Troy Hellwig

Long story short, I have had the head off of the 951 since covid. I am finally putting it all back together and as you can guess all my lifters have bled down and are squishy. Should I:
1) Clean and flush with brake clean and install as is
2) Fill them with oil soaking them and pulling a vacuum on them till no air is in there
3) Soak them in oil overnight with no vacuum (hopefully putting some clean oil in there but not getting it rock hard)

Thanks for the advice!
Troy

mj951

When I had mine out I soaked them in oil (#3) and made sure they went back where they came from.

GrantM

The vacuuming and filling with oil is ideal. Soaking them in oil for a few days is probably fine.

GPA951s

I use a vacuum pump.. a glass jar hooked to vac pump.. you would be surprised by how much air ( bubbles) come out of the oil itself.

Troy Hellwig

Update:

I used carb cleaner to try and clean the outside and inside of each lifter. Some I felt I was able to fill with carb cleaner but others did not. Shook the lifters clean and sprayed compressed air to dry them out.

I put each lifter in a jar and pulled a vacuum on each. I was surprised at how much air came out of each one. I was surprised but even still submerged in oil the buttons were soft.

I’m thinking that I may end up replacing all of them. Some of them have a bit more resistance than others but some of them are still quite soft.

Droops83

The vacuum method is a great idea. I have always used a more direct method---there is an ancient plug-in portable camping stove at my shop, most often used for heating Porsche gearbox parts in a bath of gear oil in preparation for installation.

I have used the same for heating hydraulic lifters in a bath of the type of engine oil the will be living in and checking that they pump up. If any lifters do not pump up using this method, you should consider replacing the lot.

Troy Hellwig

Second update!

Saw on Reddit a video of a user using a syringe to force oil into the lifters through the side hole. I gave that a shot with an oil squirting can and they all pumped up! All are pretty hard and I went ahead and installed the cam tower and promptly found two stripped m8 threads in the head! Now onto the next problem (time for a heli coil or two).

The vacuum I pulled was probably not enough to get all the air out. The vacuum is powerful (it’s made for ac systems) but the jar and lid were probably just not robust enough to pull hard enough.

Droops83

I strongly recommend Time-Sert threaded inserts for repair versus Heli-coils, they are far better suited for use in aluminum alloy, especially for a critical application like the 944 cam tower bolts. Heli-coils are OK for use in steel and iron, but they really need to have a hole where the tang of the Heli-coil can bottom out to enable a strong thread insert. The special tap that comes with the Time-Sert kit is used to form the threads of the insert to the tapped threads of the over-bored hole, and the counter-sunk bore and shoulder of the thread insert help to lock it into place.

Also, I have posted this ad nauseam on this forum over the years, but you should replace all the cam tower bolts with new ones from Porsche, part # 900 067 214 01