5 replies to this topic

[ianjobber87]

Hi all, 

 

Bit of a confusing one when bringing a very long term project out of hibernation. 

 

Engine is a 1380 a+ with mechanical fuel pump, 123 dizzy and brand new 1.5" SU. 

 

The car normally starts and runs fine when cold. gets up to temp and comes off choke fine, no smoke etc. but once driven for more than 10 mins I get the oil pressure light coming on. 

 

I have cleaned/ replaced the oil pressure switch and release valve. new oil + filter seems to cure it for a while then same again after some use. The engine doesnt knock or anything under load. oil looks very clean on the dipstick (no swarf etc on dipstick of when drained oil) but seems a bit thin (is halfords 20/50 classic) 

 

Do you think this could be the mechanical fuel pump causing the oil to become thin? or maybe its running rich and getting past the rings?

 

Any ideas?

 

Thanks, 

 

Ian

[DeadSquare]

Is the oil level creeping up the dipstick ?  Which it will if the oil is becoming diluted with petrol.

[cal844]

Lift the dipstick out, then sniff the oil does it smell of petrol?

Edited to say that I use the Comma Classic oil (Same as the Halfords stuff) And never have an issue even if doing 6 or 8k miles if daily driving the mini.

What mileage is on your current engine?

Edited by cal844, 29 March 2019 - 09:53 PM.

[BaronVonchesto]

check if your oil pressure release valve is getting stuck. take it out, clean it all round, look for pitting etc. take a paper towel, spray some wd-40 on it, wrap it wound a pencil and stick it into the block with the release valve out, use it to clean all round. then put the release valve back in.

 

with the engine warm but not hot, take out the dipstick, note the level the oil is at, then wipe it and put it back in. then wait for the engine to get hot and see the oil pressure. if its low take out the dipstick and see if the oil level is much higher, also see if theres a petrol smell. if yes you may have petrol in the oil which is a big problem.

 

else you probably have a failing oil pump. when the oil gets hot it thins so its normal for the pressure to drop a little, but if the pump is failing it cant pump the thinner oil at the right pressure.

 

also you do have enough engine oil in the engine right?

[DeadSquare]

Before we start wondering if it only happens with a full moon and an R in the month. may I suggest that you buy / borrow / fit an oil pressure gauge and get some accurate information about the actual pressures.

[Cooperman]

Fit an oil pressure gauge and thus have an accurate reading of the oil pressure when hot, cold, at high revs, at mid-range revs, at tick-over and then you will  have your answer.

As a guide an engine in good condition, when at normal operating temperature, will have around 60 psi at 5000+ rpm, 45 to 50 psi at 3ooo rpm and 20 to 25 psi at 1000 rpm. That is assuming a good 20w50 oil.

Figures slightly below that don't necessarily mean an immediate engine re-build is due, but that the engine is 'getting on in its life' and that there is some wear in the bearings and oil pump. You can then plane for the re-build at a later date.