Oil Pressure Fluctuating Issue - Part IV

[mochsl99]

This is my fourth thread on this issue... I've been battling it since June of 2012.

I contemplated just extending an existing thread, but I have some video I want to share, and figured I'd provide a summary and save anyone interested in helping the trouble of reading through multi-page existing threads.:

• Part I: Original incident
• Part II: Gauge install and initial readings
• Part III: Oil Pressure Drops Suddenly Then Recovers

In 2012 and 2013 I had a couple incidents in which my red oil pressure light came on, then would go off. The threads above document the entire scenario pretty thoroughly. Suffice to say, driving along and "beeeeep" red oil pressure warning light. Pull over, sit and stew, pull codes, etc. Turn engine over and everything is normal, no warning light, engine running fine. In the end I put a full-time oil pressure gauge in (because a mechanical gauge in the garage never showed anything really amiss... this is an intermittent problem).

As the Part III thread describes, the pressure gauge revealed fluctuating oil pressures, so I decided to have my local Audi mechanic pull the oil pan and replace pickup tube, check for sludge, etc. Mechanic did so, and the pan showed absolutely no signs of sludge. I can post pictures of that tomorrow. There was really nothing of great note. Some plastic debris and the like floating around in there. The pickup tube had bits of particulate matter in the screen, but nothing close to significant blockage. Had the mechanic clean the pan thoroughly, replace the pickup tube, and away I went.

Unfortunately, I continued to see fluctuating readings on the oil pressure gauge. Given that I felt like I had crossed off all the possible causes, I tried to convince myself I was just seeing faulty readings from my newly installed oil pressure sensor. Sometimes it will run steady for days or weeks, then suddenly start dropping precipitously, then recover. Lately, it's been pretty steady on the good side, very little in the way of plummeting oil pressure readings.

Drove up to go skiing this weekend, and noted how steady the pressure was. Patted myself on the back. Probably a big mistake.

Driving back up the hill toward the Eisenhower Tunnel today, the gauge was going crazy. Dropping to like, 10 PSI at 3300+ RPM, climbing to 50 PSI, dropping to 11 or 12. Just all over the board. Right as I topped the hill and entered the tunnel, pressure dropped to about 2 or 3, and "BEEEEEEEP!!!!" Audi's own oil pressure warning light comes on. Uh oh.! So, looks like my installed gauge was not faulty after all. Both it and Audi's internal pressure warning system agreed, the oil pressure was near ZERO.

Worst place in the world for this to happen, by the way... Sunday ski traffic starting to build, 1+ mile long tunnel with no break down lane or any place to stop. I dropped into a lower gear and revved the engine hoping it would crank back up, and miraculously it did, creeping back up to 10 or 11 PSI, then staggering up to the teens and twenties. Made it out of the tunnel, let it mostly coast down the hill, and nursed it home.

Video of pressure readings on the drive home.

So, now what??? Everything I've read indicates the oil pump failing would be sudden and complete. It's a fairly simple mechanical pump. Given there's no sign of sludge in the pan or pickup tube, oil level is normal — what could be causing this?

[bw86]

You sure its not a bad sensor? Your engine would be extremely loud with such low oil pressure.

[mochsl99]

You sure its not a bad sensor? Your engine would be extremely loud with such low oil pressure.

Anything is possible, I suppose. It seems extremely unlikely that my aftermarket pod-mount oil pressure gauge would show catastrophic low oil pressure and at the exact same moment the built-in Audi oil pressure warning sensor would alert for the same issue... two bad sensors warning at the same time?

[seanf86]

do the oil pumps on the 1.8 have a ball and spring check valve to limit oil pressure? I've never dug that far into a 1.8 to see. if so I'd say it needs an oil pump. Possibly oil filter adapter gasket that bolts the filter adapter to the block could cause an intermittant leak if theres a small crack in the gasket.

[old guy]

There is a piston and spring pressure limiting valve located on the oil filter housing. Might be worth checking the spring to make sure it isn't broken. (#3 and #4)

[mochsl99]

do the oil pumps on the 1.8 have a ball and spring check valve to limit oil pressure? I've never dug that far into a 1.8 to see. if so I'd say it needs an oil pump. Possibly oil filter adapter gasket that bolts the filter adapter to the block could cause an intermittant leak if theres a small crack in the gasket.

If there were a leak/crack in the gasket, would I notice oil loss? There doesn't appear to be any oil coming off the engine anywhere, and oil levels are remaining stable.

I assume replacing the oil pump would mean pulling the pan again...

[seanf86]

Not if that gaskets cracked and dumping down back into the block via the breather part

Look up the gasket on ecs for a picture you'll see what I'm talking about

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[mochsl99]

There is a piston and spring pressure limiting valve located on the oil filter housing. Might be worth checking the spring to make sure it isn't broken. (#3 and #4)

Excellent information... That's what I'm looking for, anything that could possibly cause this that hasn't already been checked off my list:

x Sludge in oil pan
x Free floating debris in oil pan
x Clogged pickup tube
- Bad oil pump
- Debris in an oil line somewhere?
- Pressure limiting valve/spring (new - thanks Old Guy and seanf86!)
- Oil Filter Adapter Gasket

If it were the oil pump, wouldn't it just fail outright? I've never had one in my hand, but my understanding is it's a pretty simple device... it either works, or it doesn't.

[seanf86]

Excellent information... That's what I'm looking for, anything that could possibly cause this that hasn't already been checked off my list:

x Sludge in oil pan
x Free floating debris in oil pan
x Clogged pickup tube
- Bad oil pump
- Debris in an oil line somewhere?
- Pressure limiting valve/spring (new - thanks Old Guy and seanf86!)
- Oil Filter Adapter Gasket

If it were the oil pump, wouldn't it just fail outright? I've never had one in my hand, but my understanding is it's a pretty simple device... it either works, or it doesn't.

yea pretty much unless the relief valve is built in, which it is not, its in the oil filter adapter which old guy pointed out, Id start at the relief valve since it looks like a pretty simple thing to check and low cost to replace.

[ryanj]

Step 1 with an oil light is clean pickup tube AND replace oil pump. The longitudinal 1.8t oil pump failure rate is incredibly high (I have replaced 50+ of these ) This will take care of oil pressure problems %99 of the time on the b6/b5 1.8t. These oil pumps can fail in many different ways. Until you replace your actual oil pump I would not condemn anything else

[mochsl99]

Step 1 with an oil light is clean pickup tube AND replace oil pump. The longitudinal 1.8t oil pump failure rate is incredibly high (I have replaced 50+ of these ) This will take care of oil pressure problems %99 of the time on the b6/b5 1.8t. These oil pumps can fail in many different ways. Until you replace your actual oil pump I would not condemn anything else

Yes. In hindsight I probably should have had them replace the oil pump when they had the pan off. It was a $600+ job, so I'm trying to avoid paying for it again if there's any possibility it's something else. I do a lot of work on this car myself, but pulling the oil pan looks like an absolute monster. I went in while the Audi mechanic was working on it, and even with the car on a lift, subframe dropped, he had a hell of a time getting the pan to finally come clear for removal. I don't like the idea of doing it on jack stands in my ice cold garage.

I'm intrigued by old guy's idea about the pressure limiting valve. I'm also considering the possibility it could be a problem in the oil breather vacuum system? I've seen a couple of posts in which low oil pressure issues were fixed by replacing/repairing the oil breather vacuum line that runs from the top of the engine down the back and connects to the oil filter housing. The notion it could be related to vacuum issues jibes with the sporadic nature of the pressure drops, and the fact that revving the engine almost always causes at least momentary recovery of pressure. Of course, that logic could also apply to the oil pump...

Again, the symptoms — intermittent pressure loss, never (or almost never) down to zero pressure — make me feel in my gut it's not the oil pump. I would think that the pump would just quit outright. Have you ever heard of one failing gradually? With symptoms like I've described (and recorded on video) above?

[old guy]

I had considered a defective crankcase breathing system and was going to post it as a possible solution until I went back and read Part 1. In Part 1 you indicated that the oil light came on when the engine was under load and going uphill. In that situation there is no vacuum being pulled on the block. I have seen cases where a defective block breather was pulling excessive vacuum on the block and causing the oil pressure light to come on at idle or when driving at moderate speeds and going off throttle. In both instances the defective breathers were pulling excessive vacuum on the block which in turn put additional load on the oil pump as it tried to pull oil from the pan.

[mochsl99]

I had considered a defective crankcase breathing system and was going to post it as a possible solution until I went back and read Part 1. In Part 1 you indicated that the oil light came on when the engine was under load and going uphill. In that situation there is no vacuum being pulled on the block. I have seen cases where a defective block breather was pulling excessive vacuum on the block and causing the oil pressure light to come on at idle or when driving at moderate speeds and going off throttle. In both instances the defective breathers were pulling excessive vacuum on the block which in turn put additional load on the oil pump as it tried to pull oil from the pan.

Yeah. The fluctuations happen under almost all conditions EXCEPT under engine rev (downshifting and thus increasing RPM dramatically will pull depressed pressure back up momentarily)... steady load at any RPM will show intermittent pressure loss (per the above video), and deceleration/decreasing RPM can trigger precipitous drops in pressure.

[mochsl99]

I'm going to check the pressure limiting valve/spring this morning.

Any special tips about removing/checking the part? What exactly am I looking for, beyond a "broken" spring?

I'm not planning on draining the oil before I check this... any reason I should?

[old guy]

I believe it is simply a spring and plunger. No need to drain the oil. You will probably get some dribble but nothing significant.

[mochsl99]

I believe it is simply a spring and plunger. No need to drain the oil. You will probably get some dribble but nothing significant.

It is indeed simply a spring and plunger... a VERY STRONG spring. It is pretty much impossible to get it back together. I have about 1" of working space between the oil filter housing and the bottom of the dipstick tube. I've been wrestling it for over an hour, trying everything I can think of in the limited space available to leverage the plug back into the threads so I can hand thread it. It's at a slight angle, and the spring pushes out with enough force that you have to use super-human string to push in while simultaneously threading. I am not super human, so FAIL.

May have to remove the entire filter housing just to get the damn thing back together. It's a classic Audi DIY challenge — extremely tight tolerances, things that were clearly put together while the engine was either outside the car or many interfering parts were removed to provide access.

UPDATE: Managed to get it back in... I think just by sheer perseverance and dumb luck. Used a small crow bar (9") and 19mm box wrench together, the crow bar to lever the plug into position (which is very difficult because the entry is offset from the angle of the dipstick tube, which is the only lever point available, so you have to twist and lever at the same time) then while holding it steady with all your might, try to get the box wrench on the plug and delicately turn to engage the threads. When it seated, I couldn't believe it. I would strongly advise against removing the plug unless you have a strategy for getting it back in against the substantial force of the spring.

Anyway, looks like that isn't the problem/cause of my intermittent oil pressure fluctuations. I'm going to look at the vacuum system next, just because I can't believe it's the pump.

[old guy]

Well.......At least you eliminated another potential source of the problem.

[mochsl99]

Well.......At least you eliminated another potential source of the problem.

And overcame another seemingly impossible Audi DIY challenge!

So, drove to the car wash and oil pressure was great all the way there, as the engine oil temp got up to operational levels (~164°F). On the way home, oil pressure was all over the place. Got home and sat letting it idle. Held steady at 14-15 PSI, 800 RPM, 164°F.

Then, when I would rev the engine to 2000 RPM the oil pressure would DROP and bounce around between 6-11 PSI. Return to idle, and it would bounce back up to 14 PSI. Did this consistently for several iterations. Turned it off and went inside to clean up dog barf (another story).

Came back out after it had sat for 20 minutes. Turned it on, and at idle it started around 10-11 PSI, then dropped to 0! No oil pressure alert (I suppose because the idle RPMs were so low). Revving the engine would pull oil pressure back up, and it settled into a normal 14-15 PSI at idle (oil temp ~160°F), 32-33 PSI at 2000 RPM, cycled back and forth from idle to 2000 RPM multiple times and it seemed pretty normal, then suddenly it did the inexplicable drop in oil pressure (down between 6-10 PSI) at 2000 RPM, 14 PSI at idle. Did this just once, then was normal again (32-33 PSI at 2000 RPM).

Video is on YouTube...

[old guy]

At this point I think replacing the oil pump is probably the best course of action. There isn't anything else to check.

[audinutt]

So when are you going to change the oil pump? Seriously with all the time you have wasted this sound be done.

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[mochsl99]

So when are you going to change tgr oil pump? Seriously with all the time you have wasted this sound be done.

I don't consider it wasted time when it could have possibly been the cause, and the oil pump replacement costs about $1,000.

[audinutt]

Diy... The pump is not that expensive. Didn't mean to offend. Just been down similar roads before and sometimes it's easier in the long run and cheaper to just do it.

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[mochsl99]

Diy... The pump is not that expensive.

Unfortunately, this is a DIY that is above my pay-grade. I've done control arms, timing belts, motor mounts and the like, the dropping the pan on these B6s looks like a total PITA, loaded with opportunities to fail. The most complete DIY direction I've found has comments like:

Before I start, this is a difficult job. If you have never replaced a transmission, engine or clutch in a front wheel drive car, DON'T ATTEMPT! I rate this a 7.5/10

and

Now is the tricky part. I wish I had a guide to tell me about the 2 hidden bolts. There are 2 windows between the transmission and oil pan. Inside these windows you will see the fly wheel. Turn the fly wheel until you see a gap in the fly-wheel and through that gap you see a bolt. You will need a LONG 5mm hex-key to get both these bolts out. Good luck finding one. I found one at Brafasco. I then modified the end with a grinder so it was a flat end and less likely to damage the hex-key bolt. REMEMBER: If you damage this hex-key bolt you will have to remove the transmission and flywheel to get the oil pan off!!!!

ummm... any DIY that requires you make your own tools is beyond my capacity. So, I'll be paying someone else to do it, which kills me because I just paid them to pull the oil pan 4 months ago! I'm actually kind of frustrated they didn't recommend/mention/offer to change the oil pump while they were in there. They knew the reason I had them pull the pan was intermittent oil pressure issues. I'm going to have a chat with them about it, anyway. See if they offer up a discount or anything.

[audinutt]

That is a bad situation. I would hope they would work with you since they didn't mention the pump when it was apart before.

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[customa4]

^^ I agree. A stand up shop should be willing to meet you halfway in this since if they recommended it in the first place it would have been done while they were there. I'm also a DIY guy but something about that oil pan makes me want no part of it. It will happen one day though, one day.

[Waspjr]

Crappy situation. And yeah the shop should do a solid and keep you as a customer. But what i would do although i know you have put alot of money into your engine. Buy another 1.8t they are everywhere and cheap like borsh do all the norms like oil pump head gasket coolant flange etc. build it up and change it out. It will save you swearing and bleeding under your car and probably only cost you a couple hundred extra.


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