So I pulled out my thermostat and found this...

[AlexGross]

I am currently tearing down the top end of a 1975 911S (my first Porsche, and first rebuild), and when I removed the internal thermostat I found this ragged piece of metal protruding from it.
The car was parked for a good 5 years before I started the rebuild, but if my memory serves it was not having significant temp. regulation issues before.
Here's a photo of it as I found it:

I am planning to clean it up and test it, but I am wondering if anyone could shed some light on what I am looking at before I go any further.

[m110]

Is it aluminum?
Another picture please

[efhughes3]

Hard to tell from that one angle. Agreed another pic or two is in order.

Why spend any time with that t-stat? Replace it. Take the potential for an old part to pack it in out of the equation.

[wildcat077]

I don't remember anything hanging out from mine when i replaced the "O" ring a few months ago ...
Like ED says,if you're not sure it's better to replace it !

Cheers !
Phil

[R_Builder]

Yes... more pics, maybe even with a ruler in the shot. Test it with a magnet. That is just weird. The oil flow must have jammed it in there, but where did it come from? FWIW, the t-sat is a simple thing and easy to test. I wouldn't give up on it right away...

[kodioneill]

Strange. need more photos.

[pjh69911]

Well that for sure didn't pass throught the oil pump. Could it be an insert in the case that migrated?

[AlexGross]

Alright, so I examined this piece of metal and discovered several things. It was just barely lodged up into the thermostat between the spring and the internal rod. It is non-magnetic, brittle, and has the obvious signs of abrasive wear (ie. some of the edges were worn smooth. It almost looks like welding slag, although it is hard to tell from the gunk buildup and general wear and tear. I couldn't find any distinguishing features or obvious machining marks. Its just under 10cm long and at its thickest its only just over 1mm thick. It is rounded on one side (I imagine from being trapped inside the rounded thermostat). I tested the thermostat and it didn't move one bit even at 200 degrees Fahrenheit. I think I did the test right--I just placed it in a pot and brought the water to a boil... So I guess I'll just be getting a new thermostat, but I am very concerned and confused on the possible origins of this scrap of what seems to be either aluminum or magnesium.

Thermostat Test @ Boiling Point:


Metal Shard in Thermostat (Thermostat ID#s: X1.224.83.000)


Metal Shard Scale:


Thermostat Port Detail:


Any thoughts? If nothing else, it makes me think that I am probably going to have to split the case

[db_cooper]

Unless you have some other sign of engine problems, noise or knocking..do not split the case.

You have the DPOs..dreaded previous owner(s).

Non magnetic and brittle..sounds like plastic or a fuel line. The port for the oil is too small for such a thing to migrate there from inside the engine case or get through the oil pump from the sump.

Therefore....it must have been installed earlier with the thermostat!

Could be an error, just dropped in during a routine repair..or jammed inside in an effort to open a failed thermostat.

As you now know..you have a bad thermostat..replace it.

Drive the car and see. It will probably be fine. Engine ran warm for sure..check your oil pressures and consumption.

Any strange knocking sounds..well, time to split the case. It is worth the effort to see how the engine performs after you do the work.

You need the new thermostat anyways.

[fanaudical]

If memory serves, there is a tube inserted in the vertical bore leading to the thermostat. Did part of that break off? Can you inspect that bore? Is there a part of the oil-pressure relief pistons at the end of that bore missing?

[AlexGross]

Non magnetic and brittle..sounds like plastic or a fuel line

The picture doesn't really show it, but it is definitely some type of metal. The places where it has been worn down show definite metallic shine, and the wear seems consistent with metal decay. Just my opinion, but here's another picture that hopefully will show what I think I see.



The thermostat will definitely be replaced, and I am glad to hear that I might not have to split the case...I have heard that with these mag cases, once they're split they usually require line boring and other machining to get back to true.

Did part of that break off? Can you inspect that bore?

I unfortunately don't have the block here at my casa, but I will make sure to inspect that bore when I get into the shop tomorrow...I hope that it is all intact, but based on the rough dimensions of the metal scrap (it seems to have the same basic curvature of that bore) I think your theory might be right. I will dig deeper tomorrow and hopefully get some more information.

Thanks for the input guys, I am always trying to learn more as I work through my first top-end rebuild.

[Walt Fricke]

Fanaudical - you are thinking of the spring guide which is part of the oil pressure system modification which Porsche did starting with the '76 or 7s. Just about everyone who rebuilds the earlier motors does this modification to them.

Among other things, this involved a different oil piston (two, actually), and a longer spring for the pressure setting part. To keep the longer spring from buckling, a tube is inserted into its bottom end. All this is in the vertical drilling which comes out at the top of the engine where the idiot light sender is, and at the bottom of the case where there is a plug with an odd and infuriating sort of screw driver slot (usually unsecrewed with a pipe wrench by us shade tree types - the later motors had a cap with a nice hex head on it)..

I thought about that sleeve, too. But 1) it is steel, and a magnet would glom onto it. 2) It has a flange at its bottom which sticks out beyond the spring. Hard to imagine how the tube could break off of the flange. There is very little force involved there. 3) it would have to get by the piston to get higher up in the engine and into any other oil passages. And 4) this drilling is parallel to, but not the same as, the hole in the bottom of the thermostat bore - too many corners to turn. If the piston were missing, you'd have no oil pressure anyway.

That about exhausts the possibilities. There is at least one steel tube cast into the case oil system in that area. Possibly more. If the one I am thinking of were to come loose, you'd have oil all over everything on top of no oil pressure - it would kill the motor, plus it can't really come loose anyway. If there are others in any of the vertical machined passages back there, they, like the one I am thinking of over by the oil cooler, are much much larger in diameter than your mystery.

I am guessing this is a foreign object which somehow fell in during some previous work on this motor. Replacing the O ring on the thermostat is part of dealing with the inevitable oil leaks in this area on top of the case (the others being a failed idiot light, a leaky breather hose, or sometimes the oil drain from the air box if you overfill the oil tank).

By the way, if you put the thermostat in a refrigerator (I use the freezer) to be sure it is really cold, and then toss it into boiling water, and there is no change in the position of anything, then the wax cannister inside is toast. You can purchase just this cannister (it is also used on the external oil thermostat which controls the right front fender oil cooling system), but I am not sure just how one would disassemble the housing you have.

I think the good news is as DB Cooper suggests - since it has been in there so long without causing problems, chances are good it wore into little tiny particles which did not plug any oil passages (because the engine hasn't blown up) and were within the embedability capacity of the bearings. The smallest passages I think are the oil spray bars over the cams, and the piston oil squirters. The cam spray bars you caneasily test and clean as part of your top end rebuild. As long as your oil temps are within spec (a working thermostat will help) and so are the pressures, and you don't get rod knocking sounds and whatnot, drive it until you decide it is time to split the case to replace bearings.

[DanielDudley]

Is it possible that someone jammed the thermostat wide open ? That would be my guess.

[inaminit]

you should consider an oil analysis of the old oil if you have enough to make up a sample volume. Most heavy equipment dealers have this service. The analysis will tell you if contaminants from the wearing down of the fo have degraded the oil and maybe caused wear damage in the engine, and may help id the fo.

[Dublinoh]

Could this be something that was used to try to retrieve a dropped dip stick...then broke or was dropped into the tank? You would think something immersed in oil would not degrade like that...maybe it was messed up when introduced to the tank. Just a guess

[ossiblue]

Originally Posted by DanielDudley

Is it possible that someone jammed the thermostat wide open ? That would be my guess.

Bingo!

That would be my guess too--it's hollow, and fits snugly into the bore of the thermostat and oil port. In addition, the thermostat does not work.

I suppose it's possible for it to have fallen by accident, but to have done so, and without the "mechanic" seeing it and to fall directly into the oil port, and to line up with the bore of the piston, and to not cause a problem in seating the thermostat, almost seems too coincidental.

[911Texan]

I'm thinking like a water-cooled guy here, but is there a redneck remedy for oil leaks akin to 'stopleak' for cooling systems whereby Bubba pours a metalic powder into his oil in hopes that it will magically migrate to and stop the oil leak? When human factors are considered, anything is possible. But it might possibly stack-up to form the "substance" you describe with time/pressure/heat. That's my WAG - Rich

[R_Builder]

Originally Posted by ossiblue

Bingo!

That would be my guess too--it's hollow, and fits snugly into the bore of the thermostat and oil port. In addition, the thermostat does not work.

I suppose it's possible for it to have fallen by accident, but to have done so, and without the "mechanic" seeing it and to fall directly into the oil port, and to line up with the bore of the piston, and to not cause a problem in seating the thermostat, almost seems too coincidental.

Actually, the t-sat can't be jammed open that way. When it opens to divert oil to the on-engine oil cooler, the insert actually moves down. It works against the prevailing oil pressure and the internal spring to do this (kind of impressive when you think about it). If someone actually jammed something in there as shown in this thread, the result would be that it was stuck CLOSED, not open.

[RWebb]

maybe someone thought they could tho...

the real question to me is should he do a time-consuming tear down of the motor because he found a foreign object in it

it's a question about risk mgmt. ...