Preventive maintenance/upkeep?

[A930Rocket]

I’m sure we all replace our spark plugs, caps, rotors, filters, etc. on a timely basis, but with potentially 40+ year old parts, what about cylinder head temp sensors*, crank sensors, etc?

I ask, because yesterday I went to start my stock 86 911 3.2. It turned over, but would not fire up. I tried multiple times and no success. I went out about 45 minutes later to grab an Amazon package and when I did, I tried to start it, and it fired right up. And it’s fired up multiple times since then.

I replaced all the items in my first paragraph, back in January. Looking at my fuses, they look like they are the originals, so I’ve ordered new ones and will swap them in, after I clean the contacts.

So, with parts that are decades old, do you let sleeping dogs lie or do you swap them out preventatively?

* A new Porsche CHT sensor is ~$340 vs a Bosch for ~$110.

[eflight]

Your engine failure to start and later start up sounds like a classic case of a bad DME relay. I would suggest you consider replacing it with a new one. That relay tends to have internal cracks on the solder joints because of the way its mounted to the floor.

[A930Rocket]

I forgot to mention, I replaced it with it a (digital?) new one, but it didn’t start right after I replaced it

[Buckeye]

I Have an 87 and replaced my sensors 10 years ago The peace of mind outweighed the cost of the parts

[rwest]

The tough thing now is that the new parts can be of such low quality that it becomes hard to decide if you’re better off with the old original part or a new one.

[Ian Comerford]

Mostly swap out preventatively as I use the car a fair bit (touring holidays, boys road trips, meets etc)and want the best reliability possible within reason. Mostly small things but the brake master cylinder nearly escaped my attention a couple of years ago, I didn’t fancy experiencing either of the two common failure modes for an MC. I service the brake calipers once a year amongst other things and have recently changed the ignition and headlamp switches.

[PopsRacer]

I had an intermittent stall/wont start issue. It was a combo of the dme relay (reflowed it and replaced the diode) and then the fuel pump was dying. Jumper the pump on the fuse panel and gave it a listen. Mine was starting and stopping, and sounded like someone shaking a bag of metal bits.

[A930Rocket]

Originally Posted by rwest

The tough thing now is that the new parts can be of such low quality that it becomes hard to decide if you’re better off with the old original part or a new one.

Yes, that’s the worry now. Are you replacing worn parts with inferior parts. I suppose, if it’s mechanical, you can inspect it to some degree, but with electrical, you take your chances.

Or if you buy factory parts, you’re spending hundreds/thousands of dollars for a part that cost much much less a few years ago. But that’s the nature of the beast owning an older Porsche.

I keep a small bag in the trunk, with spare electrical parts, fuses, jumper cables, etc. in, just in case something happens on the road. The list will grow, as I replace parts soon.