New 931 owner questions
11-01-2015, 12:03 AM
#1
Three Wheelin'
Thread Starter
New 931 owner questions
Recently bought a light green (PO repainted with a metallic BRG color) 80' 931 and have a few questions that i'm sure is common knowledge and for which most have solutions already.
-was a plastic cowl (bottom of windshield) added in later years to improve drainage? i have not secured my storage/garage unit to store it yet and it rained for a whole day, ton of water leaked through an area just behind the (main) blower motor, but i then realized i left it on max defrost because the main BM doesn't work, so the trap door was open the whole time, was it just this?
-dash.. mine has the most terribly warped dash i've seen in an old car, do aftermarket fibreglass/ABS repro's exist?
-transmission rebuild, what is the most common mode of failure for 1st gear not including the fact that it wears the fastest in any transmission, do adjustments need to be made that most owners don't care to read up on that makes them wear out prematurely? i know OB 928's had weak synchro's, is it the same on these?
-oil burning, reading up on this it seems like these old motors were designed with technology and tolerances that require a more traditional thicker oil to be used, and that much of the reason they burn oil or otherwise leak is that people don't use the correct weight, i just did an oil change with Castrol 20W50 and it seems to have improved the burning, however for some reason i found the hot side exducer housing to center housing nuts to be loose, not sure what someone was thinking, and it burns consistently in all conditions so it must be leaking from the center housing around the O-ring into the turbine housing
Point me in the right direction! Thank you!
-was a plastic cowl (bottom of windshield) added in later years to improve drainage? i have not secured my storage/garage unit to store it yet and it rained for a whole day, ton of water leaked through an area just behind the (main) blower motor, but i then realized i left it on max defrost because the main BM doesn't work, so the trap door was open the whole time, was it just this?
-dash.. mine has the most terribly warped dash i've seen in an old car, do aftermarket fibreglass/ABS repro's exist?
-transmission rebuild, what is the most common mode of failure for 1st gear not including the fact that it wears the fastest in any transmission, do adjustments need to be made that most owners don't care to read up on that makes them wear out prematurely? i know OB 928's had weak synchro's, is it the same on these?
-oil burning, reading up on this it seems like these old motors were designed with technology and tolerances that require a more traditional thicker oil to be used, and that much of the reason they burn oil or otherwise leak is that people don't use the correct weight, i just did an oil change with Castrol 20W50 and it seems to have improved the burning, however for some reason i found the hot side exducer housing to center housing nuts to be loose, not sure what someone was thinking, and it burns consistently in all conditions so it must be leaking from the center housing around the O-ring into the turbine housing
Point me in the right direction! Thank you!
11-10-2015, 03:08 PM
#3
Pro
Recently bought a light green (PO repainted with a metallic BRG color) 80' 931
Nice
ton of water leaked through an area just behind the (main) blower motor
Check for rust under your battery area, very common to rust due to batery acid and leaks into the interior..
-dash.. mine has the most terribly warped dash i've seen in an old car, do aftermarket fibreglass/ABS repro's exist?
Dash caps, like a fitted plastic cover, and dash mats, fitted carpet cover exist..
-transmission rebuild, what is the most common mode of failure for 1st gear not including the fact that it wears the fastest in any transmission.
Very common to have 1st and 2nd gear syncro issues on the g31 transmission. I hear that worn shifter coupler bushings can exagerate the problem. Pretty much all of these boxes need to be rebuilt due to weak synchros but they are the strongest of the 924-968 transmissions as far as power delivery capabilities. Check if yours has LSD either by lifting the wheels and testing, or looking at the # which will end in /12 for LSD. These boxes with LSD are quite sought after.
The dogleg 5 speed in the S1 931's (G31) has the best weight distribution charactoristics, most of the weight infront of the rear wheels. It is very very strong as far as maximum power capability, it is a Porsche 911 (915) box, but it has synchro issues, always has..
-oil burning, reading up on this it seems like these old motors were designed with technology and tolerances that require a more traditional thicker oil to be used,
Yes heavy oil and make sure it has a lot of zinc/zddp, maybe go with an additive, for solid lifters, flat tappets..
and that much of the reason they burn oil or otherwise leak is that people don't use the correct weight,
I don't know about that, but you will get increased cam/bucket wear if you don't have enough zinc. Most oils nowadays don't have as much zinc because its hard on cats.
i just did an oil change with Castrol 20W50 and it seems to have improved the burning,
Probably need a zinc additive to protect your cam with that..
however for some reason i found the hot side exducer housing to center housing nuts to be loose, not sure what someone was thinking,
You mean the bearing housing to turbine housing connection loose I imagine, yeah that sucks. Hope your turbine didn't contact the turbine housing..
and it burns consistently in all conditions so it must be leaking from the center housing around the O-ring into the turbine housing
There is no such O-ring, but yes the turbo may very well be leaking oil and it getting burnt. Very likely..
Without getting too technical it sounds like you are going to need your turbo rebuilt..
Point me in the right direction! Thank you!
924board.org is a good direction..
Nice
ton of water leaked through an area just behind the (main) blower motor
Check for rust under your battery area, very common to rust due to batery acid and leaks into the interior..
-dash.. mine has the most terribly warped dash i've seen in an old car, do aftermarket fibreglass/ABS repro's exist?
Dash caps, like a fitted plastic cover, and dash mats, fitted carpet cover exist..
-transmission rebuild, what is the most common mode of failure for 1st gear not including the fact that it wears the fastest in any transmission.
Very common to have 1st and 2nd gear syncro issues on the g31 transmission. I hear that worn shifter coupler bushings can exagerate the problem. Pretty much all of these boxes need to be rebuilt due to weak synchros but they are the strongest of the 924-968 transmissions as far as power delivery capabilities. Check if yours has LSD either by lifting the wheels and testing, or looking at the # which will end in /12 for LSD. These boxes with LSD are quite sought after.
The dogleg 5 speed in the S1 931's (G31) has the best weight distribution charactoristics, most of the weight infront of the rear wheels. It is very very strong as far as maximum power capability, it is a Porsche 911 (915) box, but it has synchro issues, always has..
-oil burning, reading up on this it seems like these old motors were designed with technology and tolerances that require a more traditional thicker oil to be used,
Yes heavy oil and make sure it has a lot of zinc/zddp, maybe go with an additive, for solid lifters, flat tappets..
and that much of the reason they burn oil or otherwise leak is that people don't use the correct weight,
I don't know about that, but you will get increased cam/bucket wear if you don't have enough zinc. Most oils nowadays don't have as much zinc because its hard on cats.
i just did an oil change with Castrol 20W50 and it seems to have improved the burning,
Probably need a zinc additive to protect your cam with that..
however for some reason i found the hot side exducer housing to center housing nuts to be loose, not sure what someone was thinking,
You mean the bearing housing to turbine housing connection loose I imagine, yeah that sucks. Hope your turbine didn't contact the turbine housing..
and it burns consistently in all conditions so it must be leaking from the center housing around the O-ring into the turbine housing
There is no such O-ring, but yes the turbo may very well be leaking oil and it getting burnt. Very likely..
Without getting too technical it sounds like you are going to need your turbo rebuilt..
Point me in the right direction! Thank you!
924board.org is a good direction..
It goes turbine/shaft-hot side rings-hot side bearing-cold side bearing-thrust bearing-cold side piston rings.
There is an O-ring on the cold side in between the bearing housing and the cold side backing plate but none on the hot side.
If the turbo cold side is leaking oil it goes through your intake and gets burnt in your cylinders.. Check for oil in your intake tract and spark plugs..
Excess oil in your intake and oily plugs = cold side turbo oil leak..
Oily plugs but no excess intake oil = engine problem like rings and valve seals etc.
Clean, non-excessive oil in the intake, clean plugs, but smoking exhaust = turbo hot side oil leak. The most common I believe. The oil pretty much gets leaked into your exhaust and gets burnt there..
These are very common occurances and it is very common to need to rebuild your turbo.. Hopefully with your turbine housing being loose your turbo hasn't suffered catastrophic damage beyond simple rebuild procedures.
11-16-2015, 02:46 AM
#4
Three Wheelin'
Thread Starter
Ah that's right, i must have been thinking about the cold side that does use an O-ring to create airtight seal. It is misaligned due to this but i doubt any turbine contact, though it does not spool very well so there could be i suppose. However the slight misalignment would probably cause spooling issues. No exhaust leaks though. Burns oil all the time, no bottom end/rotating assembly noise so it's probably just the turbo. I bet it started leaking and someone attempted to change it but said F-it.
Can't i just retrofit a K03/K04 onto this for simplicity? Even a K03 is still adequately sized for a 2.slow.
Whats the parts availability for trans? I haven't done much internal work with trannys so i'm not sure exactly what i'll need but i'd imagine just synchro sleeve and the gear?
Can't i just retrofit a K03/K04 onto this for simplicity? Even a K03 is still adequately sized for a 2.slow.
Whats the parts availability for trans? I haven't done much internal work with trannys so i'm not sure exactly what i'll need but i'd imagine just synchro sleeve and the gear?
11-19-2015, 09:18 AM
#5