1990 S4 Auto "Yearly Service"
03-05-2008, 07:45 AM
#1
Burning Brakes
Thread Starter
1990 S4 Auto "Yearly Service"
Yearly service just completed and all initially "A" OK.
Checked TB tension and spot on. Topped up oil in tensioner. Due for a TB chance again next year.
Checked TB alarm circuit, neat alarm in digital dash, first time that I seen it. Hope I never see it in anger.
Checked out engine cooling temperature system as temperature was slightly fluctuating around 87 to 93 degrees C. Checked all sensors and found resistance too high (outside of specifications) on cooling water sensor at bottom of radiator. Noted that at ambient temperature the resistance reading was infinity. Temperature needs to be greater than 79 degrees to get a ohm reading. Pulled plug and cleaned up pins and spade pieces. Reassemble with dialectic grease and when Bosch 2 pin plug re installed with wire circlip resistance was within specifications. Carried out a full fault finding exercise on fans and flap operation as per WSM. Test need to be carried out with engine at operating temperature. Need to test output circuits to the fans and required to purchase 100Kohm resistance in line with analogue ohm meter. Output voltage was as per specks at around 7 volts, All now working as designed. Purchase new thermostat gasket and cover "O" ring to be installed to finish off this system check. Car now operating around a steady 87degrees C.
Check flexplate forward clamp. No movement since I installed with Loctite nearly 2 years ago. Flexplate flat and no gap where I painted splines behind clamp. I tried to take a reading of the thrust bearing clearance, but I was working against the resistance of the flexplate. Approximate reading with magnetic base dial indicator 0.008 to 0.009 TPI. When last I took the reading with clamp loose I got 0.008 TPI. (I said I would check this out for Bill Ball as he believes that it is possible. Yes possible but you do not get the definative thunk as the crankshaft bumps up against the thrust bearing).
Auto Gear Box.
Checked out for leaks, slight leak at "O" ring nut from reservoir to sump pan. Nipped up and now tight. ATF level checked cold and hot, spot on.
Been haveing some problems with firm shifts, and I have been gradually moving the "T" piece on the modulating valve anti clockwise, but this was hit and miss approach.
I have a small pressure gauge and got on my lathe and turned up a nipple to fit in the modulation valve test point to take my pressure gauge. Run gear box up to temperature and found that the pressure was 92 psi or 6.34 bar and it should be 4.2 bar +/- 0.05 bar. Turned out the pressure adjustment around 5 turns and achieved around 61 psi or 4.2 bar as per specification. This pressure was measured with the vacuum line removed. I measured the vacuum at idle and 50 km/hr and the vacuum was minus 58 kpa or -0.58 bar which was considered excellent. When I took the motor RPMs up and back to idle the vacuum went from -0.4 bar to .64 bar.
Checked bowden cable for control pressure adjustment, OK as per specifications. Ther is no adjustment for the control pressure as it is controled by the modulation pressure.
Whilst I was in there I checked the starter interlock switch with a 4mm drill shank and checked the gear selector cable in "N", however, I needed to remover the acutating lever and when I reassembled I missed getting the starter lockout switch lever correctly into the hole in the acutating lever. To cut a long story short I broke the starter lockout lever inside the switch. I sourced a 2nd hand part and I drilled out the 5 rivets on the old switch to check out the internals. I maybe able to repair it at a later date using two pack epoxy glue with suitable wire strengthening pieces. Set up new switch in "N" as per the WSM and check gear change bowden cable, no adjustment necessary.
Previous during the service I checked the drive shaft boots and all appeared to be OK, however, when I was running the transmission in different gears, I noted that LHS outerboot, looking from the rear of the car, had a crack in one of the bellows. I replaced both inner and outer boots, cleaned and inspected CVs - excellent condition and boxed up drive shafts.
Took car for a run today and totally different car. Gear changes up and down the range "smooth as", When car up to temperature carried out a TC stall test, excellent result around the lower stall speed of 1750 rpm. I now need the check shift points, up and down, for the A28/16 transmission as per the WSM.
Total out-of-pocket expenses all up was around $250.00, not counting my retired time.
Tails 1990 928 S4 Auto
Checked TB tension and spot on. Topped up oil in tensioner. Due for a TB chance again next year.
Checked TB alarm circuit, neat alarm in digital dash, first time that I seen it. Hope I never see it in anger.
Checked out engine cooling temperature system as temperature was slightly fluctuating around 87 to 93 degrees C. Checked all sensors and found resistance too high (outside of specifications) on cooling water sensor at bottom of radiator. Noted that at ambient temperature the resistance reading was infinity. Temperature needs to be greater than 79 degrees to get a ohm reading. Pulled plug and cleaned up pins and spade pieces. Reassemble with dialectic grease and when Bosch 2 pin plug re installed with wire circlip resistance was within specifications. Carried out a full fault finding exercise on fans and flap operation as per WSM. Test need to be carried out with engine at operating temperature. Need to test output circuits to the fans and required to purchase 100Kohm resistance in line with analogue ohm meter. Output voltage was as per specks at around 7 volts, All now working as designed. Purchase new thermostat gasket and cover "O" ring to be installed to finish off this system check. Car now operating around a steady 87degrees C.
Check flexplate forward clamp. No movement since I installed with Loctite nearly 2 years ago. Flexplate flat and no gap where I painted splines behind clamp. I tried to take a reading of the thrust bearing clearance, but I was working against the resistance of the flexplate. Approximate reading with magnetic base dial indicator 0.008 to 0.009 TPI. When last I took the reading with clamp loose I got 0.008 TPI. (I said I would check this out for Bill Ball as he believes that it is possible. Yes possible but you do not get the definative thunk as the crankshaft bumps up against the thrust bearing).
Auto Gear Box.
Checked out for leaks, slight leak at "O" ring nut from reservoir to sump pan. Nipped up and now tight. ATF level checked cold and hot, spot on.
Been haveing some problems with firm shifts, and I have been gradually moving the "T" piece on the modulating valve anti clockwise, but this was hit and miss approach.
I have a small pressure gauge and got on my lathe and turned up a nipple to fit in the modulation valve test point to take my pressure gauge. Run gear box up to temperature and found that the pressure was 92 psi or 6.34 bar and it should be 4.2 bar +/- 0.05 bar. Turned out the pressure adjustment around 5 turns and achieved around 61 psi or 4.2 bar as per specification. This pressure was measured with the vacuum line removed. I measured the vacuum at idle and 50 km/hr and the vacuum was minus 58 kpa or -0.58 bar which was considered excellent. When I took the motor RPMs up and back to idle the vacuum went from -0.4 bar to .64 bar.
Checked bowden cable for control pressure adjustment, OK as per specifications. Ther is no adjustment for the control pressure as it is controled by the modulation pressure.
Whilst I was in there I checked the starter interlock switch with a 4mm drill shank and checked the gear selector cable in "N", however, I needed to remover the acutating lever and when I reassembled I missed getting the starter lockout switch lever correctly into the hole in the acutating lever. To cut a long story short I broke the starter lockout lever inside the switch. I sourced a 2nd hand part and I drilled out the 5 rivets on the old switch to check out the internals. I maybe able to repair it at a later date using two pack epoxy glue with suitable wire strengthening pieces. Set up new switch in "N" as per the WSM and check gear change bowden cable, no adjustment necessary.
Previous during the service I checked the drive shaft boots and all appeared to be OK, however, when I was running the transmission in different gears, I noted that LHS outerboot, looking from the rear of the car, had a crack in one of the bellows. I replaced both inner and outer boots, cleaned and inspected CVs - excellent condition and boxed up drive shafts.
Took car for a run today and totally different car. Gear changes up and down the range "smooth as", When car up to temperature carried out a TC stall test, excellent result around the lower stall speed of 1750 rpm. I now need the check shift points, up and down, for the A28/16 transmission as per the WSM.
Total out-of-pocket expenses all up was around $250.00, not counting my retired time.
Tails 1990 928 S4 Auto
