sandvik951

Is the valve guides a weak construction on the 993 tt engine ? I have heard that the heat from the turbos will make them leak oil.

Felix

As the aircooled engines evolved they were subject to more extensive emission and noise regulations necessitating higher running temps and inclusion of under-engine noise shields that trapped heat. Add turbos to the mix that generate higher net heat through both greater retention and higher power output and you're not helping things. Add stop and go driving as traffic increases and cooling flow lessens and things are a bit more stressful still. So exhaust valve guides are under a lot of load to transfer heat from the valves but everything's hot already. And then Porsche's choice of guides seems softer than necessary and the guides wear stressing the valve stem seals and oil gets burned up. You can read stories here about valve guide replacement at 20K miles and at 100K miles; I think usage and ambient temps play a big part.

sandvik951

Is it possible too check this before buying a car ?

Felix

Yes, get a leakdown test done by a mechanic how knows how to do one

Geoffrey

A leakdown test will not specifically tell you that the valve guides are bad. However, if the leakdown test shows leaking past an intake or exhaust valve, it MAY be a result of worn valve guides allowing the valve to wear the valve seat and lose the seat concentricity.

The best way to check for valve guide wear is to remove the valve spring and seal to test for valve play.

ca993twin

My (very limited) experience is that fewer turbo than NA cars seem to have valve guide and SAI issues. I'm guessing that the SAI is taken care of my the greater heat in the turbo engine. I'm wondering why it "seems" that fewer turbos suffer from valve guide wear... perhaps the wear is there, but with all the HP available, the turbo engines don't suffer much performance loss? Or am I being delusional... again?