39 replies to this topic

[CantBeat@Classic]

Just this morning i drove my 1976 mini clubman estate for about 1/2 a mile or so and then the oil pressure light started to glow.

It says in the handbook that the red light on the left is the ignition light and should glow with the ignition switched on and go out immediately the engine is started. which it does exept when its idling it glows which tells me the idling is too low.

It also says the oil pressure warning light should glow when ignition is turned on and also go out soon after the engine is running (it did till this morning) and if the light continues to glow stop the engine immediately and investigate the cause (which it is). start by checking the oil level. ( i have)

i checked the troubleshoot in the haynes mini manual its says:

Low oil pressure (check sender or gauge before condemning engine):

*oil level low or incorrect grade. (Its not low and its the correct grade).

*overheating. Its running normal (by gauge)

*oil pressure relief valve defective (haven't checked)

*oil filter clogged or bypass valve defective. (new oil filter, haven't checked bypass valve)

*oil pick-up strainer clogged (haven't checked)

*oil pump worn or mountings loose (haven't checked)

*worn main or big-end bearings (haven't checked)

so theres still loads of possibilitys but i wanted to try and narrow it down to 1 if possible

the light only comes on when the engine is warm and only comes on when idling, it turns off with a little throttle but it shouldn't come on with the engine started and if the pressure light comes on but not the ignition light its definitely more than just an idling issue

[Noah]

Have you seen any leaks recently? A leak would cause a loss in oil pressure...

[Alex_B]

I would do an oil change, doing it when warm may indicate the oil is thinner than it should be so oil change and refill with good quality mineral 20w-50,

buuut the fact the engine oil pressure light comes on under 7psi oil pressure means when it comes on it can mean the big end bearings have been running dry which unfortunately means an engine rebuild normally,

I would do an oil change personally, look out for bearing material in the oil (white metal) and if the oil is clean of bits of metal then you may have got lucky and just keep an eye on any signs of the lower end knocking but if there is bearing material in the oil its a rebuild on the cards

[Stevie W]

Aaah I remember all those old Haynes manuals checks!!!

Its worth checking the oil pressure switch first off as these do fail occasionally (perished or holed rubber diahpragm).

Next most common problem is a jammed open oil pressure relief valve.

Both of these are worth looking at before fearing the worst!!

Steve.

[CantBeat@Classic]

i cant say ive seen any leaks i changed the oil a few weeks back but there was a split in my funnel causing oil to go down the back of the engine and now getting a couple droplets everytime i park and when i changed the oil there was some small metal fragments on the drain plug (nothing white) but i checked this in the manual and its normal to have some metal swarf there apparently and already fearing the worst but going to do the small things working up to the pump if nothing works before that i went for a quick drive 30 mins ago and its always glowing now so i'll be taking the bus to work tomorrow

[Fast Ivan]

my advice would be to use a pressure gauge to see what pressure you have before you do anything else.

[tiger99]

First, get an oil pressure gauge. You may as well make it a permanent fixture, with a T piece for the warning light switch, as it is useful, but for now, just plumb it in temporarily and see what it says, at idle and when revved.

At best, you have a faulty pressure switch, not expensive. At worst, an engine rebuild is called for.

Edit: As I was a bit slow in typing the above, Rob Mac beat me to it, about the gauge. I expect that others will be along to say the same thing. An oil pressure gauge is so very useful in spotting problems at an early stage....

Edited by tiger99, 21 March 2013 - 08:49 PM.

[Carlos W]

what oil did you put in when you changed it?

[CantBeat@Classic]

comma 20w50

[KernowCooper]

Have you seen any leaks recently? A leak would cause a loss in oil pressure...

Not strictly true a leak would cause a loss of oil, which eventually cause a loss of oil pressure due to contact between the crankshaft bearings and crankshaft, but I knew where you were coming from.

[Noah]

Have you seen any leaks recently? A leak would cause a loss in oil pressure...

Not strictly true a leak would cause a loss of oil, which eventually cause a loss of oil pressure due to contact between the crankshaft bearings and crankshaft, but I knew where you were coming from.

You knew where I was coming from.....Partly because I remember a thread of someone complaining about a loss of oil pressure and it turned out they hadn't done up the sump plug.

[Ethel]

Get an oil pressure gauge

If you had a leak from a pressurised oil gallery you'd certainly know about (it it'd like an arterial bleed in a war movie) the transfer pipe into the filter housing, relief valve & pressure switch/gauge are the only places this is at all likely, virtually all leaks are from worn seals or failed gaskets where there's only crankcase pressure - if you have the breather pipe hooked up to your carb it will actually be slightly less than atmospheric pressure if your piston rings don't have major blow by issues. Thinking about it, a water pipe vs a leaky bog cistern would make a better analogy.

Back to the original problem, the relief valve would be the first suspect. When the engine is cold the oil is thicker so lifting the valve is an easier route back to the sump for it than squeezing through the galleries and bearings. A gauge will give you more information and more confidence that your engine isn't about to go into melt down. The stock pressure switch is set so low that it's more an indication of a broken engine than a warning to prevent you getting one

[CantBeat@Classic]

hey guys i think ive solved the problem i aint gonna celebrate yet but it was the oil pressure switch. i still got a few questions such as how come the new switch sticks out so much ive tightened it to the right torque setting and i can still see about 5mm of thread i was told its a tapered thread whats that? and also with the old switch the oil pressure light used to come on straight away after turning the ignition on but now its delayed by 10 seconds or so how come? cheers guys

[Ethel]

A parallel sided regular thread would leak along the threads,they have to be loose enough to turn. Taper threads are just like a tapered stopper in a bottle only with a thread to pull it in & secure it.

[CantBeat@Classic]

im sorry i dont follow?