After Flexplate adjustment, smoke from the front of the engine. Related???
03-13-2010, 01:37 AM
#1
Rennlist Member
Thread Starter
After Flexplate adjustment, smoke from the front of the engine. Related???
Hi all,
I just made my first flexplate adjustment (on the 93 GTS/auto) and when I started it, I had a little smoke coming from the front of the engine--it had the smell of burnt rubber or plastic(?) There was also a periodic weird sound that I could best describe as rocks rattling in a can. I immediately turned off the engine and tried to see where it was coming from but I couldn't find it. Could it be related?
I adjusted the pinch bolt by loosening it and letting it slide back on the splines. I did not do move the flexplate back and forth (preload) as described on some Relist pages. I then retightened the pinch bolt and put locktite on it. Buttoned everything up and... here I am.
I don't want to run it for fear of making something worse. But, for lack of anything else to do, I'm now taking a look at the timing belt and check its tension. Any other suggestions??? For all I know, it could just be the alternator going out or something, but I don't want to take any chances.
Thank you / Bruce
I just made my first flexplate adjustment (on the 93 GTS/auto) and when I started it, I had a little smoke coming from the front of the engine--it had the smell of burnt rubber or plastic(?) There was also a periodic weird sound that I could best describe as rocks rattling in a can. I immediately turned off the engine and tried to see where it was coming from but I couldn't find it. Could it be related?
I adjusted the pinch bolt by loosening it and letting it slide back on the splines. I did not do move the flexplate back and forth (preload) as described on some Relist pages. I then retightened the pinch bolt and put locktite on it. Buttoned everything up and... here I am.
I don't want to run it for fear of making something worse. But, for lack of anything else to do, I'm now taking a look at the timing belt and check its tension. Any other suggestions??? For all I know, it could just be the alternator going out or something, but I don't want to take any chances.
Thank you / Bruce
03-13-2010, 01:43 AM
#2
Nordschleife Master
Pull of the timing belt covers and inspect the timing belt before running it again.
The warning light on the dash has a 3 min delay so it is useless in this instance.
The warning light on the dash has a 3 min delay so it is useless in this instance.
03-13-2010, 03:52 AM
#3
Bruce.
The only effect of the flexplate has on the front of the engine is the clearance between the thrust bearing and the crankshaft thrust faces causing it to shuttle back and forwards.
As the flexplate migrates, the thrust bearing moves from the forward face to the aft face and when migration of the flexplate clamp takes place the majority of the time the thrust is taken by the aft face of the thrust bearing caused by the pre load from the flexplate.
It is unfortunate that you did not check the bump clearance of the thrust bearing (fore and aft) to see weather the thrust clearance is within specification. If there is wear on the aft face of the thrust bearing it will gradually move the ancillary "V" driver pulleys on the crankshaft out of alignment with the driven pulleys on the A/C compressor, the alternator, the power steering pump and the air pump. However, as the timing belt driver sprocket is in axial alignment with the crankshaft so the timing belt will track forward or aft into the correct plain alignment if all the idler and tension rollers are in axial alignment with the crankshaft.
This small movement should not have any effect on the "V" pulleys, as they can take some misalignment, however there wear rate on the "V" belts will increase marginally, unnless there is excessive clearance between the thrust bearing and the crankshaft thrust faces. When all is said and done there should not be any smoke of rubber smells issuing from the front of the engine unless something is fouiling the belts or the electrical cables or there is an electrical short.
I would recommend that you check the bump clearance of the thrust bearing before you do anything further, to get this major item out of the way to verify that the thrust bearing is OK.
I would also check the timing belt by rotating the crankshaft by hand and have someone check the condition to the timing belt through the dudy suction holes at the top of the timing belt covers. If there is any out of alignment or damage to the timing belt, remove the covers for a full inspection of the timing belt.
Before boxing up check the tension of the timing belt and also check the condition of the tensioner, top it up with engine oil and check for leaks from the rubber boot etc. Also check the horizontal alignment of the timing belt, this is done by checking where the belt is running on the crankshaft and the cam driving sprockets. The belt should be tracking around the middle to the sprockets right through all sprockets, tensioner, guide pulleys and lube oil pump.
Any out of alignment should be rectified. On weak point is the fulcrum pin on the tensioner.
WYAIT check each ancillary "V" belt for condition, cracking or fraying and tension. Also check for any wear on stationary part from the "V" belts and check for any shorting with any of the electric wiring in this area.
If all is OK, when you are boxing up ensure that the electrical wire connection for the timing belt alarm is installed correctly.
You may wish to check the alarm system by undertaking a test as laid out in one to Porsche Technical Bulleting that is supplied with Jim Moorehouse's Technical CD.
If I have missed anything or made a mistake I'm sure it will be picked up and posted.
Tails 1990 928S4 Auto
The only effect of the flexplate has on the front of the engine is the clearance between the thrust bearing and the crankshaft thrust faces causing it to shuttle back and forwards.
As the flexplate migrates, the thrust bearing moves from the forward face to the aft face and when migration of the flexplate clamp takes place the majority of the time the thrust is taken by the aft face of the thrust bearing caused by the pre load from the flexplate.
It is unfortunate that you did not check the bump clearance of the thrust bearing (fore and aft) to see weather the thrust clearance is within specification. If there is wear on the aft face of the thrust bearing it will gradually move the ancillary "V" driver pulleys on the crankshaft out of alignment with the driven pulleys on the A/C compressor, the alternator, the power steering pump and the air pump. However, as the timing belt driver sprocket is in axial alignment with the crankshaft so the timing belt will track forward or aft into the correct plain alignment if all the idler and tension rollers are in axial alignment with the crankshaft.
This small movement should not have any effect on the "V" pulleys, as they can take some misalignment, however there wear rate on the "V" belts will increase marginally, unnless there is excessive clearance between the thrust bearing and the crankshaft thrust faces. When all is said and done there should not be any smoke of rubber smells issuing from the front of the engine unless something is fouiling the belts or the electrical cables or there is an electrical short.
I would recommend that you check the bump clearance of the thrust bearing before you do anything further, to get this major item out of the way to verify that the thrust bearing is OK.
I would also check the timing belt by rotating the crankshaft by hand and have someone check the condition to the timing belt through the dudy suction holes at the top of the timing belt covers. If there is any out of alignment or damage to the timing belt, remove the covers for a full inspection of the timing belt.
Before boxing up check the tension of the timing belt and also check the condition of the tensioner, top it up with engine oil and check for leaks from the rubber boot etc. Also check the horizontal alignment of the timing belt, this is done by checking where the belt is running on the crankshaft and the cam driving sprockets. The belt should be tracking around the middle to the sprockets right through all sprockets, tensioner, guide pulleys and lube oil pump.
Any out of alignment should be rectified. On weak point is the fulcrum pin on the tensioner.
WYAIT check each ancillary "V" belt for condition, cracking or fraying and tension. Also check for any wear on stationary part from the "V" belts and check for any shorting with any of the electric wiring in this area.
If all is OK, when you are boxing up ensure that the electrical wire connection for the timing belt alarm is installed correctly.
You may wish to check the alarm system by undertaking a test as laid out in one to Porsche Technical Bulleting that is supplied with Jim Moorehouse's Technical CD.
If I have missed anything or made a mistake I'm sure it will be picked up and posted.
Tails 1990 928S4 Auto
03-13-2010, 04:19 AM
#4
Rennlist Member
If the you lowered the pipes, could you have dropped something into the exhaust? I lost a pair of nipper pliers in one once. I was embarrassed, but got over it. Doesn't explain smoke, though.
03-13-2010, 09:05 AM
#5
Rennlist Member
Thread Starter
03-13-2010, 09:26 AM
#6
Rennlist Member
Thread Starter
It is unfortunate that you did not check the bump clearance of the thrust bearing (fore and aft) to see weather the thrust clearance is within specification. If there is wear on the aft face of the thrust bearing it will gradually move the ancillary "V" driver pulleys on the crankshaft out of alignment with the driven pulleys on the A/C compressor, the alternator, the power steering pump and the air pump. However, as the timing belt driver sprocket is in axial alignment with the crankshaft so the timing belt will track forward or aft into the correct plain alignment if all the idler and tension rollers are in axial alignment with the crankshaft.
I checked the condition of the other belts--tension and condition seemed okay, but more to come.
Landseer – I don’t think I left anything in there, but ya never know. I travel all the time so it’s rare I can start a project and finish it at one time. When I put it together, I used shorter bolts for the 2 rear bolts on the flywheel cover. There should be just enough clearance now so I don’t have to drop the exhaust to remove the cover.
And BTW – This is the first time I’ve used the Porken lift bars--they are the shiznit!
Thanks again / Bruce
03-13-2010, 09:42 AM
#7
Burning Brakes
I agree with all above about checking the crank shaft end play (bump clearance).
How long had it been since the engine was run previously? If the end clearance is in specification and the timing belt looks good you still have the question about what happened. Noise and smoke are generally not signs of good things but they may not be related to each other. Any oil leaks in the front area of the engine, say around the oil fill? Not sure about the newer engines but my 85 has a deep pcket on the right side of the coolant bridge center connection that will fill with oil - the jacking of the car to work on the clamp may have caused oil to dripple out of that area onto the engine resulting in the smoke. The noise sounds like something maybe laying on the engine or in one of the exhaust pipes, any chance a squirrel thought the open end of the exhaust pipe was a great place to put nuts for later?
Please let us know what you find.
How long had it been since the engine was run previously? If the end clearance is in specification and the timing belt looks good you still have the question about what happened. Noise and smoke are generally not signs of good things but they may not be related to each other. Any oil leaks in the front area of the engine, say around the oil fill? Not sure about the newer engines but my 85 has a deep pcket on the right side of the coolant bridge center connection that will fill with oil - the jacking of the car to work on the clamp may have caused oil to dripple out of that area onto the engine resulting in the smoke. The noise sounds like something maybe laying on the engine or in one of the exhaust pipes, any chance a squirrel thought the open end of the exhaust pipe was a great place to put nuts for later?
Please let us know what you find.
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03-13-2010, 10:08 AM
#8
Team Owner
dont remove the fan shroud on the GTS just take off the top hose.
