ZD30 - Name that tune!

[3VILC]

So somebody pulled the pin and the grenade seems to have blown, so before I start stripping it down I thought i'd take a video and see if anyone can pinpoint what the noise might be.. I suspect its burnt a small hole in a piston but since I've never killed an engine I'm not too sure what that would sound like.
Camera won't focus on the blowby fumes very well but is coming from down the back of the block somewhere cant quite see where, but when you take the oil cap off the vapour at the back stops hence I'm guessing its blowby escaping somewhere. Doesn't appear to be any oily mess or leaks anywhere (yet) and at the moment seems to drive ok apart from the hell of a racket under load and the oily smell in the cab haha. Not that I plan on driving it anymore like this of course, just had to get it home from where it was.
So if anyone could offer some insight into what would cause a noise like that would be a help as to what to expect when I strip it down



Cheers,
Clive

[Crash bandicoot]

It's too metallic in sound to be just a melted piston something is hitting something else in there.

[3VILC]

Dropped valve was on my list of ideas..would've imagined that would be a more noticeable loss in power and a lot of misfiring tho.. exhaust note sounds normal, bit of smoke when revving but not heaps

[Crash bandicoot]

nah the valve stem hole vs the volume of gas trying to escape through it would still give some compression.

you'd need a descent size hole (milk bottle top or bigger) to loose any and all effect of the piston travelling up to T.D.C even at 800 times a minute(800 rpm idle)

[Crash bandicoot]

dont bother fixing just start lookin for a qd32.

[3VILC]

I suppose that's a good point considering the compression in a diesel, definitely a hole in something anyway. I'm kinda thinking the vapour coming from the back of the block means there may be a hole in that too although I'm hoping not. Pretty sure theres no seals or hoses down there it could be coming from unless its blowing past the main seal and coming out an inspection hole in the bellhousing.
Not sure how much work a QD32 is..that is another option if theres one around cheap enough..there is a terrano exactly the same at pick-a-part at the moment that I suspect has done the same thing that I can maybe raid spare pistons etc from. Had just started doing the NADS mods too it too, typical haha.
Its a nice truck otherwise, and its a giant paperweight now so might as well fix it one way or the other, don't owe anything on it

[tweake]

the blowby through the filler cap is normal.
the blowby at the back not sure on, could be the oil drain tube on the back of the head has broken. find where its coming might tell you what the noise is from.

[Crash bandicoot]

I suppose that's a good point considering the compression in a diesel, definitely a hole in something anyway. I'm kinda thinking the vapour coming from the back of the block means there may be a hole in that too although I'm hoping not. Pretty sure theres no seals or hoses down there it could be coming from unless its blowing past the main seal and coming out an inspection hole in the bellhousing.
Not sure how much work a QD32 is..that is another option if theres one around cheap enough..there is a terrano exactly the same at pick-a-part at the moment that I suspect has done the same thing that I can maybe raid spare pistons etc from. Had just started doing the NADS mods too it too, typical haha.
Its a nice truck otherwise, and its a giant paperweight now so might as well fix it one way or the other, don't owe anything on it

not going to know untill ya pull the head off i spose, aslong as the blocks not damaged the pick a part option might be your best bet, there was a guy on TM in the naki selling qd32 for $400 bare block and head

[churchill]

It looks like its a manual so check the Dual Mass Flywheel first especially if the sound is coming from the back of the engine. How many km's has it done and has the DMF ever been changed? They're supposed to be changed every clutch change. I don't know about diesels but I know that a petrol will really start behaving badly with a holed piston or a dropped valve and it sounds like it's actually idling and revving ok. That blow by doesn't look too bad either for a diesel but as I said earlier I'm not as familiar with diesels.

[churchill]

It looks like its a manual so check the Dual Mass Flywheel first especially if the sound is coming from the back of the engine. How many km's has it done and has the DMF ever been changed? They're supposed to be changed every clutch change. I don't know about diesels but I know that a petrol will really start behaving badly with a holed piston or a dropped valve and it sounds like it's actually idling and revving ok. That blow by doesn't look too bad either for a diesel but as I said earlier I'm not as familiar with diesels.

[3VILC]

Nah tis auto. I'm sure it doesn't usually chug blowby that bad. The camera really struggles to focus just how much is coming out

[Crash bandicoot]

I can tell you one thing though, if you do rebuild it, use BD30 rods and pistons or aftermarket pistons and rods, the zd30 runs the largest gudgeon pin size vs smallest piston mass of any nissan engine with the qd32 following close behind. the effect the fastest heat saturation point...reach that point and it's all over rover

the reason the qd32 doesn't blow up is because it isn't as highly strung as the zd30.

the qd/td werent designed or required to meet the stringent emissions laws that the zd had too being a later engine, hence does not run as hot and have the god awful emissions controls to make them eat its own fumes like the zd is made too..

[tweake]

Nah tis auto. I'm sure it doesn't usually chug blowby that bad. The camera really struggles to focus just how much is coming out

they do blow that badly. part of that is due to the big open aera from sump up to the rocker cover.
however if its blowby coming up the rear then it may seam less than it is.

just check that oil return hose and also egr pipe. well known for breaking egr pipes.

[Crash bandicoot]

and also of note my td27 is gettin 350 thou and still doesnt blow the cap of when undoing it, you almost had to catch that.

[3VILC]

Yeah there's a fair bit of pressure in there the camera just doesn't show the amount of vapour coming out. It done 280 so thought maybe I'd picked a better one

[slide]

That's a shit ton of blow-by!! Far more than what would be considered excessive, and much more than normal. I'm guessing its blown out tappet cover gasket at the back? The noise is hard to hear location from not being next to engine, but my bet is a damaged piston (and probably a scored up bore). Probably not a hole in it, maybe cracked or scored up. I doubt it'll be a damaged valve as it doesn't take much of a valve bend/ burnt valve to loose most compression and hence it would idle on 3 cylinders, which it sounds not to be. Also doesn't look to be shaking lots like its running on three.
Valve damage would not explain the extreme blow-by, unless piston damage was also there. But with both you really wouldn't expect it running on all four.
Piston damage would explain the blow-by.
I can't pick from the video sound- does noise get worse when engine revved up? or stay about the same?

[3VILC]

Actually, of course, that blowby would be coming from the split in the rocker cover gasket! Duh. Lol that explains that at least. At one angle yes you can briefly make out just how much blowby is coming out visually. The sound changes as revs increase and worse under load. No water in oil or vice versa but does seem to have burnt most of the oil driving it home

[Crash bandicoot]

Actually, of course, that blowby would be coming from the split in the rocker cover gasket! Duh. Lol that explains that at least. At one angle yes you can briefly make out just how much blowby is coming out visually. The sound changes as revs increase and worse under load. No water in oil or vice versa but does seem to have burnt most of the oil driving it home

just spoke to a mechanic mate in pilbara, they run a fleet of these things, showed him the vid, he request you take the rocker cover off and inspect the cam shaft's for correct timing.
conjecture over the phone lead to it having a broken glow plug bouncing around the cylinder,cracking the piston or holing it,
possibly a stretched timing chain, snapped a dowel,or broken cam resulting in the piston meeting an open valve.


"not uncommon" was an understatement and said your lucky, most only make to around 175000 kms before going boom.

[3VILC]

Rockers covers off, cams looks good no wear not broken, chain looks good condition and tight. Can't see anything unusual thus far. Glow plug tip is a possibility.
Given the cost of a zd30 in reasonable condition I've even contemplated finding a crashed or cheap VG33 R50 and swapping that in, not sure how much work I'd be taking on guess it should fit with the fuel tank swapped as well

[tweake]

have you found where that blowby is coming from out the back of the engine ?

[3VILC]

3 posts back
Found a qd32t out of an R50 with trans at a good price so might consider swapping that in.
As far as I can work out so far apart from the wiring, just need to swap the cross member section of the subframe and it should all bolt up

[tweake]

3 posts back

oops missed that. time for coffee.

sounding more like hole in the piston.
there was a crowd around doing conversions, they did quite a few navaras.
tho the qd32t will be less power until you can wind the wick up.

[3VILC]

I thought they were meant to be roughly the same but QD has a fraction more torque. Not too fussed tho rather go for the reliability

[tweake]

I thought they were meant to be roughly the same but QD has a fraction more torque. Not too fussed tho rather go for the reliability

off the top of my head terrano zd30 about 130kw, QD32t 110kw (someone mentioned 105kw and i think i've seen 115kw mentioned ?, may be a few different versions around) and zd30 has a boot load more low rpm torque thanks to the variable turbo.

[3VILC]

If it was ever running as it should be. Can handle that, don't expect it to be a race car unless a VG33 one comes up at a good price, I assume that conversion would be much the same with changing the fuel tank and lines as well to get the efi pump.
Thinking QD is probably the best option overall especially with a complete setup available at a good price. Know I need the engine cross member, the gearboxes are the same I believe apart from the bellhousing so guessing the gearbox cross member is the same. Not sure if I'd need to swap the instruments tho. obviously the engine and trans looms but picking the body loom would be the same as with most Nissan's of the same chassis family

[3VILC]

Got as far as getting the intake and half the exhaust out today. What a mission to dismantle, need a 5yr old Asian boy lol. Manifold is grubby but not clogged at all. Did discover the EGR was already blanked tho, without disconnecting the throttle plate, since these engines close or partially close (not sure which) the throttle during egr to force the engine to suck from the egr port there's a prime candidate for over rich mixtures right there ecu thinks it breathing thru the egr but theres no airflow there. Got the glow plugs out, all intact so not one of those broken. Next mission get the head itself off, yay most of the bolts are either under the cams or the injectors lol

[tweake]

....... Did discover the EGR was already blanked tho, without disconnecting the throttle plate, since these engines close or partially close (not sure which) the throttle during egr to force the engine to suck from the egr port ........

not quite.
the swirl port valve does that partly at low rpm. but otherwise the patrol/terrano zd30 doesn't use an intake butterfly for egr, it uses the variable turbo to create extra back pressure to force more egr in. the navara version has normal turbo and has intake butterfly partly close for egr.

[3VILC]

Good point, there's only one hose on that diaphragm not 2
The plot thickens. Pulling the head will hopefully reveal more, mostly out of interest more than anything, it'd be fair to assume it's probably buggered with that noise and blowby.
QD swap is looking like the best idea, seems it will bolt in easy enough just whether everything can be wired up and made to work properly.
Emailed Kaiapoi Repowers, they weren't really willing to share anything useful other than they could do it for 5500 drive away

[3VILC]

Bit of an update for those that are following/offering ideas.
Managed to finally dismantle enough to get the head off this arvo. Bearing in mind this is the first diesel I've had apart so not entirely sure what one would consider normal for a diesel pushing 300thou.
Everything about the head looks OK.
#3 has a bit of carbon in the chamber, and on the ends of the injector and glow plug and a small amount further up the injector suggesting the copper gasket leaks a little, don't think this would cause a major any more than a leaky valve seal and certainly not the noise.
#2 looks pretty good to me, black coloured but no real buildup.
#1 and 4 both white coloured patches in the chambers and on the crown? Does this perhaps indicate a hot burn like a very pale spark plug?
Pistons can wiggle a little bit in the bores with a finger either side, assume this means the rings are not as tight as they should be a might cause a noise but wouldnt happen all of a sudden.
So I guess that leaves a bearing of some description has gone south, or the hot? Pistons have cracked underneath or broken a piece of skirt off.
Next mission draim and pull the sump in search of bit of metal

[fh2014]

So no piston and valve wedding? I was looking forward to wedding photos !