Timing Belt Experiences
I bought a MY '85 in 1987 and currently have a '93. FWIW, here is my experience/thoughts on the belt failure issue. I only had one problem in 12 years of 928 ownership and it was my own fault.
I drove the '85 (32 Valve) 130K miles before I got the '93. I bought the '85 from a dealer whose wife had driven the car. It was about 400 miles from my house and the belt light came on while I was driving the car home! I had it serviced and the light would continue to come on. After about five times, the mechanic figured out that the connector for the sensor was vibrating and setting off the sensor. As the miles passed, I began to figure out that the belt light would come on first when you wound the car out to 6000 RPM, then, 5000 RPM etc. over a short period of time. I would then, usually within a week or so of first seeing the light, get the belt serviced. Never knew to replace the water pump and never knew to replace rollers, tensioner, etc. (although I'm sure the mechanic checked, replaced, and charged me when necessary).
In the Summer of 1989 Houston flooded as I drove home from work. The car sat in water that got up to the bottom of the car (I could hear the water rapping on the floor). I managed to drive it up onto a median as the car would just barely move. I could hear a loud clicking/tapping noise. Had it towed to the dealer. The belt had jumped a couple teeth apparently because the bottom of the belt was in the water and was slippery enough? (I don't know). Fortunately, there was no damage.
At 125K miles my water pump failed and I bought a rebuilt unit from Tweeks. They gave me a dandy 1 year warranty on the pump. My mechanic installed it. I was travelling down the freeway at a leisurely 2000 RPM and my belt light came on. It didn't occur to me that this situation was different than the above scenario where the light first comes on at high RPM. The other problem is that on the '85, the icon lights up and doesn't go off until you restart the car. On the '93 with the digital display, every time you cancel the warning it resets the sensor so you can see every time the sensor goes off. Anyway, I continued down the freeway and about 100 miles later the dash lit up like a Christmas tree as I slowly coasted to the side of the road. The bearings in the water pump were freezing up and the smooth side of the belt was being dragged over it until it started shredding. I don't know why the car didn't run hot though. Needless to say, Tweeks offered me a new water pump (would YOU want it?) and I waited a month and then paid my mechanic $6,000 and drove away with 32 brand new valves and a new view on life.
I just had the belt done on my '93 last Fall at 32K miles. I was told subsequent to the pump failure above that the bearings used in rebuilt pumps are not the same as the bearings in Porsche pumps. I HAVE NO IDEA IF THIS IS TRUE OR NOT. Just to be safe, I had them put in a brand new pump from the dealer. I also told them to replace any roller, tensioner, rubber piece, plastic piece, gasket, etc. that the could reach.
My experience is that the belt needs occasional attention and that the belt tension light is very reliable, the digital version being better than the older ones. (Caveat: I do not know if cars prior to '85 have the belt warning system) The warning light never failed to come on when the belt needed attention. I was always warned (just didn't heed the warning one time!) The belt never just broke. There is a difference between 6000 and 2000 RPM. Leaky water pumps should be addressed immediately! And lastly, I never lose sleep or worry about my belt while I'm driving.
Randy Grubbs (aka: 6600 RPM all the time)
'93 Black/Black 5 Speed
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