Hi Everyone,

New here and recently rebuilt and turbocharged my '92 Miata. Had it remotely tuned and it was running great, just had a minor oil leak I couldn't track down. Decided to have my mechanic repair the leak due to lack of free time right now. He ended up redoing the rear main seal and the oil pan RTV. When I got it back I noticed a very mild ticking that wasn't there before. It quickly turned into a loud knock and I ended up getting it towed.

I now have the engine apart and found a spun bearing. Other than that, the damage didn't look too bad. Getting the crank looked at this week and going to replace all the bearings, as well as clean out the block the best I can.

I wanted to get everyone's thoughts on anything else I should do to help prevent it happening again, as well as what may have caused it. It looked like the mechanic went a bit overboard on the RTV, so I'm wondering if some plugged up an oil passage and caused it. Didn't see any plugging anything when I got it apart, but that's not to say maybe it only happened briefly.

Thanks!

 

I would check the oil pump. Was the screen clogged? Or did a piece of rtv make the relief valve stuck open? Also I would look into getting a new oil warmer, incase any bearing material gets stuck in it and it's easy to miss.

 

Thanks for the reply. The oil pickup screen did have bearing material plugged in it so I’ve cleaned it all out. I will look closer at the oil pump and check the relief. It’s a boundary oil pump so I would think it should be ok as far as any damage. No oil warmer on mine as it’s a ‘92. Thanks for the suggestions, just want to avoid it happening again. Going to be very careful with the rtv when I put the pan back on.

 

you sure the mechanic put oil back?
replacing an oil seal shouldn't give you rod knock....or you already had it and just happened to get worse.
in any case.
did the rod overheat?
diud the crank overheat?

 

He said the tech did the seal as well as the pan gasket, which is just sealant on these motors. So rtv could definitely be the culprit.

OP did you have an oil pressure gauge? Notice any low dips or fluctuations?

Gotta say though, if the bearing was far enough gone that you had chunks big enough to clog the pickup screen, you should check that rod’s big end bore very carefully. It may have started to ovalize. I’d recommend really deep cleaning everything you possibly can; pull the cams and lifters, clean all those oil passages out, pull the plugs from the block and clean those passages, etc etc. and yes absolutely pull the pump apart and clean/inspect closely. I’d also say clean out the crank oil galleys too.

 

This...

If bearing material plugged the screen, then there are tiny pieces of the same that made it past and have gone into the oiling system. If you're going to re-use the block then everything that touches oil needs to be disassembled, thoroughly cleaned inside and out and rigorously inspected. Take it to a machine shop and have the naked block and head hot-tanked (with the plugs for the oil passages removed). You can elect NOT to do this - and you might even get away with it - but odds are that there is a piece of metal lurking somewhere with your name on it that will find it's way onto a critical surface and you'll be doing this all over again.

 

Well put, and all solid advice. Maybe also check the cam caps for wear or gouges, 1.6 heads are cheap enough it could be worth replacing if they're all torn up. The tapping you initially heard was probably a lifter starving for oil/pressure.

If you do wanna go more minimal approach, which I can understand from a time/money standpoint, you'll wanna pay the most attention to everything pre-filter in the oiling system. The oil filter can do a pretty good job of stopping most bigger particles from getting through, but remember the pump and bypass valve are pre-filter, so it will have ingested anything big enough to get through the mesh on the oil pickup screen.

Godspeed bud, let us know what you find!

 

Thanks for the great advice everyone. I’ve sourced another engine from a wrecker so I’m going to just use the crank from that one. Will definitely get the machine shop to look at it first. Will be taking the entire block apart and giving it a good cleaning and inspection as well. Will be nice to have two motors to mix and match parts from. Should hopefully have her back on the road before too long.

 

Filters do bypass and the OE filters have a low setting. I would also remove the oil galley plugs from the head.

 

Yeah, will most likely get it looked at and hot tanked at the same time the crank is at the machine shop.