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I'd like to begin by saying thanks to everyone here. I've been mostly lurking and scouring every thread I could find on timing/balance belt, water pump, variocam, and front end seal service. Between here, Clark's Garage, Pelican, and other forums, I've learned a lot.
I just bought my first Porsche last month, a 1995 968 with 60k miles on it. The belts and one tensioner were last replaced at 57,628 miles in October of 2010.. It was one of the red cabs recently on ebay. Even though it runs well right now, I was too nervous to drive more than a mile to go get it inspected because of the horror stories I've read about broken belts and variocam pads and chains. I decided I'd replace everything of concern before I put any real miles on it. I'm glad I did. I'm well into disassembly now and here's how the upper pad looks:
Pretty groovy. Nice pits too.
The cam lobes look great and so far I don't see any broken teeth and only very light spalling. I will be replacing the chain, pads, crush washers, pressure tube o-ring, both belts, all rollers, all front seals/sleeves/o-rings/mylar gaskets, water pump,thermostat, and crank and cam bolts. I've ordered all of the parts and have a flywheel lock, belt tension gauge, pin wrench and Loctite 574 ordered as well. I have some Loctite 243 for fasteners and may use Zep Aerogel NC that I already had to lube the o-rings for assembly (still researching it). To retain the cams I milled and drilled two pieces of phenolic much like another fellow did with some oak and bought some TDC stops to screw 3/8-16 all thread into. I plan to check the timing on the cams as well so I've ordered the tool to pressurize the variocam unit. Luckily I already had indicators, posts, clamps, point extensions etc. because I've worked as a machinist for nearly 30 years.
I will be adding to this thread as I go along so that the next fellow traveler will have yet another example of what to do and hopefully NOT what not to do! Please let me know if you can think of anything I've forgotten.
On a side note - I took compression readings and though they are consistent, they are lower than I'd like to see. I had the variocam solenoid unplugged when I did it and wonder if that has any effect. I had the throttle wide open but forgot to pull the fuel pump fuse before checking. Anyone have insights on these readings?
Those are lower than you'd like to see. Was the car warm when compression tested. I would stop and run a couple more tests while you can. If you are going to replace all those old parts, you should know the engine's full health first in case you need to do something else also. Here's what I would do:
Warm the car up and perform a leak down test on each cylinder.
Then warm the car up again and perform the compression test again.
Then spray a few drops of oil in each cylinder to do a second compression test.
Repost your findings for feedback! 150-160 might be totally fine. But it's good to know if a little oil makes a difference or not and also leakdown numbers will help paint a complete picture.
Good luck
Ouch. I've already got it torn down pretty well. That would be a lot of putting back together before I can run it again. The car was very cold - about 30F cold. I will definitely recheck as you described once I get it back together and post the results. I sure hope the rings aren't leaking severely at 60k miles.
That's what I'm hoping for. I worked on it this morning in the freezing cold again for a little while before work. I had a stuck bolt holding the adjuster to the ear of the air conditioning compressor that I sprayed with PB before work yesterday and worked back and forth a couple turns. I sprayed it some more this morning and got it out. It did take a couple threads of aluminum with it but I'm pretty sure it will still take torque. If not, I'll drill it for clearance and use a longer bolt with a nut. I cleaned the aluminum stuck to the threads with a pick and bead-blasted the bolt. I also got the fan assembly and lower timing cover out this morning. I rotated the engine to TDC on the cam gear and will check to see if the crank lines up next.
I'm going to buy a set of leak-down gauges tomorrow and record values with the engine cold. It will be interesting to compare these cold values I'm taking with the numbers after testing the engine at normal operating temperature.
I had to order a leak-down gauge and while I'm waiting on the crank locking tool, I'm cleaning some things up. Here's before and after bead-blasting the valve and fuel rail covers. I blew the media off with air, sprayed them with brake parts cleaner, and will wash them in the dishwasher to make sure all of the blast media is removed from the valve cover. Wifey told me I couldn't wash them with dishes I also blasted the valve cover screws and air conditioning compressor adjuster. I thought about zinc plating the hardware but I think I will skip it.
I could have probably saved a little money if I knew the ins and outs of all the different parts sources, but that's why they call it a learning curve. I bought from multiple sources, not only for cost reasons, but to spread my business and get a feel for each supplier. I didn't add the cost of tools that could be used on other cars into my Excel sheet. Until now, I had everything I needed to work on any of my cars but they were Toyotas, Mazdas, Triumphs, or BMW. I'd never needed triple-square for ANYTHING. I do now!
If you have blasted the bolts, I would recommend getting them plated. Otherwise they will likely rust in short order. With cam cover and fuel rail cover blasted, would be a good time to have them powder coated.
Thanks for starting this thread. I'm doing my belts (they're four years old, and look and feel brand new, despite my car being a heavily abused track car - I think I'll wait at least five years before the next belt job), and will at least inspect the timing chaln pads as best I can. If there's any hint of wear on the top one (the bottom one is very difficult to see), I'll replace them, and will post pictures along the way. The pads are only five years old, though, so I suspect they're OK.
12-18-2019, 11:54 PM
Another Belts/Seals/Variocam Thread
I also blasted the valve cover screws and air conditioning compressor adjuster. I thought about zinc plating the hardware but I think I will skip it.
