Vetus water lock

[Sybaris]

Hi,

I have a Vetus LP 50 water lock installed on the exhaust side of my generator (Onan). The generator is under the water level, and I have an anti-siphon valve on the water line feeding into the exhaust outlet.

A few weeks ago a local mechanic changed the diesel filter on the generator and then cranked it for a long time to get it started. He also changed the oil.

Next day I ran the generator, and after about 30 min it stopped with a blown safety fuse. I checked the oil and noticed it was way above the max mark on the dip stick and assumed that perhaps the mechanic had filled too much oil, and that perhaps the fuse went because there was too much oil rather than too little.

I emptied about a liter of oil until the dip stick indicated a level close to but below max.

Having thought I had fixed the problem I started up the generator again, and again it stopped after about 30 min, and again the dip stick indicated more than max level oil.

I figured that oil cannot reproduce by itself (it would be great if it did), leaving the only other possibility of it being mixed with sea water.

I left it like that and went sailing for about 2 weeks and am now looking at fixing the problem.

Question 1: my mechanic explained to me that the Vetus water lock has a built in non-return valve which stops the water in the exhaust pipe from going back into the engine. Does the LP 50 actually have a non-return valve?

I ask this because looking at some old YBW threads I found one that talked about water ending up on the engine side of the water lock if the engine is cranked for a long time when it doesn't start, and this water can of course flow back into the engine. Having dismantled the LP 50 I can confirm that if I pour water into the outlet side it will eventually come out through the inlet side, i.e. my LP 50 does not have a non-return valve, or it is mal functioning. If they should have one i need to buy a new LP 50 but they are pretty darn expensive.​

Question 2: can I clean out the engine with something other than normal engine oil in order to get rid of all traces of salt water?

Question 3: I don't have any Vetus muffler after the water lock. Does anyone have any experience with those regarding if they actually reduce the exhaust noise noticeably more than with only the water lock?

Cheers,
Per

 

[rob2]

The water lock is basically a catcher for the water left in the exhaust line when you stop the engine. When running, the expansion of exhaust gases blows all the water clear of the exhaust, but as it stops, the water being pumped will collect in the water trap as there is no exhaust pressure to blow it clear. There is no valve in it! Where do these "experts" get their training?!

The anit-syphon valve does have a valve in it which opens under suction to allow air into the line once the pump stop, breaking the potential syphon.

What worries me, is that your oil sump is filling whilst running. If it were water, you would see the difference as it would either not mix or if conditins were right it would emulsify the oil. I'm afraid it is more likely that the piston rings are stuck and unburnt diesel fuel is being blown past the pistons into the sump and that mixes readily with the lube oil. As to cause, there are a couple of main contenders. If the rings were already stuck, through lack of use, it might explain why it took so long to get the engine to start. Alternatively, as the engine was pumping all the time your engineer was trying to start it, watser may have been sucked back through the exhaust valves once the water trap was full. That may have been sufficient to rust the rings, making them stick in their grooves.

Does the engine fire up immediately, or do you have to spinit up fast before it catches? In good condition, it should fire as soon as it turns - lost compression which would accompany sticking compression rings would need a fast spin to get it going. I would be inclined to drain the sump, as the condition of your oil is compromised, and remove the injectors to pour some Redex or similar into the chambers to try to free off the rings - let it soak for a day or two before giving it another try.

The other thing I'd try would be another engineer!

I have both water trap and muffler in my exhaust system (14hp) and I do believe there is some extra reduction in exhaust noise - I can hear the tappets over the exhaust note. Maybe I should do some sound proofing of the engine box.

Rob.

 

[earlybird]

Hi,

.Question 1: my mechanic explained to me that the Vetus water lock has a built in non-return valve which stops the water in the exhaust pipe from going back into the engine. Does the LP 50 actually have a non-return valve?

It doesn't. Your mechanic is wrong.
If the oil is milky in appearance, it's water getting in.
One possible route in could be the head gasket, damaged by the mechanic's earlier cranking efforts.

 

[Sybaris]

If the rings were already stuck, through lack of use, it might explain why it took so long to get the engine to start.

Does the engine fire up immediately, or do you have to spin it up fast before it catches?

Hi Rob and thanks for a really quick answer.

The generator had not been used for 7 months, but my thought was that it did not start immediately because I had tapped some diesel from the water separator pre-filter during the winter so there was probably some air in the line.

Once he got it started after a lot of cranking it started immediately the next day on my two tries.

I kept the oil that I tapped and will have a look at it when I get back to the boat (I am at an internet access place now). I can't remember having seen separated water however.

What is Redex? and are there any other brands?

I will follow your suggestion and try to find some Redex tomorrow morning and then reinstall the LP 50 (which is now empty).

BTW when I removed the LP 50 there was quite a bit of water coming out of the pipe connecting the exhaust to the LP 50.

Cheers,
Per

 

[PuffTheMagicDragon]

There is a basic precaution that is frequently overlooked when installing a water trap. The volume of the trap (given in the specs) has to be much greater than the maximum volume of water that than can be contained in the part of the exhaust pipe that comes out of the trap right up to the highest point of the anti-siphon loop.

 

[vyv_cox]

A common problem when engines are slow to start is that the cooling water, if being pumped continually, fills the trap and the exhaust pipe and begins to back-fill the engine. It enters the exhaust valve, sits on top of the piston until the compression stroke, when it can be driven down into the sump. This may be what happened when your mechanic was trying to start the engine. Normal advice is to turn off the water pump supply during prolonged attempts to start an engine.

Redex is upper cylinder lubricant. At one time it was quite popular to add it to fuel but in reality it offers no benefits. In this case it might help, but kerosene with a little oil added would probably be just as good.

 

[SHUG]

Vetus have two anti siphon valves which are identical in external appearance. One has an internal valve and the other has a venting tube which gives a tell-tale jet of water. If either of these is blocked or if the tell-tale is below water then back-siphoning will occur.
I am pretty sure that the water lock does not have an integral anti-siphon valve.

 

[rob2]

Glad that others have filled in the bits I forgot to explain! That's the beauty of the forum when dealing with the written word - several approaches will make the true meaning clearer.

I must admit I'm not familiar with the Onan generators. If it's a twin cylinder it is possible that one cylinder is fine and giving you "perfect" starting characteristics with the other being dragged along. I've had a main engine do this, the good cylinder was carrying the other which was only really noticeable by the lack of power with the throttle cranked open. Sorry about the direct reference to Redex - a bit of a giveaway about my age! In my teens it was common practice not to add it to the fuel as intended but soak it into the combustion chamber overnight to burn off carbon deposits on starting. The engine would spit out sparks and smoke like a bonfire for a few minutes, but it put off a proper decoke for a while.

Best of luck with sorting your problem.

Rob.

 

[Sybaris]

Hi All,

Thanks for all the help, much appreciated.
I have not had any time to work on the generator today but have the following few information tidbits to add:

- the Onan I have (MDKD 8Kw) has three cylinders
- it gave off a lot of white smoke during the two 30 min periods I ran it
- I saved all the tapped oil in a container and had a look last night and it was not at all milky, and there was no clear film of water on top
- I checked the anti-siphon valve which looks to be in good nick
- the generator has always started up very easily (we have had it for 6 years but it is from 1986)

My next steps are:
- to remove all oil from the engine, and then fill up with the correct quantity
- to fit a tube to the cockpit instead of the anti-siphon valve just to be on the safe side
- to re-install the Vetus water lock which now is empty
- and then start up and see how it goes

I will keep you posted on my progress.

Cheers,
Per

 

[Dave_Seager]

If your engine is definitely gaining "oil" and not water then it is almost certainly diesel fuel. If that much fuel is leaking into the engine then there is a significant risk that it will find its way into the cylinders and cause the engine to run away. A runaway could easily destroy the engine. It would be wise to try to track this down before running the engine again.

 

[Graham_Wright]

A common problem when engines are slow to start is that the cooling water, if being pumped continually, fills the trap and the exhaust pipe and begins to back-fill the engine.

At the LBS, I cited this to a Beta engineer. He reckoned he was not true as the air/fuel mixture ejected during running is no greater in volume than air alone when not firing. Granted, the velocity is different. Comments?

 

[Dave_Seager]

At the LBS, I cited this to a Beta engineer. He reckoned he was not true as the air/fuel mixture ejected during running is no greater in volume than air alone when not firing. Granted, the velocity is different. Comments?

Even ignoring the increased temperature of the exhaust gases, the hydrocarbons from the liquid fuel have been converted into exhaust gases which will occupy a larger volume than the unburned fuel.

 

[rob2]

I would disagree with the Beta engineer as the throughput of air/fuel mixture with an engine before starting is still in its original state. Once ignited, the exhaust gases are expanding as they leave the engine - the fuel has now gone from liquid phase to ignition products in the gas phase and HOT - still expanding to reach atmospheric pressure. Many people know to their cost through flooding their engines that this can be empirically proven - at the worst time!

The steps to put the generator back for further experimentation are good. The replacement of the lube oil and reinstating everything has to be done, but before repeating the process of trying the engine, it would be preferrable to check compression on all three cylinders. That would reveal either a blown head gasket or sticking rings without diluting the oil or risking a run-away. If you're not familiar with a runaway, the engine starts sucking the (largely fuel) oil up into the cylinder past the sticking rings and with unlimited fuel available it accelerates and cannot be stopped except by blocking the air intake - a measure not devoid of danger itself, particularly when in a panic.

Rob.

 

[vyv_cox]

At the LBS, I cited this to a Beta engineer. He reckoned he was not true as the air/fuel mixture ejected during running is no greater in volume than air alone when not firing. Granted, the velocity is different. Comments?

If the air/fuel mixture didn't expand on ignition the internal combustion engine would never have been invented!

Plenty on these forums have filled their engines with water in this way.

 

[ARE]

Hi All,

Thanks for all the help, much appreciated.
I have not had any time to work on the generator today but have the following few information tidbits to add:

- the Onan I have (MDKD 8Kw) has three cylinders
- it gave off a lot of white smoke during the two 30 min periods I ran it
- I saved all the tapped oil in a container and had a look last night and it was not at all milky, and there was no clear film of water on top
- I checked the anti-siphon valve which looks to be in good nick
- the generator has always started up very easily (we have had it for 6 years but it is from 1986)

My next steps are:
- to remove all oil from the engine, and then fill up with the correct quantity
- to fit a tube to the cockpit instead of the anti-siphon valve just to be on the safe side
- to re-install the Vetus water lock which now is empty
- and then start up and see how it goes

I will keep you posted on my progress.

Cheers,
Per

As the Onan MDKD is not a current model, I guess it has worked happy for a number of years with the vetus water locks. I do not think this is your problem.

If the oil level in the sump is rising and you are not seeing any creaming of the oil with water? I suspect that the sump is filling with diesel.

I would advise that you do not run the generator until you find the cause, because if it is diesel then the oil level will increase until the oil/fuel mix will bypass the piston rings and the engine will run away to max speed and distroy it's self.

The first place I would look at is the fuel injection pump as this is lubricated with fuel and has seals keeping the fuel out of the engine block. If one of these seal is leaking then you will get fuel entering the oil in the sump.

regards Anthony (aftermarket manager@Cummins Onan)

 

[pappaecho]

The Vetus antisiphon valve will "snuffle" when the engine is running. It it does not snuffle it aint working

 

[david_bagshaw]

As ARE above has indicated

Diesel is getting into your oil, either by a leaking front seal to the injection pump, or via a mechanical lift pump diapham if fitted. (our onan has an electric lift pump, but is somewhat later)

The oil will somewhat thinner by its dilution, but the real danger is crancase blow by containing diesel, going into the cyliders causing a run away.

 

[pappaecho]

White smoke is definately an indication of water in the oil. I had the same problem with a Beta engine with blocked anti siphon valve, and the engine below waterline.
As there seems to be some debate as to whether the rise in oil level is due to water or diesel, you can quickly solve that problem with a moisture test on the sump oil, which clearly should not have water in it!

 

[Sybaris]

Thanks Guys,

This is giving me a lot of good feedback and tips.

pappaecho mentioned a moisture test so I searched the web to find out more on how that is done and found this article:
http://www.machinerylubrication.com/Read/327/water-oil-analysis
Reading this it seems to me that determining that there is water in the oil is not as simple as finding a layer of water on top of a sample, which means that the water in the oil is still a possibility in my case.

We have friends here for a few weeks and I have not had much time to work on board, but I took a few hours this morning and did the following:

1) I emptied the sump (4 liters) and filled up 3.5 liters of new oil (the engine takes 3.8 liters but I didn't empty the oil filter).
Note: I had previously emptied about 1.5 liters (see my earlier post), and now 4 liters, i.e. a total of 5.5 liters from a sump that should hold 3.8 liters.

2) I reinstalled the Vetus water lock which was now totally empty.

3) I decided to try with my existing anti-siphon valve which I had removed and could not see any fault with.

4) I now realize the risk of running with diesel in the oil but decided take the chance based on the fact that the engine has a safety stop if it goes above 1900 rpm's

- The generator started up immediately and ran seemingly fine.

- Water was coming out of the exhaust (but I didn't check how much / minute).

- While running it was giving off more white smoke than it has previous years.

- I ran it for 40 minutes with a light load (around 2Kw out of the max 8Kw) and it ran fine.

- I checked the oil afterwards and it was nice and clean and did not seem to have increased in quantity (the dip stick when just over max with totally clean oil is not exact to read)

I did not want to test my luck by running it longer than 40 minutes and will try again tonight or tomorrow.

If it now is working fine (not yet definitive) what was the problem? here is what I think could be possible explanations:

- The engineer filled the engine with 5.5 liters when he changed the oil a few weeks ago.

- It was water that had mixed with the oil due to the way the engineer cranked the engine when he started it.

What next?

- I think it might be a good idea to service the injector pump and will look into that next week.

- I would like to find out how to check the compression in each cylinder.

- I will test run it some more and keep monitoring the oil.

 

[ostell]

4) I now realize the risk of running with diesel in the oil but decided take the chance based on the fact that the engine has a safety stop if it goes above 1900 rpm's

But the safety stop probably works by reducing the output of the injector pump. The diesel in the sump oil is not under the control of the injector and so there could still be runaway using this fuel in the cylinders.