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Low Oil Pressure Still After Teardown 2.0l

10K views 51 replies 6 participants last post by  informatted 
#1 ·
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.
 
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#3 ·
Already have it torn down, but I am planning to do that aswell. The engine only has 100k miles on it so shouldn't be that bad (and initial impressions match that). But I am hoping that if my new oil pump that I have coming doesn't fix the problem then maybe a gallery or something is clogged.
I did end up taking off the oil cooler and oil cooler flange and cleaning both. Nothing out of the normal. Oil flange bypass valve seemed fined, and so did check valve. Also blew air through the oil cooler baffles via a poly tube and my lungs and air passed easily, no back pressure indicating a blockage.

I'll check the bearing tolerances again probably once I get the new oil pump.

So my check list has come down to either something i've done hasn't been done correctly or
Some oil gallery is plugged, cam shaft journals are piss, or oil pump is bad.

Crossing my fingers that once/if I fix the low oil, the knocking will go away aswell. But it is pretty loud so not sure. Not as loud as rod knock though, almost certain it is piston slap. But from the bottom, cylinder one seems fine.
 
#4 ·
Also, does anyone know if the thrust washers contribute to the oil pressure. They aren't thrust bearings and main purpose are to support the axial motion of the crankshaft but was wondering if they also greatly impact the oil pressure. I've heard some people have run their engine without them completely.

Also maybe I shouldn't have included the upper thrust washers as they haven't been included in the picture of the manual. But it says arrangement may differ from illustration, plus the kit for my engine came with them. Plus they seemed to have a spot.
 
#9 ·
Update: Still broken
Just threw in a new oil pump, checked and cleaned the oil filter flange (checked the check valve and relief valve, both seemed fine). Also replaced the oil cooler located on the oil filter flange.
Also threw a new cam shaft in since the old one had a little scouring, even polished the camshaft caps.

Thinking about calling it quits, out $500 could of bought a new used engine
 
#20 ·
Those oil pressure relief valves are for the piston oil nozzles. Once the oil pressure gets to a certain point, the valve will open and oil will be forced to the bottom side of the pistons. There is one per nozzle. One nozzle per cylinder. They also hold the nozzle to the block. Basically its a hollow bolt with a ball/spring that will break away at a certain pressure.

Yes, it's an oil pressure release valve, but nothing to do with the lubrication system.

Oil pressure is caused by the restriction of the oil passages. The more restriction, the more pressure. Pumps do not make pressure, they just push the oil. The restriction is why there is pressure. That said, if the bearing clearances are too large, then the restriction is less and so is the oil pressure. Scored cam journals is a problem. If your trust bearings were no good, I would have a hard time believing that if you installed new ones that the thrust spec is in spec.
 
#24 ·
And they were. I had to replace all main bearings because of significant metal fragmentation on the sides of the bearings. The rod bearings looked fine but replaced them just in case.
I also doubt the oil jets have anything to do with my low oil pressure. I picked up a new head from the scrap yard that looks to be in great condition. Now I just need some time and motivation to put it on.
This will be the 4th? time ive tore into the engine trying to fix the problem.

I think the new head will fix the oil pressure problem because I suspect the camshaft journals and caps are the source of low oil pressure. It annoys me that they don't have removable bearings that I could replace.
The knocking still worries me but i'm hoping that a new head magically fixes it? I'll take a look at piston 1 and see if there are obvious problems and if i'm smart I will pull it out, but I doubt it.

Another question/concern.
The rod journals and caps have bearings (duh), but those bearings don't have a tang to keep them in place. Why would a company do this? (The journals and caps don't have a groove for the bearing tangs either so it is suppose to be like this I know).
At least the main bearings have one.
 
#25 ·
Why would a company do this?

One thing you should do, is give them the respect that they've earned. You may not believe this, but they know way more about that engine than you ever will. Once you give them that respect, then you will understand there are different ways to accomplish a task. I suggest that you embrace the new technology. I used to be just like you and complained regularly. Now that I have drank the Kool-aid, it's much easier to fix cars.

They no longer need the tangs because they have enough crush to keep the bearings from moving around. Since that is the purpose of the tangs and they figured out that they do not need them. The money saved from additional machining can be used for something else. Same way with the cam bearings. It's money saved by not having bearings. 99.9% of the heads will last long enough that they will never wear out. Yours are not worn out, they are damaged.

I'm really puzzled that you have a knocking noise and you are not going to figure out the cause of this noise. My crystal ball shows an engine being taken apart a 5th time or maybe another engine is being installed. Still pretty cloudy.

Maybe doing by the book may be a good idea isn't that bad of an idea?
 
#26 ·
I took the engine apart multiple times in search of low oil pressure, with the first fix being the main bearings and thrust washers because they had obvious damage. I checked everything else during that first fix and it was all up to spec. Once that didn't fix the problem I decided it best to replace the rod bearings, pump, tensioner, oil cooler, and check the oil filter flange since those all could of been affected.
I'm taking this as a learning experience, not necessarily on how to fix the engine, but on familiarization on what each thing does and how it all links together. I'll tell you something, I can tear this engine down in record speed now. The only part that frustrates me is getting the timing belt on, usually takes me longer than everything else combined.

Anyways, once I was done messing with the bottom end, and still had low pressure I had 2 resort to looking at the top end.
I'm running on a tight budget, currently not working with plenty of free time so not exactly doing all the preventative maintenance and that jazz, just what I see as broken and will need fixed. Unless the part is dirt cheap and easy enough to replace.

Now that I have tore into the top, I realize it isn't that bad to work on. So threw a new cam in and polished up the caps crossing my finger that it would fix it. Of course it didn't, but I didn't expect it to really. Did see a slight improvement which gives me the motivation to replace the head.
Grabbed a niceish used head from the scrap yard the other day and will be installing it once my new gaskets come in a week.

And yes, the knocking still worries me, but it definitely isn't rod knock and I suspect it is piston slap but could easily be wrong. The thing is it happens when revving up at about 2000+ rpm and above, while engine is cold and warm. I have it isolated to cylinder one and it seems to decrease or go away when the fuel injector or plug wire is pulled.
I checked from the bottom and the piston, walls, and everything looked fine. Also has good compression. So im hoping it is something with the valves or something that will make itself evident once I pull the head.
 
#27 ·
Also, im getting the new used head ready for install and noticed the cylinder one has more carbon buildup on the valves and in the exhaust port. All 3 other exhaust valves have clean stems when looking through the exhaust port but the 1st one has carbon buildup on the stem.
Im assuming that this is either rich fuel or oil. If it was fuel it would likely be on all valves, so judging this im leaning towards oil. And the source of oil would be a leaking valve guide seal?
 
#29 ·
My $.02. That knock is deep. Not pistons and I suspect loose rods. Did you plastigage the bearings? I doubt if that noise is anything related to the cylinder head or any of its components. That is not piston clearance issues either. With bearings that were seized, maybe the oil port in the crank is blocking off the oil supply to the rod.

Do as you wish because I know you have financial and time issues, but I would be looking for another engine to learn from.
 
#30 ·
When you say loose rods, what do you mean? I replaced and checked all rod bearings so they definitely aren't loose.
The knock is isolated to piston/cylinder 1. Also the bearings never seized. Just the main bearings received damage from shifting due to bad thrust washers.
Could there be a problem with the wrist pin in cylinder 1 causing that knock? Otherwise im still suspecting piston slap. I wonder if the crankshaft has shifted to far forward or back causing the piston to not be centered. Either way youd think more pistons than just cylinder 1 would be making noise. I suspect once I pull the head in a few days i'll have my answers. Although if it is the wrist pin then i'll have to take the pan back off.
 
#31 ·
Upper rod bushing.

The crank moves forward but the pistons does not. So the crank rod journal travel would not match the piston rod journal travel. Something has to give for this to work. That leaves the rod, rod bearing, upper rod bushing, or piston. Since you had the head off, I suspect that you checked the cylinder bores, if not, then it's certainly wise to do that. Maybe it would be a good idea to measure the bore to check if it's out of round.

I'm suspecting that the upper rod bushing is the problem because it has a lot of load in a smaller surface area. Should be simple to check. Unbolt the rod and see is you can twist it or pivot it side to side. Within reason, you probably should not feel any play.

When you say you checked something, you may want to elaborate on what you did. When you say new, is it new? New used part? For instance, you mentioned you checked the pistons. My idea of that is certainly different than yours. If you did check them like you should, then you would not ask yourself if this is pistons slap. Your measurements would prove that.

How would piston slap cause low oil pressure? I can't think that it would.

Remember, you are working on an engine that needed a complete rebuild. That would mean you would have new pistons, bearings, and a huge machine shop bill. You are going about this like you have a love affair with this engine. There are many more engines just like this that are much less time/money consuming than the one you got. I would look for another one.

Sounds like I'm talking about your girl friend. :D
 
#32 ·
Haha,
well I actually just got the head off today, I have a junkyard head that i'll be replacing it with. The car at the yard was scrapped due 2 a broken drive shaft, engine was in good condition.
When I say I checked the pistons, i'm referring to when I had the crankcase off. I just did a visual check and tested for obvious play. Everything seemed fine, and also everything seemed the same for all 4 cylinders.
There are 2 problems, the low oil pressure and the knocking. I'm not saying the knocking was causing low oil pressure, sorry for the confusion. The knocking is a problem separate but could of been caused from damage due to low oil getting to the rod or I even thought there was a slight chance it was still lifter knock.

Im replacing the head just because of the damage to the camshaft bearings, which are part of the head and not separable.
Just got the head off today, and the head of the pistons all seem fine as well, so i'll probably drop the pan and pull out cylinder one's piston and check further. I assume you are correct when suspecting the piston pin being the problem (you referred to it as the upper rod bushing).

Sum things up: I will be getting the junk yard head ready for install, I have to replace the valve stem seals on cylinder 1 (and all others but) because it seems there was excessive carbon on the exhaust valve for that cylinder which I assume was a leaking seal.) Then I will be lowering the pan again and checking the oil spray jets for problems and also check the oil galleys by blowing some compressed air and pushing a plastic coated steel wire through. Then I plan on removing the piston from cylinder one and checking it all over and probably throwing in a known good used piston and rod. Will also check the cylinder more in depth. I will then clean off some carbon and reassemble everything.
If that doesn't fix the low oil pressure and the knock then I will call it quits. No worries, I learned a lot. Last thing I might try is swapping injectors and checking all the timing system again to make sure it isn't preignition or something causing spark knock.

Anyone have any other tips or thoughts? Feel free to leave some input. Once my valve spring compressor comes in tomorrow I will be slowly doing these things over the next few days.
 
#37 ·
ah yes. I just re-read your original post. you say the rod bearings seemed okay, but not perfect? when you are working with clearances of about 1 thou, things really need to be perfect. if one of the big end journals looked marked/scored in any way, that's not good news.
 
#39 · (Edited)

This all looks like normal piston wear after 100,000 miles to me. I assume it doesn't need replaced. What do you guys think?


There is a very slight polished area on the underside of the piston by the wrist pin. This showes the connecting rod is rubbing here. But it is only on one side and it isn't a groove, just a polished area. Is this the source of my knocking and what is causing the rod to not stay centered?
 
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