Major problems with ZD30...

Greetings,

Agreed to help out a mate with an 02 D22 ZD30. He'd been told he needed a new head, and quoted $4,500 for the work. He doesn't have that kinda money available presently (he's had a shocking year), but desperately needs the truck running again so he can get up to Gladstone to be with his sick wife.

I took a look at it for him and found the coolant bubbling at a little under normal operating temps. Told him while it might be the head, we could replace the gasket for a price he *can* afford, and it might do the job...

Got some specs and stuff faxed over from Nissan, but failed to notice the cam bearing cap bolt torque figures weren't there until I went to tighten them on Saturday night. He / we didn't want to sit around waiting until Monday for the specs, so I made a (bad) judgement call and proceeded to torque the bearings by hand.

Engine back together and running beautifully on Sunday (turned out to only be the head gasket - w00t!), so he loads up, hooks up the boat and starts out. Half an hour later, the cops brought him back - he'd broken down 2 minutes up the road (although we drove it around for half an hour while testing). We recovered the boat and truck, and hit the key. Sounded like a broken timing chain.

Pulled down the engine, and found the timing chain intact, but the sprocket spinning on the cam gear. Broken locater dowel. Nissan only sell the dowel attached to the gear so $62 later I fit the new gear, properly torque the cams (I had overtightened for sure originally), reassemble engine and start. Idling like the chain's a tooth out. Pull it back down again to find the chain lines up properly against the sprockets. However, found that the dowel has broken *again*, allowing the sprocket this time to only move about the distance of a tooth (I had also now gotten the torque spec for the bolt that holds the sprocket and gear onto the cam, and assume I hadn't tightened that far the first time around).

I'm now extremely apprehensive to touch this engine again until I know exactly what's going on. Unfortunately, though, the owner *really* needs his truck on the road again, like a week ago

Any clues? I don't suppose any of you are intimately familiar with this engine and also located in Brisbane?

Any help at all would be very, very appreciated. Nissan won't help any more...

Cheers,
Mattt.

My mates Patrol spec got pulled down by Nissan for a BS issue.

They are complex but not BMW complex. PM Shonky as he has a manual which he may be happy enough to send you some pdf's.

I have a ZD30 Patrol manual, I will have a look later this afternoon. I am happy to put up the info.

Give me 4 hours as I have things to do.

Dave.

Hi Dave,

Thanks, but I already (now) have the Patrol / ZD30 service manual - for our purposes, the information is accurate ;-)

My main concern presently is why does it keep breaking that dowel? I spoke to Nissan again this morning, and they tell me the only *known* issue with that dowel is when the sprocket/gear is torqued incorrectly, particularly where the technician uses a rattle gun to do it up. We used a spanner the first time, and a torque wrench dialled to the correct spec the second, so it can't be that.

I'm also a little concerned that it's an interference engine, so the chances are pretty good that a valve's been hit when the dowel went the first time (he was driving it then...).

Cheers,
Mattt.

G'day pulse,

It might be time to put the sprocket on the cam and leaving the glow plugs or injectors out, get a socket on the crank and turn the engine over by hand feeling for any tight spots, but it is strange that it went for an hour before breaking the sprocket in the first instance. I'm assuming you've checked all that all the valve clearances are correct, though the clearances shouldn't get tighter once the engine is warmed up but they may.

For it to shear the dowel in the sprocket there has to be something hitting somewhere, I'd guess the shear force on the dowel would be upwards of 1 ton so it has to be hitting something to do that in my opinion.

Hi Shonky,

I rather tend to agree, hence being hesitant to even touch it again until I know exactly what's going on here.

There are no unusual mechanical noises (other than an occasional "clack" when I release the key, but I don't know whether it's normal and we're just hearing it a lot louder with the timing and rocker covers, etc, removed) - if it's bent a valve, and the piston is tapping it or some such, do you think that could cause the cam to tighten, under some set of circumstances, enough for the dowel to fail? To my way of thinking, probably not, but I just can't see what's wrong here - it's *definitely* built properly (heh... this time around)...

Cheers,
Mattt.

Awww, crap...

Just spoke to Nissan about where I could pick up a new cam sprocket (as that's the only way to buy the 20c dowel...) this afternoon as they're not open on Saturdays. The only one in Australia is in Alice Springs :-(

Cheers,
Mattt.

I guess it could be a bent valve, but I would think if a valve has hit a piston somewhere and bent the stem, and then the cam has come along and pushed on that valve which has then broken the dowel, you should be able to see which valve it is by checking the clearances cause I'd bet the valve with the bent stem will never come back up to the correct height once the cam is at zero lift.

Anyway, I gotta pack to go away on a trip and won't be back till some time Sunday so good luck with it mate, if I think of anything else between now and then I'll let you know.

Agreed - I did have a quick look at them, but didn't rotate the engine and check the 6-odd that were down. All of those were being pushed down by cam lobes, but it's certainly a possibility that one of them won't come back up ;-)

Enjoy your trip

Cheers,
Mattt.

Did you pull the cam bearings out ?

Are you sure they went back the right way.

Dave.

Hi all,

Update:

Had a diesel mechanic come out as a second set of eyes, etc, this morning...

We removed the glow plugs and cranked the engine some.

Verdict: 2 bent / sticky intake valves (and, of course, the broken dowel - we set up a test harness, as it were, using a cut piece of an appropriately sized drill bit today so save breaking another expensive, currently unavailable sprocket / dowel combo).

Will remove the head on Monday and replace / lap new valves, and rebuild with another new sprocket / dowel combo.

The prognosis is, basically, that on the first rebuild where I didn't have the torque specs for the bearing caps and cam sprocket bolt to hand, I've overtightened the cam bearings and undertightened (heh - I just invented a new word ) the cam sprocket retainer bolt. It all held up while we test drove it for about half an hour but, having half-loaded the truck and now towing the ~2t boat, the dowel failed when he was decelerating 2min down the road and down-shifted to second.

The second time the dowel failed was probably immediately when I started the engine after rebuild #2 - probably (but we're not entirely certain or convinced) a piston tapping a valve against a cam, or perhaps even faulty manufacturing of the dowel / sprocket assy.

Hopefully, after the *next* rebuild, all will be well...

The owner is borrowing a truck to get him up to his wife, and says he shouldn't really be complaining about a 9-day head job

Will keep y'all informed as to a result after this rebuild

Oh yeah - I did pull the cam bearings out (need to to get to the two inside rows of head bolts), and they certainly put back the way they came out ;-)

Cheers,
Mattt.

Glad to hear it sounds like its all sorted. Also good that your mate got up to see his missus, hopefully his luck changes somewhat.

hey guys, looking at buying a 2007 d22 zd30 navara with 147,000 kms on it and just wondering if it is worth it? and if it is, what are some things that i could do to make it more reliable/powerful?