I have a slow leak on the passenger side on the bottom of my engine and can’t find where it’s originating. Has anyone used an oil dye with success?

Most of us just look at the usual suspects: valve cover gaskets, oil cooler seals, push rod tube seals, oil pressure switch, rear main seal, missing t-stat bolt, distributor o-ring, oil fill tower gasket....

Oil dye could sure offer clues, though.

I used it a lot when I was still fixing cars for a living. It works great, provided you can actually see where the leak is coming from. Usually on a /4, I will do what I call a "full service". Replace the seal on the fan end of the crank, the oil cooler seals, the oil pressure switch, the sump plate gaskets, the drain plug washer, the pushrod tube seals, adjust the valves, and put in new valve cover gaskets. Whenever I do a clutch, I replace the flywheel end crank seal too. That about covers all the places a 914-4 can leak.

Right now, Frody seeps between the oil pump and the case. It takes a while to get low, and I am not too worried about it. I will get it the next time the motor is out of the car.


On a /6, it is much more complex. To get everywhere it could possibly leak, you have to pull the timing chain boxes, and that means retiming the cams. And the oil return tubes don't come out unless you pull the cam carriers. So I evaluate what is leaking and just fix that. Elwood has a slight leak on the left timing cover. I need to pull it and fix the leak, but I have not had any time for anything other than the engine for Igor, so it is waiting for the winter.

Motor oil will fluoresce under a black light as milky white, the dye helps though.

I'd clean your engine as good as you can, run it, and then shine the black light on it. I have the most success with this at night as I've just got the little "Smart Light", which is a small fluorescent black light

Part of the problem with air cooled engines is the oil migrates with the airflow from the fan.

Clay's advice is good though, there's really just a handful of places a 914-4 engine can leak

I had not thought about using a black light shining on the oil without the dye. I have a newly rebuilt motor with all new seals and everything is very clean. I think I'm getting a leak from one of the push rod tubes. I'll try the black light.