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.
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.
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!
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.
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.
I can offer clarification of the parts/procedure required to cure inter-cam timing chain rattle on 1986- 32v motors. The chain tensioner is starved of oil pressure at idle thanks to pressure loss through vestigial oil galley holes that *used* to feed an extra journal on the early style camshafts (1985 only?). The galley holes were originally plugged with a metal pin protruding from a rubber plug that filled the unused "bearing". Especially on the exhaust cam side, the rubber plugs distort from heat & pop out of their holes, causing the aforesaid lack of oil pressure & chain rattle. Every description I read of this problem & it's solution mentioned 2 vestigial holes at the rear of each head. I in fact found 3 holes on the right bank, and can only assume that the left bank also has 3 vestigial holes. Make sure you order *3* of the new style plugs for each head you plan to fix.
(3) 928 105 262 00 - oil galley plug
(1) 928 104 447 09 - valve cover gasket (85-)
(4) 928 104 443 08 - spark plug grommet (85-)
(13) 928 104 115 02 - valve cover grommet (85-)
(13) 900 123 144 30 - M10x14x1mm (?) Aluminum Crush Washers (buy them at
a VW/Audi dealer or from Wurth)
1327 W. 31st St.
Chicago, IL 60608
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