Misfire running on 3 cylinders

peiphil · Apr 17, 2013

thundershorts said:
no surprise rock auto doen't have access to that piston. It is a item that normally rock auto would buy from a dealer who discounts but they would lose money filling your order. if you were to do as Peiphil suggests, using used piston and used rings, and not putting a nice 30 degree crosshatch using a 240 grit hone, you'll have a smoker, as the cyl glaze will prevent seating for the used rrings or new ones for that matter. I feel certain Jason knows better than to attempt that. As I said, rock auto would not even be a consideration for me to find parts. Did you try J.C.Whitney? They are about as useless.

That is just your your opinion and is not a fact.
Unlike a gas engine his block most likely still shows the original cross hatch hone marks

thundershorts · Apr 17, 2013

True, it most likely will still show crosshatch., however the hatch is visible through the glaze that forms on cyl walls and is quite smooth. unless the glaze is removed through honing, the rings will never seat properly. That is the facts, however you are welcome to dispute them. on the next engines you build, try not removing the glaze and give us a report on how that works out.

thundershorts · Apr 17, 2013

Jason, all the shortblocks supplied for last couple years are built with geared bsm. I think that engine hydrolocked to break the piston. a ceramic gp tip would have pocked piston and head but not the cause that split the piston, which in that case, bent/damaged rod as well. These engines were never intended to be rebuilt, hence no oversize pistons available as well as undersized bearings for certain application.

TDIJetta99 · Apr 17, 2013

that engine didn't hydrolock.. they bend rods when that happens..

Not sure where you get your info from, but I can get .5mm oversized pistons for BHW's easier than stock size.. undersized bearings are easy to get too..

peiphil · Apr 17, 2013

thundershorts said:
True, it most likely will still show crosshatch., however the hatch is visible through the glaze that forms on cyl walls and is quite smooth. unless the glaze is removed through honing, the rings will never seat properly. That is the facts, however you are welcome to dispute them. on the next engines you build, try not removing the glaze and give us a report on how that works out.

I have quite a few HUNDRED German and English diesel rebuilds under my belt.
I do not type what I dont know!

thundershorts · Apr 17, 2013

well let us know what happens when you don't remove cyl glaze

peiphil · Apr 17, 2013

thundershorts said:
well let us know what happens when you don't remove cyl glaze

And let us know what you see when you remove your shorts!

TDIJetta99 · Apr 17, 2013

I tried leaving the glaze once.. never again.. 90k later and it still burned oil..

peiphil · Apr 17, 2013

thundershorts said:
well let us know what happens when you don't remove cyl glaze

Also do you know?
Are you a mechanic?
You seem to type from a book and not experience
Argue with a fool yeay

peiphil · Apr 17, 2013

TDIJetta99 said:
I tried leaving the glaze once.. never again.. 90k later and it still burned oil..

I typed to just give a slight rub by hand with a bit of emery cloth
A ball hone wil drop a lot of very nasty stuff into the crank case
A clean wipe with emery will work good followed by a clean rag.
Funny how your oil rings didnt get through the so called glaze but it run ok?
When ever I use used rings I measure end gap in the cylinder and give them a light sanding on the out side edge.
Common sense is not always that comon

turbocharged798 · Apr 17, 2013

thundershorts said:
well let us know what happens when you don't remove cyl glaze

There really is no such thing as cylinder glaze. A smooth cylinder just mean the cross scratches have worn off and the rings have polished the surface.

TDIJetta99 · Apr 17, 2013

peiphil said:
I typed to just give a slight rub by hand with a bit of emery cloth
A ball hone wil drop a lot of very nasty stuff into the crank case
A clean wipe with emery will work good followed by a clean rag.
Funny how your oil rings didnt get through the so called glaze but it run ok?
When ever I use used rings I measure end gap in the cylinder and give them a light sanding on the out side edge.
Common sense is not always that comon

I never really worry too much about dropping stuff into the crankcase since the oil pan is off and everything is really easy to clean..

Ya the engine ran just fine.. just went through a fantastic amount of oil and after a few long HARD runs with a tow dolly and another car strapped to it, the oil consumption was reasonable enough to put the car into service, but it used about a quart in 1500 miles..

peiphil · Apr 17, 2013

turbocharged798 said:
There really is no such thing as cylinder glaze. A smooth cylinder just mean the cross scratches have worn off and the rings have polished the surface.

For a lot of years I flew around Alberta for Alberta Power Canada which included the Canadian/American Dew line in the Arctic.
Ya hungry polar bears trying to get through a barred window to try to eat you!
Lots of times you had to work with used parts because you had no other choice
I never even once had any issues using a used piston and rings in a diesel engine in the REAL world.
Like I said carefull with the sandpaper on the block and the used rings as well and it can and does work!

thundershorts · Apr 18, 2013

I've just finished building an Austin mini engine that someone tried the scuff method rather than crosshatch. It ran great, but the blow by caused by the rings that never seated squeezed oil from everywhere, plus the new pistons were improperly fitted. I apologize for stating unavalibility of oversize pistons....I was told that a few years ago so that has changed. Hopefully, this broken piston will have a happy resolution in Jason's hands, and I'm wrong about the cause of the piston failure.

TDIJetta99 · Apr 18, 2013

It's hard to tell without it right in front of me, but I doubt the broken glow plug caused immediate damage.. The issue that starts happening over time with 83 dings in a piston, especially in a tuned engine, is hot spots.. pistons don't like sharp edges.. Eventually the piston gets weakened from different areas of the piston being unevenly overheated..

I've seen a few engines where foreign objects cause the piston to break, and it's MUCH more violent than just a piston with a crack in it..

thundershorts · Apr 18, 2013

Must be a a pretty severe crack to cause zero compression, more like its separated. From what I've read here on the forum, the ceramic from the gp often ends up scoring the wall probably as a pulverized abrasive.

Chrismak · Apr 18, 2013

Wow you guys sure do get into some Spirited debate on here.

Crosshatch & Glaze. Sounds like a TV show, Starksey & Hutch if anyone is old enough to remember those guys.
Anyways good clean fun and hopefully we all can learn something.

I sourced a used piston from Www.arizonaimports.com

$148 including shipping. They do have 3 left if anyone else is in the market.
Only caveat is they want a written authorization for CC signed and faxed back to them.

Talk to nice girl named Aysel.
Jason I will touch base with you when this comes in and hopefully I can get it over to you.

thundershorts · Apr 18, 2013

Sounds like a positive start . hopefully the piston is in good condition and of course correct. getting rings and whatever else should be quick through Jason's sources.

TDIMeister · Apr 18, 2013

Just remember that 1-2 and 3-4 pistons are paired.

Chrismak · Apr 18, 2013

TDI,

How do I determine which piston is mated to which.
I mean are they numbered 1,2,3,4 from front of engine bay to back.

Stamped on piston? Are 3 and 4 slightly different weight?

All I can determine from stamping is #2 in triangle and 80.96 which I believe is the diameter and an arrow -->. Facing front of engine.

That# 2 in triangle I thought was the piston # but its same on them all?

thundershorts · Apr 18, 2013

I guess its a question as to whether the used parts yard is sending you the correct piston. if they had the engine apart,pistons and rods, they might not know which came from where unless they looked at rod#. you can probably buy the rod as well if needed.

turbocharged798 · Apr 18, 2013

The rods are not numbered for bore, they are numbered for weight. All four rods are exactly the same.

As for the correct pistons, it will be pretty obvious which is a 1-2 piston and 3-4 piston.

TDIJetta99 · Apr 18, 2013

the valve reliefs are arranged differently on 1&2 versus 3&4..

However......

I got a set of OE BHW pistons that were identical.. they had the same size valve reliefs for the intake and exhaust valves so they would work in any position..

Chrismak · Apr 18, 2013

So how do I explain this to someone in A yard in Az.

Firs off the one thats shot on my car nearest the cabin is #4 right?

So how can you tell from looking at them. I know you say obvious, but are 3 and 4 heavier
Or the valve relief on top is different?

Chrismak · Apr 18, 2013

Ok I got it now with the valve relief.
I took a couple of pictures..

This is #1 & 2. The semi circle is bigger and to left of piston.

This #3 &. #4. The bigger semi circle cutout is to the right.

TDIMeister · Apr 18, 2013

I think the bowls are also a bit off-center. On a used piston it may not be possible to distinguish the markings on the piston crown surface. I could only suggest that you take a picture of your number 4 piston and ask for a corresponding picture for the piston you're buying, noting the front position of the engine in both cases. Then compare very carefully.

newlitemotorist · Apr 18, 2013

The pistons are different because the head design is mirrored from cylinders 1, 2 and cylinders 3, 4. Meaning that on the front two cylinders, the intake and exhaust ports are opposite of the back two cylinders. This changes the placement of the injector as well since they are offset due to the larger intake valves which explains the offset combustion chambers. That is why the reliefs and the bowls of each pair of pistons are exactly mirrored from cylinders 1, 2, and 3, 4.

TDIJetta99 · Apr 18, 2013

contact them and let them know you need a piston for cylinder 3 or 4.. the weight should be the same across all 4.. it's the shape of the valve pockets, and possibly the bowl although with the replacement pistons I got it didn't seem like it.. I might be confusing the BHW pistons with a set of crafter pistons I have here too.

thundershorts · Apr 19, 2013

I seem to remember that for gp faults, the ecu sees the cyl at the flywheel end as #1. Not that it would matter for this discussion but if you were ordering new piston it would. VW cyl numbering is reverse of normal front to back?

thundershorts · Apr 19, 2013

Jason, is this type of failure assoiated with tuned tdi's with the increases in temp and pressures?

Misfire running on 3 cylinders

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