996 C4 3.4 burnt valve? Repair, rebuild or sell as is? - Page 1 - 911/Carrera GT - PistonHeads UK

I'd be grateful for some advice from those with experience of the economics of repairing early 996s. I have a 2000 996 Carrera 4 Tiptronic, now on approximately 150,000 miles. Services every year and oil changes every 6,000 miles. The car has an interesting engine history. From memory, Porsche replaced the original engine at around 70,000 miles, and that replacement engine subsequently received a full Hartech rebuild at around 80,000 miles. It has now developed another problem. There is no compression on cylinder 4 and the garage currently suspects a burnt exhaust valve. They say it can be repaired, but obviously until the engine is opened up it's difficult to know precisely what will be found and how large the bill might become. My question is really about the economics rather than the technical possibility of repairing it. I don't need the car and, realistically, I'm unlikely to use it very much even if I have it repaired. At 150,000 miles, and being a C4 Tiptronic rather than a particularly valuable 996 variant, I'm conscious that I could spend many thousands of pounds on the engine without adding anything like the same amount to the value of the car. My daughter has been using the car for the last 5 years. Oh, and she's getting married next year which means I need to watch the finances more than ever. On the other hand, it seems a shame to give up on an engine that has previously had a proper Hartech rebuild, particularly if the present problem really is confined to a burnt valve/head work rather than something more fundamental. So what would those who know these cars do? I'd particularly like to hear from anyone who has faced a similar zero-compression/burnt-valve problem on a 3.4. Once the engine was opened, did the repair remain relatively contained, or did it turn into a much larger rebuild? And economically, where would you draw the line? If it were a £3–5k repair I can see an argument for doing it. If opening it up turns it into a £10k+ job, I'm much less convinced, given the mileage and value of the car. The alternative is simply to sell it honestly as a complete 996 with a known engine fault and let somebody who wants the project take it on. I'm not trying to maximise every last pound from it. I'm really trying to work out whether repairing it is sensible or whether I'd simply be throwing good money after bad. Any experience of what a car like this is worth repaired versus as-is with the engine fault would also be very useful.

The conundrum is presumably further complicated by the fact that the car is currently drivable just a bit short on performance? Whereas if you strip it down and decide the rebuild cost is too high then it’s non drivable and just a box of bits? Which will have a big impact on its value and saleability. In my experience of Porsche engine rebuild costs your lower target of £3K is highly unlikely to be achieved unless you are doing most it’s the work yourself. £5K gives you a fighting chance as long as the job goes well and it’s straightforward. However at this age and mileage then mission creep is highly likely, coolant pipes, engine mounts, exhaust studs etc etc all ripe for replacement. I would hazard a guess at somewhere between £5K -£8K would see you home and hosed. This does feel like a lot of financial commitment for a high mileage, unfavored spec car. I guess it comes down to what you want out of it going forwards, are you emotionally attached to it, Is it a family heirloom or just a car on the fleet? I vote for get rid now. But that is easy for me to say

Totally agree with above Not a Porsche but paid more than the value of my Audi V8 for an unknown head problem this year. I love the car, it's in good condition and I knew lots of maintenance would be done. I had a very good garage with reliable ish quotes but as you say until they strip it it's unknown. I was relatively lucky but still it adds up with gaskets, machining, new gubbins etc So either find a very good specialist with good labour rates or as it sounds like you've had your fun and your heart is not in it then put it up for sale, eBay auction or similar

You could list it very factually with plenty of photos on eBay and similar as a project requiring some known work. Keep to to what you know and specification driven only to prevent comeback (ie ensure expectations are met but don’t over exceed or under represent the car and this will give you the market value). Once you have that figure you can work out if it’s worth investigating having the work done (to ultimately sell it?) or letting someone make an offer to take away. You just never know, there could be someone itching for your very specification / problem to buy and fix as their own project or to repair a sound but crashed donor. I’ve personally had the tips and manuals and while I’d prefer a manual, I know others that won’t have them for ease of driving and prefer the tips. The 4’s also make good all year round cars and have their fans, there’s a 911 for every driver and every driver can find a 911 for their needs. The market is volatile at the moment but you are speaking to someone who has the worlds biggest blind spot regards sunk cost fallacy, it sounds to me if you could wave a wand and the car be gone you wouldn’t be too upset…. The C4 996 is a good car and the engine fix could give the car near immortality in a collection as a fourth car that does low miles, see what you can get for it on 911.com or similar? Portiacraft do some decent engine rebuilds if you decide to keep the car and their costs are low despite being in North London. Let us know how you get on…

One possible option if you want to maintain a similar experience but minimise the risk of open ended expense on what is a high like car is to sell as is for whatever you can get and then buy a 986S. It’s largely the same car, but a really nice low mile one can still be had for sub £10k privately.

You should also get input on the 911uk, 996 sub-forum. Many informed and helpful owners there. The early 996 is one of the best ' driver's ' cars that Porsche ever made. I had one for 9 yrs (from 2002). 996 C4 tip. like yours.

996Type said: You could list it very factually with plenty of photos on eBay and similar as a project requiring some known work. Keep to to what you know and specification driven only to prevent comeback (ie ensure expectations are met but don t over exceed or under represent the car and this will give you the market value). Once you have that figure you can work out if it s worth investigating having the work done (to ultimately sell it?) or letting someone make an offer to take away. You just never know, there could be someone itching for your very specification / problem to buy and fix as their own project or to repair a sound but crashed donor. I ve personally had the tips and manuals and while I d prefer a manual, I know others that won t have them for ease of driving and prefer the tips. The 4 s also make good all year round cars and have their fans, there s a 911 for every driver and every driver can find a 911 for their needs. The market is volatile at the moment but you are speaking to someone who has the worlds biggest blind spot regards sunk cost fallacy, it sounds to me if you could wave a wand and the car be gone you wouldn t be too upset . The C4 996 is a good car and the engine fix could give the car near immortality in a collection as a fourth car that does low miles, see what you can get for it on 911.com or similar? Portiacraft do some decent engine rebuilds if you decide to keep the car and their costs are low despite being in North London. Let us know how you get on Many thanks for this very helpful reply. I will see if there are, or have recently been, any similar cases on Ebay. Portiacraft is a good shout. It's currently at a garage in Vauxhall but I don't know their appetite for engine repairs. I guess it'll be worth something like £11k once done. If it costs £5k to fix then any bids around £5k as it might be what I should aim for?

Purely playing devils advocate but do the insurance company know the condition? What if hypothetically it burnt up in an EV fire? Quite common these days

What's odd is that when the fault first occurred it logged P0301, P0302, P0304, P0305 and P0306 — misfires across both banks — do you think the zero compression on cylinder 4 accounts for all of those codes, or do we need to establish whether there was another underlying cause?

My daughter had been driving the car for about an hour without fault. The oil and coolant temps were fine. Then a CEL came on and the car started to misfire. She drove another 5 miles until she reached a service station on the dual carriageway, then called me. I knew that there was a cheap code reader in the passenger door pocket and she pulled the codes which showed misfires on all cylinders except number 3. No other fault codes were present.

Who knows. But if there's no compression in cylinder 4, then it's pretty likely there's something mechanical wrong with that cylinder. Unless there's something very basic gone wrong like a loose / missing spark plug.