drnd

Hello All,

I'm having a ppi done this friday. Car is a 97 993 C2S. 25,000 miles. Service tech says compression and leak down not necessary. Should I request it anyways. What will this test give me? What about diagnostic test for the fault codes? Is there anything specific I should watch out for? I've read about he SAI codes and problems with it. What test can be done to detect this? As you can tell this is new to me and I have learn so much on this site.

thanks to all.

trojanman

Loads and loads of posts on this topic. I have my own opinion based on getting burned by the SAI fire (I threw a check engine light 85 miles after purchase and am now faced with a top end repair). The following should be a bit of help, I think... it is copied from a post I made on this subject... "be diligent" is my best general advice.

my impression:

diligent preventative maintenance (i.e., check valve replacement every 10k-15k miles) may delay the carbon build-up in the SAI ports, but it will happen eventually.

as for the valve guides, they ARE going to wear... whether you get 25k or 100k before you're burning so much oil that it's time for a top end, well that's a bit of a crap shoot and is based on many, many variables (where, how often, and how you drive; frequency and quality of oil changes; and SHEER LUCK!).

since I've been to hell and back regarding this issue, I do have recommendations for prospective 993 buyers:

- don't put too much stock in Carfax; mine proved to be misleading
- don't substitute anything for due diligence (get a good PPI, interview prior owner(s), review maintenance records in detail and consult with mechanic regarding any questionable items)
- include a valve guide check as part of PPI... if your mechanic is very good/experienced, they should be able to determine the current "play" of the exhaust valves inside the guides to get a subjective sense of the integrity of the car's top end (this will cost more but i believe is worth it if you're really interested in the vehicle)
- some have encouraged a leakdown test be performed as part of the PPI... these are apparently more diagnostic than a simple compression check
- in general, just DO YOUR HOMEWORK! make it your goal to learn more about the car than the seller does... know the factory codes under the hood, understand every mod that's been done, and finally (as many others have said) set aside a few grand for post-purchase issues that will likely come up (if nothing else, you'll have some $ for mods!!)

Just $.02 from a newbie who's been through this recently.

ientre9y11

Definitely do a search. There are tons of posts. I believe Steve Weiner has commented on this, he is the resident expert.

Given the magnitude of the investment and the cost of a compression and leak down test you would have to be crazy not to get the tests done.

It is kind of like using a cut rate car hauler to transport your baby. Penny wise, pound foolish.

Evan

Nick - just saw your thread (after I sent you an email).

Where are you getting the PPI?

C4S_fan

Lets say the full PPI costs you $450 on a (probably) $45,000 investment.... that sounds like *really* good choice on spending your money to me. I'd rather know definitively what I'm getting, versus taking a chance...(irrespective of miles)

mike cap

drnd,

IMO unless you're going to be there to witness the compression/leak-down test it's a waste of time and money. First of all we're talking about an engine with about 600 hours or so of runnning time on it, so the chances of a valve or piston ring problem is low. Second, the compression/leak-down test has to be done with a hot engine (like the tech wants to work on a red-hot engine) to have any value and is a very specific procedure involving the correct pressures, bleed-down rates and orficies. If you are not familiar with this procedure and are there to watch, save your money and let the tech concentrate on more important possible squawks.

Valve guide wear, same deal. IMO it's a waste of time/money on a 600 hour engine. You won't find anything other than normal wear.

The most important things are:

- Records, records, records!
- Does the car run strong and "track" properly? Have Evan drive the car for a while to make sure it "feels" like a correct 993 should.
- Talk to the PO about oil use and service history. No oil use = no piston ring or valve problems.
- Look for repaint, body and fender damage and undercarrige damage. An engine is an easy fix, while a crash or off-road adventure is a nightmare as long as you own the car.

Good luck. Sounds like a nice car.

TheOtherEric

My experiences agree with Mike. My 1st 993 had compression readings around 220-240 psi. The car was a dog, which I proved empirically (via a dyno and on-track acceleration runs). My 2nd 993 had compression readings around 190-200. Strongest 993 I've ever driven. Your money would be better spent sticking it on a dyno, seriously. Isn't that what we care about anyway?

Some here say that leakdown tests are too inconsistent/inaccurate to be useful. Do searches and come to your own conclusions on that.

chris walrod

Compression test at a minimum. A leak down will also be valuable. Either test should shed light on how well that sixer seals, combustion wise. A car can have 2 miles on it with a downshift overrev and have bent valves. FWIW..

Besides, the lower set of spark plugs are easy to get to, allowing relatively quick testing. Shouldnt cost a whole lot, generally under $500.

ventoGT

OtherEric--what was your "dog" putting out at the dyno versus the strong car out of curiosity? Sorry to hijack the thread, just interested to know.

Father of 3

Where are you doing your PPI at? I'm in the Pasadena area as well. If there is a good shop in the area, that would be great.

drnd

Doing PPI in New York( Prestige Porsche). I live in Pasadena. Quote for PPI $230, leakdown test $345, compression ?. Does that sound high to you guys? PPI tommorrow so not much I can do now. I have a rennlister looking at the car on Saturday. Should I do compression or leakdown, neither, or both? Don't have much time to decide.
Car is 97 993 C2S, 25,000 miles.

Father of 3

That seems like alot. I think I did a PPI at TRE for $450 that included a leakdown and compression test. I would personally have the tests done if everything else in the deal checks out. If the car is otherwise clean, has the right color combo, right options etc., I would do.

drnd

Does seem high, but buying car out of state. PPI at the porsche dealer. However right now I don't have other options since it is scheduled for tommorrow. I just have to bite the bullet. For peace of mind that the car is in top shape. It's better than buying a car and finding problems out later.

Dr. No

I would do both tests, but would try to go to a reputable independent shop. Seems high to me too, I just paid $230 for a PPI including compression/leakdown tests - and it bought great peace of mind.

trojanman

That $230 should at least include the compression test... I've been told that if the compression test shows all cylinders hold pressure within 5-10% of each other, you may be able to blow off the leakdown? Someone with more experience chime in please.