bluejam

What are the first signs/symptoms of the guides wearing?

You guys are scaring the crap out of me!

FLYT993

Oil consumption, i.e., guzzling a quart or more every 1k or less.

slapshot

Hi Jack! My understanding is (and I must qualify that I am no expert and mix stuff up all the time, LOL!), that operating temperature and the like influence the carbon and deposits, hence the plugged SAI ports, etc., thus casuing one to pull the CEL code when the ports get clogged. Degenerative valve guides lead to more burn off and carbon getting through, and thus plugging up the ports/intakes. Again causing the CEL. So, the carbon build up and CEL problem with regard to the SAI ports "can" be a "symptom" of degerative valve guides. But that is only one symptom.

Often we all do the flushes, etc. to clear the ports, and not flag the CEL, and . . . in Cali to pass smog. That said, the ports can clog and your valve guides can be relatively OK. The gold barometer for valve guide wear is how much oil is used and the play in the actual valves which certain shops can measure without pulling the engine.

To try to steer back to your question, often it is recommemed that a cooler engine is a longer lasting, less carbon producing engine. Just my summation. The bigger issue and the impression I walked away with was: Cool or not, CEL code or not, the valve guides will wear (and are wearing) mainly because the OEM material alloy they are composed of is sub-standard, and . . . it just wears (some argue prematurely, others argue as it should as it was not meant/built to last forever and Porsche was not concerned with such obsolesence - obviously it is a universal fault but has not been addressed at all by Porsche).

So certainly, we can jump through hoops to keep the car cool (remove lower engine cover, secondary oil cooler, vents, etc.) which help and may prolong a dreaded CEL for SAI ports being plugged (96-98 MYs), but the valve guide wear (wasting) is going on concurrently as a natural and organic result of simply running the engine. Thus, it is not as simple as cooling or tweaking to prolong engine life, rather the original components were faulty in the first place, thus making for an internal engine part that is prone to degredation and eventual failure (being a smoky oily running engine) simply due to normal use. Combine this defective component with the natural wear and tear on any engine as it exceeds 50K, 100K, etc. and thus the expenses to properly rehabilitate increase exponentially.

Bluejam, not to scare, but . . . no sense in denying the reality of the situation, nor thinking a quick fix (flush, secondary oil cooler, etc.) can prove to be a silver bullet to a comprehensive and organic issue - engine wear). And two or three years ago, when the internals of the core/top end, were still experiencing less wear, thus less need for peripheral "while we're in there replacements", it was not as much of an issue. At the end of the day, it really is attributable to Porsche's build and something we must simply budget for and live with or get out of the series.

Steve Weiner-Rennsport Systems

Oil consumption. When you are using a qt every 700-800 miles, you are ready.

This should not scare anyone; it merely serves to remind people to do their due diligence about the true ownership costs of these cars before they step into the driver's seat so they are not ambushed when the car needs repair.

I think the reality check is to understand that these cars are just not new any longer and some things simply wear out. If you think 993's are a potential problem, try a 996-997,.... Once out of warranty, look out.

Porsche has (like ALL manufacturers) decided that revenue from parts should be equal to, or exceed revenue from car sales and have become quite aggressive in pricing the "just-in-time" air-cooled parts inventories. Its not pretty but its reality.

Now,.....maintenance pricing nationwide varies with local labor rates as well as work ethics, and I would not be too hasty to condemn any shop trying to do the right thing and save the customer some $$$$ in the long run. Some folks do try to pinch pennies when repairs are required and the shop needs to make sure that the car doesn't come back for the same, or related issue.

This is a really a VERY complex situation given all the physical variables and human factors at work here so please bear in mind that the above is a gross simplfication.

slapshot

It may be a gross simplification, but you said in a few lines what I fumbled and bumbled with over many. "Situational awareness", key in almost all aspects of life, Porsche ownership being no exception. And though it goes without saying, if anyone is an expert on our cars and Porsche, it's Mr. W. Thanks for providing input!

fast_freddy

I too had my top end done at the same shop as Vic (oddly enough I have his old car too) and gave him the exact same instructions as Vic did, replace/repair anything else that looks suspect while you are in there. He didnt have to, so he didnt. He gets my business now even though its a pain in the butt driving 180 miles and all. I shouldnt complain though as our Maryland friend meantioned above drove 475 miles or so to do the same thing.

DaveM993

Steve, it can't be this black and white. My car has 16K miles and has burned 1 qt every 900 miles since 4K miles when I got it and that has not changed. It is far from needing a top end.

Mike J

Having rebuilt my own motor I can attest tothe complexity and time it takes to do it right. There are lots of parts, gaskets, nuts, nuts, bolts, sealants, LOTS of O rings never mind the great tolerances inside these engines. When parts go together there is no slop ; they are machined just right. It took me way more hours than a mechanic would charge to do the rebuild so my hats off to those guys who can do a quality job on a rebuild on a time budget. One thing I did do though...I did not get cheap and reuse anything that was marginal. Again, do it once and do it right.

Having looked at both the SAI passages and the heads I would say the biggest problem is the passages are just too small...I enlarged mine when I had the heads off but who know how long it will last. The good thing is I have the ability to take it all apart, the bad is it cost money to do that (seals, gaskets, alignment). So I am just making sure I avoid the short runs, run the engine nice and hot every time I use it and drive it.

I do not know how much more realiable the 993 is compared to the 911SC's for instance. I suspect we will also start to see other failures in electrics (starters, alternators, bad connectors, frayed wires, ignition wires) and sensors as well. These cars are expensive to maintain for sure and the only way I could afford it is by doing it all myself, which I like anyways. If I was marginal on affording one and did no know which end of the wrench means business I would be scared too....

I guess that does not help much...

Cheers,

Mike

droy3

I must say that I truly appreciate this thread. I'm in the process of finding a 993 and at least I can do so with my eyes open.

BobbyT

Thoughts that keep all this in perspective for me is how fast other cars depreciate, while our 993s hold their value quite well, and what else is out there that really entertains and excites?

993Dave

I've just gone through gone the CEL issue myself. I think it is now the generally accepted knowledge that the valve guides wear more quickly than we would like. As such, they are likely to be the reason any of us decides to crack open the engine. I agree with the basic premise of this thread, then, that the valve guide fix offers a prime opportunity to do a full overhaul on other parts that may be wearing.

However, it is possible to survive the CEL experience without a $12K rebuild. It seems to me that some prudence can still be exercised. First, does the CEL/SAI problem really require the replacement of the valve guides at this time? In my case, it did not, according to my mechanic. 85K miles of a lot of in-town driving clogged my SAI ports, I guess, so cleaning them out was sufficient in my case. Lesson: don't assume (as I did) that the valve guide job must be done immediately. Second, if you do have to replace the valve guides pretty early, at, say, 60K miles, does it really make sense to try to do a whole bunch of other stuff "while you are in there"? How much else is going to be worn out at that time? I would hope that the basic mechanical bits would still be well within their expected life span at that point. Inspect and replace obviously worn or consumable items, of course. But I would be leery of a shop that recommended a whole bunch of additional work that early in the car's lifespan (not that I'm suggesting that any of the shops mentioned above have). I'm not trying to be cheap, just wise.

As noted above, it seems that "situational awareness" is key. And the experience and knowledge of people here is a big part of that. (Incidentally, I do not consider myself as someone with "knowledge;" just "experience". )

bluejam

If I had read a thread like this prior to purchasing my '95 87k miler, I may have become scared off, but it is too late. I love her and will do anything for her.

Sorry for noob question, but are there any threads that describe proper driving, i.e, RPM at certain gearing sequences, etc. I keep reading about daily redlining, "drive like you stole it". Also the manual says not to warm it up before driving.
Many of these operations defy my prior thought of "babying" a car.
Any insight is appreciated.

And for Steve W from Rennsport, do you have recommendations for my maintenance here in PDX? I am a jet tech and not afraid to turn a wrench with a good manual but I need a lift.

Thanks in advance.

Garth S

" Valve Guide & Top End - In Your Future ~ The Cheap Man Pays Twice"

A sobering reflection - and close to one that has haunted me somewhat over the 10K miles added in my two seasons to achieve 72K on the car, for that milage appears close to the median where many face the valve guide issue - and whatever else may be considered wise to include so as to avoid the pitfall in the threads title .... of 'paying twice';
In this isolated region, there are 6 known 993's - of which I've seen only one: expertise is in short supply for any form of R&R, let alone a top end job - so DIY is the rule. Casual conversation with the Dealer suggests a teardown to the case to be in the $25K+ realm , partly due to the insane pricing structure for OEM parts.
That's the down side. The upside is that the engine consumes less than a liter of oil in 8KKm/5K miles, and runs perfectly. As many Rennlisters 993s have done so for considerably more that 100k, the future looks bright - especially at 5k/annum .
So what to do? .... in a reverse twist, 'it' is already done .... an insurance policy of sorts. On a dolly in the garage is a VRAM motor and G64 box with 25K miles 'experience' behind them. Purchased with the car,I subsquently agonized a bit and had considered either selling them, or installing them in the car and selling the 72K pair, or just admiring them as an appreciating asset ... especially as the top end repair prices continue to escalate. For the moment, they represent a very tangible coverage
In any event, this provides some contingency for trouble free, long term ownership - and as complete low milage motors occasionally appear for considerably less than a top end job, it may be an alternate solution for someone. I would not have gone off on this tangent were it not another recent thread where a 'lister was debating paying $25K for a rebuild ( metal shavings in the filter) on a $35K car ... that will still be worth $35k after that investment. Complete used motors sometimes go for ~$8K, and rebuilt long blocks are advertised for less.

JasonF

Is there a "safe zone" for valve guide wear that kicks in once a car reaches a certain mileage?

For example, my new-to-me '95 C4 just turned 90k and has only used 1 quart of oil in 3,000 miles of mainly in-town driving. Is it naive to assume that relatively low oil consumption at this mileage means that the guides are in decent shape at as a result I should be ok for the near future?

Or does valve guide wear accelerate at some point and one day you're in great shape and the next there's white smoke billowing out the back of the car?

NP993

I'm sorry to say, but it really is that black and white. Your guides are worn. They probably weren't fit properly from the factory -- the QC in this regard is said to be terrible. I've talked to a couple of techs with a lot of experience on 993's and they've said that in doing some 3.8 conversions and top ends that involved tearing down very low mileage 993 motors, they've routinely found guides that were already badly worn. Such is life. That quart that is burned every 900 miles -- that oil is getting into the combustion chamber and ignited along with fuel and air. It doesn't get there magically.