What is a D-chunk?
 

I saw this term used with regard to watercooled cylinders. . . can anyone enlighten?

Its when the cylinder fails and a large D-shaped chunk falls into the cylinder. Apparently Porsche failed in the engineering department when designing the water cooled engines.

Yeah, but they made a staggering profit on all those things,.....................:)

I agree. GM did the same thing and look where it got them. ****ty products may only last awhile, but the memory of those products lasts a lifetime.

http://www.lnengineering.com/996_34_...ailure_001.jpg

3.4 996, classic D-Chunk failure.

The same situation applies for these engines, as well.

Its replacement (2009) appears to be a major upgrade since its an all-new engine but only time will tell,...:)

I like the way that everyone is so negative on the newer watercooled engines, but has forgotten about Porsche's past:

- 2.7 engines that leaked oil new on the showroom floor
- Pulled studs
- Failed tensioners
- Broken headstuds
- Intermediate shaft bearing wear (1968 1/2)
- CIS airbox explosions
- Dry-sump oil pressure / scavenge problems
- 964/993 valve guides (air valve clogging)
- Distributor vent problems
- 3.2/3.3 rod bolt failures

My point is that there have been problems with Porsche's engines from day one, these watercooled ones are not necessarily better or worse. I tend to think that the number of failures has been pretty low, when you consider the total number of cars sold (Boxsters, Caymans, and 996/997s).

Just my opinion...

-Wayne

Maybe its just me, but the Japanese don't seem to have the same rates of failures that the Germans do. Mitsubishi has crank walk issues, not sure of Toyota's problems, Honda has tensioner issues, etc. But by in large they are relatively trouble free. I expected better from the best engineering firm in the industry. Its like they intentionally cut corners to make a big profit at the expense of a quality product. I realize Porsche has to make money, but for the money they charge they could at least catch up to the Japanese. Don't list the JD Powers studies as I think they are marketing ploys.

I don't like to bash Porsche either... but I have to agree with Brett. The some of the later model Porsches are getting a bad repuation for engine issues. I would say in this day and age one would expect better from what is supposed to be a premium car.

The 996/997 watercooled engines except for the GT-3 or Turbo are junk. Everybody I have talked to that has a late model with over 40,000 miles has gone through at least one engine. The quality is gone and nobody will be vintage racing those engines in 20 years. I have to think what this will do to Porsche's reputation. (Though they don't seem to be worried about it, too busy stuffing money in their bank account.) I have heard the motivations for the new architecture engine (from the aircooled) was the labor of assembly.

aws

We shall see how the new 998 DFI engines hold up.

No intermediate shaft- the cams are driven directly from the crankshaft which has been determined to be stiff enough for the new,stronger timing chains.

And more new stuff like the DFI and the stronger oiling system...

Yes, I am sure the new engines were designed to cut assembly time and they do. Apparently it was a 24 hour process to assemble an aircooled motor where the watercooled motors are down to 12 hours. In my opinion that is still too much, but what ever "works".

Although if you have to put three in for every good one, it doesn't come out cheaper......

Wayne,

Let's not forget the Solex carburetors that resulted in holed pistons, a problem so intractable that it led to Webers in February 1966! You have to wonder why they went from centerlubed cams to spraybars, as well- probably to keep the valvetrain and heads cooler in an effort to avoid detonation!

No engine is without its issues and these historically have been solved through further development by the Factory. It has not kept them from being the most victorious sports car manufacturer in history.

along the lines of general comments on German auto engineering - Was reading on a BMW forum where a guy put a BMW OHC V8 in a 3 series. It really took some work and the engine needed to be set at an angle in order to fit. One guy made the comment why not use the latest SBC like used in the Corvette. Lighter, smaller, more power and more potential, more reliable, cheaper, better fuel economy. This could be slightly off topic.

My turn...

997.1 Carrera S (2005-2009)

New smaller intermidiate shaft bearing can still fail.

When enlarging the cylinders to 3.8 the water jackets surrounding the cylinder were reduced in size resulting in heated pistons scoring the cylinders until the cyl wall comes apart.

Water pump impeller blades come apart and since the blades are so freaking close to the block they can and have destroyed the block when they fail. Plastic impeller blades come apart also and when they do, pieces of the impeller get lodged in the water jacket causing the engine to over heat and can destroy the pistons and cylinders.

These engines run so hot because of the reduced size of the water jackets around the cylinders Porsche installed a temp gauge that doesn't rise above 175. I took my car out for a very hot spirited drive recently redlining shifts down shifting for several hours the oil gauge read 250 and my temp gauge was still sitting at 175!

Oil squirters you say, well the oil squirter only squirts the bottom of the piston. If they would have pointed the squirters toward the top of the piston where it was really needed there might not have been any D chunk problems.

Own this car??? Want it to last for awhile at least:

Change water pump every three years.

Change oil every 3 k miles Motul or Joe Gibb NO Mobil 1!!

Upgrade you chain ramps.

I'm not doing it. I just sold mine. Freaking time bomb car. And from Porsche no less. I'm going back to my slow 993.

And I might add that every Porsche I ever bought I still own except for this POS 997.1 S

Mm,, don't blame PAG- we keep buying their products even though the bean counters are in charge even in the engineering dept! Why do you think they are the most profitable car company in the world. Just look at the launch of PCCB binders. Advertising that they can withstand race conditions- ya try to take one of those Gen 1 to the track and see what happens and see if they will back them up....ya those days of driving your 911 or...to the track and back are gone. Latest is the separation of the coolant lines on the 996-997 engines.....some one must have said, ya let's save $, let's ' glue' the critical fitting together vs welding them as in their race cars.
I just hope that when these hoses let go, no one us behind them - thus causing a crash...PAG should reexamine the Toyota floor mat $$$million law suit payout. This concern has finally reach the DOT dept...triggering an investigation.
My take, especially the new gen of P car owners are just posers...ya I drive a Porsche. My .02 cents

In one word...development....
Any engine design goes through it...the more years of the basically same design sorts out the problems and you end up with a very reliable design.
Some engines need more development than others...but the high HP to size ones are in need of more tender care than the old truck engines.
Bob

Ya sure- tell Toyota that with their floor mat law suit.

Please add the cylinder base leak on the early 3.6 to the list;)