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Discussion summary
YOUR RESEARCHCylinder Carbon Build Up - Normal?
Leading reported evidence
Inspect cylinders
Performed · outcome unconfirmed
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Performed · outcome unconfirmed · Original poster
Cylinders are smooth with no scratches (he only inspected the cylinders from the spark plug access - he did not take the sump off and scope the engine from the bottom as per Jake Raby's procedure).
Leading evidence: 'Inspect cylinders' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check ring seal/engine health' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Performed · outcome unconfirmed · Original poster
He did an oil change and inspected the filter and there was no metal.
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Performed · outcome unconfirmed · Original poster
The car sat over the winter and I had changed the oil in the late fall.
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Performed · outcome unconfirmed · Original poster
I had my spark plugs and tubes replaced at my local mechanic recently (date in the pictures is wrong).
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Suggestion
Also do a blow-by test to check for ring seal/engine health.
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Performed · outcome unconfirmed · Original poster
Cylinders are smooth with no scratches (he only inspected the cylinders from the spark plug access - he did not take the sump off and scope the engine from the bottom as per Jake Raby's procedure).
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I had my spark plugs and tubes replaced at my local mechanic recently (date in the pictures is wrong). He took these pictures inside the cylinders. Checking to see if this carbon build up is normal or cause for concern and if there is anything I should do about it?
Car is a 2001 C4 with around 72,000 miles.
Looks kind of wet/gummy to me, you getting blue smoke at your tailpipes and consuming oil? I recently had the heads off my 1999 996 with 77K miles, and the little carbon build up I had was dry/sooty and cleaned up with a brass hand brush.
It has a tiny bit of smoke on start up, but I think that is normal. Doesn't consume any oil and no soot on the tail pipes at all. I agree that it looks a bit gummy but the pictures are really not very clear.
I only notice a very small amount of smoke on start up (one or two seconds) when the car has been sitting for a few days (only noticeable if you are right behind the car). You can see a small amount of oil in cylinder 4 and 6 in the pictures. The car had been at his shop for a few days while he waited for a new coolant tank (cracked). He had a much better look at the cylinders with the camera then the pictures I received and his comments were:
1. Cylinders are smooth with no scratches (he only inspected the cylinders from the spark plug access - he did not take the sump off and scope the engine from the bottom as per Jake Raby's procedure).
2. Felt that quality of the fuel used by the previous owner could be what caused the build up (I have only owned the car for a year).
3. I asked him about using a fuel additive "cleaner" before my next oil change. He stated he does not really like to use them but would get back to me with what he thinks would be best.
4. He did an oil change and inspected the filter and there was no metal. Not surprising because the oil had basically no miles on it. The car sat over the winter and I had changed the oil in the late fall. I did not request him to change the oil as part of the service but he did anyway - oh well there are worse things. No sense taking him to task as I live in a small town and he really is the only mechanic that works on Porsche.
Fuel grade doesn't cause carbon build up but burnt oil does. If it only does it for a couple seconds on start up then that's usually the sign of worn valve guides and or old valve guide seals. Some carbon build up is normal excessive amounts aren't. Hard to tell from those pictures if that's excessive or not. Doesn't look too bad to me.
Thanks very much for the information and your opinion on the carbon build up. I will do some searching and reading on rennlist regarding the valve guides and seals.
That looks nasty to me. Not so much the carbon built up, but the oily look every where. It actually looks like the carbon is wet and breaking off due to the excess oil. The carbon build up should be dry or slightly wet, but that looks like it is soaked.
I think you should do an AOS test to confirm the operation of the AOS. Also do a blow-by test to check for ring seal/engine health.
Hopefully it is just an AOS failing and allowing too much oil mist into the engine and wetting the complete interior of the intake tract and dripping down into the cylinders.
Thanks for your help. I will check with the mechanic to see if he can do the AOS test when the car is back in for a front inner CV boot later this week.
The test result from the crankcase pressure are as follows:
1. cold start up - 22.9 MBar or 9.2 inches of water
2. Engine warm - 17 MBar or 6.82 inches of water
My mechanic listed the Normal range as 9.9 to 17.4 MBar and the failing range as 22.4 to 29.4 MBar.
I have observed the car multiple times started after sitting for a day or so and when it was warm and there is no smoke that I can see.
Let me know your thoughts. I was planning to run the car till November and do the IMS, RMS, AOS, Water Pump, and whatever else next spring. I will probably put around 7,000 kms on the car from now to November.
- 6.82 inh2o is on the high side of normal, but equally important is how fast does it get there? It should be instantly. We recently has a member here who tested theirs and it was a normal range of -5 inh2o but took 20 seconds to get there indicating a delay in AOS function !!
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