jaudette3

A friend is looking for a 964 based on my enthusiastic recommendation and was told the following by the local Porsche dealer (which has very little credibility with me and other Porsche enthusiasts here in Central Oregon):

964 and 993 series are subject to carbon build up in the exhaust portion of the engine due to the gasoline used here in the states and a fix runs in the $10K range.

Any truth to that?

Thanks for the input.

Regards,
John Audette

wellcraft290

i have heard on a 993 you have carbon buildup.. happened to a friends and was not cheap to have it scraped etc... not sure why or if on the 964

Steve Weiner-Rennsport Systems

Hi John,

Carbon buildup happens for two reasons, barring a mechanical problem:

1) Excessive oil consumption due to worn/loose guides.

2) Normal byproduct of using today's unleaded fuels and cheap gas makes it worse.


#1 is no revelation as most of these cars have had this since new and its resolved when a valve job is done.

#2 has been an issue since the demise of leaded gasolines (1978) and its managed by the regular use of a high quality fuel additive such as Techron, LubroMoly and a few others.

jaudette3

Thank you Steve.

Regards,
John

flankenspeil

high revs and good quality fuel will help prevent/clear-up carbon deposits

altarchsa

I think the Dealer is partially correct.

I started to buy a 993 at a great price from my stepson ($17K for a 96 model) who is a buyer with one of the national used car dealers The check engine light was on, so I did some research on the 993 Forum and found the following:

There is a small passage through the head that recirculates exhaust gasses to the intake. It is prone to fouling from carbon build-up. There is a procedure using a decarbonizing product shot into the system, but it is only sometimes effective. Otherwise a top end removal is required, so it would be expensive, and one of those "while you're in there...................

The 964 does not have this design.

I have seen a moderate carbon build up on top of the pistons, even very soon after cleaning, when I've done the rebuilds on my motor. There was not a lot of build up in the exhaust ports, so I don't thnk the Dealer is accurate to include the 964's in his appraisal. Sounds like he may be trying to sell a later model or new car for more $$$.

ian89C4

When I did my rebuild, I had moderate build-up, nothing the could not have been left alone, but I did take a plastic scraper and a cupping brush to the inside of the combustion chambers and cleaned off the piston heads. I have an 89, so I don't think that a 993 would be that bad. Sounds like he is trying to get more money out of the deal. I would say just run some addatives and some good fuel through the system and she should be good to go.

roblav

WHen I recently rebuilt my 100K mile 964 engine, the carbon buildup on the exhaust valves was the worst I have ever seen.

ian89C4

Good call, mine only had 70K, I only did a reseal, as it was leaking pretty badly.

H2ono:

How many miles does this 993 have on it?

Indycam

If you want to clean out the carbon a water injection system will work wonders .
I took the head off a water cooled motor with a cylinder head gasket leak , one cylinder was perfectly clean , the other three had bad carbon build up . Right then and there I understood that even accidental water injection really did clean out a motor . If you want to clean out a motor , I would suggest doing it just before an oil change . The other thing would be to shut off the water injection long before you shut off the motor so that the water that will have gotten blown by has a chance of being boiled off .

frankvan

Indy,
Is there a water injection system available that isn't fitted to an engine that can be used for this?
The only ones I've seen are installed on the engine and I haven't seen one in probably more than a decade. (Last one IIRC was on an dodge hemi dragster).

bgiere

Besides Techron you may want to have a look at Seafoam.

Indycam

http://www.summitracing.com/search/?...njection&dds=1

http://www.jegs.com/webapp/wcs/store...ater+injection

http://www.google.com/search?hl=en&s...r+inj&gs_rfai=

springer3

993 owners live in fear of the CEL from a clogged air injection system. This is the first I have heard of carbon build-up problems on a 964.

forstephan

In that case , no smoke? Engine running flawlessly full of power and revs?
But unusual residue on bumper? And burning 1 quart every 400 miles
thank you for your help