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My unscientific babble about the chain of events Posted by SWEDECAR [Email]  (#112)  [Profile/Gallery]
(more from SWEDECAR) on Sun, 23 Jan 2005 11:58:59
In Reply to: how they came up with cca 4% have problems is the, question of the day, Sun, 23 Jan 2005 11:25:35 Members do not see ads below this line. - Help Keep This Site Online - Signup |
We know that the new cylinder head bolts installed from 1997 up until (at least) 2001 was of some inferior quality/strenght/coating and also undertorqued from the engine factory due to either a malfunctioning torque machine or wrong specs.
This meant the clamping force working on the head gasket was less than good and it might have been a slight seepage of coolant entering the engine oil or combustion chamber and an equal amount of combustion gasses entering the coolant, oil system and crank case.
This constant mixing of fluids and gasses together with people using low quality (read quick lube places) oil or running the car too long between changes using Saab oil and listening to the dealer/car maker that proclaims 10,000 mile between oil changes are good enough.
Also forgetting about that "most" driving is seen as "severe" driving conditions in the car manufacturers eyes. Many people don't think that the Sunday drive to church ones a week could be called "severe". But that type of driving is one of the worst ones and the oil should be replaced at shorter intervals.
So here you have an engine that is slowly mixing fluids, creating sludge, and a driver that do a lot of short trips and cold starts under long period of time changing the oil every 10,000 miles at the best.
On top of this you have a oil screen at the bottom of the engine where the mosquito net look alike screen is so fine that it traps each and every little curnel of dirt and sludge instead of picking it up and sending it to the oil filter.
As time goes by this oil screen is slowly getting more and more clogged up and the amount of oil (and oil pressure) reaching the engine is getting less and less, raising the temperature of engine and oil, creating more sludge, and we are looking at a down spiral vicious circle until the engine croaks due to lack of lubrication.
And people that have been changing the oil on a regular basis say, every 5 or 10K but stayed with the 6 month whatever comes first intervals, have gotten the contaminated oil and particles out of the engine and never accumulated a large amount of dirt clogging the oil screen. So even though they still have the cylinder head bolt problem they never reached the full down spiral syndrome.
But this is only my grassroot mumbling opinion and the truth from the car maker might be someting completly different.
Cheers
Anders
, Sat, 22 Jan 2005 19:21:16
, Sun, 23 Jan 2005 18:38:13
, Sun, 23 Jan 2005 19:51:09, Sun, 23 Jan 2005 11:58:59 <-- Viewing This Message, Sun, 23 Jan 2005 18:24:11, Sun, 23 Jan 2005 11:21:47, Sun, 23 Jan 2005 12:05:25, Sun, 23 Jan 2005 15:43:43, Sun, 23 Jan 2005 18:54:12
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