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I’m picking up a new to me 2000 C4 Cabriolet with 80,000 miles tomorrow. IMS, clutch, and RMS were completed and have about 2000 miles on them. I’ve been reading forums and watching videos and stumbled upon Renncast with Jake Raby episode 18 on YouTube about intermix and Y2K syndrome. At one point he says he wouldn’t trust a MY 2000 996. Am I setting myself up for guaranteed heart ache with this car or will a good maintenance schedule morel likely than not keep this car on the road for another 80,000 relatively trouble free miles?
Y2K did not affect your car. That's ridiculous. And yes, I lived through it while being a computer consultant.
no, no. You misunderstand.
There is an issue with the cylinder heads from model year 2000 that apparently causes frequent cracks and an oil/coolant intermix issue. Something about the manufacturing process in 2000 that affected the quality of the heads. Nothing to do with Y2K computer issue that was much ado about nothing. I’m just wondering how common an issue this really is or if it’s been overblown.
It's easy to scare the beejezus out of yourself sifting through all the posted material regarding the 996. Find one you like, have a proper PPI performed, and if it meets your needs then go drive the wheels off it!
There is an issue with the cylinder heads from model year 2000 that apparently causes frequent cracks and an oil/coolant intermix issue. Something about the manufacturing process in 2000 that affected the quality of the heads. Nothing to do with Y2K computer issue that was much ado about nothing. I’m just wondering how common an issue this really is or if it’s been overblown.
Agree with others, get the car inspected.
As a side note..
Jake Raby was the one that coined the phrase "Y2K syndrome" in reference to MY2000 3.4L engines. This is because of the amount of submission tickets that came to Flat 6 Innovations with cracked heads and intermix with the 3.4L engines that year. This was the time that our very own Skip (PorscheTech3) was working with Porsche. Here's what he says...
Jake Raby was the one that coined the phrase "Y2K syndrome" in reference to MY2000 3.4L engines. This is because of the amount of submission tickets that came to Flat 6 Innovations with cracked heads and intermix with the 3.4L engines that year. This was the time that our very own Skip (PorscheTech3) was working with Porsche. Here's what he says...
Thanks for the response. Sounds like it’s a real issue but if I’ve had the car inspected, there are no intermix findings, and everything else is good, I should be able to sleep well at night as long as I’m on a good maintenance schedule?
It would be interesting to know the % of 2000 M96
engines impacted by this. Also the % of those that were tracked regularly. It’s interesting to hear anecdotally that 9/10 intermix issues are due to a cracked head, but how many total does that represent? Looks like approx 19,500 996 Carerra and Carerra 4s were made. How many of those have had intermix issues due to a cracked head?
From what I’ve read, it seems like water pump failure is a common precursor due to the plastic bits being sucked into the cooling passages within the cylinder head. Statistics on that would be interesting too.
Thanks for the response. Sounds like it’s a real issue but if I’ve had the car inspected, there are no intermix findings, and everything else is good, I should be able to sleep well at night as long as I’m on a good maintenance schedule?
It would be interesting to know the % of 2000 M96
engines impacted by this. Also the % of those that were tracked regularly. It’s interesting to hear anecdotally that 9/10 intermix issues are due to a cracked head, but how many total does that represent? Looks like approx 19,500 996 Carerra and Carerra 4s were made. How many of those have had intermix issues due to a cracked head?
From what I’ve read, it seems like water pump failure is a common precursor due to the plastic bits being sucked into the cooling passages within the cylinder head. Statistics on that would be interesting too.
if that’s the case, then you should change the water pump as soon as your acquire the car, and replace it every 3-5 years. Don’t use the pump with the metal impeller - I heard it will wreck your block when the bearing goes awry.
also consider replacing the thermostat with a LN low temperature unit. It opens sooner, and from what I’ve read, mitigates the formation of hot spots. If the cylinder head is indeed weak, then the hot spots will surely push it over the edge.
IMHO, now that its been decades since the m96 inception, seems its more of a 3.4 'water pump impeller failure syndrome' than a y2k problem. See what Len Hoffman the m96 head expert thinks...
to see video of a 996 3.4 M96 head being pressure tested, revealing a microscopic crack that was not visible to the naked eye. This particular head was a prime example that a head can not be judged to be crack free without being pressure tested. We know where to look, but we couldn’t find this leak point until we subjected the head to 60PSI air pressure.
Click here to read an article about our high-tech crack repair process.
Anytime an engine overheats it’s no big surprise when it leads to a cracked head.
But in many cases overheating was not reported. Indeed I often hear, “My engine did not overheat, so why did I end up with a cracked head?”
I can not give a definitive answer, but I have some ideas.
–I have flushed water pump impeller blade(s) from many -but not all- of the cracked heads I’ve repaired. Even if the pump has shed just one blade, if that blade makes its way to one of the very narrow internal head passages that feeds coolant to a specific area, that area will see a severe spike in surface temp. And if that area is one of those discussed in the Crack Repair article as having a thin cross section a crack is very likely, if not certain to appear. In this case the overall coolant temp would be within the normal operating range, but localized overheating will occur. A guage would be of no help in warning of this sort of overheating.
If the head failure occured after the replacement of a water pump that shed one or more blades, I believe there is a high likelyhood that we can pin it on a blade lodging in a critical passage.
It’s hard to justify pulling the heads after a water pump failure when the engine did not overheat. But these pieces floating through my engine would worry me. Seems like something of a crap-shoot. I would expect that the water pump was replaced because of some sort of overheating scenario. I believe it is pretty likely that the blades from these pumps don’t all break off at the same time; meaning at least one has probably been lodged somewhere in a head for some time. Even a brief, minor overheating event that was caught quickly by the driver can be harmful if one or more passages in a head is already clogged from pump blades. Crack propagation can occur over time and may begin with one major event, like a pump failure, blown coolant hose, etc, but take some period of time to spread from the water jacket to the surface.
–On engines that did not suffer a pump failure or overheating event, but still managed to crack a head a potential explanation could be that the thin areas that typically crack are gathering points for casting stress. With the head mounted to a precision fixture on a mill, dial indicator mapping of the machined surface upon which the follower housing sits reveals that this surface warps, much like the deck of a head will. Every crack I’ve seen walked across this surface. On the M96 3.4 heads – which comprise over 90% of the cracked M96 heads I’ve seen- I routinely measure .002″-.005″ variance from twisting and sagging of the surfaces. These variances are evidence of stress. The act of cracking serves as a form of stress relief for any casting.
These stresses are very much like earthquake fault lines. When the stress reaches threshold a crack will appear. Of course thermal shock increases the stress on these areas. The sort of stress caused by rapid warm-up of a cold engine could be enough to push the stress level past the threshold point. Heavily loading a cold engine greatly accelerates the rate of heating- and therefore expansion- of the cylinder heads. That significantly elevates the stress throughout the casting and could certainly lead to or hasten the formation of a crack. This condition would be magnified in winter months. And I have seen plenty of cracked heads in the winter months.
"996 CYLINDER HEAD CRACK REPAIR
October 20, 2016HoffmanHome, Porsche2 comments
We have seen cylinderhead cracks in all models of M96 engines used in 986 Boxsters and 996 911’s up to and including model year 2001, but the 3.4 996 cylinderheads are far and away the worst offenders.
Some of the cracks are very large and easily spotted, others are less obvious, and some are down right microscopic. Click here to see a video of one of these tiny cracks discovered during pressure testing. Visual inspection is not adequate for detecting leaking cylinder head cracks, as some are no larger than a pin head at the surface, as was the case with the head in the video. We had no idea where the leak was till we hit it with 60psi air pressure. Yet when we milled away the tiny leak point, we found a fair size crack beneath the surface. It is very common for small surface cracks to be atop a much larger crack, especially in the floor of the oil galley, where the leak in the video happened to be.
Every crack has been in one of five areas beneath the follower housing.Never in a combustion chamber or deck area.
Early 3.4 heads and some 3.2 heads had just two (instead of 3) coolant expansion plugs beneath the lifter housing. These heads have two locations that are subject to cracks.
I have never seen a head that had more than one crack, but over time among the two & three plug heads I have observed 5 specific crack locations Each crack has it’s own unique fault line and a crack in any given position will follow pretty much the same path from head to head.
Some radiate from one of the coolant expansion plugs over toward the nearest spark plug well.
Others migrate from a valve guide bore across the machined spring well and end at the nearest spark plug well.
Most cracks occur on the outer cylinder positions, but on occasion the center cylinder produce a crack that runs from a spark plug well across an exhaust spring well and end in a valve guide bore.
Occasionally the plug well to spring well crack will continue from the spring well on to the nearest head bolt bore. These are the worst examples, but we can repair them too.
Most of the cracks that gravitate toward a valve guide bore head toward an exhaust guide. However, the 3.4 heads that have just 2 coolant expansion plugs beneath the lifter housing will sometimes crack from a spark plug well to an intake guide bore. I have not yet seen this on a 3 expansion plug head.
With over 25 years of cast aluminum crack repair to draw upon I have developed routine repairs for every type of crack that we see with these heads. The type that run into a guide bore are much more involved than the type that don’t and are therefore more expensive to repair.
Crack repair requires a very specific series of processes to end up with a reliable repair. And the cracks that run through the valve guide area are the most demanding. Even shops that say they can repair cracks will often shy away from these challenging repairs, or worse do a poor “repair” that will get through the warranty period but fail down the road.
Our repairs aren’t just a patch, they actually strengthen the casting. Every crack that we have seen with these heads has been to one of several specific areas I have identified as being skimpy in aluminum. When excavating the crack for welding we have a specific pattern that we cut in one of our mills to expose the entire weak area, not just the crack. As a result the finished repair has more material in the cracked area than it did previously.
This is done using advanced welding techniques that involve the use of our custom built casting oven. Pre & post heating temp and cycle times are very precisely controlled. Duration of the welding process is closely monitored to ensure the casting is not overheated. We adhere to minimum weld cycle times divided by a specific period of time in the oven between weld cycles. This technique prevents the welding operation from introducing new stresses to the casting. When the weld work and intensive pneumatic peening of the weld is completed the casting stresses in that area will be long gone. What’s left is a much stronger casting.
Next up, a pressure test. Once we have confirmed the integrity of the weld work it’s CNC machined with proprietary custom carbide tooling, then pressure tested again for added confidence in the finished repair. We have yet to have a single failure of a repaired head, and we know that some have been stressed hard on high-performance and even competition engines.
It’s worth noting that as of 11-23-16 we have repaired 3 heads that went into service and later cracked in a different location. At least one of them was a dedicated track/race car. That’s 3 out of nearly 125 heads, so the odds are pretty favorable. In all three cases the new failure point was repaired and the heads put back in service. We have no practical way to predict these future failures and therefore can not guarantee that the repaired casting will not crack elsewhere at a later time. We can only guarantee our work, and that the head passed multiple pressure tests before leaving our shop.
The large crack in the photos above is the most common crack we see with these heads. A lot of people think it’s a death sentence. And for good reason. I liken this repair to open heart surgery. It requires very specific skills, tools, knowledge and techique, in this case a major excavation of material and extensive welding and cold peening followed by a series of complex, precision machine-operations. The overwhelming majority of shops out there are not equipped to perform this surgery, but it’s routine for us. Our patients go on to live full throttle lives."
05-27-2024, 01:13 PM
Y2K Syndrome?
The large crack in the photos above is the most common crack we see with these heads. A lot of people think it’s a death sentence. And for good reason. I liken this repair to open heart surgery. It requires very specific skills, tools, knowledge and techique, in this case a major excavation of material and extensive welding and cold peening followed by a series of complex, precision machine-operations. The overwhelming majority of shops out there are not equipped to perform this surgery, but it’s routine for us. Our patients go on to live full throttle lives."