Finken
New Member
Hello. I live in Norway and have an old boat with BMC 1.5. When the engine has reached its normal running temp, the oil pressure is approx 5-7 psi at 800 rpm. Does this mean the engine is worn out? Or is it just the oil pump? Or?? 
BMC 1.5 low oil pressure
- Thread starter Finken
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maxi77
Well-Known Member
That certainly sounds low, mine is about 40 and 50 on load. When was your oil changed last is a first question, and what pressure do you get at say 1500 rpm.
Mind you in my youth playing with vintage cars we used to feel any pressure at idle was OK as long as you got near to normal pressure at normal revs.
Mind you in my youth playing with vintage cars we used to feel any pressure at idle was OK as long as you got near to normal pressure at normal revs.
vyv_cox
Well-Known Member
That is a very low figure. The combination of various leaks is the cause and from here it is impossible to say where they are. There is a relief valve in the oil gallery and the spring inside could be broken, allowing oil to bypass. Main and big-end bearings may be worn but you would probably know that from the noise. Oil pump could be worn, as you suggest. Some of these BMC engines had a bypass valve in the oil filter that opened when it was blocked. Could be worth checking.
You could try going to a heavier oil, maybe a 20/50. As already said it's the pressure at working revs that is important, should be 30 psi minimum.
You could try going to a heavier oil, maybe a 20/50. As already said it's the pressure at working revs that is important, should be 30 psi minimum.
TQA
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I have lots of time on that engine. That pressure is very low for that model. It should be at least 25 psi even for an older engine with some wear.
One check to make before you pull then engine is to see if the oil is contaminated with diesel. This happens if the lift pump diaphragm leaks diesel into the sump. Pull the dipstick and see how the oil drips off it [ when cold ]. If it is watery and drips very quickly then maybe all it needs is an oil change and a new diaphragm.
A possible cause is a badly seated pressure relief valve but I have never come across one so it is a forlorn hope.
If you go for a rebuild almost all parts are available as it is still widely used in the UK on canal boats. Google bmc 1.5 diesel parts for lots of suppliers.
One check to make before you pull then engine is to see if the oil is contaminated with diesel. This happens if the lift pump diaphragm leaks diesel into the sump. Pull the dipstick and see how the oil drips off it [ when cold ]. If it is watery and drips very quickly then maybe all it needs is an oil change and a new diaphragm.
A possible cause is a badly seated pressure relief valve but I have never come across one so it is a forlorn hope.
If you go for a rebuild almost all parts are available as it is still widely used in the UK on canal boats. Google bmc 1.5 diesel parts for lots of suppliers.
higler
Well-Known Member
I would check the oil pressure swich first of all, they do play up as I found out last year. Oil pressure was only showing 25lb running at 1900 revs, changed the pressure switch and found I had 55lb and still good. N
maxi77
Well-Known Member
Another thing to check is the connections, I was getting wild fluctuating readings and found the connectors on the display were almost falling off, some judicious tightening and all is tickety boo
Narrowboatseb
New Member
1500 bmc diesel oil pressure
I have Totaly rebuilt my 1500 bmc. My oil pressure is fine, but I don't seem to get much flow to the head. The rocker shaft stays full as it runs, and it drips oil from all the rockers, but not very quickly...... I seem to remember more oil flow? The valves don't seem to get splattered / splashed....... there is oil flow ..... But...... All the oil ways are clear....... How much oil should there be? I can run the engine at idle and the oil doesn't overspill the edges of the head..... Are the valves mist fed or splash? Please help!
I have Totaly rebuilt my 1500 bmc. My oil pressure is fine, but I don't seem to get much flow to the head. The rocker shaft stays full as it runs, and it drips oil from all the rockers, but not very quickly...... I seem to remember more oil flow? The valves don't seem to get splattered / splashed....... there is oil flow ..... But...... All the oil ways are clear....... How much oil should there be? I can run the engine at idle and the oil doesn't overspill the edges of the head..... Are the valves mist fed or splash? Please help!