need help with B8 S4 coolant-oil mystery

[JSL4]

Hello, All,
I've been reading along for awhile, but this is my first post (fairly new member) about the car (2011 S4 MT, no mods) I've tried to search, but haven't found anything on point yet. I don't really know much of anything about fixing cars, so if (when) my ignorance shows through (or too much info), please forgive me!

I've had the car since 2018 and had no real issues until ~ May 2022, when a warning/message appeared on car info system - "coolant expansion tank low" (or words to that effect). Car did't overheat. Got under hood quickly and found expansion tank empty. When I removed the cap, I heard a little whoosh of air (like there was suction within system?) I filled expansion tank and went on my way.

At oil change/inspection Aug. 2022, very small coolant leak noted - dried coolant at bottom of engine compartment. Shortly after this, yellow "oil low" light comes on, seemed weird, since I just had the oil change, but regardless, I put in ~ 450 mL oil, and went on my way. For what it's worth, before all of this, car didn't seem to consume much oil - I'd get the yellow oil light on after ~ 4000-5000 miles after oil changes, and would then need to add about 400-450 mL about every other month until next oil change.

Sept., 2022 - "low coolant" message comes on again, and expansion tank again empty. Again quickly filled, no overheating. Car into shop for coolant leak diagnosis - passed "coolant block test", but leaks found at: PCV housing, upper valley transfer pipe, water pump slightly seeping from seal. Fairly significant replacements/repair done at this point - new water pump, T-stat, PCV assembly, coolant pipes, crankcase ventilation cover gasket ( invoice also mentions oil separator under crankcase gasket heading - not sure if that's the same thing?), along with alternator drive belt & supercharger belt, and oil / filter changed.

Oct. 2022 - after picking up car, drove about 30 miles when bad misfire developed, EPC and "check engine" lights on, and coolant level down to 1 inch below "min" line on expansion tank. Car back to shop - pressure tested coolant system, and held pressure - suspected air pockets may have been in system, eventually filled, accounting for drop coolant level. Bad ignition coil / spark plug found, and replaced, curing misfire, dash lights out. Oil not discussed.

Oct., 2022 - drove car for about 200 miles when yellow "low oil" came on, and a few minutes later red "low oil - add oil immediately" light came on. When I lifted the hood, that apparently reset the oil warning lights - they went out. Called the repair shop - actual low oil problem doubted (just had oil change) - suspected sensor wires loose, corroded, etc. I was wary of over-filling oil, and per discussion w/ repair shop, was to just keep lifting hood to reset lights, until I could get car in for inspection. MMI oil level gave messages about "warm car, engine off - read in two minutes", but I couldn't get a reading from it.

Dec, 2022 - car sat for a month, not driven, while recovering from surgery. Once I began driving it again, oil lights would come on every couple of days - I'd lift hood, which turned off lights, and I'd go on my way. No oil added.

Jan., 2023 - got a dipstick (ECS #06E 115611H) and placed it the other night - it came out bone dry. My first thought was dipstick too short, but further research suggests it's the right one. So I had the car in for an oil change (different shop), just to find out how much oil was really in the car - 3.4 quarts! I asked my brother-in-law (retired mechanic) where all the oil went - he asked if I'd looked at the coolant lately. I had not - the level was staying about the same, and temp steady/normal. So I looked at the coolant in the expansion tank and it looks like a milkshake - thick, creamy, orange/pink. I called the repair shop with this info, and there was discussion about whether any of the coolant system repair work might somehow be connected to the current situation - unclear. I had thought I had read about coolant in oil being an indication of possible PCV failure, but maybe that was not about 3 liter engines. Other possible explanations were also discussed - bad cylinder head (?). I haven't noticed any oily substance out of the exhaust pipes, or abnormal smoke from exhaust.

I would be eternally grateful for any thoughts, suggestions, diagnostic ideas on the possible/likely causes of the situation (what to check/test first, second, etc) and any thoughts on where those three quarts of oil went.

Thanks so much in advance for any help you can give,
JSL4

[S4Gibbs]

Lots to unpack, but this all sucks man. Sorry to hear it.

Hypothesis:

2018 --> May 2022: Your car's PCV failed and/or developed a coolant leak from waterpump and/or thermostat housing.

May 2022 --> Aug 2022: You refilled your reservoir with coolant yet continued to drive(for 3-4 months) a car that just finished consuming an entire reservoir worth of coolant. [o_o]

Sept 2022: The car underwent repairs that resulted in new problems manifesting that were not present before the shop touched it.

Sept 2022 --> Jan 2023: Milkshake = Oil mixed with Coolant. One possibility is that the PCV issue was not repaired adequately and caused oil to mix into your coolant. However, there are several potential causes of oil mixing into your coolant. I assume there's oil under your oil cap as well?

[JSL4]

Hey S4Gibbs,
thanks for the reply! It does suck, and not cheaply, either! But the car's been great, and I knew (sorta) what I was getting into, so absolutely no complaints. I can see I should have dealt with the coolant loss sooner (duh). There is oil under the oil cap (amount seems normal/what I am used t seeing) and it and the oil on the dipstick (halfway between min-max) look clear, light brown - not cloudy, milky, streaked with anything, discolored, etc (oil just changed, though).

I'm wondering in particular about the math - oil three quarts low, coolant expansion tank has oil in it - but it was filled entirely with coolant went it left the repair shop, and hasn't overflowed (level stable), so where have the fluids gone?

It'll be into the shop on Friday, so I'm crossing my fingers, but I'm just trying find out what I can ahead of time.

Thanks so much again, and please pass along any further thoughts (whenever it's convenient - I don't mean to drop into your evening too heavily - I'm gonna' have a beer and watch TCU-Georgia shortly! Car's staying put 'til Friday)
Take care,
JSL4

[S4Gibbs]

I'm not sure I can provide much more insight from behind my keyboard unfortunately.

What's the shop's explanation of the milkshake, oil level, and new EPC light situation that seems to have all occurred immediately after their work? It could be a number of things.

[JSL4]

Thanks again - I know it's going to take someone getting into it to figure it out. It'll be into the shop tomorrow, I'll post an update afterwards. Apparently (per my research and somewhat limited understanding), seems like bad head gasket or leaky oil cooler seem to be among the more common causes of the milkshake (although I've read a cracked block could also explain, but less likely, car re-inspected prior to repair to look for other major issues - none found, and power still ok in car). I haven't found much written to indicate the repair work performed might explain this, but the timing of it all...well, I don't know what to make of it.

[S4Gibbs]

The head gaskets are actually pretty stout on our 3.0T and rarely cause issues. 9times/10 if a 3.0T owner is reporting milkshake, the mixing of fluids is occurring at the PCV.

Did the shop use a PCV rebuild kit or install a whole new PCV unit?

Accidentally swapping the throttle body vacuum hose connections can cause an EPC light(and potentially pull vacuums in weird places?).

Also, there's a thin PCV breather hose/line that comes out of the top of PCV(on driver's-rear part of the top of PCV) that can fail and cause the same issues as a bad PCV unit itself. This line on some 3.0T engines should be replaced as part of a good PCV job, as some variations of this hose(check-valve vs electronic valve) have been known to fail. Can't recall which hose variant had most of the problems. Hopefully they replaced that line while they were in there or at least tested if the check-valve still functions.

[JSL4]

Thanks, again - I really appreciate your insights. I am somewhat relieved and very embarrassed - I am so sorry for passing on inaccurate info - there was no milkshake - first thing done when at repair shop this morning was to actually pull some fluid out of expansion tank with syringe - looked clear, fine - I did not aspirate the tank when looked at the coolant - my mistake - appearance in the tank is different than pulling fluid out and looking closely. Again, sorry!

New parts were used for PCV, but it does not appear that the PCV breather hose or check-valve were replaced.

Oil consumption issue not solved. Repair shop looked on computer, saw TSB on excessive oil consumption, and said first, we should perform oil consumption analysis. First step (replacement of crankcase pressure regulating valve) already done, next step is to update Engine Control Module software, then perform oil consumption testing - remove, measure and replace oil when low oil light comes on / in a month, whichever comes first, shop to add and log amounts of all oil added - there's a more detailed protocol, but that's the gist, I think).

TSB reference #: Group 17, No. 16-74 (2030197/17) (aka 17 16 74 2030197/17), June 7, 2016, from PRODEMAND website.

Repair shop thinking behind this was (as I understood it) - valve-timing, amount of lift (??) and other settings controlled by computer module, and may effect oil consumption. TSB issued to address excess oil consumption (apparently, software update will modify settings and correct any oil consumption problems that might be due to valve timing, or lift, or other functions controlled by computer).

I asked repair shop - "but what about the work you did?" - oil separator in particular, only because it had to do with oil system. Repair shop said that crankcase felt like it had good vacuum when they started car - so oil separator unlikely to an issue. Repair shop wanted a better idea, I think, of how much oil was being consumed, and maybe verifying that there is/is not a software component to the issue (?) before starting down various diagnostic explorations.

Per repair shop, software update must be done by Audi, so I called nearby Audi dealer to schedule appointment for software update per TSB. Audi service dept didn't seem to know what I was referring to (TSB) at first. After some discussion on their end, they came back on the line and said they were reluctant about touching car, concerned that if they change software and then something (else) goes wrong with the car, they might be blamed. They wanted more info, though, so I'll be sending them the TSB. Audi also said that if car consuming > 1 qt / 1000 mi, right off the bat, the official recommendation is a piston-ring job (est $15K!).

None of this seems to explain the oil loss following the repair - computer software didn't appear to be causing any oil consumption problems in days/weeks/months before repair, so that theory seems questionable. I'll be watching dipstick closely until some of the above gets ironed out.

[S4Gibbs]

No worries man.

I highly doubt the oil issue is software related.

If there are no external oil leaks and oil isn't getting into the coolant, there are only 2 possible causes of your car's oil level being 3quarts too low after only a few 100 miles: Either your engine somehow burned the 3quarts of oil, or the shop perhaps did not fill it properly. I'm hoping the latter is true to avoid immediately guaranteeing the need for serious engine work/replacement. However, driving your car with only ~50% of it's oil can also cause serious problems.

Are you seeing any blue'ish smoke or any noticeable changes to exhaust fumes?

Whatever you do, do not let another shop/dealer work on your car for now. You should work with the shop that did the PCV repairs to investigate this issue. If you absolutely must continue driving your car, I would monitor your oil level for any changes after every drive. I'm hoping the shop just didn't put enough oil in initially and that hopefully no serious damage was done by driving it with such low oil.

[JSL4]

Hey thanks!

I doubt the software theory, too. Maybe he's just trying to establish a baseline (?) for further investigation, w/ the update.

No external leaks, garage floor clean, engine compartment clean except for random smudges, doesn't seem like oil seeping, leaking, but my powers of observation leave something to be desired...No oil in coolant. I'm sure hoping the same on the "low fill". but will be checking oil regularly, driving as little as possible. And weirdly (?), last night, the oil measurement function on MMI starting working properly, I think - it has oil level higher than dipstick.

It's funny (I guess), the last thing the guy at the shop said when I left yesterday is that he could guarantee me the car left the shop w/ oil topped-up after cooling system repair. I don't know if this could be related, but In between coolant system fix and the oil lights starting up, ignition coil and spark plug replaced.

I know what you mean about driving it w/ low oil - holding my breath that it'll hold up. New engine ~ $3500 - 5000 on eBay!!

No blueish smoke - exhaust fumes look usual - thin, white, small amounts.

I really appreciate in particular the tip on other shops - there was some temptation to get other eyeballs on it, but I get what you're saying. Hopefully won't be necessary. And I can kind of see where the Audi dealership is coming from. I'm going to look into the TSB/ software issue a fair bit more before getting that done - dealership, even if they would do it, couldn't until mid-Feb.
Take care.

[JSL4]

Hey S4 Gibbs and any other readers,
thought I should update the post (in case people might be subscribed to it, or following along somehow).

Not a whole lot to write home about lately.

Oil consumption problems still not resolved...I took the car to another shop (European specialists, this time) for diagnostics only - PCV checked and apparently working ok. Not sure what vacuum pressure reading was, but going back tomorrow - shop says it's had luck putting sealants into cars consuming lots of oil, so they're going to try. No diagniosis on oil consumption problem, though. "That can be tough to figure out" is what I'm hearing. I've just recently come across some other posts in the B8 forum, in the thread "PCV replacement", so I've asked in that thread whether the software update might, somehow, be helpful in light of all this. . Some of the discussion over there touches on the issue.Will post back when more is known. Take care.

[LowKeyLoki]

You need to figure out which part number PCV valve was installed, if it was ending in AC you don’t need ECU update, if it ended in AH you need the ECU flashed by dealer to upgrade the software to run on the 150mbar PCV valve. This ONLY applies to B8s that have not upgraded to the AH version, all B8.5s have the 150mbar version.

[LowKeyLoki]

Everything has been talked about in this thread already:
https://www.audizine.com/forum/showthread.php/950353-PCV-Correct-Part-and-ECM-Update

[JSL4]

Hey LowKeyLoki,
thanks for pointing me to that info - I missed it in earlier searches! That's helpful - I did get the AC version of the PCV installed, so I'll keep looking for other explanations for oil loss.

[LowKeyLoki]

No problem man, your next move should probably be check compression on each cylinder and then maybe performing a leak down test if no issues with compression. Could be a worn or sticky by valve or valve seat or worn rings etc.

[JSL4]

Thanks, again LowKeyLoki, - much appreciated - I'll post back once I check into that stuff

[ccssid]

@JSL4 ...sent you a PM