Have '98 6 cylinder, 145k miles.

Found oil leaking out of two of the nuts that hold the rear exhaust manifold onto the head (no oil above or below the nut, it drips from the nut, to the bolt and fals onto the exhaust). Replaced the VC gaskets last month.

Did chemical test for hydrocarbon gasses in the radiator - turned out none present and no smoke out of exhaust. So, blown head gasket seems unlikely.

Is there an explanation for oil coming out of the exhaust manifold nuts other than a cracked head?

Is there a downside to trying oil leak additive?

 

Hi Steve -

Wondering if you ever had any success diagnosing and/or repairing this leak. I am helping a friend with his 97 Lexus ES 300, exact same motor, and his engine has the exact problem you describe. Cover gaskets are new, no leaks, no oil showing except for the exhaust nuts (each has a small drop of oil on them). Any info appreciated; cheers, Joel

 

Suggest not using oil leak additives.

Might find a dye that can be added to the oil and viewed under UV light. Perhaps there is a trail of oil above or in some other area that can't be clearly seen.

If you are sure it is the stud you can remove and reseal the treads with something like Permatex Copper RTV sealant. Make sure you clean the threaded areas of oil and allow the sealant to cure 24 hours.

As a quick and dirty remove the nut and install a copper crush washer under it. This might keep the oil inside the bolt hole of the manifold.

 

Thanks Joey P -

I am concerned simply in that I see no signs of oil from any other place...but I would not think that the exhaust studs somehow penetrated into areas where they could channel oil to leak. But I don't really know the engine so maybe they can leak oil.

I don't care for additives either and what I'm hoping is that, once I completed the work (replacing both valve cover gaskets (NO leaks now), spark plus and tube seals, PS pump, two motor mounts, both drive axles, and rear springs and struts), that I've simply not driven it far enough or gottten it hot enough to burn off the spilled oil, engine cleaner, etc.

We'll see, I return it to the owner this afternoon.