To rebuild or not to rebuild
07-06-2009, 10:11 AM
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To rebuild or not to rebuild
I don't post very often on here, but I do read almost everything and I was hoping for some insight from people who've had their engines rebuilt. I will try not to be too long-winded so please bear with me:
I just got back last week from another 1600 mile round trip through the back country lanes of France with some like-minded friends. Three 964's, an AudiTT and an Aston Martin Vantage. (We do this once/twice a year). As usual it was great fun and the car was as ever, superb. The car has done 110k miles and I can pull top speed in the car no problem, it revs beautifully, oil pressure is good, oil temp stays cool. It NEVER smokes, even on overrun, acceleration etc.. the car does not smoke at all through the exhaust. It does however leak a bit.
It has leaked like this for the 5 years I have owned it, not enough to affect oil levels, not really any noticeable drips on the road ( very few occasionally) and so on but after a long run, especially at high speeds I do get a film of oil deposited on my rear bumper and halfway up the engine cover. As I say, it's always been like this but I've lived with it as the engine has always performed so well. The engine bay itself is dry and oil-free so the leaks are coming from low down, then on high speed runs the airflow must push the oil out the back of the car and up onto the rear.
This year it seemed to me that my oil leak has become slightly worse. The deposits on the rear of the car are a bit heavier and I noticed it seemed to use slightly more oil this year. Nothing major, but noticeable nonetheless.
I spoke to JZM last week regarding top-end or full engine rebuilds and got some very useful info regarding that and will probably bite the bullet some time later this year. Finally to my question:
I love this car, will be keeping it for a long time yet so ultimately I will get the engine done in any case - and I will almost certainly go for the full rebuild rather than just the top-end. However, the chap I spoke to at JZM was absolutely adamant that at 110k miles the car would be 30-40bhp down on power! Also, that it would definitely be sucking oil through the valves and burning it through the exhaust. I told him the car never smokes but he insisted that it would, but I may not be able to see it at 100mph-plus on overunn. However my driving friends have all confirmed NO smoke comes out of the back of my car at all, at any speed, and additionally the exhaust pipe is oil-free and dry so it is NOT coming through the exhaust.
Firstly, my car keeps up easily with the other 2 964's, and even holds it's own against the Aston so how can it be that down on power just because it's done 110k miles?
Secondly, from those of you who have had your engines rebuilt did you notice a significant performance change? It seems a lot of money to spend just to cure an oil leak but if there are other significant benefits then fine.
As said, I'll be doing it at some point anyway but the longer I can put it off the better (for my wallet) but would love to hear the opinions of you guys who offer such fantastic knowledge and insight on so many threads on this forum. Thanks in advance....
Best
Alex
PS, my baby looks like this:
I just got back last week from another 1600 mile round trip through the back country lanes of France with some like-minded friends. Three 964's, an AudiTT and an Aston Martin Vantage. (We do this once/twice a year). As usual it was great fun and the car was as ever, superb. The car has done 110k miles and I can pull top speed in the car no problem, it revs beautifully, oil pressure is good, oil temp stays cool. It NEVER smokes, even on overrun, acceleration etc.. the car does not smoke at all through the exhaust. It does however leak a bit.
It has leaked like this for the 5 years I have owned it, not enough to affect oil levels, not really any noticeable drips on the road ( very few occasionally) and so on but after a long run, especially at high speeds I do get a film of oil deposited on my rear bumper and halfway up the engine cover. As I say, it's always been like this but I've lived with it as the engine has always performed so well. The engine bay itself is dry and oil-free so the leaks are coming from low down, then on high speed runs the airflow must push the oil out the back of the car and up onto the rear.
This year it seemed to me that my oil leak has become slightly worse. The deposits on the rear of the car are a bit heavier and I noticed it seemed to use slightly more oil this year. Nothing major, but noticeable nonetheless.
I spoke to JZM last week regarding top-end or full engine rebuilds and got some very useful info regarding that and will probably bite the bullet some time later this year. Finally to my question:
I love this car, will be keeping it for a long time yet so ultimately I will get the engine done in any case - and I will almost certainly go for the full rebuild rather than just the top-end. However, the chap I spoke to at JZM was absolutely adamant that at 110k miles the car would be 30-40bhp down on power! Also, that it would definitely be sucking oil through the valves and burning it through the exhaust. I told him the car never smokes but he insisted that it would, but I may not be able to see it at 100mph-plus on overunn. However my driving friends have all confirmed NO smoke comes out of the back of my car at all, at any speed, and additionally the exhaust pipe is oil-free and dry so it is NOT coming through the exhaust.
Firstly, my car keeps up easily with the other 2 964's, and even holds it's own against the Aston so how can it be that down on power just because it's done 110k miles?
Secondly, from those of you who have had your engines rebuilt did you notice a significant performance change? It seems a lot of money to spend just to cure an oil leak but if there are other significant benefits then fine.
As said, I'll be doing it at some point anyway but the longer I can put it off the better (for my wallet) but would love to hear the opinions of you guys who offer such fantastic knowledge and insight on so many threads on this forum. Thanks in advance....
Best
Alex
PS, my baby looks like this:
Last edited by Seight; 08-25-2010 at 05:38 AM.
07-06-2009, 10:49 AM
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Do you know the specifc source of the leak?
It is not normal to have oil on the bumper and rear engine cover.
I would do a bit more trouble shooting before committing to a rebuild.
As for losing 30-40hp, I think that depends on which components are out of tolerance and not the mileage. If they are so adamant about that then have them do before and after dyno runs to prove their point.
Regards,
JNeteler
It is not normal to have oil on the bumper and rear engine cover.
I would do a bit more trouble shooting before committing to a rebuild.
As for losing 30-40hp, I think that depends on which components are out of tolerance and not the mileage. If they are so adamant about that then have them do before and after dyno runs to prove their point.
Regards,
JNeteler
07-06-2009, 11:12 AM
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It's a slippery slope.. Do you run with the undertray, that stops a lot of the drips showing up. It's all the little 'extras' that make the bills add up - shot tinware, about £1000 to replace all of it and then two years later it's rusting so you take the engine out again and get it powder coated. And while you're in there, may as well put a new clutch in; may as well go for the lightweight flywheel then. Ker-ching ££££! If you're keeping up with your friends, and you can live with a few drips and a light coating of oil on the rear (might stop the tin rusting) then keep saving for the inevitable. My engine was hugely improved after a rebuild, but the fact that there were 5 broken studs didn't do much for it beforehand.
07-06-2009, 11:25 AM
#4
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You didn't mention if you have to add oil - that is how you determine if you are truly losing oil.
And the engine rebuilder may tell you things to encourage business, so take that advice recognizing the source!!
And the engine rebuilder may tell you things to encourage business, so take that advice recognizing the source!!
07-06-2009, 12:56 PM
#5
Nordschleife Master
Little, tiny black oil specks on the back cover & bumper, eh?
My car had the exact same thing (@ 87k? miles) when I bought it in '06.
My wrench 'spotted' this right off as he first walked up to the car. (They were invisible to me till he pointed them out.)
He put it to crapped-out camshaft end seals.
Replaced those seals (two green o-rings, 999.707.287.40) -- requiring no top end-off disassebly -- and all's been clean going on 20k miles.
Cost was approx. $400, as I recall, and mostly labor, as the two seals are trivially inexpensive.
An experienced wrench (or, Rennlist!) is a God-send when you're starting out.
My car had the exact same thing (@ 87k? miles) when I bought it in '06.
My wrench 'spotted' this right off as he first walked up to the car. (They were invisible to me till he pointed them out.)
He put it to crapped-out camshaft end seals.
Replaced those seals (two green o-rings, 999.707.287.40) -- requiring no top end-off disassebly -- and all's been clean going on 20k miles.
Cost was approx. $400, as I recall, and mostly labor, as the two seals are trivially inexpensive.
An experienced wrench (or, Rennlist!) is a God-send when you're starting out.
07-06-2009, 02:07 PM
#6
Nordschleife Master
The description of your car sounds very similar to mine albeit that mine's got more miles on it. Even though I've yet to have the opportunity to max it out, the way it pulls suggests that there's no reason that it won't. Like yours it's free revving, there's no smoke, it uses half a litre of oil every 3,000 miles or so and leaves a couple of small drips after a good run out (doesn't leak when cold). Yet I'm in the same dilemma. 
In my case the Porsche specialist recommends the engine be dropped to attend to the leaks which have been spotted on the barrels, power steering pump, camshaft nose seal (?), a leak on the gearbox and anywhere else that shows up when it's out. Also, to replace the difficult to access rusted tins (I've done the easy ones already). While they're honest enough to say that they might find other stuff when 'they're in there' that could cause extra expense, they agree that the engine feels very strong and it drives very well. So, unlike your specialist, they're not suggesting that all these engines require x an y and will be down on power when they get to a certain mileage.
I use the same specialist as Sten which is Unit 11 and he's right about the 'extras'.....I'd be very surprised if I would be able to resist having the LWF put in while they're at it.
p.s. I think there's a ghost in the back of your car!
In my case the Porsche specialist recommends the engine be dropped to attend to the leaks which have been spotted on the barrels, power steering pump, camshaft nose seal (?), a leak on the gearbox and anywhere else that shows up when it's out. Also, to replace the difficult to access rusted tins (I've done the easy ones already). While they're honest enough to say that they might find other stuff when 'they're in there' that could cause extra expense, they agree that the engine feels very strong and it drives very well. So, unlike your specialist, they're not suggesting that all these engines require x an y and will be down on power when they get to a certain mileage.
I use the same specialist as Sten which is Unit 11 and he's right about the 'extras'.....I'd be very surprised if I would be able to resist having the LWF put in while they're at it.
p.s. I think there's a ghost in the back of your car!
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07-06-2009, 03:39 PM
#8
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it sounds like your engine leak is dripping thru the rectangular holes in your engine tray...
when i purchased my 1990 964 4 months ago i was well aware of the oil leak in the engine... the leak is at the case bolt which is a common problem with the 89-91 engines...my car currently has 113K miles.
in the service records there is an invoice from the dealer at 50K miles explaining that the leak is from the casebolt and the car has been driven roughly 65K miles since the invoice...there is no noticeable oil on the rear bumper however there is a small drip that falls thru the rectangular opening in the engine tray which is quite annoying.
to remedy this, i have designed a wire mesh plate that is wrapped with an oil absorbent marine pad that is inserted between the engine and tray and catches the drip...it does not restrict the airflow to the engine and therefore has done the trick for now...the wire mesh keeps the pad from sagging or flapping on the edges.
i intend on fixing the leak by reviewing one of the posts that explained removing the bolt and using a high temperature silicone sealant which should seal it....i know this technique is used on 993 valve covers to stop them from leaking thru the valve cover bolts.
pehaps using a pad like this would help eliminate the oil drip problem for you until you are ready for a rebuild?
when i purchased my 1990 964 4 months ago i was well aware of the oil leak in the engine... the leak is at the case bolt which is a common problem with the 89-91 engines...my car currently has 113K miles.
in the service records there is an invoice from the dealer at 50K miles explaining that the leak is from the casebolt and the car has been driven roughly 65K miles since the invoice...there is no noticeable oil on the rear bumper however there is a small drip that falls thru the rectangular opening in the engine tray which is quite annoying.
to remedy this, i have designed a wire mesh plate that is wrapped with an oil absorbent marine pad that is inserted between the engine and tray and catches the drip...it does not restrict the airflow to the engine and therefore has done the trick for now...the wire mesh keeps the pad from sagging or flapping on the edges.
i intend on fixing the leak by reviewing one of the posts that explained removing the bolt and using a high temperature silicone sealant which should seal it....i know this technique is used on 993 valve covers to stop them from leaking thru the valve cover bolts.
pehaps using a pad like this would help eliminate the oil drip problem for you until you are ready for a rebuild?
07-07-2009, 03:08 AM
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As Garrett asked, what's your oil consumption? If it's acceptable (say less than a litre every 800-1000 miles), I wouldn't bother rebuilding just yet. I had both my 964s rebuilt due to oil leaks, the first one only after it got through a litre in 200 miles. Both of them had the oil over the rear bumper/engine cover and dripped a bit.
07-07-2009, 03:22 AM
#10
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Save your money for a bit. RSA #2 is pretty much like your car. So I clean the back end off at the end of every track day. No idea what oil consumption is as it gets driven 1-2K miles/yr., 95+% track use. Now at 136K miles of unknown history, it runs equal to any other car of similar wt/hp ratio I ever come across.
07-07-2009, 04:30 AM
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Thanks for all your responses. I see that several of you have or have had very similar symptoms to mine.
In answer to your questions:
The car uses approx a litre of oil every 2500 miles, so within acceptable limits I believe.
Yes, ha! The ghost in the back of the car is my 4yr old son, who by the way loves the car as much as I do. "Can we go in the Porss".
Yes I run with the undertray which does hide the oil drips I guess. I'm abosolutely sure that the oil drips are collecting on that undertray then blowing back in the airflow at speed.
I think I'll also take it to have it determined where the leak(s) is /are coming from. The thing is I don't want to spend hundreds on chasing leaks when that money can go towards the eventual, inevitable rebuild.
So I guess I'll wait and see how the rest of the year goes - with the car AND my wallet. thanks again....
In answer to your questions:
The car uses approx a litre of oil every 2500 miles, so within acceptable limits I believe.
Yes, ha! The ghost in the back of the car is my 4yr old son, who by the way loves the car as much as I do. "Can we go in the Porss".
Yes I run with the undertray which does hide the oil drips I guess. I'm abosolutely sure that the oil drips are collecting on that undertray then blowing back in the airflow at speed.
I think I'll also take it to have it determined where the leak(s) is /are coming from. The thing is I don't want to spend hundreds on chasing leaks when that money can go towards the eventual, inevitable rebuild.
So I guess I'll wait and see how the rest of the year goes - with the car AND my wallet. thanks again....
07-07-2009, 05:01 AM
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NO NO NO
If it aint broke don't fix it,is my motto,way too expensive to fix an oil leak
Stick it on a dyno and dis-prove your builder about the 20 to 30 bhp loss
Just run it till it stops,then rebuild 110k miles is not that much.
Cheers
Stick it on a dyno and dis-prove your builder about the 20 to 30 bhp loss
Just run it till it stops,then rebuild 110k miles is not that much.
Cheers
07-07-2009, 06:49 AM
#13
Burning Brakes
Hi Alex, i'd recommend waiting until it gets worse before biting the bullet. I remember passengering in your car around Brands a few years ago and the engine felt very strong. The amount of oil you are losing is not bad at all, i was losing about a litre per 500 miles when i decided to rebuild, plus my oil pressure was around 1 rather than 5! As for the 30-40hp loss that JZ mentioned, they said the exact same thing to me when i enquired about my rebuild! i didnt believe it, especially when i could run alongside a freshly rebuilt 964 without losing any ground. When i had mine done, sure it felt a bit stronger, but not 40hp stronger.
07-07-2009, 07:30 AM
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Engine rebuild
Dear Seight
I had the same questions as you are up against on rebuilding my engine. My 92 Carrera 2 ran great on the street and track. Two years ago planned to drop the engine to fix a few oil leaks and decided to perform a compression test first. Found 4 cylinders around 170# and two at 70# compression (120,000 miles). My oil pressure was at 4 bars so decided to tear it down and rebuild the top end. To make a long story short the exhaust valves were warped and had them rebuilt, new piston rings and all new seals. Replaced engine tin, new clutch and new plug wires. Runs like a champ now.
Dear Barney55 - I would not run the engine till it breaks. Once an engine starts any major break down and metal shavings start spreading your engine replacement price jumps considerabky. Metal shavings throughout the engine and cooling system causes you to replace all your oil cooling hoses and front radiator. Plus reusable engine componets like the oil pump and oil paths throughout the engine become risky metal entrapments. Rebuilding an engine is cheaper than purchasing a complete newer engine. Resales on a Porsche with it's original engine holds a better value. Do not wait till a catastrophic failure.
I recommend you have a compression test and leakdown test performed to determined best action steps: 1.) just seals, 2.) top end rebuild, 3.) or total rebuild.
As noted earlier it is a slippery slope once an engine is pulled - where do you stop spending. We all must cross that bridge and decide what is safe, what is preventative maint. and what is smart to change.
Definately drop your plastic engine undercover for inspection. Many times just a close inspection, shared photos on this website or clarified findings, you can get great advice from our fellow 964 owners. I have, and I thank the many kind and helpful Porsche enthusiast on this website.
Good luck Seight and we look forward to hearing your findings to help if we can
Best regards
Tall02
I had the same questions as you are up against on rebuilding my engine. My 92 Carrera 2 ran great on the street and track. Two years ago planned to drop the engine to fix a few oil leaks and decided to perform a compression test first. Found 4 cylinders around 170# and two at 70# compression (120,000 miles). My oil pressure was at 4 bars so decided to tear it down and rebuild the top end. To make a long story short the exhaust valves were warped and had them rebuilt, new piston rings and all new seals. Replaced engine tin, new clutch and new plug wires. Runs like a champ now.
Dear Barney55 - I would not run the engine till it breaks. Once an engine starts any major break down and metal shavings start spreading your engine replacement price jumps considerabky. Metal shavings throughout the engine and cooling system causes you to replace all your oil cooling hoses and front radiator. Plus reusable engine componets like the oil pump and oil paths throughout the engine become risky metal entrapments. Rebuilding an engine is cheaper than purchasing a complete newer engine. Resales on a Porsche with it's original engine holds a better value. Do not wait till a catastrophic failure.
I recommend you have a compression test and leakdown test performed to determined best action steps: 1.) just seals, 2.) top end rebuild, 3.) or total rebuild.
As noted earlier it is a slippery slope once an engine is pulled - where do you stop spending. We all must cross that bridge and decide what is safe, what is preventative maint. and what is smart to change.
Definately drop your plastic engine undercover for inspection. Many times just a close inspection, shared photos on this website or clarified findings, you can get great advice from our fellow 964 owners. I have, and I thank the many kind and helpful Porsche enthusiast on this website.
Good luck Seight and we look forward to hearing your findings to help if we can
Best regards
Tall02
07-07-2009, 07:59 AM
#15
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Replacing seals is not expensive. I have replaced the camshaft cover seals and the oil pressure sending unit seals. Both crumbled when I removed them. Engine is still dry.
Rebuilds are for engines down on compression, or suffering from wear enough to be making noise. Assuming there are no faults in fuel system, ignition system, and engine control system, the only way to lose 20 - 30 HP is to have compression loss. High-mileage engines with good compression are actually stronger - less friction loss because the parts are just a bit looser. Check compression. If that is fine, you will lose just a bit of power from the rebuild until the new engine breaks in.
The problem may be finding a mechanic willing to do seal replacement. Money on parts mark-up is much easier to earn than money earned by labour.
Rebuilds are for engines down on compression, or suffering from wear enough to be making noise. Assuming there are no faults in fuel system, ignition system, and engine control system, the only way to lose 20 - 30 HP is to have compression loss. High-mileage engines with good compression are actually stronger - less friction loss because the parts are just a bit looser. Check compression. If that is fine, you will lose just a bit of power from the rebuild until the new engine breaks in.
The problem may be finding a mechanic willing to do seal replacement. Money on parts mark-up is much easier to earn than money earned by labour.