1.8T dreaded oil pressure light

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JogiahMk4
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1.8T dreaded oil pressure light

Post by JogiahMk4 »

So a bit of background first , I recently rebuilt my agu for the second time , first time was coz I hit an unmarked speed hump, everything seemed to be fine until the low pressure oil light flashed and I ran a main bearing


The second time I think was due to a bad crank turned ,can't be sure but a big end on cylinder 2 ran.

Now freshly rebuilt , crank turned to 20 thou this time , new oil pump (Arco) new 20 thou main bearings (KS) and new 20 thou big end bearings ( king),along with a set of new rings as well , rods were also snet to the engineer and number 2 was resized to spec, the others tolerances were checked and all was well. Primed the new oil pump , let the motor turn over without fuel or spark for a good 5 minutes after filling in some 5w 30 oil and after my first long drive with the car, the oil pressure light came on


I've hooked up a mechanical oil guage to where the oil pressure sender goes and cold readings are all within spec but once the engine gets really hot and the fans kick in I'm only getting 0.7 bar at idle and about 1.5 bar at 2k rpm . Has anyone experienced anything like this ? The pick up was cleaned before being put back In as the oil pump didn't come with one . I'm really scratching my head on this. I can only think that the oil tolerances between the bearings and crank are off but I don't see why this could be everything was done properly.


Could a bad oil pump also give good cold oil pressure but bad hot pressure? Should I clean out my OEM oil pump which I took out on the first rebuild and see if that does better ? Or is this definelty a bearing clearance issue ?
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THANAS
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Re: 1.8T dreaded oil pressure light

Post by THANAS »

What is your current idle oil pressure, when cold?
JogiahMk4
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Re: 1.8T dreaded oil pressure light

Post by JogiahMk4 »

It was well over 2 bar
JogiahMk4
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Re: 1.8T dreaded oil pressure light

Post by JogiahMk4 »

THANAS wrote: Wed Jun 23, 2021 7:51 am What is your current idle oil pressure, when cold?
Pulled the sump off , found out the big end clearances were way off , over 0.076 mm on plastiguage , spoke to the engineer , he said king bearings can be problematic, he is coming to mic the journals tommorow.


The bearings were pretty cheap to be honest , like R250 , not sure of that can give me such a big oil clearance though ,was hoping to get a different opinion on king bearings , not the race ones . And any suggestions on what I should use instead ?
JogiahMk4
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Re: 1.8T dreaded oil pressure light

Post by JogiahMk4 »

THANAS wrote: Wed Jun 23, 2021 7:51 am What is your current idle oil pressure, when cold?
Engineer cut the crank wrong size , he said 20 though when it was actually 30thou ,luckily we caught it before hand
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missioner
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Re: 1.8T dreaded oil pressure light

Post by missioner »

Good luck getting 30thou bearings.

VW motors are only available in even numbers iirc
'87 Golf 1 Olde Skewl OEM+
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