Will a Compression Test Screen a Cayenne for the Piston Scoring Defect?
03-23-2014, 03:11 PM
#1
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Will a Compression Test Screen a Cayenne for the Piston Scoring Defect?
Apologies if this has been answered. If it has I could not locate here or elsewhere.
Is there a definitive way to screen for the factory defect that causes the scoring in a pre-purchase inspection?
Looking at purchasing a 2004-2007 Cayenne and concerned about engine risk on an out of warranty vehicle. (I realize that this may be a low probability event, but it is a clearly a factory known issue.)
Thanks!
/jp
Is there a definitive way to screen for the factory defect that causes the scoring in a pre-purchase inspection?
Looking at purchasing a 2004-2007 Cayenne and concerned about engine risk on an out of warranty vehicle. (I realize that this may be a low probability event, but it is a clearly a factory known issue.)
Thanks!
/jp
03-23-2014, 05:36 PM
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Thanks for the quick hit back. Should have provided more info. I am shopping east of the Mississippi in the US. A good chunk of the inventory I am seeing is from north of the Mason Dixon line, so winter temperatures drop well below freezing (and well below the temperatures Jake sites at which damage is happening).
03-23-2014, 06:43 PM
#5
Rennlist Member
Any reason not looking for cayennes in Florida? They must have a gazillion of them for sale there. Don't have to worry about cold weather over there. Mike
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03-24-2014, 11:16 PM
#8
Nordschleife Master
either method will work. If it were me, I would compression check plus leak down all the cylinders. This will give you a great idea on how strong the engine is!
03-26-2014, 03:12 PM
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Piston Scoring FAQ (Here's what I learned. 955 Buyers Stay Awake))
Thanks so much for all the responses. Much appreciated. Terrific forum.
After reviewing a number of individual scoring reports, 2 weeks of 955 shopping, coming perilously close to buying a likely scored S, and seeking the counsel of the fine folks at Raby Engine Development, here's what I've learned.
1) Would the defect that causes piston scoring be caught by a compression test/draw down?
2) Is there any way to screen for the defect that causes piston scoring in the pre-purchase inspection?
3) What is the cheapest cure if you have a Cayenne with the piston scoring?
4) What about the 4.8?
5) Have your seen any scored 4.5s as far north as NC or VA?
6) So how to mitigate the engine failure risk?
7) How many engines are affected?
After reviewing a number of individual scoring reports, 2 weeks of 955 shopping, coming perilously close to buying a likely scored S, and seeking the counsel of the fine folks at Raby Engine Development, here's what I've learned.
1) Would the defect that causes piston scoring be caught by a compression test/draw down?
No. The issue starts well below where the compression is built in the cylinder. (Raby, March 2014)
2) Is there any way to screen for the defect that causes piston scoring in the pre-purchase inspection?
No. The wear starts below the piston ring position at BDC. This means that even a bore scope isn't effective at seeing the wear, because you cannot access the problem area. (Raby, March 2014)
3) What is the cheapest cure if you have a Cayenne with the piston scoring?
Haven't found a cost effective solution. My salvage man claims he found a 4.5L for $5K. The Raby replacement with Nikasil cylinders lists for $22.5.
4) What about the 4.8?
We see the same issues despite model year. (Raby, March 2014)
5) Have your seen any scored 4.5s as far north as NC or VA?
Yes, we've seen a few. Honestly its all in luck, you can't avoid the chances completely. (Raby, March 2014)
6) So how to mitigate the engine failure risk?
- Turbos Only - Much Lower (but not zero) Scoring Incidence
- Southern CTs Only - Pull Autocheck. Make sure every datapoint in the car history was logged in a zipcode where the average Dec/Jan temp is above freezing.
- Screen Hard for Maintenance - With a Land Cruiser this might be overkill. With the 955, perhaps not.
- PPI - Including Compression/Leakdown. Bore Scope if OCD.
7) How many engines are affected?
It's hard to know and Porsche clearly does not want hard data in the public domain, but here's what I found. Most is anecdotal. Draw your own conclusions.
- Rebuilds are pacing at 10/week this winter. (Raby, I believe I read. Can't find the quote now.)
- Porsche quoted a core fee of $30k on a warranty replaced engine.
- I have seen a number of "run and drive" Cayennes S with clean titles at the Copart auction. Copart is a salvage auction; mostly insurance wrecks. Dealers seeking to auction excess or non-conforming inventory would typically look to Mannheim or a similar dealer auction. Either an uninformed dealer is placing the car in the wrong auction; or the dealer is seeking an uninformed buyer in a public auction. Before my scoring enlightenment, I had George at Salvage Research ($19 report; salvageresearch.com) chase down a couple of these. Same pattern each time. Dealer places car at auction. Recycles through auction until someone meets minimum bid. Car disappears for 2 weeks and 500 miles, then back to Copart. Rinse and Repeat. These were largely northern cars.
- Got to final negotiations on a beautiful silver CS in Jersey over the weekend. Seller told me I was "overthinking" the purchase; then vaporized when I raised the piston scoring issue, inquired if suggestive noises had been heard, and requested a compression test be included in PPI.
03-27-2014, 10:03 AM
#11
Drifting
What exactly would score a cylinder below the piston ring at BDC? And if it were scored there, how would that negatively affect performance?
I've personally never seen an issue on a 4.8, but then again, I don't deal with catastrophic failures on a daily basis.
I've personally never seen an issue on a 4.8, but then again, I don't deal with catastrophic failures on a daily basis.
03-27-2014, 11:07 AM
#12
Race Director
How much of a skirt is there on a 4.8 piston?
03-27-2014, 12:57 PM
#13
Racer
You may be over thinking you purchase, nothing is 100% and even if you purchased an engine like this, drive it because it appears from your description it is a non-issue to the operation of the engine.
03-27-2014, 03:35 PM
#14
The GTS has a squirter block like the CTT so the skirt is oiled thus minimizing the scoring potential.
The downside is slightly higher oil consumption. Having narrowly missed a $14k engine replacement (CPO), I would gladly pop for a few extra quarts of oil.
BTW, I recently sold my '05CS and picked up an '08 GTS 6-speed. Great truck that is a blast to drive.
The downside is slightly higher oil consumption. Having narrowly missed a $14k engine replacement (CPO), I would gladly pop for a few extra quarts of oil.
BTW, I recently sold my '05CS and picked up an '08 GTS 6-speed. Great truck that is a blast to drive.
03-27-2014, 03:46 PM
#15
Burning Brakes
I'd imagine that a scored cylinder in a high performance engines would become worse very quickly and can go from oil burner to seized engine with little warning.