ZD30 Vibration at low RPMs

[Thomo]

Hi Everyone,

I've been lurking on and off in this forum since buying my D22 STR back in 2011, and it has helped me out many times with fixing my Navara. I recently bought a new ute and sensing she was about to get sold, my Navara developed a pretty serious rattle/vibration. I was hopping to get some advice on what the problem maybe.

My Navara is a 2004 model with a ZD30 has 390,000km. The motor is stock except for the EGR mod, and a catch can. I have maintained and serviced it myself the whole time I have owned it.

The noise developed gradually while driving to and from work recently. By the time I arrived back home the engine was making quite a lot of noise and vibration. I thought the exhaust by pass pipe to the EGR system had broken again, but this was not the case and I could not find any other exhaust leaks. I checked the oil and coolant levels and found no issues there (no mixing between the fluids). I have not had the oil pressure or check engine lights appear on the dash. The motor still makes its normal power, does not blow any smoke, does not stall, and is easy to start.

I have only taken it for a handful of drives since, and the severity of the vibration seems vary a lot. This weekend I drove it about 40km and found that the vibration is worse at low RPMs/when the motor is off boost, runs relatively smoothly above 2750 RPM, and the vibration disappears completely under engine braking.

Eliminated suspects:
Exhaust leak: Would explain the noise, but not the vibration. Have not been able to identify any.
Head gasket: Plenty of power, no smoke, no oil in coolant or vice versa.
Bearings/Rotating assembly: Vibrations decreases with increased RPM, no vibrations under engine braking.
Turbo: Makes boost.

I suspect the problem has something to do with the injector pump, but beyond that I don't really have the experince to tell. Perhaps the timing is out at low RPM, and the vibration is a sort of "pre-detonation" (which isn't really supposed to be possible in a diesel). Any leads or thoughts on this issue would be greatly appreciated! I will take it to a mechanic friend soon, however I respect his time and I want to have a good theory of what the problem is.

Thanks again,

Matt

 

[tweak'e]

noise/vibrations is extremely difficult to diagnose over the net.

first thing to check is oil before or after the turbo in the intake pipes.
if overfilled with oil you can get enough oil going into the intake to make the engine run on oil, which will run really rough. even with some catch cans it can be enough to blow right through. if oil after turbo it may be failed turbo.

check fuel filter and that there is no air being suck into the fuel line. that can change the injection timing.

otherwise i would suspect injectors.
.

 

[Horatius]

I had an issue once where the nav (basically same model as yours) gained a really noticeable vibration at low revs. It was after I had been doing a bit of work on it and took it for a 4 wd trip for the day. Had me perplexed for a while, but I realised when I eventually started noticing oil leaks as well.

Seems I was in a bit of a rush when I hooked the catch can (provent 200) back up and put the pipes on arse about lol. IOW I blocked off the crankcase ventilation. Changed the pipes back around, gave it a degrease and all good again, no oil leaks, vibration gone.

A long shot perhaps, but what type catch can have you got? Any chance it could be blocked?

 

[BarneyB]

What about clutch, pressure plate, flywheel?
Maybe if something has failed (partially).....it could be moving around at low revs. But at higher RPM the centrifugal forces are "locking" it back in place?
(just a random thought...)

 

[Thomo]

Thanks for the replies guys,

@tweak'e and Horatius. You might be on to something there guys. The intake manifold has been quite oily for some time, and I hadn't had the time to take it off the road and fix it. I presumed the oil over the intake manifold had been coming from the rocker cover, but I had never considered the oil leak it would be coming from the turbo itself. That being said, it has been that way for a long time. Something must have changed for it to start causing such a severe problem. I will look into it more tomorrow.

@BarneyB The clutch is close to worn out but I am reluctant to replace it as I am selling the vehicle once i get it running well again. I think if this were the case the vibration would be more consistent. It wouldn't disappear under engine braking for example. Sometimes it's really loud when the motor is cold and quietens down a bit once it warms up, other times it doesn't quieten down at all.

Also, is there a way to do a one off donation to the forum?

 

[Thomo]

Hi guys,

After cleaning out the first intake pipe after the turbo this morning and taking it for a quick test drive, the problem had seemed less severe. It still sounded very sick, but it was a bit quieter and a bit smoother.

However after starting and stopping it a few times on the drive way, it started to get louder, and began to miss. Then while idling, it stopped firing, lost all compression and I could hear the rotating assembly inside the motor spinning until it came to a stop after a few seconds. When trying to start the motor, the only noise it makes, aside from the starter motor, is the sound of the rotating assembly spinning.

I think I likely have a timing failure. As I lost compression in all 4 cylinders at once, it says to me that there is at least one pair of valves open in each cylinder.

I think the path of action is clear. Remove the rocker cover and inspect, and if I can't find the issue there check the timing chain. I just need to weigh up whether it's worth it to me to fix? or just sell it as it is? I can't say I like being defeated like this after 10 years with this ute, but it is getting outside my skill level. I don't think it would be worth it to pay a mechanic to do this.

Does anyone know if the pistons interfere with valves?

 

[tweak'e]

if its busted a timing chain the head will be toast, tho if it turning over freely then its no longer hitting any valves.
i would pull the rocker cover and timing cover off. you could have broken the pin on the cam sprocket and left the cam sprocket loose, that might explain why it was running badly.

 

[tweak'e]

one simple thing is check is the intake butterfly is open when cranking. if its pulled shut, the engine will act like it has no compression.

 

[Thomo]

Turns out I have a broken crankshaft, somewhere between the front bearing and timing sprocket. The timing chain and the front pulley do not move when cranking the motor.

If I want to save the old girl, I'll need to get the engine rebuilt or a replacement engine. Does anyone how much these might set me back?

I'm not entirely sure what the ultimate cause of all this trouble was though. The crankshaft shouldn't break for no reason. I think the valves contacted the piston (I heard a few metallic noises before the engine stopped) and this increased resistance broken the crankshaft. Any thoughts on this would be appreciated, but the only real way to know what happened is to pull the engine apart.

 

[tweak'e]

well that truly sucks.
sounds like a strange fault, maybe just a weak point that finally let go.
i doubt valves hit the head first as you would not be turning it over, plus they tend to snap the cam pin (failing that the chain) only possibly is the balanced shafts seized which is really odd. or something fell down into the balanced shaft gears, a sudden jam could snap a drive shaft.