3.6 Watercooled engine, problems?
Discussion
Thinking of returning to the fold after quite a while away, my last car was a '99 996 which I ran trouble free for about 14 months. Now looking at the facelifted version of the 996 fitted with the 3.6 engine. Does this have the same sort of problems (real or otherwise) with the RMS as the 3.4? Or any other well documented troubles?
Cheers
Steve
Cheers
Steve
Homer J said:
Yip, RMS is still an issue on the 3.6.
Too get away from "The issue" you need to go up to the rareified levels of Turbo or GT3 ownership.
Too get away from "The issue" you need to go up to the rareified levels of Turbo or GT3 ownership.
Do a search ... They are not without an occasionally leaky RMS too y'know ..
Two 993 owning work mates of mine have both had their crank seals changed due leaks.
Point is , in 10 years time , there'll be 1000's of leaky 996's scattered around the countryside adding to that lovely tradition that so many 3.2 / 964 owners already enjoy....
BIG DEAL
I think the 3.6 engine is pretty robust, but best to maintain the Porsche Warranty if you are nervous of big bills.
RMS is just an oil seal. Dampness or a minor leak isn't a big issue, but it is covered under warranty, or c.£750. I think there is a new design of seal and fitting kit which reduces the likelihood of repeat failures.
RMS is just an oil seal. Dampness or a minor leak isn't a big issue, but it is covered under warranty, or c.£750. I think there is a new design of seal and fitting kit which reduces the likelihood of repeat failures.
The main reason for the failures is because the hole that the seal fits into is not always in line with the crankshaft but the old type of seal needs it to be 9having relatively little "pinch".
The new seal is made from that plastic memory type material and seems to allow itself to realign in the housing in line with the crankshaft - so after a while it lines up OK - unless the hole was too far out in the first place.
Baz Hartech
The new seal is made from that plastic memory type material and seems to allow itself to realign in the housing in line with the crankshaft - so after a while it lines up OK - unless the hole was too far out in the first place.
Baz Hartech
Despite the responses of the overly defensive 996 owning sheep here ,I work with a couple of guys who've worked at Weissach who are nodding their heads at this moment.
The problem unfortunately, is still apparent even in the 997s.
The Porsche 911 of choice for most of the engineers I've talked to from Weissach is the 993 but they need you to continue to keep buying new Wasser pumpers of course 
Despite the mud slinging attempts- this design flaw isn't an issue on 993s or earlier or on the 996/997Turbos/GT2s.
We'll cover the liner problems and intermediate shaft issues in later lessons
The problem unfortunately, is still apparent even in the 997s.
The Porsche 911 of choice for most of the engineers I've talked to from Weissach is the 993
but they need you to continue to keep buying new Wasser pumpers of course Despite the mud slinging attempts- this design flaw isn't an issue on 993s or earlier or on the 996/997Turbos/GT2s.
We'll cover the liner problems and intermediate shaft issues in later lessons
Marquis_Rex said:
Despite the responses of the overly defensive 996 owning sheep here ,I work with a couple of guys who've worked at Weissach who are nodding their heads at this moment.
The problem unfortunately, is still apparent even in the 997s.
The Porsche 911 of choice for most of the engineers I've talked to from Weissach is the 993 but they need you to continue to keep buying new Wasser pumpers of course
Despite the mud slinging attempts- this design flaw isn't an issue on 993s or earlier or on the 996/997Turbos/GT2s.
We'll cover the liner problems and intermediate shaft issues in later lessons
The problem unfortunately, is still apparent even in the 997s.
The Porsche 911 of choice for most of the engineers I've talked to from Weissach is the 993
but they need you to continue to keep buying new Wasser pumpers of course Despite the mud slinging attempts- this design flaw isn't an issue on 993s or earlier or on the 996/997Turbos/GT2s.
We'll cover the liner problems and intermediate shaft issues in later lessons
Matches the information I got too.
Not happy at all...
The problem did not exists much in the older cars because the hole that the seal fits in was machined at the same time as the hole that the crankshaft fits in and therefore was always in line. The Boxsters and 996's and 7's are not machinied at the same time so not neccessarily in line and therefore the error can be more or less in different engines depending on a build up of errors and also the natural tendency for a machined aluminium casting to stress relieve with time. Machining in line is fool proof but machining seperate parts is not because all machining needs tolerances and the design allows for even minute errors of the highest individual accuracy to add up in one direction and result in quite a bit out of alignment in the end.
If the crankshaft carrier was longer and extended into the hole that the seal presently fits in and had say an o ring seal and a smaller hole for the RMS that was machinied at the same time as the crankshaft holes - then it would be OK
Baz
If the crankshaft carrier was longer and extended into the hole that the seal presently fits in and had say an o ring seal and a smaller hole for the RMS that was machinied at the same time as the crankshaft holes - then it would be OK
Baz
Hi Baz
I was under the impression that Porsche have a tool that slides in place of the seal to check that the tolerance is correct on assemble of these engines. My thoughts are they would have been better mounting the seal in a bolt on housing .These m96 engines look far more complicated in design and manufacture than the supposedly more exspensive GT1 & Turbo units. With a bit of modification one of these M96s dropped in a Cayman would give a GT3 a run for its money!!!
I was under the impression that Porsche have a tool that slides in place of the seal to check that the tolerance is correct on assemble of these engines. My thoughts are they would have been better mounting the seal in a bolt on housing .These m96 engines look far more complicated in design and manufacture than the supposedly more exspensive GT1 & Turbo units. With a bit of modification one of these M96s dropped in a Cayman would give a GT3 a run for its money!!!
Well we have tested the run out by putting a magnetic dial guage on the end of the crankshaft and rotating the crankshaft while measuring the run out of the seal housing and they are not in line. I also doubt that Porsche would manufacture a crankcase set and then discard it because the oil seal hole is a little out of line - so they must presumably have accepted a tolerance here that is too much for the seal design.
The design is clever using a separate crank carrier especially with the cast in hard locations for the shells but They could have extended it for the RMS.
The whole design is a very cost effective one using circlips instead of nuts (for things like gearbox shafts etc) SO I DOUBT THEY WOULD WANT A BOLT ON CARRIER WITH ALL THE COSTS OF BOTH MAKING IT AND ASSEMBLING IT IN LINE.
But - hey - I am not Porsche and I don't know what goes on IN HOUSE only what I can see and measure and the seals leak and the hole is out of concentricity - I think that gave me the clue.
The new seal should take up the out of alignment (and again this new design seems to confirm what the problem was by making something that will try and fix it.
I think RMS mark 10 may just do it!!!!!!
Baz
The design is clever using a separate crank carrier especially with the cast in hard locations for the shells but They could have extended it for the RMS.
The whole design is a very cost effective one using circlips instead of nuts (for things like gearbox shafts etc) SO I DOUBT THEY WOULD WANT A BOLT ON CARRIER WITH ALL THE COSTS OF BOTH MAKING IT AND ASSEMBLING IT IN LINE.
But - hey - I am not Porsche and I don't know what goes on IN HOUSE only what I can see and measure and the seals leak and the hole is out of concentricity - I think that gave me the clue.
The new seal should take up the out of alignment (and again this new design seems to confirm what the problem was by making something that will try and fix it.
I think RMS mark 10 may just do it!!!!!!
Baz
Baz
I read on one of the american sites that the company that casts the cases for Porsche had a very high regection rate,30%,I believe,in the early days,Something about not letting the cases weather enough before machining. This was not only causing the cases to distort after maching but also not allowing the Lokasil to settle properly in the cylinders. Seems that Lokasil liners are porous sleeves comprising of 25% silicon & 75% air are cast in the cases.During the casting the air disapates leaving the silicon remaining locally and are affected if machined to early,this can then cause void problems later.
Regarding the seal porsche supplied there dealerships with a steel ring that was a copy of the seal size only with a couple of thou clearance.When a car came in with a seal leak they were to try the ring in place of the seal. If the ring slid in easy no problem,fit mod seal and reassemble. But if the ring did not slide in easy, then fit a new engine!
The yanks to be bit more concerned about customer well being than we are, Still Porsche must have a shed load of old engines somewhere,I would like to take a couple of there hands to play with!
Keep up the good work because as I said in my first posting a few days ago I would not have bought a water cooled Porsche if it was not for companies like your selves and Autofarm who actually do something about resolving the problems rather than just keep taking customers money.
Many thanks Bob
I read on one of the american sites that the company that casts the cases for Porsche had a very high regection rate,30%,I believe,in the early days,Something about not letting the cases weather enough before machining. This was not only causing the cases to distort after maching but also not allowing the Lokasil to settle properly in the cylinders. Seems that Lokasil liners are porous sleeves comprising of 25% silicon & 75% air are cast in the cases.During the casting the air disapates leaving the silicon remaining locally and are affected if machined to early,this can then cause void problems later.
Regarding the seal porsche supplied there dealerships with a steel ring that was a copy of the seal size only with a couple of thou clearance.When a car came in with a seal leak they were to try the ring in place of the seal. If the ring slid in easy no problem,fit mod seal and reassemble. But if the ring did not slide in easy, then fit a new engine!
The yanks to be bit more concerned about customer well being than we are, Still Porsche must have a shed load of old engines somewhere,I would like to take a couple of there hands to play with!
Keep up the good work because as I said in my first posting a few days ago I would not have bought a water cooled Porsche if it was not for companies like your selves and Autofarm who actually do something about resolving the problems rather than just keep taking customers money.
Many thanks Bob
Dunit, thanks for that, aluminium castings can be heat treated to avoid the weathering of cast iron (cannot remember what the process is called - sorry) - but what it cannot avoid is the stress relief that occurs when the original metal is machined and some of it is removed. As a casting cools - some of the metal cools quicker than other parts and is it shrinks it sets up stresses within the material. Machining relieves some of that stress and results in distortion. Furthermore when the crank cases are put together all the bolts also add stress across the casting. The rear of the crankcase is a very open thin area of cast aluminium prone to movement - but the main problem is with tolerances.
Every machinied part has to have a tolerance - a size between which it is OK to use or not. The more parts that go together to form a unit - the more the tolerances can work against you.
The way the 996/Boxster is designed - even if the castings are stable - the are a lot of potential errors.
The crankshaft is held within 2 aluminium casings. Each one will have a thickness tolerance and then the position of the hole in the assembled cases can have an alignment tolerance.
This assembly then fits within machined recesses in the crankcase - each of which will have a depth tolerance and a positional tolerance.
Dowels locate the one within the other - and each dowel position will have a tolerance as will each dowel itself have a size tolerance.
By the time the whole thing is put together - I add it up to have a potential number of at least 13 tolerance limits.
Now if each individual part was manufactured to an individual tolerance of say 0.025mm (which is extremely accurate) there is a possibility that if all the tolerances go against you - the position of the crank and RMS hole - could be 0.325mm out of alignment.
All this is impossible with the old design as they are all machined at the same time in a line.
In my view it is therefore mainly a design problem that will be resolved when a suitable seal is invented.
There are many photographs and an explanation of Lokasil in my description of 996 engine problems on our web site www.hartech.org that you may find interesting.
There is an analogy there that may help you picture it better - because the air is just the space in between the granules!.
Thanks for the nice comments.
Baz
Every machinied part has to have a tolerance - a size between which it is OK to use or not. The more parts that go together to form a unit - the more the tolerances can work against you.
The way the 996/Boxster is designed - even if the castings are stable - the are a lot of potential errors.
The crankshaft is held within 2 aluminium casings. Each one will have a thickness tolerance and then the position of the hole in the assembled cases can have an alignment tolerance.
This assembly then fits within machined recesses in the crankcase - each of which will have a depth tolerance and a positional tolerance.
Dowels locate the one within the other - and each dowel position will have a tolerance as will each dowel itself have a size tolerance.
By the time the whole thing is put together - I add it up to have a potential number of at least 13 tolerance limits.
Now if each individual part was manufactured to an individual tolerance of say 0.025mm (which is extremely accurate) there is a possibility that if all the tolerances go against you - the position of the crank and RMS hole - could be 0.325mm out of alignment.
All this is impossible with the old design as they are all machined at the same time in a line.
In my view it is therefore mainly a design problem that will be resolved when a suitable seal is invented.
There are many photographs and an explanation of Lokasil in my description of 996 engine problems on our web site www.hartech.org that you may find interesting.
There is an analogy there that may help you picture it better - because the air is just the space in between the granules!.
Thanks for the nice comments.
Baz
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