101 replies to this topic

[bmcecosse]

Unfortunately - it 'could' be that the rubber O ring between gearbox flange and block flange is damaged or missing. I doubt it's the relief valve - and yes - I have had great success with the ball bearing as a relief valve - it NEVER sticks, but the spring does need to be 'calibrated' to prevent the pressure going too high. If you can't find anything else - you will need to lift the block off the box to check the O ring and the pick-up pipe......

[booton]

but if it was the oring it won't pick up at all would it. as if i prime its fine for the day.

really don;t want to split it, it's all plumbed in now.

and the oring was deff there and brand new.

[bmcecosse]

Can't really see what else.... possibly faulty oil pump although I would be v surprised...... - are you using super-thin oil ? 20W50 is the stuff to use.. You say there is no oil pressure - but is it maybe just taking a couple of seconds to show on the gauge?

Edited by bmcecosse, 20 November 2011 - 10:33 PM.

[MRA]

Ball and spring oil pressure relief on a road car....

Its a racing mod, it will just lead to engine failure due to pulsing of the pressure, use a plunger as the designers intended, lets face it Rover would not have fitted a plunger if they could get away with fitting a ball and spring which would have been considerably cheaper if there was not a good reason for it.

[racingbob]

years ago i had a race engine built and the boss at the engine recon place gave it to someone else to finish off

guess what !

he put the oil pump gasket in wrong way

so i get the engine put in could not get oil pressure, engine had to come out see why

and thats what it was

[Cooperman]

The possibilities seem to be, therefore:

1. 'O' ring missing
2. Oil pump gasket in the wrong way round
3. Poor quality oil pump allowing 'drain-down' and not self-priming.
4. Slightly blocked of 'squashed' pipe to gauge
5. Some sort of 'DGS' (dirt, grit or s**t) lodged in the relief valve seating.
6. Too thin an oil being used - needs to be a good quality 20w50.
7. Big-end or main bearing journals out of tolerance, but this is very unlikely.

If it's not 4, 5, or 6, then it's an engine out job.

[Gulfclubby]

Just because thinner oil results in less oil pressure doesn't necessarily mean there is insufficient oil flow to lubricate the engine, in fact, the opposite may be the case. The engine part (short block) of a mini engine/gearbox unit would work just fine with a 0W30 oil, it's the gears that need the thicker stuff. But oil pressure says very little about how well the gears are being lubricated. At least that is what I gathered after reading through several elaborate articles about oil. There seems to be appallingly little consensus even among so called experts.

[booton]

um
well will have a play on the weekend. will see what i can do. i personally think due to the problem it could be the oil pump as its draining down over night and then needing to be primed. i don't know what else would do this.


could it be any chance the pressure switch. or would that just not work.

[Cooperman]

You mention the pressure switch; does this mean you don't have a gauge? It would be a good idea to fit one whether there is a major problem or not.
I have had a problem with a poor quality pump draining down and not self-priming again, but it took more than just over night.
Let's just revise what the symptoms are. Does it not self-prime at all so far as you know, or does it just take a long time to re-prime? If the second, how long is a long time?
If you have a gauge, what is the pressure at, say, 4000 rpm when warm?
If there is no gqauge it could, perhaps, be the pressure switch only operating at a higher pressure. The 22 psi switches used in competition cars do take longer to go out, of course, but only a few seconds longer and then only when cold.

[cooperrodeo]

When I had this problem with my Morris 1100 at about 40000 miles (nearly 45 years ago!), it took ages for the oil pressure to appear. Needless to say this didn't do the bottom end a world of good and cost me a fortune.

[booton]

think i will buy a gauge to see what pressure i'm getting.

[bmcecosse]

Good plan - it's THE most important addition to a Mini.

[bmcecosse]

I never had any problems with ball relief valve - never noticed any 'pressure fluctuations' on my gauges (in different cars) - in fact if anything it was even more steady than the bucket valve. I can't think why a ball would induce 'fluctuations' - it has a nice thin seat contact with the taper in the block and when it opens there is plenty of space around the ball for the excess oil to escape back to the sump - so less tendency for excessive pressure when the oil is cold.

[Gulfclubby]

The increase in pressure with cold oil simply results from the fact that it is less fluid and thus doesn't flow as easily through the galleries and various moving parts in the engine. Since the relief valve does not affect the flowability of that part of the engine at all, simply more oil is dumped back into the sump instead of passing through the oilways. This results in less lubrication and cooling in the areas where it matters and is one of the important reasons for engine wear. This is also the reason why you'd rather have a very thin oil when cold instead of the thick ones. But as the oil heats up, it gets "thinner" and as a results can flow better. This is true up to a certain point. Again, from what I understand, the problem with oils is that there is no oil that is thin enough to provide ideal viscosity when cold, while at the same time being stable enough to still have acceptable viscosity when hot. Thus the hotter the engine is when hot, the thicker the oil has to be when cold, causing more problems such as wear, hard starting etc.

My personal conclusions from all this reading on the subject is that oil pressure is indeed an insufficient means of judging the lubrification of an engine, instead a flowmeter of sorts would be equally interesting. The fact that Minis share one kind of oil for both the engine and the gearbox only further complicates things, a lot, which is why nobody else does it anymore in modern cars.

[bmcecosse]

All the above is well known - problem with the bucket valve is that there is little space around the bucket for cold/viscous oil to escape to the sump. The ball has much more clearance - and thus much less tendency to give false/high pressure when the oil is cold........