39 replies to this topic

[stevede]

Hi all

 

Some of you may be aware I have been building a new engine for my mini.

 

The unit is now in and after a few minor hicups is running well (updates on my build thread)

 

The issue I have is that the oil pressure does not register for the first few seconds when cold, and for a little longer when hot. Even if the engine is only off for a few moments 

 

I had problems getting pressure at first start up, but that may have been the way I primed the pump.

 

When the engine is running, I have 70psi cold 2000 rpm and when fully up to temp I have 50 psi around 2500 rpm, 60 - 65psi  max at about 4k, dropping to 25 at idle. (idle is about 1500 at mo because of cam, plus fueling not yet set accurately)

 

There was definately a gasket between the oil pump and block, but it was the thin paper one that came with the gasket kit. (no additional sealant) Pump bolts were torqued as per the manual. Pump is a minispares high capacity turbo pump. Oil for the run in is Halfords classic 20/50

 

My thought process is that I have a leak and that the pump is draining down as soon as the engine is switched off. Would this happen so quickly?

 

Does this sound a logical diagnosis?  I guess I will see bearing damage longer term if I leave and do nothing.

 

Would fitting a new (better quality) gasket be a likely cure?

 

If so, is it practical to strip and do this work with the engine in situ? (I really don't want to have to lift the motor out if I can avoid)

 

Any advice, alternative suggestions / places to check appreciated

 

Thanks in advance

 

Steve

Edited by stevede, 28 August 2013 - 07:10 AM.

[mailman]

My freshly built engine does very similar things. I believe it is just the oil draining out of the pipe to the gauge, and down to the sump/gearbox.

I'm sure someone else with more experience of different engines and different oil pressures will be able to help more.

[jagman.2003]

Just a few thoughts. Worth checking if it's a delay in oil pressure or delay in the gauge responding. I have heard of people bleeding the pipe to the gauge to get any air out. Similar to brakes. The air compresses before providing realistic pressure. Does the oil pressure light respond immediately? Maybe worth trying another gauge in case it's sluggish. Now for the obvious, is there a new o-ring between the block & gearbox? I have never tried changing the oil pump in situ. But I suppose it might be possible. Once you've got the flywheel & housing off. I think by the time I've got there I would prefer the engine out.

[stevede]

Thanks for the replies, they are appreciated.

 

The light only goes out as the gauge starts to move so fairly certain this is not the issue. Same gauge & light sender that came off the old engine and I never experienced this scenario.

 

The "O" ring was definatley there. I was obsessed about forgetting it and checked several times before puting the 2 parts together. My understanding is that I wouldn't get any or, very low pressure if this was damaged or missing. The pressure seems fine once it has come on line.

 

I'm sure removal & re fitting of the pump will be a pain in situ, I just can't bring myself to lift the entire unit at this moment unless I have to.

 

Regards

 

Steve

[stevede]

Just driven home from work and if you stop the engine, the light is on almost immediately as you would expect.

 

If you re start the engine within a few seconds, the light goes out instantly and pressure builds on the gauge.

 

Leave it for 15 seconds and the delay before light out and gauge pressure returns. 

 

Would the pump drain that fast?

 

Didn't mention earlier that it has a centre oil pick up as well. Gasket was placed between pipe & block

 

Regards

 

Steve

Edited by stevede, 28 August 2013 - 05:56 PM.

[The Principal]

Have a read of this thread - http://www.theminifo...re#entry1784818

[stevede]

Have a read of this thread - http://www.theminifo...re#entry1784818

 

Hi and many thanks for your reply.

 

I have had a look at that thread, but the problem I have isn't the oil pressure when running, that checks out okay.

 

The issue I have is the delay getting pressure after the engine has stood, even for a very short time.

 

Can anyone confirm my earlier comment that the problem is likely to be the gasket seal on the oil pump to block please?

 

Thanks once again.

 

Regards

 

Steve

[GraemeC]

It could be.

I have heard of wrong bolts being used in the pump before now that are just too long and don't nip it down properly. Can't remember the details though.

[stevede]

It could be.

I have heard of wrong bolts being used in the pump before now that are just too long and don't nip it down properly. Can't remember the details though.

 

Thanks Greame

 

I used the bolts that were on the old pump, they were only tightened lightly to the spec in the haynes. IIRC to around 8ft lbs

[KernowCooper]

Just for info my engine has now done 2500 miles since the rebuild and has a high capacity pump and the 22psi comp switch idling over when hot I have 50psi and if I shut it down I can count 1,2,3,4,5 and watch the gauge fall then the 22 psi oil switch brings the light on, so its not a instant loss of pressure. I run Millers Classic 20w/50

[stevede]

Just for info my engine has now done 2500 miles since the rebuild and has a high capacity pump and the 22psi comp switch idling over when hot I have 50psi and if I shut it down I can count 1,2,3,4,5 and watch the gauge fall then the 22 psi oil switch brings the light on, so its not a instant loss of pressure. I run Millers Classic 20w/50

 

Many thanks

 

I'm going to give bleeding the pipe a go first, simply because it's the easiest thing to try. Failing that, I guess I'll have to dig to the pump and have a look see.

 

Regards

 

Steve

[stevede]

Engine has been out today, replaced the gasket on the oil pump, re primed etc and when spinning on the starter I still have no pressure.

 

I'm suspecting an air leak in the pipe work to the pump. If this as the case, would I get pressure at all? Remember that I had good pressure when the engine was running, just not for the first few second on start.

 

I'm going to have to pull the engine and full strip I guess.

 

Any other ideas before I do?

 

Thanks

 

Steve

[stevede]

Another update

 

I dropped in at Uttoxeter today and picked up a new oil pressure switch, a ball bearing pressure valve and a fresh oil sender pipe for testing.

 

Fitted the bearing & new switch before fitting the new pipe so I could see what was pumping on the starter.

 

It probably took 15 - 20 seconds before some oil came through the pipe and ironically, even with the pipe in free air (well a bottle) the light actually went out

 

Fitted back to the gauge and I couldn't replicate but the battery was going a bit flat.

 

Took the oil filter off and spun the starter and within 3 - 4 seconds there was oil coming out of the pipe. As I type this, I'm thinking to another thread that said about air in the oil. Honestly, I didn't twig that one until now so didn't take much notice.

 

If I had knocked or damaged the "O" ring (block to G/box) or the pipe was damaged (leak at the G/box pipe union) would I actually get any oil, or, would a slight leak give the symptoms I have.

 

 

Turbo high volume oil pump. Would this make any difference?

 

Someone on TMF must have experience, please help?

 

 

Thanks in advance

 

Steve

Edited by stevede, 01 September 2013 - 03:21 PM.

[minimuk]

Steve,....just read your concern, your numbers in the beginning of this tread are the same as my 998, never had any problems for the last 15000 miles, oil is thicker when cold hence pressure will be higher to go around, when oil is hot, it will be thinner hence no need for hard work and pressure will drop to 50 or idle 25, I would get worried when drops under 20% on idle. So I am not so sure whether you should wreck yr brain on this one....

 

P.S. did you speak to Shifty about this??

Edited by minimuk, 01 September 2013 - 04:47 PM.

[stevede]

Steve,....just read your concern, your numbers in the beginning of this tread are the same as my 998, never had any problems for the last 15000 miles, oil is thicker when cold hence pressure will be higher to go around, when oil is hot, it will be thinner hence no need for hard work and pressure will drop to 50 or idle 25, I would get worried when drops under 20% on idle. So I am not so sure whether you should wreck yr brain on this one....

 

P.S. did you speak to Shifty about this??

Hi Minimuk, many thanks for taking the time to reply

 

My concern is not the pressure, I'm fine with that, it's the time it takes to show a reading on startup, even after the engine has been stopped for a matter of seconds.

 

Regards

 

Steve