Low Oil Pressure at Tickover

[Guest]

I have a Volvo MD7A 13 HP 2 Cylinder Diesel 1981 Vintage..

Over the last couple of season I have had a problem will low oil pressure alarming at tick over when the engine has been used for more than about 20 minutes.

A slight increase in throttle in neutral will stop the alarm…..

I started by replacing the sensor, which did not solve the problem. I then fitted an oil pressure gauge that showed that when under load the engine runs at approx. 40psi, but drops off to less than 10 when ticking over.

After some advise and a lot of discussions a friend and I decided to bring the engine into the cabin, turn it over, remove the sump, and replace the oil pressure relief valve. This was done over last winter.

The problem has reoccurred this season.

My next ideas are to:

1. Change the oil from the standard Volvo recommendation (15W40 I think) to something that stays thicker at higher temp, but I have no idea what to use.

2. Increase the tick over slightly.

3. Ignore the problem!

Any ideas or suggestions would be gratefully received.

Happy Sailing

Andrew Trayfoot

 

[vyv_cox]

Your 20 year old engine is feeling its age. Not only is its oil pump struggling to supply the pressure needed, due to leakage across and around its gears, but when the oil gets to its destination it meets increased clearances that further reduce the pressure.

There is really no easy answer. Replacement or refurbishment of the oil pump alone will help but ideally the big-end, main, thrust and camshaft bearings all need to be replaced. Of course, they will not fit their worn journals perfectly so the crankshaft needs to be reground (you can get away with the camshaft)

Unfortunately your previous advice was not worth all that much. Changing the oil pressure relief valve spring rarely achieves any worthwhile improvement, whereas changing the bearings would have made a major difference. Since the major part of the work is hauling out the engine and stripping it, it is well worth doing as much as possible while you are in there.

To your questions I would say:
1). Increasing the oil viscosity is the last resort. Change to a 20W50 may help slightly, but not for long.

2). Very short term solution. All you are doing is increasing the flow, and therefore the pressure, a little. Increased clearances will increase exponentially, so it won't be long before you have to increase tick-over speed a little more, and then a little more.........

3). Definitely not. The sooner you act the cheaper it will be, although the words "Volvo parts" and "cheap" do not sit happily together. At the very least change the oil pump and big-end bearings. Wait much longer and a shaft regrind will certainly be required, although check ovality in any case.

 

[steve_cronin]

Bearings do eventually wear....

.it is inevitable.

Your thicker grade engine oil will give an increase in blood er... sorry OIL pressure but just like a failing human vascular system will eventually result in death.

Now I'm not sure if your Volvo has a pre-heater (glowplug) but I would suspect that you would have a problem starting from cold without it if there is general wear in the engine although worn/glazed bores won't cause low oil pressure it is a sign of general wear.

If raising idle speed doesn't cause any nasty noises when engaging/changing gear then this will give you some respite. Your engine might well need a new set of bearing shells and if appropriate a crankshaft re-grind. Possibly the oil pump itself is worn. Whichever it is I suspect that your trouble is just that - wear.

Sorry to sound so depressing.

Steve Cronin

 

[Guest]

Re:Bana skins and egg white

Too late......you should have carried out a yearly service like it says in the manual,just because you cant see it doesnt mean to say it isnt there.

If I were you Id get a full recon as doing the okey kokey (putting it in and taking it out )with your engine will eventually wear you down at least with a recon you get a full guarentee.

 

[AndrewB]

Oil Pump.

If the tickover rate is right, the engine quite definitely has enough oil, and the oil-filter isn't sludged, then I'd go with the suggestion that the problem is most likely with the oil pump struggling. Could be wear (no pump lasts forever), could be sludge build-up, might just be damage if something has broken internally and then run through the pump.

There is not necessarily a lot else wrong, but ignoring this problem would not be good.

I don't know the Volvo, but the pump is normally right underneath the engine, and should be accessible with the sump box off. You will need to lift the engine.

 

[Guest]

Loss of pressure is mainly due to wear of the crankshaft big ends and journals bearings as well as the oil pump. Bearings and pump tent to wear out at the same rate. You do not have to overhaul the engine if you can accept that oil pressure at tick over will be low. It will get worse slowlly, however it may take years and for as long as the engine starts easily then there is no problem. In the meantime, use high viscocity oil, or add additives to increase the oil viscocity (Halfords) and increase the tick over rpm to overcome the alarm issue.

 

[philip_stevens]

I would suggest that this winter, remove the engine and replace both big end and main bearing shells. It is possible that one - and it only takes one - big end or main bearing shells (two to each) may have wiped the white metal surface. If this is the case, it can weat into the bearing surface causing further expensive damage.

As an ex-MN engineering officer, I have seen this on big diesels -25,000shp and above - and its not a pretty sight - nor job to change a complete conrod! It once caused us a four day hard work stay in Auckland to have the main bearing repaired after a five day limp across the Tasman sea on five cylinders instead of six!!! I even have a piece of the white metal that melted out of the side of the bearing.

I would think the most likely reason for low oil pressure at low revs is with the bottom end bearings - either big ends or main bearings.

regards,
Philip

 

[Guest]

Andrew,

This has come up regularly, and I've spoken to Volvo Penta Technical to confirm my own views. Your engine, at this age will not be harmed by low oil pressure at tickover. This is confirmed by the fact that you need only a little throttle to put the light out. The important thing is that you ahve sufficient oil pressure and flow at cruise rpm.

Just ease up the idle rpm to illiminate the oil pressure warning and forget all about it. Pat Manley 'Engine expert' PBO

 

[vyv_cox]

A stitch in time...

clearly no longer applies, at least to Volvo engines. Andrew, when you run a big-end in the course of the next year or so, have no worries because:
a. Volvo apparently said it won't happen
b. Pat Manley says it won't happen and will reimburse all costs that may be incurred by following his advice.

 

[chippie]

All good advice . however if you want to postpone the inevitable I would suggest trying an oil booster which will definitely be cheaper.
I had a similar problem in a Peugeot 504 car years ago and used a product called Moreys oil additive the problem went away. Yes, I know the marine environment is different but as this product was in a one litre bottle I think it represented a fairly large proportion of what was in the sump.
Dont forget to take out a litre or so from your engine before using.
Just a thought .

 

[Guest]

Thanks to all for your advice..

Whilst the engine was out I did look at the cost of new oil pump, bearing shells, regrinds etc and came to the conclusion that it was not worth spending the money ...

The engine has done 3 cross channel trips with the problem and still starts easily and runs well.....

I think I will go with the advice of upping the tick over and possibly adding an oil additive. That should at least put off the problem until there is enough money in the kitty to buy a new Beta engine - Unless someone knows another source of engines at a lower cost (I reckon that I won’t see much change out of £4k - £4.5K if I buy a Beat).

Thanks again to all..

Andrew

 

[vyv_cox]

You may like to look at http://www.the-oilman.com/questions/link4.html before investing in additives. All major lubricant manufacturers are strongly opposed to the use of these compounds, which may react with components of their product, causing filter blockage and other problems. Changing the viscosity of the oil to something heavier is one thing, but adding all sorts of uncontrolled goo is something else.

 

[Guest]

so wht grade of oil would you suggest?

 

[philip_stevens]

There is no reason to junk the Volvo to get a new one just because of problems now. It will be far cheaper to recondition the Volvo than getting one of the new Japanese clone engines.

I worked on a pleasure boat for a few years with one of the oldest engines I have seen. It was regularly serviced to Board of Trade standards, and only eventually changed for a more powerful diesel. It was a Kelvin petrol/diesel, that was started on petrol, and when up and running, changed to diesel.

Think about the advice against additives, and think about having it reconditioned. It may be less than you think - and less than a new engine.

As we have all intimated, if the oil pressure is dropping off at low revs, something is worn and allowing oil to pass freely.

I have regard for the information passed on to you by Pat Manley and his informative articles, but I wish people would not sign themselves as "experts". I am far from being one - even after 25 years as an MN electrical officer.

regards,
Philip.

regards,
Philip