Condition of 1.6TD engine

[wilharper2000]

Hi,

I rebuilt my 1.6td idi engine about 70k miles ago, new pistons etc.

Car ran brilliantly, good power etc but always burned 1 litre oil per 1000 miles. I never worked it out.

Anyway, car is undergoing a restoration and I pulled the engine for an inspection.

I found the bores looking generally in really good condition apart from some scoring in cylinder 4. Two of which I can catch my nails on.

Does anyone have experience of this kind of cylinder damage? I have a spare block which i'm tempted to just get bored and use the O/S pistons from my current block, but i'm not sure if current block is actually ok.

I havent measured anything yet (i know this will be the crucial part), but cylinders seem to be in good shape with cross hatching still very evident.

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[Prairieview]

Well, so many unknowns:
no idea how well the super-tight bore spec was kept when the block was bored on the rebuild. No idea how precise the assembler was on placement of the ring gaps, etc. when assembled.

There is a chance the initial break-in run was too brisk and over-heated the rings.

Is there any etching on the piston top directly under where the pre-chamber opens directly above the front of the piston?

To me, it looks like whoever drives this engine has the BAD habit of going FULL-THROTTLE when the engine is stone cold. The aluminum piston swells long before the cast iron block expands. If that is the case, the back side of the piston probably has scuffing on the skirt and into the rings.

The vertical marks don't look like they are bad enough to catch finger nail. But, if they do, must be at least 3/4 of one thousandth deep.

A guy needs to see the condition of the piston.

Was there any hint of knock at cold start-up? A knock which reduced or disappeared with engine heat?

 

[iluvmydiesels]

when you did the rebuild you sanded the cross pattern into the cylinders?
it doesnt look right. it looks like you broke it in wrong or didnt give enough time for break in. for one. can see the scuffing too. that and what prairie suggests can be your oil consumption.

 

[wilharper2000]

I’ll pull the no.4 piston today to have a look at its condition.

Car has only been driven by me for those 70k. I am absolutely sure not to give it full throttle until car has been running for 10 mins or more. However approx 50k of those miles have been quite high speed motorway driving. I also had one trip to France where it was hot and was doing some quite heavy driving. I think that’s the hottest I’ve seen it get, though still nowhere near the top of the old Mk2 golf temp gauge.

A possible other factor I noticed when pulling engine was an 82 degrees thermostat for a 1.3 vw petrol engine. When I originally rebuilt the engine I elected not to replace the thermostat as it was quite new and genuine (previous owner installed it however).
Wondering if a combination of slightly lower temperature block, and possible lower flow rate through the thermostat when warm would contribute.

 

[wilharper2000]

Piston has corresponding score and impact at bottom of piston, can't really figure out what would cause that.
Score also has visible depth when viewed at tight angle.
Would this be enough to cause oil burning?

 

[iluvmydiesels]

one thing i meant to say at first, is your cross-hatch sanding, you have the right angle, not the right technique.

your piston that discoloring is that the ring burning? and some of the discoloring goes down to the second ring.
noticeable scoring on piston and cyl, whether its your, and only source of oil consumption(??).
oil consumption on an old MK2 TD was about 1qt per 1k miles(?? i forget for sure, if thats the aprox amount). that was back then, as a good freshen up or rebuild, it shouldnt be that much. it can tho.
a compression test could show you quite a bit, you took 'er apart though.
when you did rebuild, how did the cylinder barrels look, did you measure. worn barrels can add to oil usage.
oil can leak externally, you may see indications of this on the ground, we ve seen our share of people not being able to see fluids leaking out. oil can get into cylinders thru valve guides, and/or piston rings. blow-by or crankcase not ventilated properly leads to oil consumption, excess CC pressures can push oil out, this is usually a vacuum leak.

 

[Prairieview]

Does seem as though that cross hatch was left pretty rough......like even more coarse than 180 grit? Or hatch was performed with no lube whatsoever.
I've ran 1.6 VW diesels since 1979. Ran them pretty hard. Very hard. Goes with the territory. I've never done this to one I rebuilt.
I have taken a lot of these part (acquisitions over the years) and most of the ones I salvage have this vertical scoring....which I always felt was a matter of too much heat or too much heat too early when fired up.
If this engine is turbocharged, that increases the potential to heat too fast.
I asked if there is any erosion on the piston top directly at the opening of the pre-chamber. That is an indication of a weak, worn, dribbling injector between firing. In that sense, the injector might well bleed down when shut off....putting diesel fuel into the top of the rings....and compromising the cylinder wall lube on re-firing of the engine.
Yes, these older 1.6's did tend to consume oil more than the newer ALH engines do. I have a few of my own rebuilds which do not consume very much...but, the oem engines certainly did.
Personally, I think these rings got cooked early on. Too hard ruthless break-in. Over time, the problem just gets worse.
But, as the other guy stated, there are several other places to lose oil in these.....I recently had a valve stem seal drive me nuts.
Myself, I would probably lightly hone this hole with like 240 hone....dingleberry style. I use cheapo Walmart wd-40 lube with diesel fuel to hone.....works fine for me.
I would check the ring lands for damage....reduced clearance in the lands. Clean everything up and go with a new seat of rings properly placed on the piston in the hole (ring gap). Then, a reasonable break-in.
These look like Kolbenschmidt pistons....not cheap. If this was your only problem with this engine...I would simply live with whatever the oil consumption will now be.
The alternative will be much more expense and work. Your choice.
In the photos, the piston top does NOT show over-carbonization. Very clean. Little bit of rough build-up around the perimeter.

 

[iluvmydiesels]

idk for sure, the last pic of the piston, the top has some carbon showing, the top of the cylinder has some carbon, its just one perspective. may be nothing, we dont have much info to this.

the thing i saw in the 1st set of pics, the cyls the cross pattern he looks to have sanded some, the angle is right, however there is sparse sanding all over, look at the top, one sanding line going this way, one going the other way. around the top of the cylinder here theres not much for the ring to break in to.
the other thing, the sanding pattern looks so shiny and prominent, not like it was broken in, by a few hundred miles to 2k or so it will break in, he has 70k on work.
and the discoloration on the top ring, and some one the second ring.
id say for one re-ring, rework cyls, whether by a good sanding job w/lube, or lite hone. (< again w/lube). check pistons, you may need new, that one has discoloring, you may need a new one and ring here. as for the piston damage, to use is a good question here as well.

 

[Prairieview]

I stand with what I posted above.
He can buy one hole of rings (Goetze) which used to be about $13.50 from autohausaz.com.

This is an old 1.6 engine. It is not a Ferrari or a Ford GT, etc. The expectation level is "lowered." He stated that the engine ran very well (something to that effect) prior to opening it up.

He cooked the rings whether or not he wants to believe it. Care will need to be taken while honing an assembled engine as the crank and it's bearings are right below there...and gravity wins. Wrapped rags, black tape, aluminum foil....whatever turns him on to keep the grit out.

If it still consumes oil...whatever...oil is still cheap. I would be dismantling the head to check for all potential oil loss reasons. The carbon on the top of the piston was VERY light. It readily came off with finger pressure.

He could have a valve stem seal or two which is not adequately doing it's job.

As long as he is going through all of this....I would make sure and take a look at the front intermediate shaft bearing as well. If you're headed for Chicago...no sense in getting out in Des Moines.

Edit: I can't tell if this is a KS piston or a Right Way Industrial from Prothe. They look very similar. If this is a set of Prothe pistons....take out ALL the pistons and go with a set of Goetze rings. Right Way pistons are actually pretty good (if not running more than stock boost), but, the rings which come with them are sheeot.

 

[iluvmydiesels]

This is an old 1.6 engine. It is not a Ferrari or a Ford GT, etc. The expectation level is "lowered." He stated that the engine ran very well (something to that effect) prior to opening it up.

i realize its an older 1.6, it looks like its a GTD tho, he may well be using it for the extra pep.
he has the top off, has problems in the one cylinder, if one ring is cooked, all are bound to be in the same shape. pull the pistons, rering, goetze are supposed to be what to go with, clean up, that means sand those cyls correctly, if you have to do some light honing,,,etc.
those burnt looking rings may be his oil consumption, take care of it now will be easier than after putting top back on, then what, take it back off?? just do it now, its not a lot of work. it may work out.
while the head is off, put in new stem seals, and check valve guides, check other stuff while your at it.
as far as the lower end with working cylinders with crank still in, pan is off, so most that is exposed is the rod journals, i clean them good with kero last, and the counterweights too, etc,etc, and the main caps.
he had to pull the oil pump to get to 4 &/or 3. so thats clear.

 

[wilharper2000]

This block was bored oversize by 0.5mm, genuine KS pistons with supplied rings. This is a Gtd SB intercooled engine with 80hp standard.

All bore work was carried out by a machinist, this included, bore, hone, plateau hone, and ring gapping.

I just assembled the engine.

Injectors were overhauled 10k ago as part of a injection pump rebuild. The shop said the injectors were leaking a bit before. However there is no pitting on the piston tops, just slight erosion at the very edge of the piston directly below the prechamber.

I may have ‘cooked’ the rings, but not really sure how. My break in was based on varying load, and did have a few hills in the first hundreds of miles.

The cross hatch looks ok, but I do see some changes to the angle, some areas showing almost horizontal which as I understand can contribute to excessive oil retention.

I have nothing to hone the cylinders out and I really don’t want to make anything worse with the block, so I may get a quote for reboring my spare block.

 

[Prairieview]

My last thoughts:
I suppose there is a chance the piston squirter on this one hole is plugged. THAT and a combo of running the new bore too briskly could do this. Or, even long-term slightly sub-overheating on this engine on a day with heavy load and high ambient temps with the loss of the oil cooling from the clogged squirter.

Once the rings (what I like to call "cook"), they loose their temper. They no longer seal.

I ONLY like/use Kolbenschmidt or Goetze rings on the 1.6 engines. And, for me, the KS are rarely available on over-size.

Both of those brands generally seal right up (seat) with proper block prep and intelligent break-in. The KS rings are hard as hell....must be higher moly content? The Goetze rings are more pliable and compliant when assembling.

What sort of confuses me is that I would expect a much higher carbon deposit on the top of the piston crown with oil coming up. Unless you were pressurizing the block and the oil was being pushed out otherwise...which is likely.

Anyway, I will always have a soft spot (maybe too much) for these earlier engines. I think they are much more fussy and difficult to "get right" than rebuilding an ALH. I still have several of them in daily service with great results.