18 replies to this topic

[Leonard]

my oil light likes to come on. i dont like it to come on. is the most likely reason for this the oil pump? it just flickers at 900rpm when its hot. if i could put a guage on what would be the lowest acceptable pressure?
thanks in advance. Leonard

[Guess-Works.com]

when's the last time you changed your oil ? and how many miles has it done..

Also the oil light on a standard mini comes on about between 7 and 10 psi which is already staving the live blood out of the engine...

If after an oil change you're still experiencing low oil pressure, then bottom line s the engine comming out the car, it could be oil pump, but more likely Mains or Big ends, certainly if the engine is a high miler.

[Leonard]

engines done about 70k. done about 4k since last change. im using 20w50 oil. engines being replaces in the summer. is there any way of tellin if its pump or bearings?

[Guess-Works.com]

They one thing to do would be to put an oil pressure guage on, if the pumps shot then even at high revs the oil pressure will struggle, but with bearings it's only at lower revs that's it's really noticable. Either way, if one goes the other not far behind...

One thing to do would be to remove the domed nut on the front of the engine and the spring and oil pressure release valve just to make sure there no swarf holding it open...

Edited by GuessWorks, 27 April 2005 - 09:01 PM.

[Leonard]

thanks ill check all that out. its a shame you cant do the oump with the engine in the car. i've noticed the light comes on more readily when the oil is hot. does this point more towards bearings?

[Guess-Works.com]

As the oil heats up, obviously the viscocity ( thickness ) of the oil reduces, which means it will flow easier, hence less pressure is required to push it through the bearings.

You can change the oil pump with the engine in but the majority of the side of the engine has to be removed for this to be accomplished..

So the clutch / flywheel and flywheel housing needs to be remove. You will then have access to the pump.

[vasi]

Hate to state the obvious, but first, try changing the oil filter.

[Dan]

That shouldn't make any difference. There's a pressure bypass valve in the filter head so that when the filter is clogged the valve opens and the bearings still get oil. Nasty, crappy unfiltered oil which probably kills them anyway but any oil is always better than no oil. Just about every engine with a cartridge filter system has a bypass valve either in the filter head or the filter itself.

[dklawson]

Since the engine has 70k on it I'd expect the pump to be rather worn. Remember, the pump sucks up the un-filtered oil directly out of the gearbox and any particle small enough to pass through the intake screen will go through the pump before hitting the filter.

Start with an oil change to fresh 20W50 and a new filter. That may help some but you'll probably find it still drifts too low the more you drive it and the hotter the engine gets. Since you plan on pulling the engine this summer anyway, you could take the bandaid approach and run a thick oil additive to keep the viscosity up. It's not a good solution but it may help limp you through until summer. Make sure you keep the oil level on the high side for maximum capacity and if possible limit your drives to shorter trips where the engine doesn't have time to get too hot.

[Bluemini]

Try checking your oil preasure switch is ok, swap it for a spare if you have one and see if you have the same probs. 20w50 is the wrong grade oil too, it should be 10w40.

[dklawson]

Why do you say 10W40 is the right oil? Every 1960s vintage British car I'm familiar with was recommended to run on 20W50. If Rover changed this recommendation through the years it's likely to be for the same reason that Japanese and American car companies did... higher fuel economy. (My new cars for example call for 5W20 which I've never even seen in the stores).

Remember the two numbers (i.e. 20 & 50 in 20W50) represent the equivalent viscosities when cold and hot respectively. This means 20W50 will act like straight 20 weight when cold and 50 weight when hot. If you run 10W40 the oil is thinner acting both when cold and hot. That's not going to help a low oil pressure reading.

[Leonard]

thanks for the help. i'm gonna connect an oil pressure gauge tomorrow and see what it is. what the relied valve setting? im guessing that it will reach this an then not go over? ill do an oil and filter change while im at it. im already using 15w40, as most people recommend this.
unfortunately, its my only car and i do long journeys twice a week. ive also got a 5 hour drive to north wales in the summer before my new engine, so hopefully this one will last! if need be i can whip out the engine and do an oil pump change one weekend.

[dklawson]

You're correct, in theory the relief valve will open when the set point is reached, preventing excessive oil pressure. The stock relief valve isn't very precise though and the oil pressure will vary all over the place. I've heard several different figures for what the relief valve should open at. The most common number I've heard is 50 psi which happens to be mid-scale on the gauges installed in early cars. There are articles on the web about using a ball bearing in place of the regular plunger, and using an adjustable spring to dial in the setpoint pressure. These do help, I have one in my car. However, if the valve is working at all, no amount of fiddling and adjusting will correct low oil pressure caused by a worn pump or bearings. You'll see low oil pressure at idle if your engine/pump is worn no matter what.

If pulling the engine out and putting a new pump in is a casual weekend job for you then I would certainly try this if the basic checks don't reveal anything. For me, that's major surgery involving borrowing equipment and fitting tasks into a cramped schedule.

[Leonard]

its not very casual to take the engine out but if it must be done then it cant be helped. i put some engine flush in and did an oil and filter change today. i took and the relief valve, there was no muck on it. it had a deep score down the side, but not on the seating face (see picture). i also fitted an oil pressure gauge, and now have 25psi at idle after a run. still not brilliant, but better. it goes up to 75psi at 3000rpm.

Attached Files

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[vasi]

You changed the filter, and now you have better oil pressure. Was I still wrong to suggest this?