Mazda 5 engine ticking... is this a time bomb?

[jmcglynn]

Latest update...
I agree with phunky.buddha on both points.... it would seem that everyone is reluctant to pull the oil pan. Even my trusted 2nd opinion mechanic, who was going to pull the pan, hasn't done so yet just for that reason... that, and because he's convinced it's not a rod knock. His own analysis of the oil doesn't indicate any internal damage, and the inconsistency of the sound itself doesn't fit a typical rod knock profile, even in the early stages. A rod knock would/should be a consistent sound, regardless of load or RPM. This ticking/knocking sound only appears after warm-up, during that mid-speed, mild-load condition. In the one case of rod-knock I've actually heard, it got worse with acceleration. Here the sound goes away when I hit the gas hard. I've been going blurry-eyed looking through the tech manuals (thanks again to flcruising for posting a link to these... very helpful), and I too have a hard time thinking it's a rod knock. So if not that... then what is it?

Our latest theory, independently reached by both my mechanic and I, is that it's the timing chain (or one of the associated parts). I haven't had a chance to query that through this forum yet, but my mechanic's internet research shows there have been a number of issues with the timing chains on this engine (which is shared with Ford Fusion). Apparently special tools are needed to get to the timing chain, so while my mechanic waits for his tool guy to show up so he can break into this part of the engine, I put it to all of you... what do you think of this latest theory?

 

[Silentnoise713]

It would help if you can upload an A/V clip on youtue so we can hear it. At the moment my vote is on valve tick. I've heard some Miatas with it and it mathes why you describe; this is a feature of Mazdas. My understanding from various owners is that it does not do additional harm but older MZR engines use HLA (Hydraulic Lash Adjuster) lifters, which are prone to valve tick. Search any previous Mazda and you'll find comments about valve tick. I just searched and it seems some Mazda3 owners are also experiencing this but I though the latest MZR use a different valve mechanism (I thought I read that but may be mistaken).

If it is valve tick, it's nothing to worry about. This is cause by using inappropriate oil weight and/or too long of a change interval. Changing 11k mile oil every three months is very different than changing 11k oil once every year, which sounds like the case bc of the low mileage for an '06. Time interval is just as important as mileage interval.

http://forum.miata.net/vb/showthread.php?t=221803

A simple thing you can try is change you oil to a full synthetic 0-20 oil (if the curret oil is 0-20 then change it to 5-20). If it goes away but comes back after a few thousands miles then you may very well have the same issues as the link above and Mazda hasn't changed all that much -does not surprise me.

(sry for iPhone typos, hard to correct )

 

[Davicho]

I also don't believe is anything deep as you have been probing for. My opinion is either as silentnoise said the valve adjuster lifters or as I had said before the intake runners or just plain cheap gas. Convert to full synthetic but I wouldn't go lower then the 5w20 weight and use premium brand gasoline. Valve lifters on our MZRs are not designed to be adjusted but can be replaced.

 

[Robotazky]

When our car was new it had a knocking sound from one or more belts. They gradually got better, but now with 40,000 miles, I'm starting to hear a little bit of noise again.

OP, after the checking around you've already done, I'd do everything I could to rule out belts also.

 

[jmcglynn]

All your latest comments are very helpful. Thank you all. The fact that my mechanic hasn't gotten the necessary tools yet has given me an opportunity to think more about this, so I spent the weekend pondering the whole timing chain issue and doing more research. In a lot of the posts I read where they replaced the timing chains, it didn't solve the ticking problem. Given that, I'm very hesitant to wanting to spend the money to do that if, in fact, that doesn't solve the problem. I'm going to have to have a heart-to-heart with my mechanic to talk more about this.

In the meantime, I think I want to get the car back and record the sound as you recommended. It would be very helpful to get that on "tape" so I can get more feedback. More to come...

 

[Robotazky]

^^^ Yes, please do record it. A video would be best.

Regarding the timing chain; I have trouble seeing how a chain could be so severely stretched out in only 70K miles. I can imagine, however, that the tensioner on the chain could go bad. My MX3 has this tiny little part that pushed really hard on a part that put tension on the timing belt pulleys. When it went bad the friction gear at the end of the valvetrain was really noisy. It clicked and knocked. IF it is this part, the noise will come from the end of the head where the belts are.

We'll eventually figure this out. When you post a video I think you'll get good results.

 

[jmcglynn]

Good point... I was thinking more likely the tensioner than the chain too. We'll see... more to come...

 

[jmcglynn]

OK... here's the latest update...

Seems I was one step behind my mechanic on this one. As I was pulling together the gear I needed to do several good recordings of the sound (both standing still and while driving), my mechanic had gotten the tools he needed and was busy stripping things down. No worries though as I had already given the go for him to do this.

During my visit this morning I was able to see the engine with the front and top covers off, and the timing chain assemblies removed. Seems we've both been watching the same YouTube videos with regards to Mazda knocks and rattles. Anyway... looking at all these bits taken apart, the smoking gun would appear to be the chain tensioner (as was suspected above). My mechanic's latest diagnostics isolated the sound to the front of the engine right where the tensioner is located, so we're both fairly confident that this is the likely source of the problem. Again, because the knock is not constant (only happens at certain speed and load), and that the oil analysis came out clean, we still can't believe it's a rod-knock as the dealer has said.

Of course, since the front is all disassembled we're going to replace the chains and all the other bits. The chain itself looks good (if a bit smaller than I expected in real life), but the chain guide behind the tensioner did have some wear that didn't look quite right both on the front and on the back, possibly due to the tensioner knocking against it. Overall it was a good tour through the bits of the engine you don't normally see. If I had my wits about me I would have brought my video camera along... bygones...

So now he's gathering all the parts and will start putting it all back together. I do have to say, after seeing the engine apart, and seeing how good it looks overall (the block, the cams and the head all looked very clean, no discoloration due to scorching or high temps), I'm feeling much better about it. Still, we won't know for sure until we get it back together and on the road... Still more to come...

 

[phunky.buddha]

Sounds better than the dealership told you... did your mechanic pull the head? If so, perfect time for some 13:1 pistons, an aggressive port/polish job, and a fat lopey set of cams.

 

[jmcglynn]

Latest update...

Trusted mechanic got the engine put back together... all new timing chain components. Still makes the ticking sound. Granted, it idles much smoother now, and the ticking is somewhat quieter, but still there. He's going to try one more adjustment to see if that solves it, but at this point we're both pretty perplexed. So to recap what we're hearing...

-There is a ticking/knocking in the engine bay that's related to engine RPM
-It occurs in the 2000-3000 RPM range with a light throttle
-It does not occur at startup or when cold... only when the engine is warmed up
-It does not occur at idle
-It does not occur when under load or full throttle

Mazda dealer diagnosed it as "rod knock" and recommended new engine, but neither I nor my trusted mechanic can concur with that diagnosis because it just doesn't seem to fit the typical rod-knock sound profile:
- The oil analysis is clean, so nothing unusual in the oil
- The sound is not continuous
- The sound does not get louder under load
- All the other reasons above

I should also remind everyone that this is a 5 speed manual. My mechanic noted that if this was an automatic, it's likely I might not even hear the sound because of the load/shifting dynamics of the automatic.

I should be able to pickup the car tomorrow, and then I can make some video recordings and post them up for everyone to hear. In the meantime I welcome any other thoughts, ideas, or experiences...

 

[flcruising]

Intermittent noises are some of the most eluding to pinpoint, as you can tell. And I'm glad the service manual was helpful to you as well or at least enlightening.

Can the sound be replicated in the driveway, or must you be moving to hear it? Does light throttle indicate that you are at cruising speed?

On the thought of lifters (tappets), my experience has been that they are noisy when idling cold, and quiet when warmed up and driving. The location of the sound is obviously from the top of the engine, not the bottom. Being hydraulic, oil flow is the main factor to their sound level and proper operation. A test that can be performed is to change the oil to a thicker weight and see if the noise changes - I would suggest 10w-30 (no you don't have to worry about damaging anything).

Spark knock (pre-ignition), as you probably know, is load related and usually diagnosed by checking/changing the spark plugs, knock sensor, timing sensor (crank/cam), a weak coil, combustion chamber cleaning, or switching to high octane fuel for a short time.

Rod knock is persistent and steadily increases with engine load and RPM. You will know eventually when the rod breaks and busts a hole in the side of the block.

Lastly, are you sure it isn't the a/c compressor?

 

[thaxman]

[No message]

 

[jmcglynn]

OK everyone... got the car back. It's still ticking, but otherwise running very well. I made this quick audio recording. I clipped a microphone to the passenger side of the plastic engine cover, and took it for a spin around town. Give it a listen and let me know what you think...

In the meantime, I'm going to make some additional recordings (video and audio) to see if I can paint a better picture of the sound.

 

[phunky.buddha]

Man, I can see why the dealership thought it was rod knock.. it definitely sounds like a hard metal to metal sound. There's a lot of extra noise to try and hear through though. Has anyone tried to use an engine stethoscope to try and pinpoint exactly where the sound is coming from? You can improvise with a really long screwdriver against the block and "listen" through the handle...

 

[Robotazky]

Man, I can see why the dealership thought it was rod knock.. it definitely sounds like a hard metal to metal sound. There's a lot of extra noise to try and hear through though. Has anyone tried to use an engine stethoscope to try and pinpoint exactly where the sound is coming from? You can improvise with a really long screwdriver against the block and "listen" through the handle...

You can also use a broom stick. It works very well.

 

[doctorz]

Are you sure that the ticking isn't there at high RPMs or at idle?

 

[jmcglynn]

Let's unpack this some more...

First... The dealer said that they did use their version of a stethoscope in their evaluation, and determined that it was coming from the bottom of the engine, which was the main reason for their rod-knock diagnosis.

Second... recording the sound from under the hood has definitely revealed more sounds coming from the engine than anyone would notice by just driving the car with the windows down (we never heard any sound with the windows up. Add in the A/C and the radio, and no one would have noticed a thing). Further, having done some work in film and video production, I know a microphone tends to pickup things that the human ear can sometimes miss. It does sound like a hard metal-to-metal sound, and the recording would indicate that it is occurring more consistently through the RPM band.

This first thing I'd like to do is make some more, better recordings and video of the sounds... particularly from a cold startup. This is usually where a rod knock will give itself away as the bearings haven't yet been fully lubricated or come up to temperature. In fact, the engine seems to run very quiet and smooth from a cold start... which is why my other mechanic has a hard time believing it is a rod knock. So some better recordings may reveal some things that we're not able to hear right now. So... more to come.

In the meantime, I got a voicemail from the Mazda dealer service manager. I kind of trashed them and Mazda on a corporate survey they sent me shortly after the diagnosis, and they wanted to follow up. I'm kind of reluctant to call them back... but I suppose I should hear if they have anything new to say.

 

[thaxman]

I don't think its a rod. The high pitch and tick interval leads me toward a valve. And its rpm range puts it right at the bottom of the VVT changeover. I know next to nothing about VVT, other than on my VTEC Accord, it felt like 15 more hp kicked in @ 3500 rpm. If I knew how the cams changed profiles when VVT changes, I might have something to offer. But if it were my own car, I would have someone eliminate that as a possibility.

 

[phunky.buddha]

You can also use a broom stick. It works very well.

Yup, that'll work in a pinch.

 

[flcruising]

That sounds external to me.