Who said S2s were boringly reliable?

[TTM]

I suppose I did, more than often on here, but after 11 years and 80k miles of 100% troublefree motoring it may be payback time...! [8|]

So I was driving on the motorway when suddenly the engine began to misfire, as if a cylinder was missing.
Lost power but got lucky to reach an early exit and a parking place, car struggles to start and idle, running very rough.
Began all the easy tests - spark on all 4 plugs, all 4 injectors delivering fuel, no result.
Had then the car brought home, tested spare plugs, spare coil, spare AFM, spare DME, spare fuel pressure regulator, no result. Car still running very roughly, pig rich on the first 3 cylinders, not quite so on the fourth.

Took the camshafts off today and this is what I found :

Until I get the time to remove the head, fingers crossed that cylinder walls on cylinder #4 aren't sratched! [&:]

 

[robdimond]

Ouch... is that the valve stem that has snapped, and the inner spring broken?

 

[edh]

ouch!! - could have been a lot worse though..

why did I buy one of those troublesome S2's instead of a nice reliable turbo? []

 

[nicksonmsport]

if you need any parts i have a complete s2 engine in the workshop for sale. its currently a full engine with ancilleries and loom etc, but i would be happy to part it up if you wanted a long block etc

pm me if interested
many thanks
nick

 

[TTM]

Good question Rob, I'm not sure which broke first, but I suppose the spring did, then the valve began to float because the main spring alone wasn't stiff enough to push the lifter well against the cam, then the piston somehow hit the floating valve which broke and got blocked in the guide? It cannot slide in the guide, which must have been damaged as well...

Nick, thanks for the offer. I will have to remove the head first and decide upon how the cylinder wall looks.

 

[Neil Haughey]

I had 2 broken valve springs after racing at Silverstone 2 years back so certainly not unusual. Quite costly though doing a full top end rebuild which was the only sensible thing to do at that point on a 160K mile old engine.

If my track/race car has proven one thing to me it is that the one thing an old Porsche does not make is 'boringly reliable', if anything depressingly troublesome is closer to the truth.

 

[MarinerChris]

My 996 turbo was boringly reliable, but it was also totally NOT engaging to drive!

I think there should be another law of thermodynamics or physics stating that the more fun a car is to drive, the more often it will need bits tweaking.. But there would also have to be exclusions to that law, when I was younger it seemed all my early cars needed constant tweaking and were boring to drive!

So what causes the valve failure?

 

[Super_Marv]

ORIGINAL: Neil Haughey

If my track/race car has proven one thing to me it is that the one thing an old Porsche does not make is 'boringly reliable', if anything depressingly troublesome is closer to the truth.

I'm not sure that's entirely a fair assessment, given the huge stresses racing/trackdaying puts on a car, over (say) moderate spirited use on the road! []

 

[TTM]

Took the head off today.

The broken valve left some marks on piston #4 but nothing to worry about I suppose...?

Pink spots (VAG coolant) suggests where the original HG could have begun to fail.

Been impressed with the amount of carbon deposits on the pistons... probably caused by running for too long with a faulty lambda sensor? Or is that normal for a car with only ~130k miles?

Looking a bit better now.

Pleased to say cylinder walls are ok. There is the odd scratch here and there but they can't be felt with finger nails []

 

[Mike_Pollock]

My 2.5 with 160k + was a lot cleaner than that and the HG was original I think.

So may be the lambda sensor - wonder what the CR was with that extra material on the crown?

 

[TTM]

Actually I replaced the lambda sensor about a month before this happens and noticed right away that the car was running much better.

We then tried the old sensor on the S of a friend, a car originally with no sensor, and it didn't work much better. He then tried another sensor and said it ran better, so we concluded that my previous sensor was out of order although I never really noticed it until I replaced it, for the sake of it, with a new one.

While the head is off, would you wise folks of the PCGB forum recommend any things to look for?

Is there anything worth doing while the head is off to improve performance, short of trying a compressor?

 

[sulzeruk]

Check your valve guides for wear, new stem seals, etc. Match the inlet manifold to the head and also the exhaust mainfold to the head as well. match the gaskets as well. This always helps with the gas flow.
Alasdair

 

[TTM]

So I figured it would be a good idea to remove valve springs while watching the Queen's Diamond Jubilee... []

Heavy carbon deposits, again :

Not quite a 4-leaf clover, but it could have been worse!

That is definitely bent...

Home-made sleeve, as without it a standard Facom valve compressor won't clear the 16V head's particular dimensions, and I couldn't be bothered spending €80 purchasing the special tool from Porsche :

Other valve springs are all intact, but you bet I'm still going to replace them :

Exhaust valve - Just look at how much carbon has stuck on there :

Any suggestion on how to remove the bent valve?
Or perhaps I will just handle the head out this way to the local machine shop...

 

[912UK]

are you going to skim the head?

 

[TTM]

I'd rather not...

 

[Copperman05]

The oil remnants look pretty dark and dirty, do you know why that is? What oil are you using?


edd

 

[J4CKO]

So is my dream to replace my 944 cab at some point with a 996 probably folly, I love the 944 and am enjoying driving it, I have kind of learnt in my 41 years that if you are enjoying something then that should be enough and not to worry about getting the next, bigger, better faster thing.

 

[TTM]

I eventually had the head rebuilt - slight reskim, all valve guides replaced and exhaust valve seats rectified, as the shop told me exhaust valves were not sealing properly anymore, which made sense considering the mileage. It came shiny-new too

While in there I replaced seals for the air/oil separator, which were very dry and would not actually seal much anymore, I added sealant around the plugs at the back of balance shaft housings, as they also got dry over time and oil seriously makes its way out of the engine from there.
Also replaced the blue coolant temperature sensor for the DME and had fuel injectors cleaned up and matched. The pads for the cam chain tensioner were hardly worn but for the sake of it I still replaced the upper pad.

The intake manifold was surprinsingly dirty with significant deposits of filth, which I got rid off with brake cleaner.
I learned that the temperature sensor at the bottom of the plenum apparently triggers the fans on when the air in the intake manifold reaches a certain level?
I suppose that is because coolant circulates in the butterfly, but I also heard '89 S2s apparently do not have this sensor?

The engine started at the first attempt on a very clear tick over, then went for a short drive - I had forgotten how much of a relaxed drive this car was
However, it feels a fair bit slower than before, even if the engine feels healthier than ever before.
Maybe the turbo being my only point of "944 reference" in the last 5 months has made me forgotten how it performed, but surely accelerating flat out in 4th on a slight incline and feel the engine lazy to build revs past 4000 rpm suggests something may be wrong?
Did I get the camshaft timing wrong or could it just be that 5 month old fuel remaining in it?

 

[333pg333]

Thom, could you actually hear the piston to valve clashing? Was the valve stem so bent it was stuck in the guide?

 

[TTM]

Yes Patrick it was a ticking sound like a very loud injector.

Here a picture of the bent valve.