96 Toyota Corolla plug missing under valve cover?

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On Friday mechanic installed new spark plug tube seals & valve cover gasket set on 96 Toyota Corolla DX 1.8 L engine with 161,000 miles to fix problem of oil getting past the tube seals. I got home & found the semi-circular plug sitting on top of the battery. Based on price of parts ($59), number (JVS-10344), & name of part (Valve Cover Gasket), I would guess mechanic bought a valve cover gasket set without a new semi-circular plug. Can I see if a semi-circular plug is installed on the vehicle without removing the valve cover? Or does shop have to remove valve cover gasket to check if the semi-circular plug is installed? Do any of the following new parts need to be replaced if the valve cover is opened back up? Valve cover gasket, spark plug tube seals, grommets? What happens if the semi-circular plug is not replaced? Is it ok to drive the vehicle back to the shop or will I end up with oil all over the belts, etc? Thanks!
 
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No worries on the plug. It's just an end seal for where the head is clearanced for the factory's machine tools do the cam journals. The round part goes down in the head and the flat spot becomes part of the gasket mating surface. It is what the valve cover sets on. The OE ones can be either rubber or aluminum and are typically sealed in there really well.
 

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So if the mechanic never put the metal semi-circular plug back into the vehicle after he changed the spark plug tube seals & valve cover gasket isn't that an invitation to lose oil all over the timing belt & other?(looks like the plug belongs under the valve cover on the side of cylinder head) Trying to insert a diagram showing the plug but appears I can't do it unless it's a url...
 
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Doog, I got one vehicle. Is it safe to drive to the shop in the vehicle with a missing semi-circular plug located on the side of the cylinder head? or will i risk getting oil on the timing belt & other if I drive to shop?
 
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The only reason that it's there in the first place is because the factory needed the room for their machining tools to machine the cam journals- so they cast a semi circular shape in line with the journals. Afterwards, it was machined to spec (to better hold a seal) and the seal was put in place with a typically judicious helping of silicone sealer. The part itself doesn't really wear out, though sometimes the sealant does weep some oil over time.
 
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I own a 94 Corolla 1.8L and have worked on it extensively. The valve cover gasket set doesn't include a half moon plug/gasket for the exhaust cam which in turn drives the intake cam. The valve cover gasket is all one piece. The FSM says to put a dab of RTV at each corner of where the exhaust cam casting is in the lip of the cylinder head.
 
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"edit: after looking at my FSM, the plug actually fits in the head next to the intake camshaft. I agree with Eric, if there was one on your battery, I'd assume the mechanic didn't install it likely because the original one was glued in place with RTV. If it was missing or damage, oil would be literally pouring out the valve cover on the passenger side near the power steering belt/pump.
 
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They include the plug in case you're building a car from scratch. You don't need it; chuck it.
 

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Drew99GT & Others: the semi-circular plug the mechanic left on top my battery after he replaced spark plug tube seals & valve cover gasket had old oil on it. it was not a new plug. doesn't that tell us he took it out & didn't put it back in? another question: why would he even need to take the semi-circular plug out if he was just replacing the spark plug tube seals & valve cover gasket? tried to attach a photo of the plug but can't find an attachment link. the schematic from the other local mechanic shows the semi-circular plug is located on the side of the cylinder head, on the timing belt side. also tried to attach the schematic but can't...
 

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Thank you all for your responses! I really appreciate your help. I think this problem is resolved---let me know if you see it differently (like if oil could leak over timing belt later on rather than immediately if semi-circular plug was not put back in the engine just under the valve cover gasket): Manager looked at the semi-circular plug mechanic left on the battery, & told me it was the old plug & the mechanic installed a new plug [which was included in the valve cover gasket set: Worldpac Ishino Stone part #JVS-10344]. I asked the shop manager how they knew if a semi-circular plug was put back in the engine without opening up the valve cover or without asking the mechanic if he put the plug back in? Manager told me there would be oil spewing all over if the plug had not been put back in.
 
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Hold on a second here! Neither of you could ascertain 100% for sure if that was an old plug or a new plug? I thought you believed it was a brand new plug but the service manager convinced you that it was the old one? Frankly, it is *impossible* to mistake an old plug for a new plug if you have any mechanical inclination. The only issue here is whether the mechanic replaced the old with the new or let the old one in.
 

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Vikas & Others: When I showed the plug to the shop manager yesterday he told me it was the older plug that was removed from the vehicle. He said it was the older plug based on the way the coating looked on the round side of plug [it had some kind of black colored rubber or silicone like product on round side of plug]. This plug was oily with older engine oil on it---it could have been like that because the mechanic handled it with oily hands while he was working on vehicle or because he removed it from the vehicle. I called Worldpac & asked what was in their valve cover gasket set (part #JVS-10344) cause I can't view the parts online at worldpac.com since they are a wholesaler. The Worldpac rep pulled out Ishino Stone valve cover set JVS-10344 & told me it contained the valve cover gasket, 4 grommets, spark plug tube seals & a half moon shaped metal piece [the semicircular plug]. He said the replacement plug in the package doesn't have any type of coating on the rounded side. So based on what the shop manager told me & what Worldpac told me it sounds like I have the older plug in my hand that was removed by the mechanic, & that the valve cover gasket kit included a replacement plug. Right now there's no evidence of oil leakage on outside of cylinder head. So here's my question: If by chance the plug was not put back in the vehicle, could there be a delayed response in spewing oil on the timing belt or leaking oil back into the engine & fail the engine? Thanks! 96 Corolla DX, 1.8 L, approx. 161,000 miles (Toyota semi-circular plug is OEM part #11183-15020)
 
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If it had silicone residue, and discoloration on one side it was the old plug. He just forgot to remove old one from under the hood. If it was left out you should have a large amount of oil leaked from the engine by now. Should be ok. I usually just reseal the old aluminum half-moons by removing the silicone from the grooves when I replace the VC gaskets because they are a very common leak path. Often leaking as much as or more than the VC gasket being replaced. Ishino gasket sets are excellent quality.
 
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Originally Posted By: cjcride
I'd bet you would see a leak within the 1st hour of running.
The first 5 minutes more like.
 
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