Nut in oil pump

[tdcockers Lurker Find all posts View Profile Close tdcockers]

Looking for an 'expert' on the 1GR-FE engine to answer a vexing problem.

We were 5 minutes into driving to our destination, when I heard/felt a very minor thump, followed a few seconds later by the oil pressure warning light. Pulled up, oil all over engine bay, towed to mechanic.

Mechanic pretty quickly discovered a decent crack in the timing chain cover whre the oil pump sits (see attached pics) and then shortly thereafter discovered a small, metal nut that had jammed the pump and caused the 'explosion'. Oddly, the screen on the sump pickup was in perfect condition, so the only way it could have gotten to the pump was via the pipe running from the pump to the top of the engine/oil filter.

So here's the question... under what conditions/circumstances could a nut of unknown origin have entered the system and traversed the oil pipe in the opposite direction to the regular oil flow so as to jam the pump?

[Bear63 Senior Member Find all posts View Profile Close Bear63]

From inside the oil filter maybe?

[tdcockers Lurker Find all posts View Profile Close tdcockers]

True, though the oil filter hadn't been replaced for around 10k. Is it possible for oil that's just been added to the engine to get picked up by the filter, or is only oil brought up by the pump pushed through? I'm wondering it I've topped up the oil, and started the engine shortly after, if there was a nut in the oil could it get pulled into the filter from the top of the block and then released back down to the oil pump after the engine is shut off?

[Leethal Advanced Member Find all posts View Profile Close Leethal]

Every engine I have seen the oil flow is from the sump pick-up (or dry sump scavenge pump ) through the oil pump and then to the oil filter or on occasion the oil cooler then filter.
Without a Design and Function manual for the engine it is hard to say but my thought is the nut has to have come somewhere internal to the oil system. Has the oil filter housing/manifold been off in the past at all? Perhaps for a relief valve issue or oil leak?
I have seen a nut accidentally dropped by the owner through his carby and "live" in the intake port of a petrol engine for several months before finally falling through an open intake valve when shut down. The result was the engine would not turn over because of the jammed nut. My point is that your nut may have been loose in the system for some time before finally landing in the pump gears.

Lee

[tdcockers Lurker Find all posts View Profile Close tdcockers]

LOL at dry scavenge pump... But yes, the oil flow is bottom to top which is what is confusing me. We had been driving for 5-6 mins before it seized, and the screen between the sump and oil pump is in perfect condition which suggests it must have been in the oil pump pre-start and took that long to get jammed (or possibly that long to crack the cover).

Re service history, other than oil changes there hasn't been anything done on the oil system since we've had it (5 yrs/90,000km), it's been perfect. I'll have a closer look at the casting if I get a chance before it's put back on and try to figure it out, but like you I would assume that it had to either be in the pump or in the filter, I thought there would be a closed circuit between them.

The only thing I can think of at this point is that one of the kidlets might have put a nut in the filter when I wasn't looking at the last change, and it's taken that long to find it's way down. I'd like to think I would have heard/noticed a nut in the filter before I screwed it on, but you never know I suppose.

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

Can you post up some more detail photos of the nut, it looks odd to me?

[chrisgrind Spammer Find all posts View Profile Close chrisgrind]

Can you post up some more detail photos of the nut, it looks odd to me?

yeah, looks like it's broken out of a housing and bought the housing with it. almost looks like a rivnut (but don't think it is).

[tdcockers Lurker Find all posts View Profile Close tdcockers]

I don't have any better photos unfortunately, but rivnut is a good guess... I thought it was something like that, used to bolt something into sheetmetal. There is evidence of a serrated surface/washer in the crease, but I couldn't identify any other material in there. Before it got crunched, I think the 2 faces would have been pretty close to the same, so possibly was clamped using a press (both sides accessible) rather than being pulled like a rivet.

Best guess of dimensions is maybe 10mm diameter with an M4 thread?

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

I'm just wondering if it is as suggested part of a housing where someone has put a bolt in that is to big and broken the bottom the back of the housing,
ie the bolt has broken through the material it was screwed into?

With regard the oil pump, I haven't looked at the one concerned but from memory with one I took off another car, the oil pump was two gears, as
they messed together it pumped the oil out, on the outlet side the gears are meshed where the outlet side the gears are meshed, if yours is simialr
then the nut would not be able to enter the pump from the filter side.

[Guest Close Guest]

Looks like bottom of a threaded hole or something from inside a rocker cover perhaps.. Not a Nut as such, but just as destructive... May as well get him to check for anything else whilst he has it that far down. Water pump, seals etc..