BMC 1.5 Oil Pressure Issue

[Norse Master]

Hi All,

 

Hoping somebody can offer some advice to resolve an issue which my BMC 1.5 has developed with its oil pressure.

 

When the engine is cold, it turns over and starts fine with 20-30 seconds on the glow plugs, however the oil pressure gauge shows as maximum/the needle goes far right.

 

As the engine warms when idling, the oil pressure drops to normal operating pressure as per it was previous to developing this issue.

 

Until the engine is fully warmed, if you add load to the engine the pressure will again increase to the maximum. As the engine gets warmer, more revs can be added until the pressure goes high again.

 

Once up to temperature, the pressure is as it was previously and does not rise dramatically when revs/load increased.

 

Running on 20w50 API CC oil. Have changed the oil and filter today. However pressure issue remains.

 

Any help would be much appreciated.

Many thanks.

[Mike Hurley]

Oil pressure switch faulty maybe.

[Jen-in-Wellies]

Welcome to the forum.

You say "has developed". Is this high oil pressure reading something that has recently started happening in your ownership of the boat? If so, what were the gauge readings before, cold, warm, idling, revs?

[Tracy D'arth]

What pressure in psi is maximum on the gauge?

Sounds fairly normal if the running under load pressure is around 40 psi, 10 to 20 psi at tickover hot.

If the pressure is regularly over 70psi hot I would  suspect the  pressure release valve stuck closed.

[Norse Master]

Thanks for your replies.

 

Yes this is a new issue that has developed during my ownership. It has just randomly started doing it, was not immediately after an oil/filter change.

 

Gauge is measured in kgcm2.

 

Warm idles around 1.5 = 21 psi.
Under load 2.5 to 3 = 35 to 42 psi.

Cold idle used to be 3 to 4 = 42 to 57 psi

Idling revs are about 650.

 

Gauge measures upto 10 kgcm2. When first turned over cold, the needle jumps straight to 10, then lowers and flickers as the engine warms.

Then once the engine is upto temperature it returns to normal readings.

[Tony Brooks]

I think that I would want to confirm the reading by attaching a mechanical gauge.

 

On the BMC it is easy enough to check the relief valve as mentioned by Tracy, although I found they tended to stick open rather than closed. Take the large hexagon off that is close to the oil pressure sender, don't drop the spring or copper washer, I found a length of dowel tapped into the valve plunger would usually get it out.

 

My feeling is that it is more likely to be a sender problem, but remember the sender needs to match the gauge, otherwise it is likely to read about half or double what it should.

[Tracy D'arth]

If it is definitely an electrical gauge I would check it with another capillary one.