Passat TD 130 - Water in Oil mystery

[spockley]

Sorry - I posted the following in the wrong thread, so am trying it again here:

Water in Oil
I have just had a very serious problem with my 2001 Passat TDi estate, in that , without any previous symptoms whatever, on starting, firstly the brake pedal felt "hard" - no servo working - , but this rectified on changing from tiptronic to auto. Then, after about a mile,the gearbox started acting strangely, and then huge clouds of oil-smoke billowed from the exhaust. After checking for obvious faults, I drove straight to a garage, who removed the dipstick, which was covered in "mayonaise", and they (of course) diagnosed "blown" head gasket. I was absolutely amazed, as the car was in perfect condition, has ony done about 48,000 miles, and is properly maintained. The VW mechanic I normally employ said a head gasket failure on the Passat diesel is extremely rare, but the garage themselves said they have had one identical case. It's going to cost me at least £800 ! At the same time, I read here, and elsewhere about the "wet carpet" problem, and, sure enough, my n/s carpets were soaking. (There had been very heavy rainfall the night before this incident). I thought there must be some connection , but nobody I have consulted can see how water from the plenulm chamber etc., could possibly have got into the sump.

This event has completely destroyed my faith in the Passat. It's the most serious and most inexplicable car failure in the whole of my motoring career (50 years). Can anybody explain how the head-to-block joint can spring such a serious leak "overnight"? As I said, there were no previous symptoms whatever. I examined the head, gasket and block on removal, and there was no obvious sign of a leak. Any ideas much appreciated.

[snapdragon]

Sounds like what happened to me apart from the last bit.
Water built up in the stupid plenum chamber, even though I cleared the drains last summer. The brake servo booster is a crap quality item and sucked in the water around the seam of the two halves and rusted the inside and made the brake pedal hard. The water could get sucked into the engine if the servo diagfragm became perforated. I too have never had such a car with so many engineering ****-ups and design faults.

[spockley]

Many thanks Snapdragon. This is just what I suspected initially, but was talked out of it by the garage, and also by "Honest John" of the Daily Telegraph, all of whom said that it was just a coincidence that the "cylender-head gasket "blew" ", at exactly the time the car was flooded with heavy rain. By now, they should have finished replacing the head, so I'll be straight round tomorrow morning to warn them what will almost certainly happen, or will already have happened when they try to start it! And then I suppose there'll be a legal battle over their almost certain mis-diagnosis. Anyway, as soon as the car comes back it'll be outed with minimum delay.

[snapdragon]

Oh dear! the garage I use (who are VAG specialists) say they have seen a lot of VWs and Audis that are around this age with this servo problem, all TDIs, never petrols. One theory is that the mechanical vacuum pump sucks harder than the induction from a petrol engine. Of course, I'm only telling you what happened to me, maybe yours is a coincidence. My pedal had been going hard for a while, and then the brakes started sticking on after a hard application which made them get too hot, so I gave up and took it to the garage!

[guyg]

I don't think it could be the brake servo on a diesel, as there is no significant manifold depression to drive it; there's normally a seperate vacuum generator run from a shaft somewhere to run the servo. Unless the exhaust from this vents into the crankcase [and it can pump water as well as air] I can't see how a partially submerged servo would cause this.

Cheers,

Guy

[spockley]

Thanks, Guy. So the mystery deepens! And I thought we had it solved.

[snapdragon]

Yes, the pump is mounted on the end of the camshaft, it is also oil-fed.
You would need to find where it would exhaust.
Being a vacuum pump, it should only really need to create a vacuum, it shouldn't actually continually pump air other than what is in the pipes and valves - unless there is a leak in the system.

[Col]

The diagnosis makes perfect sense to me.

Servo rusts due to pool of water in plenum.

Servo diaphragm then fails as it's exposed to water (probably suddenly)

Vacuum pump on engine then becomes a highly efficient water pump drawing water from rusty servo via perforated diaphragm striaght into engine via vacuum pump.

Looks like a classic headgasket failure.


It makes further sense with the hard brake pedal as well.

Please let us know how you get on. Hopefully the garage will admit defeat and sort it the way it should have been.

A bonus that you can take from this is that the headgasket should effectively have been changed free of charge, which also means your cambelt would have been changed FOC which would be due on your car within 12k.

[guyg]

Still not sure about the servo - does the vacuum pump actually vent into the crankcase? You say the carpets were wet, but was the servo actually submerged, was there any water in the plenum?

Could it be an oil cooler failure? - this seems more likely; hot oil and pressurised water next to each other...

My experience of head gasket failures is that they usually [though not always] fail across the cylinder to water junctions because this is where the greatest pressure differential is.

Check out the cheaper options first before they charge you for a H/G change you might not need.

Cheers,

Guy

[Frank.A]

Hi All,

The vacuum pump is driven off the rear end of the camshaft.It exhausts its air and lubricating oil into the rocker cover,which is why so much air and oil enters the induction system from the crankcase ventilation hose.This creates major problems in the USA where combined with poor quality diesel it can block EGR valves and choke the induction sytem after 50k miles such that engines will not run over 3000rpm.

I think that the plenum chamber/brake servo/vacuum pump senario is very likely.

I have removed the 'frills' from the plenum chamber drains and resealed the pollen filter housing with mastic rope and silicone to prevent water ingress into the cabin under the carpets where it drowns the convenince modules.

Check out the US TDI forums for more horror stories.

http://forums.tdiclub.com/

Best,

Frank