When do you know its new Turbo Time? (75tdi)

Hello all,

Long time lurker, with so much information in older posts
Not had much need to ask again.

However my car just in for a service at independent VAG specialist, Straightline Performance Malvern Worcestershire.

I asked them to check over the turbo particularly the waste gate as I've had a few limp home mode turbo over boost moments recently.

However they have just called having looked at the turbo pipes and noticed a little oil leaking. They are investigating further... but when do you know its Turbo Referb time?

Cars done 110K , not heard any very odd noises, maybe noticed the odd smokey start, but car hasn't been drinking oil.

So whats the expert opinion

Mark

2002 TDI SE Bose & Factory Towball
 
Mechanical turbo failure, especially on the 75, is incredibly rare and they can go on for far longer than you'd expect if serviced correctly (ie the right oil is used).

If you're getting limp home, is this triggered when on high load? The first suspect is always plumbing - you've probably got a boost leak. The reason you're getting overboost triggered is that the pressurised air is escaping somewhere, so the turbo keeps working harder to meet the manifold pressure it's meant to as determined by the ECU map until it hits it's safety limit and cuts out to prevent damage.

I would get your garage to check the condition of all the rubber hoses in the intake tract - check for signs of splits/ cracking, and also check the condition of the intercooler - there have been a lot of instances of the intercooler casing cracking due to vibrations.
 
Thanks Dan,

Been taking those things on mind.
Would make a good poll, limp home and resolutions.

It was more the OIL found leaking from pipe connected to turbo.
Off to pick it up now I'll find out which pipe.

Wondering what are the signs that these reliable units do need a rebuild?

Mark
 
Which pipe had oil in it? You'd expect some oil residue in the inlet manifold to be honest - due to the exhaust gas recirculation blow-back from the crankcase breather. You may find a bit of oil in the intercooler as well.

Because of electronic control of boost levels, combined with the mechanical wastegate, modern turbos rarely fail due to overpressure (which damages the turbine blades and/or casing and will go bang - bits of turbo end up in the intake manifold). The more common cause of failure is the main thrust bearing seizing up due to oil starvation - that's why it's essential to use the right oil and to change the oil frequently. A bearing that is losing its life may be shown by seeing how wobbly the turbo bearing is - if it moves "quite a bit" then it's a bit knackered. You might also, but probably might not, start to hear the turbo whining more than usual.

The other thing is that turbos can be repaired pretty easily, and certainly can be overhauled/ refurbished. They are very simple mechanical devices, albeit operating at very high RPM.

The 90PS turbo is slightly different though as it has "variable vane geometry" to give it improved bottom-end power. There are many cases of these vanes getting stuck (due to oil/ carbon deposit build up on the vanes) and then the turbo toes into limp-home mode. Again though they can be repaired/ refurbished.

Most turbo problems are due to plumbing as mentioned above.
 
From late 2003, the turbos are VNT too, according to vince form stealth, which is why they get more torque when remapping.
John
 
Well just got the little one back. The guy had just come back from a diagnostics run and the turbo was reading low boost. 1200mbar rather than 2000mbar (if it was mbar units) on the driving test.
So it looks like its not cutting the mustard, and its not feeling too pokey.

Looks like a recon unit in the offing, or should I go recon and remap :D

I assume its best to stay well away from these variable vane units being that an 02 plate I guess I have the simple type.

About to move to east midlands (Derby / Leic/ Notts border)
Any garage recommendations or would a trundle down to stealth seem the best action. Looks like the job often takes a few days with the turbo being sent off for referb...

Thanks for your input so far

Mark
 
Wait!
You already knew you weren't reaching full boost your car was hitting overboost protection mode and limphome. The question not answered by this test is why.

As stated above with boost problems check first if you have a split hose or cracked intercooler before writing off an expensive turbo.

Hoses, cheap, common failure
Intercooler, fairly pricey, common failure
Turbo, expensive, rarely fails.

Getting a remap when you have boost problems won't help either you'll still fail to make stock boost, although the process of remapping may show you where the faults lie.
 
Hi Dan dropping into "limp home mode" has been very infrequent,so maybe there is a slightly damaged pipe, have to see if it still doing it. But the car has been feeling low on power which is why I pulled forwards my service, hoping a new set of filters would be the answer. But instead a little bit of oil was on turbo pipe and this on the road test was found to show how boost.

I'll try to have a look at the intercooler, make sure that they haven't missed anything.

What mileage have most turbos managed before service?
 
Hi there
Basically, the car drops into limp home mode when overboost protection is triggered, and if you have a small leak this is probably only enough to trigger it when the car is on full load at the moment (but it will only get worse) - take it out and try driving up a hill in a highish gear on full throttle so that the engine is having to work hard. In that instance, the leak will prevent the turbo reaching its peak boost within its maximium turbine tolerances and will shut down to prevent damage.

I'm not sure exactly where the intercoolers tend to crack - I suggest you do a search on this forum for intercooler cracks and see what others have found as this has happened to quite a few members - doing a visual inspection with the intercooler in situ might not show you enough - you may have to get the bumper off.

As to mileages for turbos - mechanically speaking if they've been serviced regularly with the right oil a turbo should last for as long as the rest of the engine, ie how long is a piece of string. However, rubber pipes perish, harden and crack and can be considered a "service item" - the rubber in car tyres have a limited life span (if they get too old they start to crack, some people on this forum have seen that on their rear tyres and have had to replace them before they've worn the tread down as the tyre wear rate is so low at the back!)
 
Back
Top