High oil pressure and oil loss - BMC 1.5

[jhodgski]

Me again...

 

Having installed a new bmc 1.5 and running it for it's first time in over 6 months, the oil pressure seems extremely high.

 

At low to medium revs (out of gear), the oil pressure is somewhere between 80 and 90 psi. Oil can be seven creeping out from the threads of various tightened nut on the engine, so I don't think it's a faulty oil pressure sensor/gauge.

 

The engine has Morris Golden Film SAE 30 oil in ( http://www.morrislubricantsonline.co.uk/golden-film-sae-30-classic-motor-oil.html ).

 

I topped the oil up before running it for about an hour yesterday. Afterwards, there was about 2mm of oil on the dipstick (checked the rockers though and they were still lubricated, so hopefully I turned the engine off just in time).

 

I'm not exactly sure from where the oil was being lost. Like I say, it was weeping out of some unexpected places, but there wasn't that much oil in the tray afterwards.

 

Was getting a bit dark to see exactly where it was coming from but I didn't notice a major loss from any single point, and I can't run the engine again till I get hold of some more oil.

 

The engine didn't appear to be burning the oil as the exhaust emission was nice and clean - the only smoke was at startup, which was white smoke.

 

The engine warmed up to about 70 degrees C and didn't go above that.

 

The engine started and stopped fine.

 

Any ideas?

 

Cheers,

James

[steamraiser2]

I suspect that the oil pressure relief valve is jammed shut. Take it out and clean it. Don't forget that the oil level will drop as the engine oil galleries and filter get filled on first start up. 80 to 90 psi is far too high.

[RLWP]

Having installed a new bmc 1.5. <snip>

 

Oil can be seven creeping out from the threads of various tightened nut on the engine

 

If this happens on the first few runs and then stops, it's the oil used during assembly creeping out

 

If it continues once you have wiped it dry a few times, we need to know which nuts. Not many are near oilways

 

Richard

[Bloomsberry]

I use the same Morris SAE 30 oil in my BMC 1.5 and in the 3.5 years I've had it the pressure has never exceeded 50 PSI.

 

The pressure relief valve seems like an obvious cause but would this result in a dramatic loss in oil ?

 

Would it be possible that the oil could have leaked into the coolant ?

[dmr]

If I stop my engine (not a BMC) and immediately check the oil its right at the bottom of the dipstick. An hour later its back up to normal.

When an engine is running there is a lot of oil splattered all over the insides of the engine which then drains back into the sump.

 

...........Dave

[jhodgski]

Cheers for the replies. I'll check out the oil pressure release valve. Where / how do I find it?

[Tony Brooks]

Its under a hexagon below and sightly in front of the oil filter mounting boss. You may have to take the filter off the block to get easy access.

 

Check the free length of the spring in case some idiot has stretched it and make sure no one has packed the spring with washer in the valve itself or in the hexagon plug. The free length is (I think) 2.849". If its less then the oil pressure will be lower.

 

There is a manual with all this information in it on the "Dutch Manual Site". Link from my own website. This site has manuals for all sorts of engines and other marine stuff.

[bizzard]

And after you've removed the large hexagon nut and spring you'll need to get the valve out of its hole. A piece of wooden dowel rod or a valve grinding stick often fits the valves hollow interior. The dowel rod needs to be a light drive fit in the valve, tap in gently with a hammer and tease and twiddle it about until it withdraws the valve. Clean out the valves recess in the block and clean the valve thoroughly with say paraffin and then lightly oil it and try the valve in and out of its hole in the block until perfectly free before refitting. If the conical seat on the valve looks pitted and unhappy it can be lapped into its corresponding seat in the block very carefully with a tiny spot or fine valve grinding paste and twiddling the valve back and forth in the block whilst still on the stick until the valve seat looks better with a uniform grey look. Afterwards scrupulously clean out ALL traces of grinding paste from the hole in the block, 'your little finger with a bit of rag on it is best for this and clean of ALL traces of paste from the valve too of course before reassembly.

[jhodgski]

Cannot find the hexagon...

 

TheRe are no hexagons just below / in front of the oil filter mounting boss.

 

TheRe is one hexagon close to the injection pump - but no spring inside it.

 

On my old engine (I won't be back with the new one till tomorrow), there is a very large (29mm) hexagon between two of the glow plugs - don't have any tool big enough to get it off with at the mo, but could that be it?

 

On the other side of the old engine, there is a hexagon, with a filter-looking rod on it when you pull it out. No spring, though...

[jhodgski]

Just found it on the old engine. Was close to the flywheel on the lift pump side of the engine. Am optimistic i'll be able to find it tomorrow now on the new engine. ..

[jhodgski]

The oil pressure release valve was indeed in the same place on my new engine. I took it out, cleaned it and put it back together.

 

I then ran the engine for about 30 mins and I don't think there was any oil weeping from anywhere.

 

The oil pressure reading was still extremely high, but my gauge / sender must be faulty as it was reading 40 psi with the engine turned off (and the pressure release valve removed).

 

I'll be ordering a new oil pressure gauge and sender today, and fitting them on Friday so hope to report back then that everything is running normally.

[RLWP]

Boat instruments - deceitful little objects!

 

The ones in cars are extensively tested along with the engine, there are tens of thousands of them, they are of a good quality with proper connectors and harnessing and just work

 

The instruments on our engines may never have met before they were fitted by the yard or the owner. They are made to be universal to go on old cars and boats and often down to a price. They wire up with spade connectors crimped onto a flying lead, cable tied to whatever is handy. Then they get left for years while dirt and oil build up around the sensor and the wire flaps about pulling the spade terminal and the rivet on the sensor until it is loose.

 

It's a wonder that they work at all for as long as they do really, and if they happen to give the correct reading - its a miracle! Then some poor boat owner tries to make sensible decisions based on the numbers that they show

 

Richard

[jhodgski]

I've just fitted a new (and matching) oil pressure gauge and sender, but the oil pressure reading is more or less at max (5 bar / 80 psi).

 

I measured the voltage on the S terminal on the gauge when the engine was running. It read 3.6 volts.

 

I then totally isolated the 'S' wire and checked it was not shorted.

 

I then measured the voltage across the output of the sender, which was approx 4 volts. Does this sound abnormally high/low?

 

So I think the extremely high oil pressure reading is genuine.

 

Could there be a second oil pressure release valve that is stuck? (The one I found and ensured was free was located near the flywheel on the lift pump side of the engine.)

 

Or what else could the cause be?

[Darren72]

We were chugging along once and our oil pressure shot off the scale. Why I looked at the dial at that second i dont know. After stopping the engine and coming to a controlled stop I found the cable had come off the sender unit thingy me bob. Is yours connected properly, any play innit?

[jhodgski]

Yeah, I just fitted a new sensor and gauge this evening. It's definitely all wired up correctly.

[MtB]

How about fitting a mechanical pressure gauge?

 

A Bourdon type gauge with a copper capillary tube connecting it to the engine instead of a wire. They seem more trustworthy, somehow.

 

MtB

[Dutchie]

I got the the same problem a few years ago , but it was the gauge which was broken and not the oil sender transmitter, ,bad wiring could also give faulthy measurement , measure the wiring with an good ohm/multimeter , also a bad massa cable on your engine can give troubles .

 

also agree with Mike that measure for sure the oil pressure with an analog gauge .

Edited December 6, 2014 by Dutchie

[jhodgski]

Cheers Mike, but it's two high readings now that I've had from two separate senders/gauges. And never had such an issue with my old engine, so am sure as can be that the problem is with this engine. And nothing left on the money tree now, anyway... :-/

[Tony Brooks]

Yeah, I just fitted a new sensor and gauge this evening. It's definitely all wired up correctly.

 

Are they matched to each other? Mixing US and European spec senders and gauges will give very odd readings. If you bought a gauge and sender kit it should be fine but if bought separately maybe not.

[jhodgski]

Hiya Dutchie, I've changed both the gauge and sender. I've also checked all the wiring, which is all fine.

 

Have just spoken to Calcutt and they have said to test it with a 'master gauge'. Maybe that means a mechanical/analogue gauge??

[jhodgski]

bizzard, I have checked the release valve again and it didn't seem to be stuck at all - ie, I could remove it by sticking my little finger in it and pulling the valve out.

 

The valve seat does have a little 'chip' in it - see https://db.tt/AlFe5NdY .

 

So I have replaced it with the (intact) valve from my old engine - but it hasn't solved the problem.

 

I didn't do any of the grinding paste stuff as I was a bit weary about it given what you'd said in another thread - esp. as the engine is now in situ and will make it very hard to do. Do you think the grinding paste thing is still worth a shot?

 

Also, would it be a good idea to run the engine for a couple of seconds with the valve removed - so we can eliminate that as the source of the problem if the oil pressure reading drops? Or could doing this damage the engine?

 

Also, the chap I spoke to at Calcutt said that having the oil at max level (which it is, on the dipstick) may contribute to higher oil pressure. Is it worth draining a litre of oil out?

[jhodgski]

Also - and not sure what this indicates, if anything - the gauge was reading about 10 psi after I turned the engine off.

 

I then removed the release valve and it stayed at 10 psi.

[RLWP]

It means that something somewhere is wrong! Either you have the wrong sender/gauge pairing, or there's something wrong with the wiring

 

You will not get 10psi of pressure 'hanging around' in the engine

 

What sender and gauge did you buy?

 

Richard

[jhodgski]

The sender is an R8916: "Oil Pressure Sender 0 - 80 psi 1/8" NPTF. 1 stud, Earthed through body of sender ( negative earth ) suitable for gauges which have 240 - 33 ohm response"

 

The gauge is a Faria 18350: "Faria Marine Euro Black Oil Pressure Gauge Pt No:18350. Black Bezel and Black Dial Face. Dual scale bar/psi 0-5 bar 12v Standard US 240-33 ohm resistance curve. Supplied complete with mounting hardware and Back Lighting 12v bulb"

 

I've double checked the wiring. As required, the gauge has 12 volts across the static terminals and I even created a new sender wire, so there's no issue there.

[MtB]

So this is twice now with separate electrical gauges you've seen readings persisting above zero with the engine stopped.

 

I can hardly believe you still trust these gauges so unquestioningly that you are dismantling and looking for a mechanical fault!

 

 

MtB