2.0 Mi16 Oil Pressure/pump Problem

[DrSarty 90 1 Cars]

Hi all.

 

There's some background below, but can I ask a direct question first?:

 

Should the oil pump chain and sprockets be able to turn independent of the crank?

 

I ask because I understand the crank sprocket for the oil pump chain is apparently a 'friction' fit of some kind and perhaps it only engages when the crank is turning. Logic tells me however that it should be a permanent connection, but currently I am able to rotate the chain with my fingers, and it'll rotate in both directions.

 

Background:

I've never had an oil pressure problem on any of my engines. I've always run a 6 bar spring in the pump and always had good pressure. The current engine has been running for over 6 months, with the gauge going straight to 6 bar reading on start up, then as the engine's warmed up, running at a nominal 4-5 bar and idling on 2-2.5 bar.

 

During some recent auto-solos on tarmac at Rockingham (with its inherent very tight turns) I've had a couple of times when the pressure's dropped right down, even showing the oil pressure (switch) light occasionally, but then recovering.

 

The other day, after a perfectly normal (and healthy) drive, I parked up, went shopping for an hour, but on restart the oil pressure gauge was barely on 2 bar with a flickering oil pressure light. No massive oil spill and oil level was good. Bugger!

 

I trundled carefully to a local garage where I got lots of attention, and I then explained things. I also noticed top end/tappet-type noise, which I gather was down to genuine poor oil pressure, as I suspect the gauge and switch are reading correctly.

 

I said I thought that the oil pump may have given up the ghost, or the chain snapped, and I had a few other thoughts (mentioned below) that I didn't voice. I was prepared to have them keep the car, me provide a new sump gasket and oil pump and have them fit it. My gut feeling though was 'it's the pump', although I know they are generally very reliable (due to their simplicity) and that they rarely fail.

 

I was fairly convinced it wasn't a gauge, switch or electrical problem, as there was a reading (albeit low) and only a flickering light. When the garage owner drove it carefully to the ramp, the gauge started creeping up then reverted to normal service, i.e. good oil pressure again. Tappet noise gone and all good again. They declared it an electrical fault, but I was confident of a real oil pressure problem, somehow and hopefully just being a glitch, i.e. some temporary blockage or fault. The car then drove fine again with normal readings, no pressure light, with starts and stops and more healthy driving. Only on start up yesterday morning (on a cold engine) did the low pressure reading and flickering light issue resurface, plus some additional engine noise. So today I removed the sump and showed my findings below.

 

I know that XU9 (1.9) Mi16 engines can have oil pressure problems on certain tight corners (due to starvation), but that 2.0 XU10 Mi and also XU5 and XU9 8v engines generally don't; something down to crank and/or rod design I believe. Anyway: I digress.

 

My Thoughts: *Please review and advise in context of the above*

- Should I swap the pump? (Can they fail, and if so how do they?)

- I thought it could be the trap do locking shut somehow and starving the pick-up, but that's not the case

- I thought it might be a chain failure, but it's intact

- I thought it could be (perhaps my worse fear) the crank sprocket 'free spinning' and therefore not turning the pump - hence my opening question. Should it turn with the crank stationary?

- Could it be a blockage in the pump incl the pick-up?

 

So my lack of understanding is really linked to the crank sprocket and I'd really appreciate some advice on how this can be fixed, IF it is the problem. Of course I don't want to take the crank (or engine) out, and was wondering if just a pump swap is the first option, but of course I'd still be concerned IF the crank sprocket seems to already be free spinning (?!). This seems a little ridiculous to me, as surely the crank sprocket should be 'fixed' to the crank so whenever the crank turns it drives the pump; my fear is that as it seems to be able to turn independently, then there's a chance - as seems to be the case - that the pump can't pump as it's not being driven properly.

 

Sorry for the long explanation and waffle, but I wanted to try and get it all down in one hit and see what you guys can offer as answers and advice.

 

Many thanks in advance.

Edited November 6, 2016 by DrSarty

[DrSarty 90 1 Cars]

Update, specifically re my main question above: having looked in the Haynes manual, the crank sprocket for the oil pump seems to show a collar with a slot to engage with a woodruff key (one of two) on the crankshaft, which means to me - as I suspected - that I shouldn't be able to turn the pump while the crank is stationary.

 

What could this mean? If the above is correct, could the crank sprocket be knackered, i.e. the teeth shagged or the collar broken away from the gear itself? Woodruff key broken?

 

What's going on? Is the sprocket a friction fit or is there a woodruff key? If there is, then that has to be the cause of the problem, and I'd suspect the sprocket itself has broken in two, i.e. a collar (which is still locked) but a now freely rotating toothed gear, which would explain why it can turn with the crank stationary.

[Tom Fenton 1,541]

The oil pump chain sprocket is clamped against its faces by the bottom pulley and bolt. This drives it. Check the bolt is tight.

[welshpug 1,657]

yep, check the bolt is clamping sufficiently.

[DrSarty 90 1 Cars]

Thanks guys. So I was right in that it IS a friction fit for the crank oil pump sprocket, i.e. the Haynes is perhaps showing an XU9 or even TU crank where there is a woodruff key, but the XU10J4 just uses the clamping pressure of the main crank pulley (22mm) bolt?

 

If (hopefully) so and this main bolt has just worked loose, do I need to lock the engine somehow to tighten it? If so, what's the best way please?

[DrSarty 90 1 Cars]

Quick check shows a loose crank timing sprocket bolt; the (22mm) one that's used to turn the engine over during cambelt fitting. It needs some threadlock I'd say and a damn good tightening.

[petert 586]

Yes, 110Nm.

[Miles 331 1 Cars]

Silly idea but modern car's don;t use any locking on anything, the late XU10 went back to a keyed oil drive which is worth doing

[DrSarty 90 1 Cars]

All sorted guys. Thanks for your help.

 

Agree with Miles, that 'next time':

A - I build an engine ground up, I'll see if it's possible to have the oil pump sprocket woodruffed or grub-screwed to the crank. And;

B - I'll ensure the aforementioned bolt is suitably tight and locked.

 

You're all stars as ever.

 

P.S. Mi16 turbo lump coming soon(ish). Need to find a rolling shell for it at some point, so look out, another Sarty project coming!