Odd Rod Knock

Hey guys, new to the Mazda forum, of course with a question to begin.

My dad gifted my an '03 Mazda Proteg5 for my 18th birthday last year, but I didn't get to drive it very long because of a rod knock that quickly developed. I found that the car was leaking/burning oil at a very quick pace, hence the knock. It progressively got worse until one day there was a loud thud from the engine bay while I was driving it, and everything died in the car (I also might note that the battery terminals were so loose that they would constantly disconnect). When I got it to a stop, something spilled out of the bottom and caught on fire, which I presumed to be the oil. I had it towed away and I was sure that I just threw a rod. It's been under a year, and I just had it towed to my new place. Since the incident I got an apprenticeship job as a mechanic, and am currently in the middle of an engine swap for my Jetta. So I decided to take a peak at it. However I discovered that the oil pan was very much intact and it still had all of the oil I had poured in the day it broke down.

Any ideas as to what might have happened?

TL;DR: Proteg5 had rod knock, very loose battery terminals, and burned/leaked oil. When driving it, there was a loud thud and everything turned off (Yes the thud set the battery terminal loose). Something spilled on the ground and caught fire. Had it towed away, and when I got it back a a few months later, I found the oil pan was still intact (I previously thought I threw a rod into the oil pan).

If any more information is necessary, I can go out and check on it. However I cannot jack it up at the current moment because my only hydraulic jack is being used to hold my transmission up in my Jetta.

These engines are known to burn oil because of stuck oil rings and valve seals.

Are you sure the noise was coming out of the bottom end and not out of the top end? I ask because these engines have solid lifters which need to be adjusted once in a while, otherwise they will make noise and possible burn some valves.

If it was from the bottom end then its probably your crank/connecting rod bearings that got worse and worse until it finally crapped out.

Maybe a bit of oil leaked passed a gasket somewhere when you were running it and caught on fire.

Everything died in the car because of your battery terminals.

The_big_dill said:

These engines are known to burn oil because of stuck oil rings and valve seals.

Are you sure the noise was coming out of the bottom end and not out of the top end? I ask because these engines have solid lifters which need to be adjusted once in a while, otherwise they will make noise and possible burn some valves.

If it was from the bottom end then its probably your crank/connecting rod bearings that got worse and worse until it finally crapped out.

Maybe a bit of oil leaked passed a gasket somewhere when you were running it and caught on fire.

Everything died in the car because of your battery terminals.

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I knew everything died because of the battery. I can still switch it to the "on" position and all the electronics still work. Just trying to pinpoint where the rod was knocking in the engine, and what I can do to fix it. Trying to figure out if it's necessary for a new/refurb engine swap, or just a rebuild.

Is there anyway that you can remember the engine speed and noise frequency? Different parts of the engine revolve at different speeds. Valve train noises are at half engine speed. Rods and cranks are at engine speed.

http://www.marinemechanic.com/site/page52.html

These engines are on so many mass produced platforms its almost always better to replace the engine with another.

You can only know rod bearing damage if you look at it. You can pull off the oil pan and windage tray (which means you have to take off the transmission) to have a look at it.

Another way is to turn the engine by hand until you know the piston is moving down the cylinder, then push it with a long extension or screw driver, if you feel it move, you found your cylinder with a bad connecting rod bearing. This usually also means your crank is no good either, unless it is worth your money machining it.

Rods can punch a hole through the block too, not just the oil pan. You might have a hole in the back of the block. There are slots in the upper girdle that you can peek through after removing the oil pan, to get a look at what's happened. The engine will have to come out either way though.

There are many parts for these engines available from scrapyards for not much money. Machine work isn't cheap, and if it tossed a rod there's a good chance it won't be feasible to salvage the crank. By your description it sounds like the bottom end of that engine is toast. If the rod or main bearings are spun, that adds even more money to the bill. The rods will need to be replaced, and the block will need machining. Keep in mind that rebuild parts for these engines aren't very cheap either.

I've got a good crank and rods that I'll sell you for cheap, if you end up needing them.

gilella said:

Is there anyway that you can remember the engine speed and noise frequency? Different parts of the engine revolve at different speeds. Valve train noises are at half engine speed. Rods and cranks are at engine speed.

http://www.marinemechanic.com/site/page52.html

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Unfortunately back when this was happening I didn't really know the first thing about cars. But from what it sounds like, I will most likely be better off getting a new engine to swap.

The_big_dill said:

These engines are on so many mass produced platforms its almost always better to replace the engine with another.

You can only know rod bearing damage if you look at it. You can pull off the oil pan and windage tray (which means you have to take off the transmission) to have a look at it.

Another way is to turn the engine by hand until you know the piston is moving down the cylinder, then push it with a long extension or screw driver, if you feel it move, you found your cylinder with a bad connecting rod bearing. This usually also means your crank is no good either, unless it is worth your money machining it.

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Figuring out which cylinder was knocking is definitely worth it. It'll make figuring out what needs to be done a whole lot easier. However if I could find an engine at the right price, I'd much rather swap engines which I actually know how to do. I can't seem to find a manual engine at a good price or from a place that seems reputable.

MrGiggles said:

Rods can punch a hole through the block too, not just the oil pan. You might have a hole in the back of the block. There are slots in the upper girdle that you can peek through after removing the oil pan, to get a look at what's happened. The engine will have to come out either way though.

There are many parts for these engines available from scrapyards for not much money. Machine work isn't cheap, and if it tossed a rod there's a good chance it won't be feasible to salvage the crank. By your description it sounds like the bottom end of that engine is toast. If the rod or main bearings are spun, that adds even more money to the bill. The rods will need to be replaced, and the block will need machining. Keep in mind that rebuild parts for these engines aren't very cheap either.

I've got a good crank and rods that I'll sell you for cheap, if you end up needing them.

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I'm not worried about machining anything because I work in a shop that has plenty of machines for it. However I think I'd be better off finding a new block.

Manual engine? You mean transmission? Don't you already have a manual transmission?

x2 for just plan to swap engine. The oil pan can hold oil on a blown motor...

The_big_dill said:

Manual engine? You mean transmission? Don't you already have a manual transmission?

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I've been told by some people that engines are sometimes only compatible with a manual or automatic transmission. Is that not true about the P5?

Vince Vu said:

I've been told by some people that engines are sometimes only compatible with a manual or automatic transmission. Is that not true about the P5?

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I have never heard of an engine from a manufacturer that isn't compatible with both the automatic and the manual counterpart, so long as its the same engine.

Vince Vu said:

I've been told by some people that engines are sometimes only compatible with a manual or automatic transmission. Is that not true about the P5?

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Definitely not true on this engine. My JDM engine came with a flex plate for an automatic, my flywheel bolted right up to it.

So you work in a machine shop that turns crankshafts, surfaces cylinder heads, etc.?

MrGiggles said:

Definitely not true on this engine. My JDM engine came with a flex plate for an automatic, my flywheel bolted right up to it.

So you work in a machine shop that turns crankshafts, surfaces cylinder heads, etc.?

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I'm not 100% sure what the rest of the crew does. I just know we have a whole bunch of machines. There's only 2 of us who do serious engine work.