slightly higher oil level

[colvic987]

i am getting a slightly higher oil level reading on the dipstick of my engine, it is noticed in the latter months of the season, so it is not a large influx of fluid, but a slower flow over a couple of months, the boat is in the water and used from late may through to late october, with a large amount of engine use during the summer holidays.

It is a md7a, with a msb gearbox, it had a new cone and cog fitted in 2001..
and the head was removed 3 years ago, and new sleeves and valves cleaned up by volvo agent...

I have emptied the sump and let it stand to see if there was any water in the oil, of which i cannot find, and i have read the recent thread on the head gasket failure and it does not overheat and when running it runs very well...

Is there any other area i can investigate:

1) can the shaft seals between the gearbox and crankcase cause a leakage to the engine sump.

2) can the fuel pump have a faulty diaphram and/or a faulty injector allow fuel to flow into the head and leak into the sump.

3) could the impellor pump housing seal be leaking into the block, (this i am sure is not happening as i havn't found any water in the sump).


or is there some other quirk of this engine which i have not investigated..

it is a md7a with raw water cooling which flows into the gearbox housing then into the engine block before exiting into the exhaust.


If it is diesel how would i notice it in the engine oil, would it separate from the oil like it would with water, or would the oil hold it in suspension...

1 baffled boat owner....

 

[chiefeng]

If you have diesel in the oil the viscocity woul be lower, the oil might be a greyish colour rather than black and if you are lucky (or unlucky!) you might be able to smell it. Sometimes if there is only a small amount of water in the oil try putting some on your fingers and rub them together if there is any tiny bubbles on your fingers then you have water contamination. I have seen the same thing work with diesel but it is not as conclusive.
Another test is to get some sump Lub oil put it in a pan and gently heat it any diesel will evaporate before the oil and you may be able to smell it (tell swmbo it's a new type of cooking oil!!)
To do a simple viscosity test get a flat piece of plastic or a mirror (something that is smooth) put a sample of good LO next to a sample of sump oil and tilt the mirror at an angle of 30 deg. If the sump oil is lower viscocity than the good oil it will run down the slope faster than than the good stuff. Simple but effective.
Hope this helps
Rgds
Bob

 

[andy_wilson]

The used oil will have a different viscosity characteristic anyway as the oil molecules will be severely worn and chopped up.

Analysis of sample by an oil testing lab would reveal if there is significant diesel present.

 

[VicS]

[ QUOTE ]
The used oil will have a different viscosity characteristic anyway as the oil molecules will be severely worn and chopped up

[/ QUOTE ] That certainly applies to multigrade oils as the viscosity improvers break down. I proved that for myself in the lab years ago. Should not happen to single grade oils though, at least not to the same extent and mabe oil technology has improved since I checked mine.

Small amounts of water may be difficult to detect in used diesel engine oil as much will be held as an emulsion by the detergents, although if there is enough to cause an obvious rise in sump level you should be able to. The classic lab method is to distill it out using Dean and Starks apparatus. If there is water in the oil you will almost certainly find it condensing in the top cover as a horrible emusified mess, and depending on the crankcase breathing in that as well.

Any seals and the lift pump diaphragm are potential sources of the trouble but the water pump should have a drain hole between the water seal and the oil seal to allow any water leak to escape and be visible. The lift pump diaphragm is the first think to check if it is diesel.

 

[stevebirch2002]

Same engine as MD6A and what has happened in a couple I have fixed is the seal between the injector pump and engine block goes, this allows a small amount fo diesel to be mixed with the sump oil thus makiing the level increase. Needs to be checked asap

 

[vyv_cox]

You can check for water in oil by doing a 'crackle test', still carried out in oil company labs to this day. Normally a steel hotplate is used but heating a steel plate on a gas ring will do just as well. Let a drop of oil fall on the hot metal surface. If there is more than about 2% of water in it it will emit a distinct crackling noise.

It is often said that a diesel engine 'makes' oil and the symptoms you describe are not all that unusual. If the rise is only slight I would not worry about it too much.

 

[colvic987]

hello steve, so if the seal has gone or on the way out, would it be right to say that over a period of inactivity, the injector pump would slowly drain off, causeing it to temporarily cause difficulty in starting for the first time it is used after its inactivity, and during its time of say, daily use,after its initial start, it starts first time every time...

i say this because this is what has been happening during this season, after a couple of weeks away from the boat, it has been initially difficult to start, (turns over at least 4 times before firing up), the norm is cold start and instant starting....

the seal you mention, is it difficult to replace or does it require special tools, or is it just a flush fit...

or is it time to call the volvo man in...

 

[Bilgediver]

The Volvo MD range of engines are fitted with a fuel pump assembly that sits withing the crankcase..Regardless of oil seals and or gaskets fuelpump plungers always have a certain leaage when the engine runs. This takes care of pump lubrication. This is minimal with new fuel pumps but as engines get older and pumps wear this leakage increases.

This leakage on the MD range is straight into the crankcase and causes fuel dilution so reducing both the viscosity and the flash point of the lubricating oil.

This dilution is addressed by following volvos's service manual and changing the oil as prescribed. Often the cost of an oil analysis exceeds the cost of a re fill and so there is no sense in even trying to exceed the recommended time between oil changes.

It is also possible for water to get into the oil at the water pump however there is supposed to be a small hole drilled in the pump body between the two seals from where water will drip and so indicate a seal is on the way out.

I suspect your increase in oil level is due to fuel leakage during the season exceeding oil usage.

John