Oil Pressure Oddness

[eeyoreish]

Mine's always taken 5 or 6 seconds to show on the gauge (normal I believe) but suddenly started to take a minute, hence the stripdown and replacement of all possible culprits. Tomorrow I guess I'll find out if I've solved that original problem or not...

[Steve V8]

4 hours ago, eeyoreish said:

Where exactly is this mysterious seal of which you speak?

Service notes (lubrication system), I thought I'd read it somewhere but presumed it was within the pickup not the filter. 

Non return valve incorporated within the oil filter, as the filter is mounted horizontally stops the contents of the filter draining back to the sump.

[Barrykearley]

4 hours ago, eeyoreish said:

Mine's always taken 5 or 6 seconds to show on the gauge (normal I believe) but suddenly started to take a minute, hence the stripdown and replacement of all possible culprits. Tomorrow I guess I'll find out if I've solved that original problem or not...

That’s normal - and the minute is very wrong 

[eeyoreish]

9 hours ago, Steve V8 said:

Service notes (lubrication system), I thought I'd read it somewhere but presumed it was within the pickup not the filter. 

Non return valve incorporated within the oil filter, as the filter is mounted horizontally stops the contents of the filter draining back to the sump.

Yes there's no valve in the pickup, hence any oil in the pipe just drains back into the sump at switch off. I have another new PNM filter which has the same non return valve as the Lotus part. It's why I wouldn't just use a 'generic' filter.

[eeyoreish]

Rechecked flow (still good) and sump level this morning and went for first startup. Good news, we have oil pressure. It built up within a few seconds on the manual gauge I've got tapped into the sender port and settled at about 4 kg/cm2 so about 4 bar. If I increase the revs a little to 2000-2500 the pressure rises only a tiny bit but then seems to drop back to 4.

So now I'm a little paranoid whether that's good enough pressure? I'm used to seeing the pressure shown on the electronic gauge in the car, which would normally be higher than 4 and before I stripped it down was actually reading 5-6 most of the time. I know that the sender is 10 bar and the gauge is only 7 so that means the gauge will show lower than the actual pressure??

Bearing in mind the engine and oil are cold is 4 bar normal or should I expect more? The manual doesn't give cold pressures but hot it says I should have min 0.35 bar at idle, 2.4 bar at 3500rpm and 3.1 bar at 6500rpm.

Could the extra gasket in the pump potentially affect the pressure I'm getting?

I've left the car standing now for an hour or so for the oil to drain down into the sump, then I'll give it another start and see if the pressure builds as quickly.

I'd just like to be sure that the pressure is good enough before I build the last remaining bits back on in case I need to re-investigate the oil pump gasket thing.

[Barrykearley]

Yup - sounds perfectly normal.

[eeyoreish]

OK, good. If it still builds quickly at the next startup I'll run it up to temp and see what I'm getting then. Just concerned that as the oil thins, that 4 bar is going to drop.

Anyone know what pressure the PRV releases extra pressure at? The manual doesn't seem to tell me.

[Barrykearley]

4 bar is lots. There’s a snapshot somewhere which shows that the oil pressure is directly linked to rpm when hot. 

On idle the tell tale low pressure was disabled by lotus below 1500rpm due to this.

found the book numbers 

[eeyoreish]

Thanks Barry, the same figures in my manual. I was just concerned that as I increased the revs slightly the pressure didnt seem to rise so worried something was bypassing the pump rotors. Maybe I'm just getting paranoid about the quality of my oil pump rebuild..😳

I'll run it up again in a while and see how it is when it's warmed up.

 

[Barrykearley]

At 4 bar cold you won’t necessarily see a rise - hot you will as it won’t be at 4 bar anyway at the same rpm if that makes sense

[eeyoreish]

Yes I think so, thanks Barry!

[eeyoreish]

On second start up with the dash gauge connected, the oil pressure built within 10 seconds, not helped by the fact that I think the needle had stuck and when I tapped the gauge it it popped into life 🙄Read 5 ish on the gauge at cold which I know from the temp gauge i had tapped into the port is actually 4 bar so the dash gauge reads higher than the pressure really is.

I've let the car run up to temperature and I still have good oil pressure at idle, just about halfway on the gauge, rising with revs then falling back to halfway at idle. Good news.

The only issue I do have is a slight mechanical whine which seems (as best I can tell with the stethoscope) to be coming from the aux housing area. It's not really audible at tickover but as the revs rise, and particularly on the overrun I can hear it. Now is that just the new oil pump rotors meshing with each other or something else?? Could I have damaged the oil pump or aux shaft bearings with all this cranking and the 1 minute tickover last weekend without oil pressure? 

[Barrykearley]

The cranking would have done no damage at all. Bearings are only under stress when it fires.

did you put a new cam belt tensioner bearing on?? These can whine if it’s a bad one

[eeyoreish]

Well I did let it tick over for exactly a minute last week...

Yes, new tensioner as the old one was well and truly shot at 3 years old

[910Esprit]

Cam belt too tight?

[eeyoreish]

Maybe, but I've made another discovery...

The noise is there at idle but if I even touch the throttle it changes or even disappears until the revs rise much higher (I could hear it in the car as I moved it back into the garage). 

Although I can hear the noise with the stethoscope on the aux housing by the cambelt pulley and on the exhaust cam tower by the pulley there, it's loudest on the inlet tower by the cam pulley so probably being transmitted by the belt. A good listen along the aux housing to the dizzy End convinces me it's not the oil pump rotors.

Plus what I've noticed just now is that the inlet pulley appears to have a very slight buckle in it 😡

In the 3 short videos I've attached here you can see in the first 2 the cambelt wandering slightly on the pulley and the inner circumference of the pulley 'wandering slightly'. In the 3rd video I've captured the noise as I slightly blip the throttle.

Now what I know is that I have 100% definitely not damaged the pulley while it's been off the car so it must have been like that for a while and I've just never had cause to look so closely at it. I also know that I had a mystery whine on the engine behind the bulkhead before the stripdown, which I put down to the cambelt tensioner which was properly knackered when I removed it. Hence I didn't look any further.

So looking at this, is it feasible that with the pulley running out of true for a while it's worn the bearing in the end of the inlet cam tower and that the noise I can hear, which seems to be engine load sensitive, is the cam effectively 'vibrating' in the bearing. Someone tell me if I'm talking complete nonsense but I'm trying to analyse logically what's causing the noise.

Im not sure that it sounds like just the belt running on the pulley else why would engine load affect it much if at all?

I welcome any expert opinions!

Looks like I need a new inlet pulley at least. Options if the cam tower bearing is worn??

[Barrykearley]

The third video sounds like cam belt whine to me.

on the first video - the belt looked to be moving but consistently- the pulley doesn’t look bent or wobbly ??

puzzling

[eeyoreish]

Good to have a second pair of eyes... you're right I think. On reinspection the pulley doesn't appear to be warped/buckled and sighting over the belt, neither can I see the line of the outer rim of it moving up and down but the line of the inner rim of the pulley definitely changes as the pulley rotates.

I've attached a couple more videos here with better light. The first one also captures the noise better too. It's sounds more like a vibration/resonance than constant belt whine?

I'm properly, properly stumped. Unless anyone has any genius ideas what this is I think I need someone who knows more about these engines than I do to see it first hand. @peteyg any ideas? Fancy a drive to Emsworth??

[Sparky]

How did you tension the belt, and to what value?

[eeyoreish]

Tensioned by hand and checked by a retired chap who lives opposite and used to build engines for Lotus, and whose experienced hand said it was OK.

On the longest free length (exhaust pulley to crank), with the engine backed off a little anti-clockwise you can get between 45-90 degrees of twist on the belt. My expert witness reckoned that was spot on and it matches the tension I can feel on the rebuilt TE HC engine belt under the bench, which was fitted by the guy who rebuilt the engine.

All in I considered both things told me we were good but I'm open to criticism! Do you think it could be too tight? Could the tension create a noise like that?

[Sparky]

I would say that's a bit tight, but not critically so.  Worth checking again, maybe a little more scientifically.

[eeyoreish]

I can definitely revisit the tension now it's run a little but could it really be the cause of my mystery noise?

[Sparky]

I've heard exactly that noise many times on Esprits.  Might be belt, might not.  But I think it's wise at this point to eliminate the belt by checking tension properly.

[eeyoreish]

Thanks Sparky, then at least I'm not alone!

And if it's not the belt? What else should I be looking at/for?

[Sparky]

It's difficult to determine.  Sometimes I think it's the alternator, but now and then maybe the cam journals?