Hi all, I'm posting this for my dad, he's having a weird issue with his E28. He's had the car since new, and has been getting very fed up with this phantom clutch issue. He and his mechanic have tried many many things, with no success. Hopefully someone can help! Copy/paste of issue and symptoms below. Please help if you can! I'm crossposting this on the usual forums too.
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My 1986 535i with 238K mi is having a persistent but intermittent clutch problem. The clutch is normal when cold, but when the engine has thoroughly warmed up on a hot day, the clutch pedal occasionally will go all the way to the floor with no resistance and without disengaging the engine from the transmission. This usually happens while one is trying to shift up through the gears from a stoplight, and suddenly the pedal is on the floor but the engine is still driving the car forward. The pedal will not return to the up position by itself, and the gears/synchros will clash if you try to force the shift while the pedal is on the floor. One can yank the shifter into neutral, then reach down and pull the pedal up from the floor, then the pedal works again and you can make the shift. The pedal can also be pulled back up with your toe sometimes, without shifting into neutral, and the engine and transmission remain engaged during that action. Once the pedal has been pulled up, the clutch usually works normally for a few times, then without warning it again goes to the floor with no resistance and without disengaging. On a really hot day the pedal may go to the floor and stay there every 2nd or 3rd time the pedal is depressed. When it happens, it does not seem to matter whether the pedal was initially depressed fully or just to the friction point – it goes the rest of the way to the floor with no resistance. In winter or with a stone cold engine in summer, the failure is never observed, so it seems to be related to temperature.
What we have tried: thinking there must be air in the system, we have bled the entire clutch hydraulic system many times, to no effect. We have also bled the brake circuit, though there are no issues with the brakes. We have replaced the clutch slave cylinder and the master cylinder at various times as noted below. There is no apparent fluid leak, since the level of hydraulic fluid in the reservoir does not drop. The problem is worse when the air conditioner is running, but that may be coincidence - the air conditioner is only running on hot days and the problem only occurs with a hot engine on hot days. In any case, turning the air conditioner off does not stop the problem once it starts.
History of clutch repairs: There was no problem with the original clutch disc and clutch hydraulic system, many years ago. The original clutch disc wore out and was replaced at 130K mi, the clutch slave cylinder was replaced at 150K mi. Problems began somewhere around 200 – 215 K, very rarely at first. The clutch master and slave cylinders were replaced at 215K because of this problem, but it didn’t stop the problem. The clutch master was replaced again at 226K, again didn’t solve the problem. A clutch pedal spring was replaced at 233K, again didn’t solve the problem. The transmission failed at 235K and was replaced, the clutch disc had significant life left and was not replaced, everything in the clutch system was inspected and bled thoroughly after reinstallation. The problem persisted, so we replaced all the hydraulic fluid in both brake and clutch circuits with ATE super blue racing fluid at 236K mi, which has a higher temperature limit than the stock fluid, with no improvement. In fact this summer with ambient temperatures near 100F, the problem is worse than ever.
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My 1986 535i with 238K mi is having a persistent but intermittent clutch problem. The clutch is normal when cold, but when the engine has thoroughly warmed up on a hot day, the clutch pedal occasionally will go all the way to the floor with no resistance and without disengaging the engine from the transmission. This usually happens while one is trying to shift up through the gears from a stoplight, and suddenly the pedal is on the floor but the engine is still driving the car forward. The pedal will not return to the up position by itself, and the gears/synchros will clash if you try to force the shift while the pedal is on the floor. One can yank the shifter into neutral, then reach down and pull the pedal up from the floor, then the pedal works again and you can make the shift. The pedal can also be pulled back up with your toe sometimes, without shifting into neutral, and the engine and transmission remain engaged during that action. Once the pedal has been pulled up, the clutch usually works normally for a few times, then without warning it again goes to the floor with no resistance and without disengaging. On a really hot day the pedal may go to the floor and stay there every 2nd or 3rd time the pedal is depressed. When it happens, it does not seem to matter whether the pedal was initially depressed fully or just to the friction point – it goes the rest of the way to the floor with no resistance. In winter or with a stone cold engine in summer, the failure is never observed, so it seems to be related to temperature.
What we have tried: thinking there must be air in the system, we have bled the entire clutch hydraulic system many times, to no effect. We have also bled the brake circuit, though there are no issues with the brakes. We have replaced the clutch slave cylinder and the master cylinder at various times as noted below. There is no apparent fluid leak, since the level of hydraulic fluid in the reservoir does not drop. The problem is worse when the air conditioner is running, but that may be coincidence - the air conditioner is only running on hot days and the problem only occurs with a hot engine on hot days. In any case, turning the air conditioner off does not stop the problem once it starts.
History of clutch repairs: There was no problem with the original clutch disc and clutch hydraulic system, many years ago. The original clutch disc wore out and was replaced at 130K mi, the clutch slave cylinder was replaced at 150K mi. Problems began somewhere around 200 – 215 K, very rarely at first. The clutch master and slave cylinders were replaced at 215K because of this problem, but it didn’t stop the problem. The clutch master was replaced again at 226K, again didn’t solve the problem. A clutch pedal spring was replaced at 233K, again didn’t solve the problem. The transmission failed at 235K and was replaced, the clutch disc had significant life left and was not replaced, everything in the clutch system was inspected and bled thoroughly after reinstallation. The problem persisted, so we replaced all the hydraulic fluid in both brake and clutch circuits with ATE super blue racing fluid at 236K mi, which has a higher temperature limit than the stock fluid, with no improvement. In fact this summer with ambient temperatures near 100F, the problem is worse than ever.
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