1986 Porsche 928 – Winter Maintenance

I had really been concentrating my efforts in 2021 on the restoration of my 1963 Jaguar Etype. See here. But as cold weather set in around Christmas, I decided to retreat to a heated garage where I could perform some much needed maintenance on my Porsche 928. In particular, there were fluid leaks that had me concerned that there might be a fire so I had basically quit driving the car.

It turned out I had a power steering fluid leak, a coolant leak, and an oil leak. The power steering leak was the one that had me worried about a fire. My repair of that issue is addressed in a separate article here.

Next I turned my attention to the oil leak. This was not an oil dripping on the ground issue. It was an oil pooling in the spark plug well issue. After a Search, it appears this is a known problem with the 928. There are some gaskets on the under side of the valve cover that get hard/brittle and allow oil to leak into the spark plug well. Mine only exhibited on the drivers side. I will not attempt to detail the replacement of the gaskets, except only to say that getting at some of the internal hex head screws that hold on the valve cover require some creativity. I got the job done without issue.

Next I turned my attention to installing replacement shocks. I had purchased replacement Boge/Sachs shocks from Roger at 928srus a few years ago at a good price but had never got around to installing them. Now was the time. There are multiple how to articles out there on the replacement of 928 shocks both front and rear. BTW, you may prefer to refer to them as dampers, struts, or even coil overs, depending on your upbringing. I just use shocks in the old school generic sense. The main drama for me on the fronts was to get the assembly out of the car. I wound up releasing the lower A arm completely, which allowed the spring/shock assembly to be removed.

Although the subject of much angst in the various how to articles, at the rear the big pin that passes through the various components come out cleanly with little drama.

My main issues of note were that the poly bump stops were toast and I decided to order new threaded rings/collars for vertical adjustment. The threaded collars had to come from Germany and wound up taking a month to arrive. I would like to give a shout out to a new spring compressor that I ordered from Amazon, the Handor Coil Spring Compressor Tool. See here. It fit the 928 springs perfectly and its robust design was very confidence inspiring.

Ultimately my parts arrived from Germany and I was able to install the new shocks at all four corners. I checked the corner weights on the car and found them to be very good.

During the downtime waiting for parts, I tackled some cosmetic issues with the dash. That effort is described in a separate article here.

Now it was time to address the coolant leak. I have a tester that you attach to the reservoir in place of the radiator pressure cap. It has a hand pump. The leak was so bad I could not build any meaningful pressure. I actually had multiple leaks. The first was the connection of the radiator hose to the block. After addressing that issue, I still could not get it to hold pressure. I made a fitting to allow me to put a steady supply of shop air, at 10 psi, on the system. Pretty soon I noted a small drip coming from the radiator. Bad news. The right hand side plastic end tank had a small leak. The car had what appeared to be the original radiator so I guess it had a good run. I bought a replacement radiator from 928srus. Replacement was relatively straight forward. But wow, I still could not build pressure. I put the 10 psi shop air on the system and did a bunch of testing with soapy water. I finally found that air was leaking out of the coolant level sensor that is located just next to the radiator pressure cap. A quarter turn with a wrench and the leakage stopped. Now I was able to pump up and hold pressure on the system. Woo hoo!

But wait, there’s more! While working on the power steering lines, I managed to break off the vacuum hose connector/check valve at the brake booster. I ordered a new one from 928srus. While I was there, I noticed another plastic vacum fitting that was broken. The dangling hose led to the cruise control unit in the fender well. I fixed that.

During a short test drive, I noticed my ABS light was on. I pulled the connector at the “brain” (mounted to the left of the clutch pedal, generally speaking) and checked resistance to the 4 sensors. The sensor on the right front was infinite resistance. I purchased a new one from 928srus and that fixed the problem.

During another test drive, the idle was wonky. I found that one of the rubber seals between the central manifold and the outer manifold was shredded. New seals for all the connections made things right.

It was now getting into April and I sensed that the AC was not working very well. Indeed, when I hooked up my gauges and measured pressures, things were not good. I had done a full refurb of the AC system right after I bought the car but I guess over the years, enough R12 had leaked out to become a problem. Since I did not sense that I had a major breech, I just added some more. I was rewarded with cool air within shop manual specs at the vent outlets. Indeed, one morning when the dewpoint was just right, I literally had fog rolling out of the vents. It startled me until I realized that the car was not on fire!

Last but not least, I treated the car to a new air filter, and an oil/filter change.

People wonder about the ownership costs of these cars. I spent about $4000 in parts for the above described effort. Not insignificant but what it is. The good news is that folks like Roger and the 928 community continue to meet the demand for parts so they are available when needed.

As you can see, this effort took some time. The results are worth it in that I now have added the 928 back into my rotation of cars to drive.