94 GTS Comes Back Strong(er)
11-07-2016, 07:06 PM
#31
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Some blocks get discolored from the salt they use on roads, where it snows....those are a project.
__________________
greg brown
714 879 9072
GregBBRD@aol.com
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
greg brown
714 879 9072
GregBBRD@aol.com
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
11-08-2016, 10:21 AM
#32
Rennlist Member
11-10-2016, 12:08 PM
#33
This was Dave's desires, not mine. His car is magnificent and I think he wanted, everything to be "fresh" while the parts were still available.
In addition, anyone with an automatic GTS is brain dead not to have a supplementary driveshaft clamp on the torque tube shaft....and I personally believe that Constantine's clamp is the best....and either the engine or the transmission must be removed to install that clamp.
As it turned out, the head gasket deterioration was so severe, this was money extremely well spent. Once the head gaskets have extra holes "eaten" in them, the water takes a short cut and not much gets back to the rear cylinders, resulting in extremely accelerated piston/cylinder wear.
This is going to be a terrible problem with the 928 engines in the next 10-15 years (it's bad enough, right now)....and Porsche will run out of pistons....long before all of the engines with worn bores are repaired.
And while we were there, we could fix the terrible piston design of the GTS engines.
We did not remove the crankshaft or touch the main bearings.
In addition, anyone with an automatic GTS is brain dead not to have a supplementary driveshaft clamp on the torque tube shaft....and I personally believe that Constantine's clamp is the best....and either the engine or the transmission must be removed to install that clamp.
As it turned out, the head gasket deterioration was so severe, this was money extremely well spent. Once the head gaskets have extra holes "eaten" in them, the water takes a short cut and not much gets back to the rear cylinders, resulting in extremely accelerated piston/cylinder wear.
This is going to be a terrible problem with the 928 engines in the next 10-15 years (it's bad enough, right now)....and Porsche will run out of pistons....long before all of the engines with worn bores are repaired.
And while we were there, we could fix the terrible piston design of the GTS engines.
We did not remove the crankshaft or touch the main bearings.
Several years ago when I still owned my Zermat '93 GTS, a chipped valve precipitated doing both heads of my 50k mile 5 spd. For a car that had been maintained to factory specs (and beyond) by the first owner and through my ownership with Greg Brown, it was shocking to see the gasket and deck conditions.
I didn't care for the extra expense, but perhaps the dropped valve was a blessing in disguise to have Greg do the top end and avoid bigger problems.
By contrast, last year when we took '78 Minerva apart, the head gasket came out in one piece and the surfaces were perfect. And that was on a 38 year old car that had 168k miles and evidence indicates the head gaskets were original from the factory!
So is it a 16v vs 32 v motor difference, or was it just dumb luck (both good and bad?)
Great job on your GTS, they are truly wonderful cars (especially after the GB treatment!)
11-11-2016, 06:10 PM
#34
Drifting
By contrast, last year when we took '78 Minerva apart, the head gasket came out in one piece and the surfaces were perfect. And that was on a 38 year old car that had 168k miles and evidence indicates the head gaskets were original from the factory!
So is it a 16v vs 32 v motor difference, or was it just dumb luck (both good and bad?)
So is it a 16v vs 32 v motor difference, or was it just dumb luck (both good and bad?)
11-18-2016, 01:33 PM
#35
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Several years ago when I still owned my Zermat '93 GTS, a chipped valve precipitated doing both heads of my 50k mile 5 spd. For a car that had been maintained to factory specs (and beyond) by the first owner and through my ownership with Greg Brown, it was shocking to see the gasket and deck conditions.
I didn't care for the extra expense, but perhaps the dropped valve was a blessing in disguise to have Greg do the top end and avoid bigger problems.
By contrast, last year when we took '78 Minerva apart, the head gasket came out in one piece and the surfaces were perfect. And that was on a 38 year old car that had 168k miles and evidence indicates the head gaskets were original from the factory!
So is it a 16v vs 32 v motor difference, or was it just dumb luck (both good and bad?)
Great job on your GTS, they are truly wonderful cars (especially after the GB treatment!)
I didn't care for the extra expense, but perhaps the dropped valve was a blessing in disguise to have Greg do the top end and avoid bigger problems.
By contrast, last year when we took '78 Minerva apart, the head gasket came out in one piece and the surfaces were perfect. And that was on a 38 year old car that had 168k miles and evidence indicates the head gaskets were original from the factory!
So is it a 16v vs 32 v motor difference, or was it just dumb luck (both good and bad?)
Great job on your GTS, they are truly wonderful cars (especially after the GB treatment!)
In the seven or so years that I have been on this forum the biggest issue (that I have seen) when looking at one of these cars has been the timing belt and water pump. If there was a car for sale the first question was when were they changed last. If the answer was that they had been changed recently it seemed that everyone was comfortable that the car was "good to go". To me is seems that now there are additional considerations beyond the TB/WP when looking at acquiring one of these cars.
I feel a lot better now about spending a little extra for the work that was done.
03-10-2017, 02:20 PM
#37
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GTS oil consumption - reasons
Some notes to add to this thread after pulling apart approx 4 or 5 motors & some discussion w/others on the GTS (15+ years running it):
1. GTS Piston Holes: For sure- either the holes should be open, or grooves/channels added below the oil control ring to allow exit of the oil scraped by the oil control ring. It's a basic engine necessity. I just saw a youtube video of Toyota guys adding holes in addition to the huge stock channels for even better return flow to the crankcase.
2. Crankcase Pressure: We noticed that blasts of oil smoke would occur during rapid, hard acceleration in GTS's and we suspected elevated crankcase or head pressure (talking with Andy @ Scan auto, Vanc). Of course, the increased crankcase pressure moves more oil onto the cylinder walls and overloads the already marginal drain system. I ran an open cell foam donut stuffed in the filler neck and open-to-air oil cap on my GTS since I had it. ie the old school oil breather cap. That was the right idea for sure. & easy to implement!
3. Water quality is huge for engine longevity. Using super clean water in your cooling system and it will last forever. Any kind of mineral contamination is bad. The water in Japan for example is horrible. Our 1989S4 60K miles had head gaskets pooched by bad water. Anything we've taken apart in BC here has been extremely clean. ie no cooling system deposits or corrosion found.
1. GTS Piston Holes: For sure- either the holes should be open, or grooves/channels added below the oil control ring to allow exit of the oil scraped by the oil control ring. It's a basic engine necessity. I just saw a youtube video of Toyota guys adding holes in addition to the huge stock channels for even better return flow to the crankcase.
2. Crankcase Pressure: We noticed that blasts of oil smoke would occur during rapid, hard acceleration in GTS's and we suspected elevated crankcase or head pressure (talking with Andy @ Scan auto, Vanc). Of course, the increased crankcase pressure moves more oil onto the cylinder walls and overloads the already marginal drain system. I ran an open cell foam donut stuffed in the filler neck and open-to-air oil cap on my GTS since I had it. ie the old school oil breather cap. That was the right idea for sure. & easy to implement!
3. Water quality is huge for engine longevity. Using super clean water in your cooling system and it will last forever. Any kind of mineral contamination is bad. The water in Japan for example is horrible. Our 1989S4 60K miles had head gaskets pooched by bad water. Anything we've taken apart in BC here has been extremely clean. ie no cooling system deposits or corrosion found.
03-11-2017, 12:17 AM
#38
Rennlist Member
perhaps I missed it...........were new piston rings installed?
would a likedown test determine head gasket health? I suspect the only true would be to pull the heads.
would a likedown test determine head gasket health? I suspect the only true would be to pull the heads.
Last edited by the flyin' scotsman; 03-11-2017 at 12:04 PM.
03-11-2017, 04:25 AM
#39
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I reckon it all boills down to user profile. Short journeys, infrequent use = low mileage. The condition of the coolant is time dependent. The glycol will probably last forever but that is relatively inert [or so I suspect?]. The anti corrosion chemical package is finite and once that is exhausted the gremlins come out to play. Owners who do not use their cars much think they are protected but after some finite period they are not.
If the coolant is not being circulated I suspect that the concentration of anti corrosion chemicals possibly depletes in more vulnerable areas like the top of the cylinder/head interface and the corrosion gremlins have a field day. Over here in the days when the 928 was quite common in Porsche circles, I have seen quite a few engines with the top of the cylinder eaten away on the water jacket side. All low milers probably just sat there hardly used.
After I lost my late 90 S4 some 12 years ago we pulled the motor [and anything else of value that was not bent]. Having seen such corrosion related damage I wanted to inspect the motor carefully to see if it was viable. To my relief when we pulled the heads the cylinder walls and the heads themselves were immaculate. My car was used regularly and well maintained with regular coolant changes and inbetween a fresh bottle of water wetter with its chemical protection package which I consider just as important as the cooling performance benefit.
The performance indicator for coolant condition appears to be pH- too acidic and off go the gremlins. Change the coolant regularly [every two years in my case] and hopefully you are in a good shape. That being said when I inspected my motor I did find some corrosion but on the inboard side of the outer casing wall. Why this happened I have no clue whatsoever- we dressed it down and coated it with a two pack expoxy metal to hopefully protect the surface from any further degradation.
Thus every two years I do a major inspection and maintenance programme and a less rigourous check every other year with an oil change every year irrespective of mileage.
I try to break down the maintenance items into probability of failure time or likely wear replacement intervals of 1, 2, 4, 10 & 20 years- based on either personal 928 experience [18 years] or the valuable info picked up on this list.
Thus:
1 year- oil, filter [if more than 4k miles covered]
2 year- oil filter [if low annual miles covered]
4 year- timing belt, ATF, ATF filter [if more than 20k miles covered], drive belts, cooling hoses, spark plugs, tyres [shot after 4 years of heat exposure].
8 to 10 years- water pump, idler bearing, fuel pressure controller/dampers, ignition leads, both fuel pumps, axle shaft gaiters, steering gaiters, track rods, ball joint boots, brake pads/discs, diff lube, Cam chain tensioner pads [not so sure on this one?], hand brake shoes, cam cover gaskets. A/C compressor/solenoid [rebuild], dist caps/rotors.
20 years- engine harnesses, CV joints, temp2 sensor, suspension bushes, wheel bearings. LH, MAF.
Clearly it is not quite as "black and white" as that and doubtless I have missed a few items but that is how I tend to plan for things with a relatively low annual mileage.
The rest I deal with as and when.
Rgds
Fred
If the coolant is not being circulated I suspect that the concentration of anti corrosion chemicals possibly depletes in more vulnerable areas like the top of the cylinder/head interface and the corrosion gremlins have a field day. Over here in the days when the 928 was quite common in Porsche circles, I have seen quite a few engines with the top of the cylinder eaten away on the water jacket side. All low milers probably just sat there hardly used.
After I lost my late 90 S4 some 12 years ago we pulled the motor [and anything else of value that was not bent]. Having seen such corrosion related damage I wanted to inspect the motor carefully to see if it was viable. To my relief when we pulled the heads the cylinder walls and the heads themselves were immaculate. My car was used regularly and well maintained with regular coolant changes and inbetween a fresh bottle of water wetter with its chemical protection package which I consider just as important as the cooling performance benefit.
The performance indicator for coolant condition appears to be pH- too acidic and off go the gremlins. Change the coolant regularly [every two years in my case] and hopefully you are in a good shape. That being said when I inspected my motor I did find some corrosion but on the inboard side of the outer casing wall. Why this happened I have no clue whatsoever- we dressed it down and coated it with a two pack expoxy metal to hopefully protect the surface from any further degradation.
Thus every two years I do a major inspection and maintenance programme and a less rigourous check every other year with an oil change every year irrespective of mileage.
I try to break down the maintenance items into probability of failure time or likely wear replacement intervals of 1, 2, 4, 10 & 20 years- based on either personal 928 experience [18 years] or the valuable info picked up on this list.
Thus:
1 year- oil, filter [if more than 4k miles covered]
2 year- oil filter [if low annual miles covered]
4 year- timing belt, ATF, ATF filter [if more than 20k miles covered], drive belts, cooling hoses, spark plugs, tyres [shot after 4 years of heat exposure].
8 to 10 years- water pump, idler bearing, fuel pressure controller/dampers, ignition leads, both fuel pumps, axle shaft gaiters, steering gaiters, track rods, ball joint boots, brake pads/discs, diff lube, Cam chain tensioner pads [not so sure on this one?], hand brake shoes, cam cover gaskets. A/C compressor/solenoid [rebuild], dist caps/rotors.
20 years- engine harnesses, CV joints, temp2 sensor, suspension bushes, wheel bearings. LH, MAF.
Clearly it is not quite as "black and white" as that and doubtless I have missed a few items but that is how I tend to plan for things with a relatively low annual mileage.
The rest I deal with as and when.
Rgds
Fred
03-11-2017, 11:52 AM
#40
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A leak down test won't show a head gasket deterioration issue, until water is running into the cylinder.
03-11-2017, 12:09 PM
#41
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I had thought you would use new rings and that the cyl. heads need to be removed to verify the gasket condition but of course by then the condition becomes more a point of interest and discussion as they would always be replaced at that stage.
Last edited by the flyin' scotsman; 03-11-2017 at 12:39 PM.
03-11-2017, 04:53 PM
#42
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As it turned out, the rings worked fine.
03-08-2018, 01:55 AM
#43
Three Wheelin'
Just read through this entire thread along with the additional one regarding the drilling of the pistons. What a great read... After the removal of my motor, maybe I will investigate the head gaskets as well... seems like I should with a 100k on the clock.
03-08-2018, 01:24 PM
#44
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I was on the "receiving end" of your previous car. I do know that the engine in that car was "rebuilt" by someone just before you bought it. That work was some of the worst I've ever seen. I've had that engine out twice, since you sold it, to repair various absurd problems......and it still leaks oil from a couple of crazy places.
Whoever worked on that engine should not be allowed to own metric tools.....
Hopefully, your new one will fair better....
Last edited by GregBBRD; 03-08-2018 at 04:38 PM.
