S2 Engine Problem... Sounds serious, anyone know of an engine for sale?

[tref]

Hmmm...

http://www.youtube.com/watch?v=4XSJWl31tJE&feature=youtu.be

It started as a miss-fire... Now whilst I am sure I can rebuild it, the pragmatic solution has to be to change the engine (well ok, most would say scrap the car and get another)... it has done 278k miles.

However... what do you reckon the noise is (ignore the tractor in the background, sorry, the other car was also still running)?

Oh, and of course, anyone know of a good spare S2 engine for sale?

Tref.

 

[edh]

sounds nasty...almost wish i hadn't clicked on the link..

The ticking noise sounds about the same frequency as the sound I got when I had a rotor arm catching on a new (volvo) dizzy cap. So suggests it's cam related? All the other sounds going on underneath don't sound very nice either.

 

[Dave928]

"well ok, most would say scrap the car and get another"!

Listening to that, the miles it's done and the dents, i'd say yes they would !

There are some nice cheap cars for sale at the moment. That sounds terminal !

Douglas Valley usually have cars/engines in.

 

[Geoff_Fields]

So this could be the last we see of your old warhorse? Time to move on me thinks![]

 

[tref]

ORIGINAL: bigdavec

There are some nice cheap cars for sale at the moment. That sounds terminal !

Hmmm... I'm not so sure on those counts... The noise started when moving it from the drive to the car port, following a miss-fire... I have a feeling this is related to the cause of the miss-fire... Compression is ok for a high-mileage engine, and it hasn't been reved at all, so I suspect that whatever damage there is is limited to the problem itself. So it could be rebuilt... but for the time...

I agree with who-ever said they thought it half engine speed, so valve-train related - that is the opinions I would value - to me the "ringing" nature of it suggests to me little end... my hearing is rubbish though...

With regards the "good cheap cars around" I'm not so sure... S2s seem to be starting at £4k... and that isn't necessarily a good one... parts are becoming harder to find... for a "cheap Porsche" I would look at a Boxster... but they're not so practical for me. At the moment Caymans still have about £10ks worth of depreciating to do before I will buy one! The problem is parts for 944s are getting harder to find, and the mileage and places I leave it, I don't want anything too "nice"... So, as usual, I have a problem!

 

[Dave928]

I was thinking 924S as a runaround.....

 

[tref]

If you are thinking of the 924S I am thinking of, I have considered that, but it is currently a total unknown...

 

[Dave928]

no, you can pick em up for 1k-1.5k. Lighter bodied and the sills don't really rot out too bad.

 

[edh]

I know that you know more about engines than I ever will Tref

First thing to do I'd suggest is to whip off the cam cover & see if there's anything obvious - maybe turn the engine by hand to see if you can recreate the knock

I also had something that sounded similar when I mis-set the valve clearances on a Crossflow - sounded horrible but was easily fixed.

 

[tref]

Yep, I had the cam cover off - nothing obvious there... I was hoping for a broken valve spring, but I haven't turned it over to check 'em all... and I would have to consider what to do if it were anyway - ok, it is an easy fix, but then the head is suffering from erosion of the water galleries that I know of... hence considering a more drastic solution for speed now.

 

[ChasR]

I hate to say it, but it sounds almost as if the piston is hitting the head. Has the car had any rattling present previously, and what is the oil pressure like?

Another engine may be the way forward. You could try the usual suspects for secondhand engines. I did know of a tidy S with an S2 engine going for £1400 which would have made a great base (OK, you would have had to stick a few bits on from your car to that one to make it an S2 with the look of a Lux. but it was a genuinely tidy car.

 

[924nutter]

That's 8 knocks per second using the you tube time base so I if that is a single piston hitting a bent valve the idle speed would be 480 rpm, (8x60) It is regular but as the number of cylinders involved goes up the idle speed would have to go down. e.g. 2 cylinders give two knocks per rev instead of one so to get the same 8 herz your engine would only just be above the 200 rpm rotational speed threshold of the dme, so that rules out all four as well because it just wouldn't be ble to run, but in any case I would expect an engine firng on three to make better than 650 rpm. If the engine is idling normaly and it cetainly doesn't appear to be rocking about from side to side, so it's sounding like it's something that operates at camshaft speed. Balance shafts are out because the whizz round at twice engine speed.

You haven't got a bent valve because you say it has acceptable compression and presumably good oil pressure. Is it possible that you have a sticking valve which isn't fully closing until the piston gives it a whack? A sticking valve will cause a bit of a misfire, and if it is the exhaust valve you would still show good compression figures because once the piston had pushed it shut it remains that way until after the compression stroke.
Have you checked that the securing screw for the rotor arm has not worked it's way out and is hitting something at one particular point on its way round, or is it not the same as the eight valve?
Has one of the many tappets failed to pump itself up due to perished seals or blocked oilway
Has the timing chain jumped a tooth? There again again if it had you would have at least four bent valves and poor compression.
Not definitive answers Trefor but more a case of what it isn't, which may be of some help.

 

[tref]

Thanks guys,

John, timing the knocks from the video is inspired!!! It idles very nicely at about 950RPM, so your timing of 480knocks per minute is almost exactly half engine speed... It confirms what I "felt" too, which is always good. Sticking valve could very much be a possibility... my only previous experience of a sticky valve though gave a more "double knock" a kind of "Ti-cup, ti-cup" kind of noise which I put down to the piston whacking it one and then the valve slamming shut.. but that was an eight-valve car with incorrect valve stem seals (don't ask!), so it could sound entirely different on the 16v.

Yes, oil pressure is good, and all under the cam cover looks fine (I was expecting to find a broken camshaft, or one tappet not in contact with the cam or similar), but I haven't checked the timing or the force necessary to depress any of the valves (I need to sit down and work out engine position in which the valves are close and pistons at the bottom of the bore for each cylinder). The cam chain looks ok, only reasonable wear on the slipper for the mileage, and the cam-chain is tight. Teeth on the cams are still there.

Chas, when you say "did" know of... is it still about at all?

Thanks,

Tref.

 

[edh]

...John's more logical deduction also points towards cam related noise. Would be nice if it was the rotor arm.

 

[Indi9xx]

Sorry to hear about this tref

From the sound I am 99.9% sure it is a big end that has failed, which due to its increased clearance is now allowing the piston to collide with the head every time it hits TDC.

This is quite typical in about 50% of big end failures on the 944 Lux and 944 S2 engines due to the close promimity of the piston crowns to the head at TDC

Typically when this happens, debris from the big end gets thrown into the lower bore area and causes scoring of the bore and often results in the piston skirt picking up on the bore causing more damage. One other side effect can be a valve collision, causing two valves to become slightly bent, making them take longer to close (sticking), which means at low rpm such as cranking, the valve has enough time to close, hense good compression, but at higher rpm such as idling, the valve takes too long to close.... often in these cases the car will pass a compression test, but fail a leakdown test, as the slightly bent valve will not seat correctly enough to seal the engine, but will be closed enough to be an effective pump.

I have sent you an email, I have an engine ready to go. I have known you for a long time now so would be happy to do you a deal on the engine and even rebate you some cash for your old engine for spares.

 

[chrismanchr]

most people would only think of bigend noise as in the bearing and crank pin but in extreme conditions the piston will travelfurther and go further than tdc

sounds like you have a solution but I guess stripping down the engine will be the only way to get to the bottom of it

 

[tref]

Indeed, I have had a chat with Jon (Thanks Jon!), and hopefully I will do both. I like to understand what has happened with things like this, but in the meantime have a solution which could see a return to the road of the Black Bomber (as the car is affectionately known) in little over a week (much to the disgust of many members of the Dorset region I am sure!).

 

[Geoff_Fields]

I couldn't possibly comment!

 

[924nutter]

Presumably if and end had gone there would be one clonk per revolution but I am not am expert, and wouldn't Tref see a loss of oil pressure? A clearance big enough to allow the piston crown to hit the head would surely mean that somewhere on the crank then were a pair(is the S2 crank cross drilled?) of exposed oil ways with a circa 3mm outlets back to the sump. It would be a hell of a pump to maintain pressure with that kind of leak, but then maybe the 944 oil pump has that capacity

 

[peanut]

sorry to hear about your woes Tref. I was even more sorry I clicked the link and listened lol.[]



I left a couple of comments on the tube but one little trick I remember from the dim distant past was to remove the spark plug leads one by one to see if there is any appreciable difference in the knocking noise which might indicate which cylinder is effected. Might narrow it down a bit .[]

If a bearing had failed badly you should see the evidence as silver dust in the crankcase sludge so you could drain the oil and stick your little pinkie up the drain blug hole see what you got.

Its possible that its not the bearings at all.

It almost sounds like the engine is dieseling ? ........like when you get 'run on' when the mixture is too lean or there is a hot spot in the cylinder head etc

Have you checked the cam timing ?