Find the Cause of Low Oil Pressure

[jakej78b]

Hi everyone! I've had my good ole jetta since I bought her at 220k miles. Engine currently has 250k miles. It's had the low oil pressure problem for roughly 25,000 miles. Shortly after I bought it, perhaps after the first oil change I did... It started intermittently throwing a oil light and blaring the alarm at me. After a while I noticed the alarm would only come on under 2000 RPM and only if the engine had a load on it. I changed the oil pressure sensor sending unit. I changed the oil pump. I changed the oil. I use VW 502 rated 5w40 synthetic oil, always. I tried adding lucas high mileage oil stabilizer in my oil... no effect, alarm continued to blare. I've been talking with Anuthee from KermaTDI trying to get the bottom of this problem because I want to get a VNT-17 in the future, but not until I've resolved my oil pressure problem. I recently pulled the valve cover and pulled the cam bearing caps on bearing #1 and #2, pictures are below... Any ideas? Any input is highly appreciated on this matter.

Car is a 2001 Volkswagen Jetta with a 1.9 ALH engine and an O2J 5 speed transmission, fully stock with a VNT-15 turbocharger. The turbocharger is not making correct boost (it is underboosting) and the turbocharger makes weird squealing noises. Could the turbocharger (hopefully) be the cause of low oil pressure? What else can I do to diagnose this issue?

Oil pressure was measured with a mechanical gauge to be around 70PSI at idle while cold, then the pressure dropped as the engine warmed up to around 7-15PSI, depending on engine load and RPM.

2001 alh cam1

• jakej78b
• Jan 21, 2021

2001 alh cam2

• jakej78b
• Jan 21, 2021

2001 alh cam3

• jakej78b
• Jan 21, 2021

2001 alh cam4

• jakej78b
• Jan 21, 2021

2001 alh cam5

• jakej78b
• Jan 21, 2021

 

[Vince Waldon]

Have you measured the oil pressure with a good gauge, engine cold and then engine hot?

 

[jakej78b]

Yes, pressure was around 70PSI while the engine was cold, then dropped to about 10PSI when the engine was hot.

 

[Vince Waldon]

Hmmm... sorry... thought I read your entire post but I see you already mentioned the pressures.

SOP at this point would be to drop the oil pan and Plasigauge the main and rod bearings (to rule out engine wear or bearing damage).

You've eliminated a lot of the other possibilities, and the "oil light starts to come on around 2000RPM when the oil is good and hot" is a classic sign of internal bearing clearances being wide enough when the engine is hot to drop the oil pressure below minimums.

Pretty common on older MK2 and MK3s now that their milages are generally getting up there.

 

[jakej78b]

Wasn't your fault, I edited the first post

I'll snap some pics under the oil pan, if pics would even help. You think just replace the main and rod bearings? I'll look for a DIY guide.

Plasigauge? Measure the diameter? with a caliper?

 

[Vince Waldon]

Pics won't mean much unfortunately cause you are looking for extra wear measured in thousandths of an inch.

This game is where Plastigauge comes in...a thin wax-like strip and that deforms in a calibrated way when crushed.

Best researched on YouTube.... here's one to get you started: https://youtu.be/q3pHb-qXZc8

The only trick is to remember that the bolts are single use, so you will need new bolts for any that you remove and test with. Doing a couple main and a couple rod bearings should give a fairly accurate picture overall, Factory Service Manual has the wear specs.

 

[Jetta2005TDI]

Try new oil filter housing. There is check valve etc inside that can cause problems. Also make sure you use Mann filters. Also if turbo seal is leaking a lot you can make yourself cap to temporarily cap oil supply line at Idle. Do not rave the engine just to see if psi will go up.

 

[TLH_TDI]

One other possibility is the piston oil spray jets. They have a check valve in them that closes off when the pressure is low forcing oil to other parts of the motor. At some point after 2000 they upgraded the check valve with one that has a stronger spring that may have been for the low pressure at idle problem. IDparts as well as ECS Tuning has them, part number 028103157A


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[BobnOH]

Bad crank and/or rod bearings.

 

[Tdijarhead]

Plugged oil pickup?

 

[jakej78b]

Oil pickup is not clogged. Vehicle has a new oil pump and pickup was inspected at that time as well as numerous other times when I have replaced the oil pans.

Oil filter housing may be the place to start although it does not appear to be leaking, it's an easy replacement I assume.

Either the bad turbocharger or the crank and rod bearings are my running theory on the problem... Both are more involved fixes, but I'm willing to do them.

I will look into the plastigauge and see if I can measure any differences in the wear on the cam, though the cam and cam bearings look great.

oil spray jets.... these can be replaced from the bottom side of the engine after pulling off the oil pan I assume?

Can not using mann filters cause low oil pressure? I don't believe I've been using mann, just wix or whatever they carry at the autoparts store... I'll start ordering mann...

Is there an upgraded oil filter housing? I'm not a fan of plastic... even though it has held up fine for all these years... Something about it just makes me feel uncomfortable in a hot engine environment.

 

[dogdots]

Post pictures of the inside of the removed cam caps please (the cam bearing surface of the cap)

 

[jakej78b]

2001 alh cam cap1

• jakej78b
• Jan 21, 2021

2001 alh cam cap2

• jakej78b
• Jan 21, 2021

2001 alh cam cap3

• jakej78b
• Jan 21, 2021

2001 alh cam cap4

• jakej78b
• Jan 21, 2021

2001 alh cam cap5

• jakej78b
• Jan 21, 2021

2001 alh cam cap6

• jakej78b
• Jan 21, 2021

2001 alh cam cap7

• jakej78b
• Jan 21, 2021

2001 alh cam cap8

• jakej78b
• Jan 21, 2021

2001 alh cam cap9

• jakej78b
• Jan 21, 2021

 

[Jetta2005TDI]

make yourself plug for the turbo supply line. Disconnect it below the filter and plug it for a minute or two and start it at idle. See if pressure increases, this will eliminate leaking turbo. Also make sure your cooling system is functioning, fans and thermostat. Remember 190 degree is not very accurate so it does not scare people too much. I have checked coolant to be at 210 and gauge still shows 190. So if your engine is running hotter than needed your oil pressure will be lower. Quick fix for hot summer days until you fix the problem is to jump your fans to run every time engine is on at slow speed and you will see much better pressure.

 

[jakej78b]

make yourself plug for the turbo supply line. Disconnect it below the filter and plug it for a minute or two and start it at idle. See if pressure increases, this will eliminate leaking turbo. Also make sure your cooling system is functioning, fans and thermostat. Remember 190 degree is not very accurate so it does not scare people too much. I have checked coolant to be at 210 and gauge still shows 190. So if your engine is running hotter than needed your oil pressure will be lower. Quick fix for hot summer days until you fix the problem is to jump your fans to run every time engine is on at slow speed and you will see much better pressure.

Good idea. Could I also just pull off the exhaust manifold to prevent the turbine from spinning at all? I've already got the EGR off and the intake would come off quite easily at this point so it's not a big hassle, really

I'm going to be putting on a new turbocharger soon anyways and It's not THAT much work to pull the one that is on there for testing purposes.

 

[Jetta2005TDI]

You need to block oil going to turbo on the engine below the oil filter. Follow metal tube or if it was upgraded it can be braided flexible line that leads to turbo. Search mk4 turbo banjo bolt thread size and make plug from brass or aluminum. I always have that plug in glow box. In the case turbo fails I can plug the oil going to turbo and try to come home slowly. In your case turbine will still spin.

 

[TLH_TDI]

P.M sent.


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[jakej78b]

You need to block oil going to turbo on the engine below the oil filter. Follow metal tube or if it was upgraded it can be braided flexible line that leads to turbo. Search mk4 turbo banjo bolt thread size and make plug from brass or aluminum. I always have that plug in glow box. In the case turbo fails I can plug the oil going to turbo and try to come home slowly. In your case turbine will still spin.

Why would the turbine still spin? The turbocharger is attached to the exhaust manifold. If I detach the exhaust manifold from the engine and pull it out, I have the turbocharger in my hand... It will not spin when I start the engine.

I do not want to run my turbocharger without oil supply for any amount of time.

I'll probably wait until it's time for my next oil change before I pull the pan.

 

[Vince Waldon]

I personally think it's a red herring anyways... that big a drop in oil pressure as the engine heats up suggests more than just a single journal bearing in the turbo opening up, at least to me.

Always hard to tell from pictures...could just be the light.. but the cam bearings look abraded to me. If so, that would suggest oil contamination at some point, which would likely become apparent on the bottom end bearings as well, as accelerated wear.

These investigations are definitely a game of whack-a-mole... just gotta whack down the suspects one at a time.

 

[Jetta2005TDI]

Turbine will still spin with the plug what I was saying. You just need to do it for 5-6 sec to see the difference. I did the test on my car and turbo is still good 6 years after that. But if you continue driving at 7 psi you will damage engine.

 

[jakej78b]

I disconnected the pipe between the egr cooler and the egr to allow exhaust gas to flow freely into the atmosphere instead of back through the egr. This in theory makes the turbo spin much slower if at all and therefore loses less oil if it were leaking? I observed the alarm coming on much more frequently in this configuration. I will get a bolt tomorrow to put in the oil supply hole in the block and I will completely remove the turbocharger to rule it out. I think I can safely say it is crack/rod bearings at this point, and at only about $80 to replace them, I think I'll go ahead and do that. Any DIYS or further advise?

 

[Vince Waldon]

That price sounds a little low... maybe things are cheaper where you are... did you include all new bolts as well? They are single-use, so gotta be replaced.

It's a pretty straightforward job... a couple hints:

- two of the mains bolts require the use of a very narrow-walled socket to get to 'em... I just angle-grind down a cheapo Harbour Freight version
- a plastic putty knife cut to the right width makes a great bendy non-scratching tool for pushing the buried bearing halfs out, and then in again
- will need proper sealant for the oil pan, as you already know from having done the oil pump
- spray can of brake cleaner is good for cleaning the journals before installing the new bearings, engine oil will work fine for lube.

 

[PakProtector]

That price sounds a little low... maybe things are cheaper where you are... did you include all new bolts as well? They are single-use, so gotta be replaced.

It's a pretty straightforward job... a couple hints:

- two of the mains bolts require the use of a very narrow-walled socket to get to 'em... I just angle-grind down a cheapo Harbour Freight version
- a plastic putty knife cut to the right width makes a great bendy non-scratching tool for pushing the buried bearing halfs out, and then in again
- will need proper sealant for the oil pan, as you already know from having done the oil pump
- spray can of brake cleaner is good for cleaning the journals before installing the new bearings, engine oil will work fine for lube.

Is this putty knife process a means of doing the job whilst the engine is still in the car? It sure sounds possible...but I am not sure...
cheers,
Douglas

 

[Vince Waldon]

Yup, you pull the bearing cap, and then the exposed bearing half, and then use the plastic putty knife slice to push the other bearing half around so that you can grab it too.

Same putty knife slice works to slide the new bearing half around and under the journal.

Works a treat, just have to pay attention to keeping things surgically clean.

 

[PakProtector]

Works a treat, just have to pay attention to keeping things surgically clean.

I am reminded that we are talking about the inside of a diesel's crank case. Maybe this surgery was taking place when there were still wood handles on things like scalpels? This would make it about the time of Rudolph himself...

I think I would have all the caps loose; I am not liking the possibility of bending a bearing shell at all.
cheers,
Douglas

 

[TLH_TDI]

I am reminded that we are talking about the inside of a diesel's crank case. Maybe this surgery was taking place when there were still wood handles on things like scalpels? This would make it about the time of Rudolph himself...

I think I would have all the caps loose; I am not liking the possibility of bending a bearing shell at all.
cheers,
Douglas

You’re not bending a bearing just the plastic putty knife around the crank journal with the caps off, pushing the bearings out without having to remove the crankshaft.


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[TLH_TDI]

Uploading error

 

[Prairieview]

The LAST thing you want to do is remove all the caps at one time. One cap at a time.


Vince is correct, but over-simplifying. There will be times when you need to use a clean wooden hammer handle to lightly bar the crankshaft over to make room to "Roll" the bearing into place.



I always use assembly lube on the tool. You inspect the plastic with each move.



The #1 and #5 are the most difficult.

 

[TLH_TDI]

Any news on your low oil pressure issue?


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[PakProtector]

Thanks for the instruction gents; I have an ALH with these symptoms too; hence my interest. This engine is not in a car, and would get new TB/WP and etc when the job gets done so it would probably be a wee bit easier than the in-car solution.

Youse Rock!
cheers,
Douglas