Travoli

Had an oil pressure sensor snap in a Honda B18C block tonight while driving around. Possibly due to a bump on Interstate 64. It is a pretty standard aftermarket (brass?) fitting for an aftermarket gauge, not OEM piece. Broke right at the outer edge of the block. A thin metal ring clung to the brass also (pic attached). I certainly don't want this to happen again, anyone got a theory as to why it would snap? Pics might have clues:

Travoli

I hear its the weight of the sender. Bummer.

Fabrik8

Brass is very soft, and very weak.. That's a lot of weight hanging off at what looks like a good distance, and brass is prone to fatigue wherever there is a big change in stress. The point at the edge of the block is where the stress is concentrated, and the brass fitting is already weak because of the thread stretch. Oh, and the weakest point on that entire fitting is where those threads are; if you notice the threaded area is smaller diameter than the rest of the fitting, and the root of the thread is even smaller than that.
Do you see how little wall thickness there is where that fitting broke? That little amount of brass with that much stress on it spells easy failure.

By the way, those plier marks on that fitting seems to suggest that you tightened the shit out of that, which is a bad idea with brass..

83Stang5.0

QFT

Fabrik8

By the way, exactly how big is that sending unit? That thing looks giant in the picture compared to the size of that adapter.

The sending unit should be fine, and as long as you can clear the old brass from the block, you should be able to remount and use the sending unit.

We usually use a short piece of flex line between the sender and the block, and mount the sender to something like the engine or the chassis with a bracket.

Don't worry about pressure drop or anything in a flex line, I don't know where people got that idea. There isn't any flow through the line, so there isn't any pressure drop. Just make sure you get as much air out of the line as you can, so the pressure isn't affected by an pocket getting squeezed. If you put the sender lower than the bung on the block, the air will bleed out of the line automatically (fill the line with oil first) but make sure you don't have any leaks at the fittings..

Anyway though, if you go that route, the sender is firmly secured to something strong, and you don't have a weight on a stick bouncing around at the frequency of the engine.

Travoli

Well, I didn't put it in personally. A well-known Honda tuner did. Which is why I am curious. Others have mentioned the over-tightening also. This fitting was put into the block 2-3 times total before running the car due to engine problems. There were no pliar marks the first time, but sure looks like something on there now.

Fabrik8

Regardless of who installed it, it should be mounted properly. There isn't anything wrong with brass fittings as long as they aren't overtightened, but if you can't mount the sending unit directly to the block (without an adapter) you should really remote mount it.

Travoli

I certainly will have it relocated. NOt sure why they would have let that out the door in the first place, it only lasted ~160 miles. Need to find out about the status of the motor first. It is a custom sending unit for a custom gauge, but a pretty standard piece AFAIK.

Fabrik8

I'm sure it's a standard sending unit, the brass adapters came from Lowes or Home Depot probably. Brass plumbing fittings don't have any business being on an engine, unless they aren't under any structural load. You can't blame this on the sending unit, it's all the fault of the adapters.

Whatever shop did this should have known better, this is very sloppy work. It's the kind of thing you put out the door and say "boy I hope this works and we don't see it again in a week". If you have to say that, you know you've done something pretty shoddy.

nftuatn

ive heard about this happening when vtec kicks in....(too much powaaa) but i dont know in your situation...