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Discussion Starter · #1 · (Edited)
Knocking and oil light lit (video)

Hi guys,

Got LS 1993 with KLZE swap.
Yesterday I went to a store to buy something and when I got back I noticed loud knocking sound from the middle of the engine (It was fairly cold day -5 celcius). Engine has knocked/tapped a bit before but nothing this loud. Today I ran it a bit in the garage and noticed that the oil light is lit. Checked the oil and its up to the full mark. What would cause loss of oilpressure and and loud knock? I'll do compression test tomorrow to see if all cylinders are good. I use fully synthetic 5w40 oil. Engine light has not lit and there are no codes...although I have not seen engine light come on after installing Probinator Chip nor there have been any codes.

YouTube - Mazda Mx-6 KLZE Knocking sound

Thanks in advance!
 

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oil pump, perhaps.

full oil doesn't mean much if it's not getting pumped into the engine...

good luck :\
 

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Discussion Starter · #3 ·
Yep, it doesn't mean much but there should not be leaking atleast. I hope the engine is not a goner since it took great effort to get it to Finland from USA.
 

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could be rod knock. bad clearances can cause your oil pressure to be low as well.
 

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Discussion Starter · #6 ·
Ok, I'll record a clip. Its not anything easy that is for sure since the sound is very loud. I think something happened (something broke) which then causes no oil pressure which then might have broken something else which ultimately causes the knock, broken valve or something like that. The sound is so bad I am afraid of running the engine at all :(
 

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Discussion Starter · #7 ·
A theory, since the engine has ticked before I think that came from timimng belt tensioner (compared the sound to videos in youtube). If the tensioner broke totally could the timing belt have jumped? If it would have jumped what would happen and how that can be diagnosed?
 

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Well there's one way you can know if it's the tensioner - if you didn't replace it like you should have when you installed the engine lol.

And yep, that could definitely cause it to skip a few notches on the belt or just make the engine stop working.

Another idea, check that there's spark to all cylinders too if you haven't. Running on 4-5 cylinders can make it sounds REALLY rough lol.

Check none of the PCV hoses are split or have came off. There's one that runs from the rear valve cover to the front, it T's off and goes into the intake manifold. I remember when I first started up my ZE and it sounded absolutely rooted! It was because I forgot to connect this.
 

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Discussion Starter · #9 ·
I have just checked the vacuum lines a month ago.

One more question, could the oil level still be low even though the dipstick tells that its full? This engine used to eat some oil but when I switched oil brand 6 months ago the level has been steady at full. I am a bit suspicious that just by switching brand causes little to no leak/burning of oil. I am afraid to add anymore oil since it seems like full already. What happens if there has been too much oil? Can starvation cause low oilpressure?

enough speculation, here is the video:

YouTube - Mazda Mx-6 KLZE Knocking sound

Hope it helps.
 

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motor = toast :(

Get that bottom end checked out!
 

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Discussion Starter · #12 ·
Guys, any helpful comments? broken cam shaft? bearings, pistonrod?

It was fully working just before, the trip I drove was just few miles, how bad it can be damaged at such a sort run.
 

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Dont Let everyone get your hopes up to fast, I had a spun a rod bearing on one of my motors and it sounded alot worse then that.. The motor actually killed when it spun (100mph) and it barely ran when I restarted it. I dont know why, but everyone with one of these cars prefers to assume the worst and not look into it.

Couple examples, This was a recent one of my motor, It sounds horrible, but it ended up being a loose crank pulley, the bolt loosend up. Every comment I got on it was that motor was junk.
YouTube - Name that sound

Also had something similar last summer, my underdrive pully broke apart. It made a metalic banging sound on the engine, everyone says the motor is shot.
Come to think about it, anytime I posted up a engine sound that resembled nocking, everyone says its junk.

What you can do (thats easy) is drain the oil and check for shavings. If you dont any shavings at all, check your timeing belt. The oil sender light I wouldnt even worry about right now.

Unfortunetly it does look like our cams can break (seen it on PT) so thats another thing to look at.
 

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You never said if you replaced the timing belt hydraulic tensioner or any other timing belt related items. Did you? If not, check that stuff. My MX6 makes a ridiculous metallic knocking sound but it's just the hydraulic tensioner.
 

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Discussion Starter · #15 · (Edited)
I have not indeed changed the tensioner nor any timing belt related stuff. Its too much of a coinsidence that that the enginesound has gone ridicilously loud and same time oil light is lit that these would not be linked. I am just trying to make the connection here. If the tensioner has indeed failed I still don't see the connection to oil pressure. I think I'll start with the oil inspection then the timing belt and finally cams. after that its out of my league.

The underdrive pulley was replaced(RR-Racing) when ZE was installed 4 years ago. Now that I think of it, I have noticed some slipping of the belt just recently in form of loss of powersteering after starting.

This was on the RR-Racing website, I have no idea if the shop did it when installing the pulley...
Please note: All underdrive pulleys for the 2.5L engine (regardless of the manufacturer) require that the thin aluminum/plastic flange on the oil pump housing be grinded off. This is easily accomplished with a die grinder (in a few minutes).
 

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Well if those have failed, it may be badly out of timing, I'm not sure if any of the belts drive a pulley for the oil pump, but if they do then there's your link.

Either way, I think your process of elimination is a fairly good, one, start with the oil then get to the harder stuff after that :tup:
 

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that doesn't sound like a toasted engine to me.

I would check that underdrive pulley I've seen a couple broken ones. (and please go back to a stock pulley if it is broken) and your timing belt tensioner before I worried about the bottom end
 

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We slipped a notch on my timing belt when we changed the water pump(had to remove everything for access) and it sounded horrible...they're a beast to deal with when you have half the engine apart...Work your way from the simplest thing to the hardest...sometimes the simple problems make the car sound its worst!
 

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Discussion Starter · #19 ·
Update after a "while" - I checked the shavings of the oil and found none. Also I checked compression levels from each cylinders and all seemed fine.

Now that I have finally some time off I'll check in to the the things you guys suggested. I'll let you know how it goes =)

one comment though: As there is instructions to shave off a piece from the oil pump housing when installing underdrive pulley, doesn't that mean that the pulley is attached to oil pump? -> if its stuck etc -> no oil pressure.
 

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Ill just add:

I had the tensioner knock happen to mine... extremely common and seems to happen on this cars at 100-120k miles.

It sounds just like this except the tensioner is RPM dependant and revving above 2250 rpms makes the tick go away completely - this is the easiest way to tell if it is indeed the tensioner.

But like everyone here says - with the oil lights on and no oil pressure, that knock sounds pretty bad.
 
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