Exhaust Valve Guide wear major issue with 993tt
07-17-2002, 04:09 PM
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Exhaust Valve Guide wear major issue with 993tt
I have spent some time reviewing the 993 group and this group's posts regarding Exhaust Valve Guide wear and then spoke at length with ANDIAL's Kevin Kelly in in Santa Ana, CA. I am hearing/reading the same issues from several different sources that tear these engines down and am becoming alarmed -
1/ 993tt's with mileages from 8000 - 27000 (highest they have done) are torn down for performance modifications only to discover that the exhaust guides are in need of replacement.
2/ 993's with lesser problem, yet majority of engines over 50K miles have exhaust guides that are in need of replacement.
3/ Any excessive noise from valve train is usually exhaust guides (when not tappets) since the hydraulic adjusters take up clearance - making the 993/993tt engines quiet when they do not have guide issues.
It makes me wonder how Porsche could possibly let this happen or is it a concession that they were forced to make due to combination of:
a/ higher than original (pre-smog 60's) design exhaust tempuratures (from current smog req + turbo)
b/ air cooled flat 6 design (cannot cool guides with coolant + exhaust heat travels back up to engine + fan cannot directly blow on exhaust side [bottom] of cylinder head)
It also makes me wonder how many 993tt's with low mileage are actually in need of Exhaust Valve Guides!
Please comment everyone.
Bond
1/ 993tt's with mileages from 8000 - 27000 (highest they have done) are torn down for performance modifications only to discover that the exhaust guides are in need of replacement.
2/ 993's with lesser problem, yet majority of engines over 50K miles have exhaust guides that are in need of replacement.
3/ Any excessive noise from valve train is usually exhaust guides (when not tappets) since the hydraulic adjusters take up clearance - making the 993/993tt engines quiet when they do not have guide issues.
It makes me wonder how Porsche could possibly let this happen or is it a concession that they were forced to make due to combination of:
a/ higher than original (pre-smog 60's) design exhaust tempuratures (from current smog req + turbo)
b/ air cooled flat 6 design (cannot cool guides with coolant + exhaust heat travels back up to engine + fan cannot directly blow on exhaust side [bottom] of cylinder head)
It also makes me wonder how many 993tt's with low mileage are actually in need of Exhaust Valve Guides!
Please comment everyone.
Bond
07-17-2002, 06:48 PM
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Bond:
Unbelievable as though it might seem, Porsche still uses that inferior valve guide material from the 3.2 all the way to the GT-3's. From what I've seen, the 3.6 cars suffer the same premature guide wear problems that the earlier 3.2 Carrera's did and the 993TT and 996TT are no exception. Even GT-3's have lousy guides. (everything else is excellent!)
3.2's, 3.3's , 3.6's, all TT's, and GT-3 Cup/RS cars use that material and it simply doesn't hold up.
Like some others, we make and use our own Phosphorus-Bronze valve guides for all of these engines to eliminate this issue, once and for all. No more problems.
Unbelievable as though it might seem, Porsche still uses that inferior valve guide material from the 3.2 all the way to the GT-3's. From what I've seen, the 3.6 cars suffer the same premature guide wear problems that the earlier 3.2 Carrera's did and the 993TT and 996TT are no exception. Even GT-3's have lousy guides. (everything else is excellent!)
3.2's, 3.3's , 3.6's, all TT's, and GT-3 Cup/RS cars use that material and it simply doesn't hold up.
Like some others, we make and use our own Phosphorus-Bronze valve guides for all of these engines to eliminate this issue, once and for all. No more problems.
07-17-2002, 09:13 PM
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Thanks for the reply Steve - what is the practical effect of this inferior valve guide issue on the purchase of a 993tt? - do I have the Tech drop the lower valve covers and put a dial indicator on each (open) exhaust valve regardless of mileage. I just hate the thought of spending 80,000.00 for the car + 6500.00 tax/license only to spend more $$ on a top end rebuild. Why not just get a water cooled 996tt with nearly the same expenditure? (even if the guides are the same rotten material, the liquid cooling MUST extend the guide life considerably)
Bond
Bond
07-17-2002, 09:57 PM
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[quote]Originally posted by Silver Bullet:
<strong>It makes sense to buy whatever car floats your boat. If the perceived cost of maintenance is too high for you, then don't do it, buy a "safe" car.
The 993 is worth whatever it costs to keep it going to those who have a passion for it. Nobody buys a sports car because it is economical.
However, don't use message boards as your sole source of information. It is natural for those of us who post here to complain about this or that or to show an unusual amount of problems. We don't post "Gee, my heat exchanger is great!", we post only things we need help with or give us grief.
Don't be so analytical with your decisions. This car is a fun car to drive, own, and maintain. It isn't cheap, but if it is what you have a passion for, you don't worry about it as much...
<img src="graemlins/soapbox.gif" border="0" alt="[soapbox]" />
Just my $0.02....</strong><hr></blockquote>
I don't catagorize "maintenance" as a top end rebuild on a 8,000 - 27,000 mile motor - this is clearly a material and/or design flaw. A good example of why one needs to be analytical in this situation is to determine if the cost premium for an 8,000 car is worthwhile vs. a 40,000 mile 993tt where one could use the premium saved to spend on fixing the material/design flaw (Steve's guides per previous post)on the higher mileage car. I guess I'm not a "Don't worry be happy kind of Guy".
Bond
<strong>It makes sense to buy whatever car floats your boat. If the perceived cost of maintenance is too high for you, then don't do it, buy a "safe" car.
The 993 is worth whatever it costs to keep it going to those who have a passion for it. Nobody buys a sports car because it is economical.
However, don't use message boards as your sole source of information. It is natural for those of us who post here to complain about this or that or to show an unusual amount of problems. We don't post "Gee, my heat exchanger is great!", we post only things we need help with or give us grief.
Don't be so analytical with your decisions. This car is a fun car to drive, own, and maintain. It isn't cheap, but if it is what you have a passion for, you don't worry about it as much...
<img src="graemlins/soapbox.gif" border="0" alt="[soapbox]" />
Just my $0.02....</strong><hr></blockquote>
I don't catagorize "maintenance" as a top end rebuild on a 8,000 - 27,000 mile motor - this is clearly a material and/or design flaw. A good example of why one needs to be analytical in this situation is to determine if the cost premium for an 8,000 car is worthwhile vs. a 40,000 mile 993tt where one could use the premium saved to spend on fixing the material/design flaw (Steve's guides per previous post)on the higher mileage car. I guess I'm not a "Don't worry be happy kind of Guy".
Bond
07-17-2002, 10:51 PM
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[quote]Originally posted by Silver Bullet:
<strong>You're missing the point. For instance, I like the 993, with or without the design flaws. Is it worth it to me to risk a top end rebuild in the first 30K miles? For me, absolutely. I will buy one over a 996 because it is what I like and want to drive. Not to say there is anything wrong with a 996, but I don't want one. It's not a matter of "Don't Worry Be Happy".
Do I like paying for a design flaw? No, but it is not the defining factor in why I buy a car or not.</strong><hr></blockquote>
Let's, for a moment, assume that I adopt the "I want to drive a 993tt no matter whar trouble it gives me, and at any cost" approach as you describe - when chosing which 993tt to purchase, one still needs to be objective in regard to the individual car, its mileage, potential outlay, etc. and arrive at its actual value - otherwise, how can one decide between two cars. No two used cars are alike and assigning a value to each attribute for each car is the only way to make the decision (esp. same color, same year cars). Learning the particulars through the group through postings is of great value in this regard. "Those that ignore history are doomed to repeat it"
Bond
Bond
<strong>You're missing the point. For instance, I like the 993, with or without the design flaws. Is it worth it to me to risk a top end rebuild in the first 30K miles? For me, absolutely. I will buy one over a 996 because it is what I like and want to drive. Not to say there is anything wrong with a 996, but I don't want one. It's not a matter of "Don't Worry Be Happy".
Do I like paying for a design flaw? No, but it is not the defining factor in why I buy a car or not.</strong><hr></blockquote>
Let's, for a moment, assume that I adopt the "I want to drive a 993tt no matter whar trouble it gives me, and at any cost" approach as you describe - when chosing which 993tt to purchase, one still needs to be objective in regard to the individual car, its mileage, potential outlay, etc. and arrive at its actual value - otherwise, how can one decide between two cars. No two used cars are alike and assigning a value to each attribute for each car is the only way to make the decision (esp. same color, same year cars). Learning the particulars through the group through postings is of great value in this regard. "Those that ignore history are doomed to repeat it"
Bond
Bond
07-18-2002, 12:16 AM
#6
I guess you can also ask how bad worn valve guides really are. For example, if they're only noisy up to 100K miles and then they cause the engine to disintegrate at 120K miles, then maybe you don't care now. You're probably going to drive yourself nuts finding a used 993/996 that has "good" valve guides.
07-18-2002, 12:59 AM
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Good point Bill - even Kevin Kelly at Andial told me that they have never torn down a NEW 993tt to establish a baseline for guide wear. Its possible that they are very loose when cold and once warmed up to those high tempuratures have the proper clearance (also possible that the "new" improved aftermarket guides could bind the valve for the same reasons). Who is going to check for the proper clearance at the 993tt's exhaust temp of 1200 degrees?
Bond
Bond
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07-18-2002, 01:41 AM
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Bond,
You go out and find the best 993TT you can and enjoy the car. If you end up having to do some maintenance on it, so be it. I know there is a lot of 993TT’s out there that have no valve guide issues.
You could also have a perfect car and get rear-ended on the freeway. Life is chances.
Rick
You go out and find the best 993TT you can and enjoy the car. If you end up having to do some maintenance on it, so be it. I know there is a lot of 993TT’s out there that have no valve guide issues.
You could also have a perfect car and get rear-ended on the freeway. Life is chances.
Rick
07-18-2002, 09:40 AM
#9
Bond
I would go for a slightly higher mileage car. I don't trust cars that are say 5 years old with 8000 miles on. Age wears on cars as much as mileage. Unfortunately the second-hand market is such that that a low mileage car is worth considerably more than one with average miles. This is due to misconception by the buyers - a lot of people feel safer buying an 8000 mile 5 year old car than one with 38000 miles. This is just ludicrous.
I would go for the best condition average miler you can find. At least that way the car has done enough miles for problems to surface and fixes to be implemented. The premium for low mileage cars is not worth it - unless you are running a museum.
It is interesting to note that statements about the fact that all 911's from 3.2 to GT3 has poor quality valve guides. This particular alleged fault has been attributed to the 993TT specifically it seems to me. A bit like the fact that all early 964's leak oil because they don't use the head gaskets. This is occasionally the case, but not at all the norm.
I would reiterate the need to relax about this, but there is nothing wrong with being analytical. It is much easier before you own one at any rate...
.
Buy what you consider to be the best car for you. If you are not willing to pay a lot on maintenance then forget about a throughbred sports car. A 996 or 964 will still cost you a chunk to run in the long term - perhaps another option is just to lease a 996TT or 996?
Sorry for long post etc..
Christer
I would go for a slightly higher mileage car. I don't trust cars that are say 5 years old with 8000 miles on. Age wears on cars as much as mileage. Unfortunately the second-hand market is such that that a low mileage car is worth considerably more than one with average miles. This is due to misconception by the buyers - a lot of people feel safer buying an 8000 mile 5 year old car than one with 38000 miles. This is just ludicrous.
I would go for the best condition average miler you can find. At least that way the car has done enough miles for problems to surface and fixes to be implemented. The premium for low mileage cars is not worth it - unless you are running a museum.
It is interesting to note that statements about the fact that all 911's from 3.2 to GT3 has poor quality valve guides. This particular alleged fault has been attributed to the 993TT specifically it seems to me. A bit like the fact that all early 964's leak oil because they don't use the head gaskets. This is occasionally the case, but not at all the norm.
I would reiterate the need to relax about this, but there is nothing wrong with being analytical. It is much easier before you own one at any rate...
.Buy what you consider to be the best car for you. If you are not willing to pay a lot on maintenance then forget about a throughbred sports car. A 996 or 964 will still cost you a chunk to run in the long term - perhaps another option is just to lease a 996TT or 996?
Sorry for long post etc..
Christer
07-18-2002, 12:40 PM
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The way I look at it is this. You do your due diligence, research, PPI etc on the car that you love. Then you write the check and move on. If something breaks it breaks. You fix it and then moan about it here on the board with your new buddies for one post and then move on. We're all dealing with pieces of machinery and stuff can happen. On the other side of the coin, this is some mighty well hung together machinery!
If you lurk at Ferrari board, people are wringing their hands over "high" mileage cars at 15k miles!
I just took the plunge on a 1996 TT a couple of months ago, so I understand your concern.
Good luck,
Scott
If you lurk at Ferrari board, people are wringing their hands over "high" mileage cars at 15k miles!
I just took the plunge on a 1996 TT a couple of months ago, so I understand your concern.
Good luck,
Scott
07-18-2002, 01:39 PM
#11
I agree with Scott. If I were to by another TT, I woudn't be afraid of a higher mileage car ( up to 45 K ).
At the time, I didn't know anything about p cars, so I wanted to get one with less than 10K miles. I don't think that was necessary, in retrospect. I was just needlessly concerned.
And I also thought Ricks comment about being rear ended on the freeway was hilarious. Very true!
Jeff
At the time, I didn't know anything about p cars, so I wanted to get one with less than 10K miles. I don't think that was necessary, in retrospect. I was just needlessly concerned.
And I also thought Ricks comment about being rear ended on the freeway was hilarious. Very true!
Jeff
07-18-2002, 01:53 PM
#12
RL Technical Advisor
[quote]Originally posted by Bond:
<strong>Thanks for the reply Steve - what is the practical effect of this inferior valve guide issue on the purchase of a 993tt? - do I have the Tech drop the lower valve covers and put a dial indicator on each (open) exhaust valve regardless of mileage. I just hate the thought of spending 80,000.00 for the car + 6500.00 tax/license only to spend more $$ on a top end rebuild. Why not just get a water cooled 996tt with nearly the same expenditure? (even if the guides are the same rotten material, the liquid cooling MUST extend the guide life considerably)
Bond </strong><hr></blockquote>
Bond:
IMHO, this is something that should be be checked on any used 964-993-TT car as part of the PPI.
If the technician discovers excessive side-play in the valves, then an allowance should probably be made in the price to accomodate a valve job sometime in the near future. At least this is what I advise my customers to do.
From what I've seen so far,...GT-3 engines, this is not confined to the air-cooled models.
<strong>Thanks for the reply Steve - what is the practical effect of this inferior valve guide issue on the purchase of a 993tt? - do I have the Tech drop the lower valve covers and put a dial indicator on each (open) exhaust valve regardless of mileage. I just hate the thought of spending 80,000.00 for the car + 6500.00 tax/license only to spend more $$ on a top end rebuild. Why not just get a water cooled 996tt with nearly the same expenditure? (even if the guides are the same rotten material, the liquid cooling MUST extend the guide life considerably)
Bond
</strong><hr></blockquote>Bond:
IMHO, this is something that should be be checked on any used 964-993-TT car as part of the PPI.
If the technician discovers excessive side-play in the valves, then an allowance should probably be made in the price to accomodate a valve job sometime in the near future. At least this is what I advise my customers to do.
From what I've seen so far,...GT-3 engines, this is not confined to the air-cooled models.
07-18-2002, 09:49 PM
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Bond,
I tend to agree with most of the earlier comments. We buy these things because we love them. It's not a rational decision. If you buy a TT, you've got to be prepared for a $3-4K surprise at anytime. About 5 yrs ago, I purchased a pristine 88 930 with 6k miles on it. 6 months later, I had to replace most of the gaskets because it started leaking oil. Cost $3k. So a low mileage car is not without drawbacks. I think a car that has been driven some is probably going to be more reliable and have the bugs already worked out. It is always prudent to find the best vehicle you can and have a thorough PPI done. If you're satisfied, buy it. Life is too short. You NEED a TT ASAP!
Eric
I tend to agree with most of the earlier comments. We buy these things because we love them. It's not a rational decision. If you buy a TT, you've got to be prepared for a $3-4K surprise at anytime. About 5 yrs ago, I purchased a pristine 88 930 with 6k miles on it. 6 months later, I had to replace most of the gaskets because it started leaking oil. Cost $3k. So a low mileage car is not without drawbacks. I think a car that has been driven some is probably going to be more reliable and have the bugs already worked out. It is always prudent to find the best vehicle you can and have a thorough PPI done. If you're satisfied, buy it. Life is too short. You NEED a TT ASAP!
Eric
07-18-2002, 09:54 PM
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i'm new to this board but i',ve owned a few porsches,my latest being a 97 turbo. i bought it with 50,000 miles plus. It came modified with GT2 turbo's,ECU.filter,and different exaust.the previous owner used it as a daily driver and i use it as MUCH as possible! I've had the car at an indicated 192 on a few occassions and almost everday at 140 and above. Don't freak yourself out,the car is rock solid,my car has 65,000 miles on it and I run it hard and know problems. I'm installing an rsr oil cooler and running euro catalyst,no muffler,coil overs and GT2 bodywork,I can't wait to run it even harder! There is NO substitute!!