Finally figured out why those cheap oil filters keep causing startup knock

After dealing with 3 customer engines that had sludge buildup last month, I took apart a few discount filters and found they don't have the anti-drainback valve that keeps oil from draining into the pan overnight, so when you crank it in the morning all the top end is bone dry until that pump catches up.

3 comments

3 Comments

ray6138d ago

Ngl, the stuck bypass valve is the part that really gets me. Did you notice if those cheap filters had any kind of perforated metal screen on the inlet side at all, or was it just a straight paper element jammed in there? Curious if they even bother with that basic piece of engineering or if it's just a cardboard tube with some glue holding the media in place.

kimblack9d ago

Three engines in one month man, you're basically a discount filter detective now. I hate the sound of dry start knock almost as much as I hate admitting I've got a whole toolbox of cheap ones from that one sale last year.

bell.jessica9d ago

Best part about dry start knock is how long it takes to figure out if it's the filter or the oil itself crapping out. Managed to get one of the "bargain" brand filters on a clearance rack and the bypass valve stuck halfway open, so it was dumping unfiltered oil right back into the pan. Thought the engine was toast for a solid week before I swapped it out with a standard fram and the noise stopped. That's the real hidden cost nobody talks about - the time wasted diagnosing stuff that shouldn't even be a problem. Makes you wonder if those discount filters are even tested before they get shipped or if it's just pure luck of the draw.