Pistons and IMS (early 996)

[CFo]

I'm a fairly new owner of a 1998 Carrera 3.4. I've heard that early 996.1 3.4s have ferrous coated pistons which are less susceptible to bore-score, and double row IMS less likely to fail.
1) any thoughts on the truth of these statements?
2) other than taking the engine apart, is there any way of knowing whether a particular car has the above? e.g. from chassis no.?
Cheers all
Chris

 

[Richard_Hamilton]

Chris!

1) Yes, the pistons are iron coated, but the main reason that the 3.4 doesn't suffer from bore scoring is that the water jacket around the liners is much less restricted that the 3.6. It is generally thought that scoring is mainly due to localised boiling on the thrust side of the liner if the engine is highly loaded during warm up, before the thermostat opens. Yes, the MY1998 Carreras have the dual-row intermediate shaft bearing, which is less susceptible to failure, but not immune.

2) You can check the IMS bearing version by removing the transmission, flywheel, and IMS mounting (after locking the crank and cams). A borescope examination should show up bore scoring.

My advice is not to dwell on it - just enjoy it.........

 

[CFo]

Thanks, Richard. Curious rather than dwelling on it, I intend to enjoy it.

 

[matbmw]

Hi, Iam fairly new to this , had my 1999 996.1 C4 3.4 for a month so still have the IMS issue hanging over me , had the oil changed straight away but no metal debris in the oil or filter , is there any other signs I need to look for?
The mileage on the car is 103, 226 with full service history and lots of bills from previous owner so iam hoping all's well . Fingers crossed.

Matthew.

 

[Pieman7]

Hi Richard how would I get to find out what bearing I have in my 2003 c4s single or double row Ims thanks simon

 

[CFo]

Single, as far as I know.

 

[wibble]

@Pieman - I am sure it can be traced via your engine number, but believe bearings were changed around year 2000. Pretty certain details can be searched on this forum or others.

@Matbmw - You cannot find tell tail signs other than what you have checked. The only conclusive way is to completely extract the bearing for inspection. Evidence only shows failures affect low volumes, so keep it serviced and enjoy it.

 

[matbmw]

Thanks for the info Tony.

 

[JagdHamster]

Fitting a low-temp thermostat is a good idea (helps with the cooling of the bores that Richard mentioned).

 

[Pieman7]

Apparently I have a single in my 2003 3.6. I have been looking into changing my Ims seems a very straight forward job. Will change the oas and oil filler tube ,RMS at the same time. also the brake line pipe over the engine. I have read up on what bearings are available etc and it's a very hard decision on the type I will fit. I spoke to some Indus what they prefer to fit and many go for the L&N bearing apart from one who I have great respect for with there knowledge of porsches and racing cars. They have had two failures with the new L&N replacement. This has pointed me in the direction now down to two types one being the ceramic needle bearing and the other the oil feed type. I've seen a video on u tube about this oil feed type which I feel does make sence. I am very surprised that the intermediate shaft doesn't have any machined slots in it so oil can get to both sides of these bearings. As in the video I watched the guy was saying that oil can pass through the bearing when stood still and into the tube type shaft thus probably not getting changed. In all fairness I'm possibly going to put a oil feed type in has anyone fitted or had one fitted. I also was surprised that all the bearings would need to be changed again at some point in there life. I would presume the oil feed type in theory would last longer.

 

[wibble]

I researched this before I bought my 996 last year. The LN ceramic bearing does seem to be best option and I believe it is an open bearing (as opposed to OEM sealed) and would assume oil would naturally lubricate the bearing. Going down this option is treating the bearing as a consumable part like a timing belt.

The oil fed option is a modification tapping the feed from unused port on the block. It also requires modification to the bell housing I believe for the pipework. This worries me slightly; 1. If that pipework fails, then possible oil starvation to the engine. 2. What are the effects on oil pressure with additional feed? 3. Are other crucial parts of the engine starved of oil? (cooling/lubricating of the liners on later engines is critical in preventing bore wear that is already a known weakness).

 

[JagdHamster]

Save your money, Gents.

Just do as per the 3rd post in this thread:

http://www.911uk.com/view...2fa026ecc16591b229c035

 

[Ripmax]

I think it's sensible to get the IMS bearing checked the first time you have cause to access it for some other reason - clutch or RMS for example. Provided you keep the oil level topped up and changed IAW the service schedule there's no reason to presume a failure of the IMS bearing is a given. It does rather depend on whether your enjoyment of the car is adversely affected by it though. I'm quite good at ignoring it! Replacing it seems to be no guarantee of avoiding a failure either though as evidenced by the warranties offered on the fixes and examples of cars having failures of new bearings, open or not.

I've had my car for five and half years and the RMS has leaked the whole time, like they all seem to. It never lost enough oil over a year to even move the level off max on the dipstick, it just looks bad when you look under the car. The water pump gave up on Boxing Day and while the car's in the garage I'm getting the RMS done. Of course the engine comes out for that so do I or don't I bother with the IMS while it's out? I decided to get it done and I've gone with the direct oil feed option. What sold it to me is that there have still been failures of replaced bearings inc the ceramic ones. And the fact that the garage wouldn't warrant anything else (because the manufacturers won't) while the DOF fix is covered for 12 months. I was also persuaded by the theory that an open bearing spins most of the oil out and away from itself and still runs dry(er) than is desirable although I don't honestly think anyone knows for why they fail or what the best fix is. Thus you'll get numerous different views on here and amongst the specialists, none of which is more right or wrong than the other.

 

[andrewcrockett]

Hi
when i bought my 2000 996 3.4 carrera i was told get the IMS bearing done even by the dealer i bought it off.Two years later im driving it doing trackdays (drop oil every third trackday)no issues whatsoever!
IMO its the porsches that are garage queens that don,t get used as much that are most likely to suffer.
Happy motoring

 

[thirteeneast]

IMS Lol.
Is that still doing the rounds

 

[mikealdren]

General consensus on IMS bearings seems to be, early dual row bearings are fine. For later bearings, take off the oil seals and they'll be better lubricated and fine too.