Turbos - oh dear, the saga continues

[Jim Haseltine]

Since I got my car back on the road following my home turbo rebuilds and 50p seal fix it has smoked occasionally on start up but with less frequency as time went on. Originally it was every day, then every second day then randomly. A week ago Sunday it threw out a massive cloud and continued to do so for a mile or so but since then nothing. Until tonight when it did it's best to blot out the sun for several miles. Along with this, yesterday while doing some other minor tasks I had the engine panel off so I could check for oil leaks - of which there were none to be seen, something I was quite happy about. What didn't please me was that I drained 250mL of oil out of each of the intercooler hoses, so it looks like my rebuilds were less successful that I first thought.
Unless somebody can think of another reason for what's happening I guess I need to bite the bullet and go for new turbos.

[IanH755]

Sorry to hear that but, with no other explanations available for that quantity of oil in such a short amount of time, I have to agree with your diagnosis and say it's probably new/repaired turbo time.

IIRC Turbo Technics do a rebuild/mild upgrade to the OEM turboes for around £800-ish (price was from around mid 2010's, may have changed).

[welwynnick]

Sorry to hear that Jim. Would that need another engine out?

I rebuilt a pair of turbos a few years ago, and some things struck me. Despite the amazing materials and manufacturing tolerances, turbos are pretty robust things. They don't go wrong as often as people perceive, and when they do, it's usually down to external factors. There's a huge list. You have to put those right as well as repairing or replacing the turbos.

In my case the failure was caused by burnt oil building up in the drain chamber in the centre housing caused by interruption of the coolant supply, and I think that's pretty typical. Therefore the oil being fed to the bearings was overflowing along the shaft and entering the turbine. There is a seal there, but not the usual sort, more like a tiny piston ring. It only stops most of the high pressure exhaust gases being blown into the oil chamber, but doesn't keep the oil in - there's only a thrower ring for that, and that doesn't work if the oil is overflowing.

If you rebuilt your turbos recently and they're burning oil again so soon, that suggests something else is going on, probably something with the lubrication / scavenging / breathing systems that's causing the turbos to push oil out the end. I know that stuff is nightmare complicated (I think the dry sump system is at the same time the engine's greatest asset and it's worst liability). So I wouldn't rush to pull the engine all over again before crossing other things off the list first.

Good luck, Nick

[Jim Haseltine]

Well, here's further. As I'd taken half a litre of oil out of the pipes and it's been burning something, I checked the oil level this morning expecting it to be low - curiously, it was still pretty much a the correct level. While I was doing that I noticed a smell of fuel from the cloth that I'd wiped the dipstick with. Called into my tame mechanic's place to tap him up about the possibility of borrowing one of his lifts for a few days if I had to change the turbos and got him to take a sniff at the oil. Definitely got petrol in it.
With a wet sump car I'd guess at one or more leaking injectors which he agreed with but then mentioned problems with Audi high pressure fuel pumps on other models which can leak fuel into the engine. So before I pull the trigger on new turbos I'll check the rail pressure and then pull the pumps and check them.
It might also explain why the exhaust always smells very rich.

[Jim Haseltine]

Don't know if I'm checking the right blocks but 106 & 140 show around 30bar at idle. After about 6 minutes 106 is now down to 20bar. 141 showed a bit over 10bar at idle and has now risen to 13bar.

Have I got this right and if so, are the figures in the right ballpark?

[Jim Haseltine]

Engine has now been off for 45minutes, 106 is showing 6bar and 141 is showing 16bar.
I generally only use VCDS for fault codes so I'm in the dark here - what should I look at and what sort of figures should I be seeing?

[Jim Haseltine]

Couple of extra bits of info which may or may not have a bearing on things:
The fuel filter hasn't been changed in the 5 years I've owned the car and may well still be the original item
It's got BMP filters which I cleaned and reoiled as part of the turbo job so may well have been over oiled.

[ruedisrs6]

Dear Jim,

to your problem with the massive amount of oil in the intercoolers. I had exactly the same issue, blue smoke at cold start, not every time the car was standing for a couple of hours, but maybe every 3-4 starts. Over two years it became worse until a day where I had substantial blue smoke on heavy acceleration and found more than 1.5 litre of oil in the intercoolers (more oil on the right). So I thought like you that the turbos are gone. I brought the car to a workshop, they pulled the engine and sent the turbos in for rebuild. When they started the engine for the first time everything was fine and also the first test drive of about 80 km was fine, but when the car was started after a weekend of non-use, it smoked like hell. They thought the rebuild was not correctly done, so they send the turbos a second time for rebuild. The company that did the rebuild did not find a problem with the turbos. After many days of searching for the failure mechanism, the workshop gave up and I had to find a solution for myself. To make a long story short: In the oil module there is a non-return valve that closes when the engine is not running. This valve in my case did not close properly and allowed oil to drain from the turbos to the intercoolers (before rebuild) or to the catalytic converters (after the rebuild) via the oil return lines of the turbos (the level of the oil tank is above the level of the turbos). To confirm this, I did two things: 1. I checked by dismounting the turbo oil return lines from the oil module if oil is flowing out of the module when the engine is off. In my case it did, up to a litre overnight 2. I used a clamp to block the oil return tube from one turbo, when the engine was off (I used the car only for short distances). I then start the engine on several days (of course with the clamp removed) and after a few days I had smoke only on the non-blocked side. I replaced the oil module and since then I had no smoke at all (was in 2018). I disassembled the oil module to have alook at the valve and it just looked fine. But it did not work properly. A perfect example how a 5 pound part can cause many sleepless nights ....
Maybe this helps.

I know that those Hitachi injectors which are quite common in VAG cars sometimes are leaking. I checked the high pressure values (need to check which measurement block) on both cylinder banks recently. If I remember correctly it stayed for several minutes above 30 bar on both sides after I turned the engine off. If it does not stay in this range or the two banks show a different behaviour, I would assume a leaking injector.

[Jim Haseltine]

The car has now been moved to leave my driveway clear for use. I suspect that the smoke I'm seeing is from oil passing the turbo seals when the engine isn't running, probably because the fuel in the oil is both raising the level well above the turbos and also probably thinning the oil.
If somebody would document the procedure for checking fuel pressures using VCDS I'd be grateful. I'm hoping that fixing this will be less costly in time and money than changing the turbos again.
I hope.
Now I'm going to have to deal with the earache I'm going to get from my other half when I tell her the car is broken again.

[Jim Haseltine]

There was no pressure in the hard lines out of the high pressure fuel pumps this morning. I've pulled the pumps, both seem ok from the outside, with oil under them on top of the cam followers which look to be in good nick - I'd have thought that if the pumps were leaking down into the cam covers the oil would have been washed away. Next task is to drain some coolant, remove the inlet manifold and take a look at the injectors. Oh, and drain the oil too because it's like water.

[Jim Haseltine]

Pulled the injectors after a struggle to remove the inlet manifold (found that somebody has broken an injector plug at some time too). All the tips were filthy with carbon and at least 3 of them were wet with fuel - a couple of days after the engine last run. Next thing is to get them cleaned and tested.

[Jim Haseltine]

Word back from the place that I sent the injectors to - "Quite honestly the worst set of injectors we've seen in a long time"

[welwynnick]

Interesting news Jim. Does this suggest that your turbos might have been OK all along?

Nick

[Jim Haseltine]

It's possible - for a given value of 'OK'. They were in a hell of a state with loads of carbon build up and wear to both the front and rear seals so if they weren't at fault they can't have been far off.
On testing, two of my injectors were leaking down while the others 'might' be ok once cleaned so I'm not going to muck about - I'll fit a new set. Question is - do I go for OE or aftermarket?

[RS6-T28RPH]

I also have the oil in the bottom of the boost pipes between turbo and intercooler, yet the turbo outlet looks squeaky clean so similar situation at a guess?

A while ago I did have a bit of a bang and a stars in your eyes moment out the back of the car, the fine oil separator diaphragm had split as well as blowing the crap out of one of the non return valves down below it. Replaced those and the white smoke has gone, still rich as you like with the odd puff of blue smoke on cold start-up but hey ho, she be alreet 156k miles on the clock on oem parts, mega stuff

fingers crossed we shall have her booked in with RE Performance soon for the upgrades