Hello, anyone looking for a puzzle? Because I've been working on my Volkswagen golf mk4 for a couple weeks now but can't seem to find the source of the low oil pressure. Below will be many details, and i'll be sure to keep you guys updated on my progress. I like keeping things short and to the point.
I'm basing my work on the Bentley workshop manual for this engine.
(TLDR: 2002 AVH 2.0L has low oil pressure (checked with manual gauge) and knock from previous owner, (hinted at running it with low oil), checked and replaced the main bearings, rod bearings, oil chain tensioner, and also checked the oil pump and tube which all seem good. No change to low oil pressure and knocking at 1800+ rpm in cylinder 1)
A couple weeks back I bought a 2002 volkswagen golf 2.0l AVH (for $550)
I just wanted the oem roof racks on it but the interior (and ac) all was in great condition and I already have a 2001 same one without ac and crappy interior so figured id pick this up.
It was a trade in at a small dealership (probably saved the previous owner $200 on a used car) and all the guy knew was that it had low oil pressure and would need some work.
I was able to drive it home the couple miles and sure enough the low oil pressure light was on the whole way, but it also has a knock. No overheating issues for the short drive though.
So here I am, tearing into this engine trying to fix it, I don't do everything by the book because im more or less using this as a learning experience (although it would be great if I could get it running properly).
What I've done so far...
Confirmed it has low oil pressure with mechanical gauge (has 5psi at cold idle, dropping to 2 when warm. At 2000 rpm it gets about 15psi, and steadily climes about 8psi per 1000 rpm. Maxes out at 40psi if im lucky.
(Btw my 2001 golf 2.0l gets 40psi minimum at idle)
Changed filter... No difference
Dropped the pan, 2 thrust washers and the timing chain tensioners plastic arm are in the bottom. Along with some silver shavings and some bronze flakes
F..k Me haha
So I changed all the main bearings (they had some major wear on the sides but not to bad on the faces)
Also had to change the center main bearing cap because it has groves for thrust washers, and the driver side thrust washer grove was worn badly.
The thrust washers wore that cap but also wore the block itself, but not as badly. After changing the cap the new thrust washers slid into place and stayed
Take note, I said I found 2 thrust washers in the pan. Both bottoms. Didn't ever find the top ones (which I understand this engine should have, although the Bentley manual isn't specific).
Either they turned into that metal sludge and flakes, or the engine never had them, or they had been removed during a previous service (which I suspect because the car had new fluids, new water pump, and a new belt tensioner.)
I also changed the oil pump chain tensioner while it was apart. Was hoping I was hearing chain slap as the knocking noise. Nope
Put the engine back together and still low oil pressure and knocking.
Pulled the injector cables on each cylinder and found the knocking was isolated to cylinder 1 (passenger side) and only was audible at around 1800+ rpm. Was louder than the adverage tick of a lifter but because of it only happening on higher rpm I figured it can't be rod knock. Anyways, lowered the pan again.
This time I checked the rod bearings and journals. Seemed okay, but not perfect. Replaced all rod bearings.
Also checked the oil pump pickup, and the pump itself. No clogs and no internal problems. Even hooked it up to the drill and ran some water through it using my finger to plug it and test pressure. Seemed perfect, ran oil through it to rinse the water out. Put everything back together.
Ran engine, still low oil pressure and knocking noise.
Im now looking into tearing apart the upper half of the engine, but must ask.
WHAT ELSE CAN IT BE?!?!
Here are some things I plan on checking (oil pressure related)
I will diagnose the knock later. Im suspecting piston slap or valves.
Oil pump seemed fine, but maybe the bypass valve or the mating surface to the block is f***ed.
Oil filter flange also has a bypass and check valve, maybe something is wrong there?
There is also an oil cooler bolted onto the oil filter flange. Maybe there is a restriction there.
Lastly could be bad camshaft bearings. Still figured that my oil pressure wouldn't be so low though.
Thanks for any input, good or bad. Engine is partially disassembled right now so feel free to ask questions.