David L. Lutz

Before taking the engine out I had a very loud tapping noise coming from the left side. I now have this cam tower apart. I suspect I have "some" bad lifters and now that they are out of the head (in order) how do I check them or determine if they are calasped or bad.

Here is what I have found so far...

I notice when full of oil the "button" in the center of the under side is very, very firm. (cannot be pushed in at all) When the lifter is empty (no oil inside) I find the button will simply move in and out easily. If I shake the lifter back and forth when it is empty (no oil) the button part just rattles back and forth. No springy feel. Very loose. But again, when loaded with oil its firm.

What does this tell me and could someone guide me thru a checking procedure? I can't seem to find any difference between lifters and I certianly don't want to reassemble with bad lifters.

Mrmerlin

do any of the lifters have a scratchy top where they ride against the cam or are any of the cam lobes worn down? Was any of the oil plugs missing IE the old style that had a round rubber plug with a little metal rod sticking out of it, (these plugs ride in the cam journals and keep the oil from escaping from the unused journals and if one was missing it could mean one or more of your lifters was not getting its fair share of oil

David L. Lutz

I checked and none of the lifters have a scratchy top, and the cam lobes look fine.

Both old style oil plugs were in really good shape (no leaking). (drivers side)

I have been checking the lifters and really don't see a problem with any of them. They fill up or maybe I should say take in oil easily and pump up somewhat and all of the buttons are free. (none stuck with crud) Everything really looks very clean.

Thanks for your post, if you can think of anything else I should check please let me know.

Mrmerlin

use the updated journal pugs they are about an inch long and are just metal pins instead of the ruubber plug/pins. I dont know of how to test the lifters, to be absolutly sure they are good but is it possible that one of the cam chans is loose,IE maybe a tensioner pad is worn down? Or one of the oil feed lines has a crack in it?

David L. Lutz

I just got the head off that side and honestly I just don't think any of the valves are bent. At least from a visual look it doesent look like any I have see here that are! (I was thinking the bent valve had affected a lifter.) Of course I am still going thru with the head/valve job as I know they are not seating good on 2 of these cylinders.

I already have the metal pins.

I too am wondering if somewhere I am loosing oil pressure to some of the lifters? I do have at least 1/16" wear maybe more on this sides tensioner pad. (Would that affect oil pressure?) I will replace that and check the lines.

Thanks again for your help.

David L. Lutz

Still a question about the lifter!

If the lifter is empty of oil should the button still have some spring to it? Or should it move in and out freely?

Thanks for your comments...

Mike Simard

Once the oil has drained that button should compress under finger pressure and spring back.

David L. Lutz

Mike,

The problem is none of my lifters spring back when empty of oil. I can pull and push the button back and forth using a magnet (with no oil, the button is very fee moving), but there is no spring in any of the lifters and I have checked them all!

If the lifter has a small amount of oil in it and I place my finger over the oil inlet hole to create a seal, then the lifter has spring.

If the lifter is full of oil the button is solid when my finger is over the hole. Once I shake the lifter and get the oil started to drain out then the button acts like a little pump if I take the magnet and plunge the button it in and out.

I have not noticed any buttons stuck, they all move free and the same distance. (ALSO ALL MY LIFTERS CHECK OUT EXACTLY THE SAME)

On a Chevy lifter for example I am use to a spring action when empty. I just wonder if these porsche lifters actually have a spring in them. They are also much larger in diameter that I expected to find.

What do you think?

Daniel Dudley

The last time I replaced all the lifters [in a ford], I found that I had exactly the same problem as when I started, and the problem was a bad con rod bearing was reducing pressure to the top end. The only symptom was lower than average pressure across the board from idle up.

With a 928, I'm not sure that would be as apparent. Tensioners do wear over time, but even so I would assume that this coud be an indicator of low oil delivery. Believe me when I say that there are lots of better mechanics out there than myself. However, it might be in your best interest to pull the oil pan and check the rod bearings before you start replacing things, especially as they are a known weak point on the engine.

It doesn't cost a lot to pull the pan, just time. Of course WYAIT, it would be a great opportunity to check/change the motor mounts, pan gasket and rod bearings. You could also adjust the flex plate if you have one.

I thought carefully before I posted this. As always, YMMV, but IMO, peace of mind is very important with a 928 engine. Good luck.

Mike Simard

Hmm...that's odd, IIRC there's a spring inside of that button and it pushes against a check ball. I don't understand why all of yours would be like that, maybe they're a different design than what I've seen? Beats me, them all being the same implies they're supposed to be that way. Do you think they're original or has someone been in the motor before? Do you have any pics?

David L. Lutz

Mike,

Here are some pics;



The button extended; (pulled out with magnet)



The button pushed in. See the spot of oil ejected when the button was pushed in. Also notice it stays pushed in.



Sorry the pic's were not better.

Thanks
David

Mike Simard

It looks like there's still oil in them and I'm not sure how they should react. I do know you can drain them by laying them with the bleed hole down overnight but I don't know if you can learn anything by any of this.

David L. Lutz

Ok, I will lay a couple on their side with the hole down and see tomorrow if any change.

Thanks again Mike
David

Vilhuer

There are infact two small springs inside each lifter. One to push check valve ball bearing up so that it closes oil flow when valve pushes piston (button) up and another spring to push lifter body up when it has space to move there. I'm not sure how critical second spring is. Oil should keep pressure chamber which is between ball and piston extended and not allow lifter to be too short for space it has. During past few years I have seen more than 100 lifters. Some of them had this second spring functional while others didn't. Only difference in use might be slightly slower pressure buildup on those lifters where second spring do not push lifter up until it gets enough oil pressure for pressure to do it.

Kevin Johnson

Dave, after hearing this from Erkka I decided that the Suzuki bucket tappets I had sitting here were of the same or greatly similar design. Porsche sublicenses technology as do many other manufacturers. Porsche and Chrysler both sublicense balance shaft technology from Mitsubishi, for example.

I took three used tappets -- they all had about the same amount of travel (spring). I took them apart serially to examine the effects of cleaning with Stoddard solvent (aka WD-40, essentially). There was a several mm increase in travel for the large spring (not the tiny check valve spring). This effect was reproduced by cleaning each tappet.

Tappet bores (I believe) are the most precisely machined surfaces in an engine. Even small amounts of deposits will cause sticking.

Try carefully pulling apart just one of your tappets and washing the parts with a gentle solvent. In doing so you will be able to see if springs are present.

I hope this helps.

If Mr. Simard objects to this chatty post, I will be more than happy to remove it.