WCS

I am looking to purchase a 993. It seems that some cars I've looked at have had their engine top end rebuilt because of carbon buildup. How many of you have experienced the problem?

Also because of potential costly repairs, I'm thinking of purchasing 3rd party warranty. Any thoughts/comments on where to go to?

Thanks.

1999Porsche911

If the top end has already been cleaned (properly), then maintaining it clear of carbon going forward is easy and cheap.

FisterD

I had this problem from Day 1 with my '96 (purchased Jan '04). The dealer I bought the car through,Cars Dawydiak in S.F, took the car back and did the SAI cleanout procedure,as per Hergesheimer Motorsports. The problem has not returned in 3K miles. They also gave me a 2 year warranty.

mborkow

"3rd party warranty"
can you get one on a car this old?

WCS

What does SAI stand for? How much did the procedure cost and how did you notice the problem? Emission failure? I was told top-end rebuild costs something like 6K.

Probabily not, that's why I asked.

FisterD

SAI= Secondary Air Injection ports. I am unsure of the cost, I think around $1000 (+ -) to clean them out.
'95 993s do not have this problem. They also get the buildup, but since they are OBDI, it does not detect it. Only '96 and later have OBDII, which detects the fault.
The problem is, it causes the CEL (Check Engine Light ) to come on, and will not allow your car to pass a smog inspection. My car had 42K miles on it, was not using any oil, and was not smoking, so I think a top end rebuild was not neccessary. The SAI Cleanout has worked just fine.

WCS

So if I purchase a car and it passed the emission, it shouldn't need SAI cleanup and would be fine with Techron like once per 3k miles?

chris walrod

Just make sure the check engine light is not illuminated once the engine is running. On that note, please verify the CEL is functional by turning the key to the 'on' position.

If the car your looking at has blocked SAI ports, the dealer may reset the ECU, which may take a few drive cycles before the light will illuminate again. Just a word of warning, just because the CEL is not 'on', doesnt necessarily mean it will stay off.

FisterD

If the car passed emissions, then you should be O.K. There is no telling, if it is on the verge of the dreaded carbon buildup problem, though, and it could happen next week, or never at all. How many miles on the car? How was the car driven? It truely is a mystery, some cars get it, and some don't.Good luck!

WCS

Hm, that's very informative. Thanks a lot.
I'd imagine the error codes history in the ECU should still be recorded, and I should be able to get a PPI to find out. In this respect, buying from a private owner may be safer than from a dealer.

BTW again, what is the recommended procedure for preventing carbon buildup? I was told Techron but didn't know how to apply it properly.

kkim

http://p-car.com/diy/sai/1/sai.htm

WCS

Yes, I know about this procedure.
What I meant was, after performing SAI cleanup, how do one keep it from happening again in daily maintenance? Can one simply add Techron in gas tank every couple thousand miles to prevent SAI from blocking again?

kkim

No, Techron won't help as the SAI passages are "upstream". Only way is to clean them out using this procedure.

1999Porsche911

There are many methods used over the years to help clean and keep clean, the intake, valves and pistons from cabon build up. On a new engine or one that is already cleaned, I annually inject a half to a quart of transmission fluid into the intake system whle the engine is running. Then turn off the engine and allow to sit for an hour or so. Then take the car out (preferable at night) and blow all the atf out of the engine. It is going to smoke like crazy, that is why I suggested at night. This procedure will keep the carbon from accumulating. This procedures is not in anyway damaging to the engine and can be done as often as you want.

For engines that already have heavy carbon build up, and you don't want to go to the expense of removing the top of the engine, the same procedure can be done, but with water. WARNING: If using water, you allow the engine to injest only a SMALL stream of water at a time. I use a 1/8 inch diameter hose connected to an intake vacuum line. What this does is in effect, steam clean combustion chamber. This method of cleaning carbon out of engine has been around for almost 100 years. Unless there are huge chunks of carbon that fall off, the particles of carbon should not effect the CATS.

The best thing to do is try to eliminate the causes of carbon buildup in the first place by using good gas, plugs and always running your engine to full temperature when you take it out. Bouncing of the rev limiter regularly also helps.

FisterD

1999Porsche911, very informative. I often wondered about water injection, once in my Mazda pick-up (years ago),it blew the head gasket, and water got onto the top of the piston, it cleaned and polished it up quiet nicely.
So do you add the tranny fluid right after the air filter?