low oil pressure, cooling jets and other thoughts
Turbo Mini Forums

OK, as you will know, the gearbox let go which has given me the opportunity to pull the engine apart and investigate other matters.

As background, the care had ok oil pressure on start-up but not great (circa 60-70psi). Once warm, I was getting 40psi full chat and down to 20psi idle. I also had a 'tapping' noise on start-up that disappeared after 30secs to a minute of idle. This almost sounded like a sticking follower and I half expected to see a swiped cam lobe when it was stripped down but nothing.

Initially put all this down to the mineral oil I was using to run in, however putting CTV in it made no real difference.

Internally, the crank is standard with standard turbo pistons; I've not pulled these out yet to check ring lands but no obvious signs of damage to the bores yet. I'm also running zetec oil jets.

now, I've started considering the facts, I've come up with a few separate topics of thought;

1) oil pump; this was purchased years ago from a local machine shop. I've no record to hand of what spec it was other than it was supplied for a metro turbo. Could this pump have been struggling with the demands of the engine?

2) oil jets; I've just reviewed the installation guide on here which has raised a couple of points;

a) do these need to be sealed down with a washer? mine are simply installed and retained with the tags - some comment was made regarding the BMW ones being a better installation from a sealing perspective. Could thinner oil when hot be bypassing the fitting and allowing a reduced pressure?

b) I put a bit of heat into a replacement one (originals were all fitted by Carl) and wondering if this has screwed the innards - there was comment on the thread regarding too much heat but the thoughts are that this would have closed as opposed to opened the valve.

Reality is, as guided by the above mentioned thread, the BMW jets can be retro-fitted to the ZETEC holes so I'm likely to go down that route, however I want to make sure I'm not missing something else

Any thoughts or ideas?

i think heat may have killed the spring inthe jet allowing it to open at a lower pressure,

also yes definatly seal them to the block some how.

can you check the pump clearances? or is it already in the bin, also how well does the pump back plate fit?

photos of the Pump;





as for the jets, my gut is to replace these with the BMW jets which would take a copper sealing washer

if the threads and holes are not spot on you will likely need a soft material to crush seal or similar
over heating the jet could never do it any good and id not think to use it
what bore to piston clearance did you run? a stone cold piston will flap its tits off if the clearance is huge its common in the burnout cars us Aussies build with huge clearances to allow the heat to swell and not lock up whilst being full chat for minutes on end
what oil pressure releif do you run?

i know that the oil pressure relif whont come into effect till way up like 5000 on my engine due to the bmw jets and VW banjo bolts with check/pressure valve

between the cross drilled cam and oil jets it bleads most of it off before the relif gets a chance i know this as i wound the thing up real tight and it didnt change it till like 5K so set the peak from that

at the end of the day its not pressure that keeps heat build up away its flow pressure is just a restriction to flow and so long as there is oil between the journals and bearings its ok given you keep heat at bay you do need some pressure tho but its realy not a lot imo plenty of engines making huge power on low pressures like 40-50 peak meny people say any more is just hp loss

15-20 psi idle is ok as its not under any load imo

that pumps fucked lol but yes bwm jets are the way imo

I'd be tempted to just block the jets off Rob.

If something is worth doing, it's worth doing half of.

why so John? I'm running standard pistons and want to give it as much as I can.

In your position Rob I would not hesitate -BMW jets, sealed to the block and a new high capacity oil pump.

I assume you will change all the bearings too ?

Andy & I didn't manage to melt standard turbo pistons on the van at over 20psi.

If something is worth doing, it's worth doing half of.

Yes, going to change shells anyway. Just been quoted £18/ jet though which is a bit pricey?

That's what mine were from BMW.

However! If I were to run jets they would be BMW. I have a block machined for Zetec ones and I think I would change it to run BMW one's still!

If something is worth doing, it's worth doing half of.

should have more than enough flow with a hc oil pump for decent pressure and to run oil jets...

I don't see the problem 20psi at idle when hot is pretty normal.

The idle pressure wasn't so worrying as the pressure under load

Its all pretty normal. Id not be worrying anyway. Than again while its apart you may aswell replace and suspect bits

the pump looks gererally shit quality to me,

I dont like the ally backed ones, I think that the rear can flex and piss oil out, sometimes you can see evidence of oil flow where crap in it has marked the surfaces.

it always pays to run a set of feeler guages over a new pump to check the clearances, I have also taken to using a bit of sealer on the plate to pump face, not too much mind! other wise it'll get into the pump, I use loctite 574,

also worth noting, if you clamp the pump up hard you can shag the oil pump gasket, and I always use the genuine gasket as it thicker/nicer.

another thing to check is that there is a restrictor betweeen the centre main and centre cam bearing, if not a load of oil can piss out the cam.

the pump is buggered rob and is the main culprit to low pressure surely,

nothing wrong with zetec jets and they are fitted in the don and just bolted in ,not sealed, if you want to see how much flow an oil pump has hammer a shrewdriver into the filter and see how much come out at 3k,

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I ruined the springs inside the zetec jets when I applied heat, for a reason I cannot quite remember. at that time I removed the little check valves altogether and ran with the large gaping holes that are the zetec jet nozzels. Oil pressure was very poor at idle but picked up when the revs did, but not hugely above 40 psi. It was relatively ok through two 2 hour dyno sessions and a dyno shoot out for Mini Mag, after which the engine was pulled and BMW jets retro fitted. The bearings all went back in as there was no damage to them.

I had to have M8x1.0 helicoils fitted in the holes for the zetec jets and I used a copper washer unter them, for two reasons, firstly the washers sealed the jet to the block better over the thread inserts, and secondly the washers lifted the jet nozzels that little bit to aid clearance of the pistons as they poked a little out the bottom of the bores.

After this oil pressure was great, but, I never did get to work out why the oil pressure would fluctuate wildly at around 40psi other than the theory that this was the point that the jets all started to open.

I then of course had a center main bearing failure shortly after, that some on TM are convinced was because nugget here forgot to install the gearbox to block Oring while fucking about with the windage tray clearnce on the H bean con rods at 1am

This last build, I blocked off the jets altogether as I was never happy with threaded inserts, or the actual location of the jets in the block, where my machinist put them. Fast Carl gets my next block, and i'm sure he will be all to happy to have me watch over him making sure it is how I want it

fwiw most of the undercrown jets i have removed from oe engines have no sealing as such, its just a banjo and relatively flat surfaces, no sealing washers. infact most manufacturers who use camshaft spray bars also lack sealing washers on there feed, which is usually a banjo. Dont really feel its an "issue" but i guess sealing washers cant do an harm.

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

Did you measure the end-clearance on the pump? that is where you lose pressure, not on a worn outer diameter (or inner diameter of the housing)...

I didn't Dave to be honest. I was more interested in the fact i needed a shifter to actually turn it

Has anyone tested the zetec jets before? I thought it would be fairly easy to rig something up and see if mine were actually working (well the valve anyway)

Not sure of the design of the Zetecs, but for mine, with the jets removed, I just used rubber tube and a foot pump. All 4 jets opened/ held at 30psi.

That was my thinking