowby problem?

Agree wiht DJ 100%.

That said...after being in the parts biz for so long, and also on the consumer end as a pro driver, I will offer up this: Lucas. Most any of the miracle engine cures will work to up the compression for a little bit, by thickening the oil film on the cylinder walls, and reducing blow-by. Lucas is the only one I would even come close to recommending, and have used it myself in many engines, to get a few more hours out of it prior to a rebuild...BUT NEVER TO MASK A PROBLEM FOR RESALE!!! That said, any time you leave an oil film on the cylinder walls in a diesel engine, you run the risk of a runaway. If your deisel pump is turned up just a bit too much, from say, trying to recoup some of the power lost due to the lowered compression...you can really have an issue on your hands. A runaway diesel is no joke, and could really be a fatal catastrophe on a boat. Listen to DJ...fix it right, or sell it as is, with full disclosure.

 

[DJ]

Re: Oil additives for blowby problem?

Skip: In my opinion your only hope is to modify the valve covers to fit much bigger crankcase vent filters. You now have a lot more CFM of air to vent out than the engine designers ever anticipated. If you install big vent filters on the valve covers you'll reduce the crankcase pressure and the oil will be back under control.

I would remove the valve covers, figure out what the biggest pipe coupling is that can fit on there, then cut out the valve covers and weld on the pipe couplings. Then get some tank breather vent filters from McMaster-Carr supply and attach them. (or if you're real clever you might even be able to find some shop-vac filters at Home Depot that will work.)

Good luck.

Band Aid.

Hopefully very obvous to a boat surveyor. If not, cheating someone is NOT the answer.

Do the right thing-disclose or Pony Up and rebuild.

 

[Luhrs28]

Re: Oil additives for blowby problem?

The OP said: "I'm looking for workarounds - bandaids - for the oil discharge problem" That's exactly the info I gave him.

You guys are confusing a technical topic with a question of ethics. There are many tricks used to get another year or two out of a tired engine before rebuilding. Are they all unethical?

 

[infideltarget]

Re: Oil additives for blowby problem?

The OP said: "I'm looking for workarounds - bandaids - for the oil discharge problem" That's exactly the info I gave him.

You guys are confusing a technical topic with a question of ethics. There are many tricks used to get another year or two out of a tired engine before rebuilding. Are they all unethical?

Yes they are if you are doing it to mask an issue for resale. The OP mentioned he may be selling the boat, so yes, this would be unethical, and possibly fatal on a boat. A Kubota two cylinder diesel tractor engine run-away while tilling the garden is different than a four cylinder volvo running away while in a boat four miles off shore. A Band-Aid in this case is dangerous to him, and to anyone on his boat.

 

[goodman333]

Re: Oil additives for blowby problem?

Hello Skipjack,

I have previously experienced a great solution for the lack of compression in my engine by using the Pro-Ma Performance Product MBL8. This amazing product is genuine with its claims and absolutely harmless for any internal combustion engine (including Gearboxes, Differentials and much more) However don't just take my word for it...have a look at some of the testimonials of other boating enthusiasts (A person with a 23 ?' Stretch Craft has saved thousands of dollars) at ... http://fueloiltreatments.com.au/Testimonials/Boat.html

 

[skipjack27]

Re: Oil additives for blowby problem?

Many thanks for the advice - more on that in a moment.

But I'm very surprised by the notes on ethics. I said:

The engine obviously needs to be rebuilt, but how comprehensive this rebuilding will be depends entirely on whether I see a future for the boat, or whether I just want to make sure it's saleable. I've already spent a great deal of money (in my humble terms) on this boat, and I'm not prepared to spend a lot more fixing it up for another owner.

My (admittedly very limited) understanding of rebuilding is that the cost of doing so can vary greatly, depending on how far you want to go in ensuring the rebuilt engine is going to last for a while. Whether I keep it or sell it, I intend to rebuild it. And, in the case of selling, this is hardly an ethical decision: who's going to buy a boat with a frankly tired engine? If I decide to keep the boat, the rebuild, though, will be much more of a "bells and whistles" thing.

Returning to the technical advice: I'm very grateful for the notes about the possibility of a runaway. NOT ONE of the mechanics who've been working on it so much as mentioned this. Instead, their advice was that if I chose to I could probably tonk around for another 5 years or more before the engine failed. So, until a rebuild is done, I've decided to limit the revs to 2800 (max for this engine is 3600). The engine gives every sign of being very comfortable at that point: no smoking or overheating, and the crankcase breather merely allows a drop of oil into the bilge every minute or so (all evidence of crankcase oil emission completely disappears below about 2800). I won't be using any additives, either.

The runaway possibility still concerns me, though, and I wonder if DJ or someone else can clarify the actual mechanics of it a bit further. How does the engine "ingest and burn its crankcase oil as a fuel"? I mean, how does the crankcase oil get into the cylinders? Does it enter from the crankcase into the cylinders by seeping past the worn rings?

Thanks,

Jeff

 

[fishrdan]

Re: Oil additives for blowby problem?

How does the engine "ingest and burn its crankcase oil as a fuel"? I mean, how does the crankcase oil get into the cylinders? Does it enter from the crankcase into the cylinders by seeping past the worn rings?

I never heard of "runaway diesel" before so I HAD TO googled it, youtube has some good video's with it too Basically, blowby causes the oil to mist, this is sucked into the breather, then into the intake. The engine uses this as a fuel source and runs away with it's new found, unlimited fuel source, until it runs out of oil and self destructs.

I wouldn't want to see this coming from hatch of my boat

http://www.youtube.com/watch?v=5zx3qKX_Pno

 

[DJ]

Re: Oil additives for blowby problem?

^^^^perfect explanation.

 

[skipjack27]

Re: Oil additives for blowby problem?

But I'm still puzzled. I thought the sort of thing DJ is warning about happens where the crankcase breather is directly piped back into the engine intake. This is not the case on my diesel.

Also: the amount of oil mist produced doesn't vary much from idle to full revs - most extra mist generated condenses in the crankcase filter into a liquid and trickles out over the rear of the engine into the bilge. This is why no-one, including me, picked up this problem until quite late. The crankcase breather filter sticks up like some kind of flag, of course, but the serious oil emission is not visible until you get down in the bilge at high revs and look under the engine to see the developing stream of liquid into the bilge. I guess I find it hard to believe that the quite spacious and well ventilated engine compartment on my otherwise small boat could build up enough oil density in the air to feed a runaway.

Finally, if enough oil mist could be generated at max revs to fill the engine compartment (which, as I said, is quite spacious for my 27' boat, being really built to house two diesels) and thus provide enough density in the air to feed the air intake to a dangerous and self-sustaining level, wouldn't raising the engine hood (roughly 7' x 5'), and thus exposing the entire compartment to fresh air, immediately starve the runaway?

Interested to hear any replies to these puzzles.

 

[Luhrs28]

Re: Oil additives for blowby problem?

Your goal should be to reduce crankcase pressure to a minimum. You can do this by installing the big breather ports/filters as I mentioned. Why wasn't it built that way originally? Because the engine manufacturer had to meet Federal emissions rules, plus a new engine doesn't have much blowby either.

When I first got my '81 Olds diesel 2 years ago the rear main seal was leaking oil badly. One day I cleaned out both crankcase breather tubes coming off the valve covers and installed new filter elements in them and the seal stopped leaking instantly, 'cause the crankcase pressure was reduced to near zero.

In my opinion with a normal engine compartment that has louvers for air circulation, and filters on the crankcase vent breathers, there should be no way you're going to have a runaway diesel.

 

[skipjack27]

Re: Oil additives for blowby problem?

Thanks, Luhrs28, for that your practical advice. I don't have the mechanical skills to implement your ideas myself, but I've recently been put on to a mechanic who is reputed to be good with diesels and will discuss them with him.

I guess, though, that rather than going to the lengths of modifying the engine, it would probably be better to live with the blowby until rebuild time.

Your final sentence was especially resonant, though: my feelings, exactly. I just can't understand how an engine setup like mine (crankcase breather vents through a filter into the engine compartment - no direct input into the intake; roomy, well ventilated engine compartment; little ejection of oil mist (as against liquid) even under very high load) could possibly sustain a runaway. And if it did start: how could it continue if I simply raised the cover over the engine compartment - which, being the transom floor, can be done in a moment. DJ and others in this thread have, however, been quite vociferous on the subject. They clearly have knowledge and experience far beyond mine, and I'm concerned about the whole thing.

In short: I remain sorely troubled.

 

[jrs_diesel]

Re: Oil additives for blowby problem?

A big thing to remember about a diesel engine, is that they don't regulate the air going into it like a gas engine does. Diesel engine speed control is done by adjusting how much fuel is injected into the cylinders. This also allows for a wide variety of air intake options, such as super or turbo charging.

Diesels can also run on a variety of fuels other than diesel fuel. Kerosene, propane/CNG for example. Or as mentioned, it's own lube oil. If ANYother fuel source somehow finds it way into the cylinders, the engine will burn that. If there is enough "other fuel" the engine can still run, even if the normal diesel fuel supply is cut off. That's where it gets scary. In a runaway, the engine can exceed rated RPM's and self destruct in a spectacular fashion. While this is bad for any diesel engine, it's even worse on a boat for the fact that it can strand the boat in open water or even catch fire.

Oil can find its way into the cyliders other than just your crankcase vent. We had a ship a few years ago (USCG) that had a runaway after an oil seal let go in the supercharger. Was not a pleasant experience for the crewsince they tried several methods to get teh engine back under control and shut down. They did not have the intake air cut off valves installed at the time.

http://en.wikipedia.org/wiki/Diesel_engine_runaway

 

[skipjack27]

Re: Oil additives for blowby problem?

In view of the warnings expressed in this thread, I got a diesel mechanic from the local Volvo Penta dealership to come down to my boat and talk about runaways.

When I described the warnings I'd received on this forum, his response was a wry smile. I guess he gets a lot of this, as a professional mechanic. In any event, he said that the chances of any kind of runaway involving the engine ingesting crankcase oil was extremely remote in these sorts of engines - not physically impossible, but no-one in his organisation had ever encountered a runaway of this kind. He did point out that in some engines the crankcase breather is directed into the intake, and in that circumstance a runaway was more probable.

Anyway, the problem is going to go away quite soon. I've decided to go ahead with a rebuild as soon as possible.

 

[DJ]

Re: Oil additives for blowby problem?

Your "profesional" mechanic is right. If you've been venting to bilge, all this time, slim chance of runaway. However, venting to bilge is NOT a good idea. Smell, etc.

I haven't seen a diesel with a "draft tube" (vent to bilge) in 10 years.

 

[roverjohn]

Re: Oil additives for blowby problem?

Most runaways that I've seen are the result of turbo bearing seal failures. The idea that crankcase blowby would cause one almost seems silly but I guess anything can happen. If it were me and your mechanic says you could run for years at lowered output I'd install a catch tank somewhere above the engine where blowby gasses can collect and hang out before venting. Some oil will separate out and then gravity will cause it to drain back into the crankcase. Very likely you'll also catch some water vapor so put it somewhere where it will stay warm to minimize this. Seems a drag to have your boat down now when you could buy a core, have that rebuilt, and then do the R&R at the same time. Sell your current engine as a core when it's out or just send it back to the rebuilder.

 

[skipjack27]

Re: Oil additives for blowby problem?

Thanks for the comments, guys.

In fact, it's now winter here in Perth, Western Australia. So, I'm going to have the engine rebuilt in the next month or so. The quote I've received from a reputable mechanic is $15k (much better than the $23k quoted by the organisation he used to work for).

If anyone happens to have any useful comments about good things to have done in a rebuild, I'm all ears.

Jeff

 

[DJ]

Re: Oil additives for blowby problem?

I assume it is a closed cooling system?

If so, make sure they do a thorough inspection for cavitation pitting in the cooling passages and cylinder liners.