Engine
Low Oil Pressure / Cam Chain Rattle
I have an 87 S4 AT with a problem that developed about 2 days ago. The symptoms are a slight
rattle on the left side of the engine (as you face it) only at idle. When the car is cold the noise
does not appear until engine is warm (probably due to increased oil pressure when cold). Noise
completely goes away above 1000 RPM. Talked with my mechanic today (have appt Mon) and
he indicated that the oil pressure appeared low at idle which is probably causing the chain
rattle. There is a hydraulic unit which lubricates the chain and if may not have the pressure to
operate properly. The oil gauge reads just over 1 when warm at idle, above idle picks up quickly
and appears fine moving between 2-5 depending on RPM. Mechanics plan is to first change
the oil and filter (since PO changed it last don't know what's in it) then if it continues I guess
we're looking at some sort of exploratory surgery. Of course I am somewhat worried that this
may be something substantial and costly.
Jason
87 S4 AT Guards Red
[one week later]
Problem is fixed. Mechanic removed the cam cover and discovered that the cylinder head oil
plugs, which are made of plastic(?), had melted slightly and had popped out. The result was oil
freely jetting through the unplugged holes (about 1/16 inch diameter) and a loss of pressure at
low idle. Loss of pressure caused the hydraulic cam chain tensioner to not get sufficient
pressure to tighten the chain and the chain rattled at low idle. The plugs are about a nickel in
diameter and about 1/2 an inch high. They are plastic except for a small metal rod (1/16) which
protrudes from one side and plugs the hole to prevent oil from passing. Porsche later
redesigned these oil plugs and are now made of metal and therefore will not change shape due
to heat. Mine on the left (3) have been replaced with the new version. Interestingly, the
replacement calls for five so the other side of the engine must only have two. Cost was about
$25 for the parts and $275 in labor. Oil pressure now 3.5 at idle, cam chain rattle gone.
Owners experiencing similar problems may want to have this checked. I do not know what year
Porsche
started installing the new version of the plugs.
Jason
87 S4 AT indischrot (now rattle free)
[two weeks later]
I had a disconcerting rattle ("clucking" sound) from the middle of the right cylnder head area at
idle. Noise not there cold or off idle). The noise was coming right from the chain drive area
where the exhaust cam
drives the intake cam.
After pulling the valve cover, I discovered the two rubber sealing plugs with locating pins
which block the oil passages at the empty rear cam journal bearing surface of the cylinder head
had fallen out and were sitting down on top of the rear oil return hole in the head. (This bearing
surface is used for the front cam bearing journal when the head is flipped around for the other
side).
With these two plugs out and the oil squirting through the unblocked passages, the motor had
a loss of oil pressure at idle sufficient to cause the cam chain tensioner to collapse and the cam
to jerk around, which
resulted in the noise I was hearing. Also why the noise was not there when cold (higher oil
pressure and tensioner working again!), and why the noise went away off idle (same!).
The motor has a total of five of these sealing plugs for the rear of the motor. The part has been
redeigned and superceded from a "sealing washer #928.105.261.01" to a "cylinder head plug
#928.105.262.00". This plug is a pin with a reduced portion which fits into and plugs the oil
passage. The pin in held in place by the cam journal bearing cap. When in place, the pin will
cannot come out the way the old rubber sealing washer did, but the pin is not very tight. You
can rotate it and move it up and down a bit with your finger.
Now finally for my question. Anybody know if these pins should be installed with gasket
cement/sealer where the pin fits into the oil passage? Or am I perhaps missing a rubber washer
which is to surround the new pin? It just seems as though these pins should fit in snugly, and
they do not. I can find no TSB or mention in the factory manual.
Any help would be greatly appreciated! Thanks in advance!
Chuck Bos
1987 928S4 AT RMB Indischrot
Well, everyone who contacted me confirmed that the stepped pins are installed dry. The
bearing caps will keep them from ever moving, and a small amount of oil seepage past the pins
is apparently insignificant.
Apparently, these early generation plugs falling out is not a rare problem, but I've seen very
little info on this. One thing for sure, if your early 4-cammer drops oil pressure a bit at idle and
rattles a bit at idle, it's time to fix it! Parts involved are minimal.
Many thanks to Jason K, Earl Gillstrom, Nuugin and Marc Thomas of DEVEK.
Chuck Bos
1987 928S4 AT RMB Indischrot
There had been a thread several months ago about low oil pressure at idle on an '87S4 and that
this is a potential problem that can easily be fixed although no one seemed to know how, there
was just a part # that wasn't referenced in the shop manual (at least not in mine that covers up
to MY '88). I finally found out where the pins go and how to replace them. Since many of us are
pulling off our cam covers to refinish and reseal this is a good time to perform this fix.
Apparently earlier 928s had longer cams that went all the way to the back cam cover bridge
(firewall end). You'll notice looking at the cams on your '87 that on the back cylinders (4 and
8)the cam ends at the cam lobe for those cylinders rather than being supported all the way to
the back bearing(hope this makes sense, take a look at yours). The cam cover bridge in the
back has some plastic oil seals that you should replace while you're in there. They plug the oil
journal to what used to lube the end of the cam. Since the cam doesn't come all the way to the
end but there is still an oil journal, if the pin isn't in place oil just squirts out the holes (approx
1/16 to 1/8" diameter). The fix is to take the back bridge off and replace the old seal with either
part #928.105.261.02 (see TSB #GRP 1 8711 which specified this part #), which is a round rubber
seal the same diameter as the cam with a metal pin sticking out that goes into the oil journal, or a
pin (no rubber seal), part # 928.105.262.00 (I believe this was used in later year cars). I'm going
to use the one with the rubber seal, it plugs the hole where the cam would ride as well as the oil
journal. I hope that it will keep oil from getting to the back seals where it may leak. The parts
are dirt cheap and the repair pretty simple.
Fred Clark