Oil leak on 26 Buick in Buick - Pre War Posted February 16, 2012 I have an oil leak on left side of engine. Coming someplace behind exhaust-intake manifold. I used dye in the oil and a black light but can't seem to see where it is coming from. Valve cover isn't leaking. Could the head gasket be leaking oil? I have never heard of it but maybe. Thanks for any help.