AAZ New head gasket gone after long journey, please help

[airhead]

Well nice and all as the inaugural trip in the camper was, I got back to my girlfriends place and there was white smoke billowing out of the exhaust. I was worried it might have been the turbo so I disconnected the turbo pipe from the intake manifold so it was running without a turbo and the white smoke remained. The smoke smells of coolant. The engine wasn't overheating though. It did get about 3/4 of the way up the gauge though on previous occasions, so I stuck the heaters on full which got it back to the half way mark. I did pull over, and I found that the auxiliary water pump was not working. I unstuck the impeller in it but it wouldn't spin itself. This was still a good 2 hours from home. The temperature didn't rise again once the heaters were on though. The white smoke issue seemed to come on very quickly. I did use new stretch bolts and got the head skimmed when I was doing the gasket change. Here are my questions...

1. Did I correctly diagnose this as head gasket failure?
2. This is only a new head gasket, and I haven't given it its final 1000 mile torquing. Is it possible that performing the final torque could correct the problem?
3. Given that the engine never really badly overheated, would the head have warped?
4. What should I do (aside from replacing the aux water pump) to prevent this from happening again?
5. Why would it have gone at all if I never let it badly overheat?

[max and caddy]

No need for re tworking on the AAZs....aux pump does very little and won't be you issue I'm certain, was it a proper metal gasket? Was the block clean as a whistle? Is it the correct head gasket...3 to choose from. So many variables !

[Aidan]

was the head crack tested ?

[airhead]

Was the correct head gasket, yes. I bought it from the place that skimmed the head. It was a 3 notch gasket. I didn't get it tested, no, but it's in getting tested now. It was definitely the head gasket that was gone. It seemed only one cylinder was overheating. It was the rearmost cylinder (number 1?) and had some marks on the head to indicate this. What might have caused just the one cylinder to overheat?

Just another point, the oil pump was weak. The oil light would flash when the engine was hot and idling but would go out when just up off idle. This is being replaced. Could this have caused it?

Here's some pics...




(I thought it was interesting that the pistons still have the manufacturers etching on them.)

[airhead]

Oh and was the block clean enough going by this pic?

[airhead]

Jeez lads this forum has gone very quiet. Has nobody else any ideas?

I found out the head passed its pressure test but your man said the valves are warped slightly and not seating properly so he said he can remachine it and get it right again. It sounds a bit odd to me but he was saying the engine will get smokey with time if I don't get it done. I'm a little suspect. Anyone have any ideas about this?

[max and caddy]

Hi can't really see from the pics where the gasket has gone...and how do know one cylinder overheated? Does look like some water got in corroding the piston top...in a word..dunno! But if the valves are bent it must of been out of time at some point, worth getting those right but doesn't explain the gasket failing..water pump is the correct one isn't it?

What did you pull the down to? Procedure?


Just has a better look....the valves appear to of left a mark on the piston crowns....so running in contact with....

[Aidan]

Jeez lads this forum has gone very quiet. Has nobody else any ideas?

There are suprisingly few qualified diesel mechanics in this day and age, and even less that post on 80-90, it has always boggled me that peeps happily swap stressed old diesel engines about, I've never seen one that could keep all three fluids in the right place; high compression + cast block + alloy head + turbo = mix that is prone to failure and so many skimmed head stories about ones that weren't right or weren't crack tested before skimming etc......

just my ho of course

if the timing was out wouldn't that affect the in bore temps too ? I know if injector goes bad it'll melt a piston so if fuelling is late or early could that not cause a problem, bent valves means it ran out of time doesn't it at some point and we know AAZ's are prone to that, bottom bolt issue being the problem. Did you fit a new bolt and have the pulley off to check it's ok down there ? Last one I saw was mullered and someone had tried to dowel it , one before that had been plastic metalled in place

wouldn't it be better to find a good complete engine, rather than try and sort this clearly dodgy one, Andrew has several stashed away

or go TDi, there seem to be more peeps on here au fait with TDi electronics than there are diesel mechanics who will share the knowledge, and at least you get a decent pulley fitting on the crank and a more modern engine

[max and caddy]

Timing can affect temps but the rattle would be a give away, retarded timing just wastes fuel but won't run hot like a petrol does smokey and hotter but not enough to cause this...cam timing is the issue here but most likely pump was out as well....I suspect the head may not of been torqued correctly or block was dirty...the AAZ head gasket is is a shim stack and can take some hammer even on a hot engine, doubt the block is warped and if the head was flat it must be down to fitment?, either way those pistons have been at some point well into the valves but I have seen these run like that for a long time...long enough to pocket the piston crowns to a good few mm! From the pic I can't tell where the gasket has gone...the black marks could be....but look like streaks of muck...

[airhead]

Just a thought... Could liquid or dirt in the head bolt holes have caused the bolts to not tighten fully and hence cause the head gasket to blow? I didn't clean out the bolt holes when I put the head back on. An oversight on my part.

[max and caddy]

Maybe but it's a long shot...what did you tourque the bolts to?

[airhead]

40NM, then 60NM, then 180 degree turn, then 90 degrees when the engine was heated up. That's what the manual said to do anyway.

Here's my list of things to rectify so far (as much for my own reference as anything else and if anyone can suggest anything, please say!)

Oil pump replacement
Auxiliary water pump replacement
Pressure cap on coolant tank replacement
Thermostat replacement
Check belt driven water pump for condition and replace if necessary
Reconditioned cylinder head with 3 notch gasket and new bolts
Clean out head bolt holes
Have injectors checked and if necessary overhauled
Make sure the coolant system is properly bled and the timing belt is properly tight
New oil, filter, coolant

Worth replacing the piston rings while the sump is off?

[max and caddy]

The bolt tourque is correct....but no need for the re tourque , just 40 60 180 (or 90-90) the re tourque is old news from the early engines.

I assume the van has been running about for a while? Could the water pump be the wrong one? Some do turn anticlockwise but look the same...

No harm doing the rings but....there not cheap, your need to hone the bores, remove the oil jets,may as well do the big end shells at same time, and you must use new rod bolts as well (£) , bet there's no change from £100 there and more time...my AAZ had 168000 on it when I took it out a golf estate for my van...I changed the big end and main shells and head gasket and fitted it, it's had a good pasting ever since including offroad and pulling a plant trailer with my t3 pickup on....still going strong after 2 years + and 5000 miles, up to you but no point spending money for the sake of it is the point I'm making, ok the AAZs if looked after

Might be worth checking the tappets as they can get damaged when the valve/ piston contact occurs and then fail in the future...look for tiny cracks in the top surface.

[airhead]

I do have to check the water pump, yes. Is there a part number I can compare or any other way to tell? Can I tell by looking at the impeller? What would the symptoms be if it was turning the wrong way? As in, under what circumstances would the engine overheat?

[Aidan]

replace bottom pulley bolt /check pulley fit on crank for peace of mind