Engine`s gone
 

I visit this forum because I enjoy reading stories about engine failures and I love to get an insight into the process of troubleshooting. I particularly find it interesting when a chain reaction of events leads to a catastrophe and turns the engine into a boat anchor in a fraction of a second, I guess that`s because of the dramatic effect and the irreversibility of the outcome. The story is somewhat less enjoyable though when the subject happens to be my car. Anyways, here it comes, I thought I share:

Yesterday on my way home the engine started making some weird noise, and stopped. I was able to pull into a parking lot with the engine off and I see this super thick white smoke coming from the exhaust. My first thought was, ok, it must be the AOS, but then I see coolant dripping from the overflow tube. Btw, the engine was not overheating, CEL was not on, there was absolutely nothing to indicate there`s something bad about to happen. I check the oil, looks fine, no signs of intermix. The oil level went up about two units though...

So I tow it home, pull the plugs assuming they are all oil-fouled. No oil, but one looks like this:

http://986forum.com/forums/uploads02...1660519016.jpg

Oops. That`s not good.

So I peek into the cylinder with the borescope and find this disaster:


http://986forum.com/forums/uploads02...1660519035.jpg


http://986forum.com/forums/uploads02...1660519064.jpg

So, this is where I am at now, I`m not sure what happened, it looks like a D-chunk failure, the liner is clearly cracked, which explains why the oil level went up. This is the engine I rebuilt two years ago from scratch and there`s 12k miles in it.

I`m undecided whether I should rebuild it again using another core or I should just sell as a roller. Anyways, just wanted to share :ah:.

That is a real bummer. Thank you for sharing and good luck with the decision.

:eek: oh-no! Sorry to see this happen.

Would be very interesting to know what caused this to happen and broke other stuff, maybe hard to tell for certain which let go first - D-chunk failure or something else :confused:

Wow!

Is that the oil control ring besides the rest of the piston?

I think it's better to look for another engine. This won't be an easy fix, because everything has to be checked, measured, new sleeves, planed and so on. I think that's a little be above a DIY job to be honest.

Very sorry for the loss.

Regards from Germany,
Markus

Thanks, Guys. Yes, the rings are broken, but the sleeve is cracked in a D-shape too, and it`s impossible to tell at this point which happened first. My suspect is the aftermarket ringset, but a complete teardown might tell more once I get around doing it, if ever.

Yes, the engine is clearly damaged beyond repair, the broken casting should be welded up and resleeved which makes no sense as it`s way cheaper to get an intact core or short block and rebuild from there. Especially because this is the base 2.5 engine.

What a bummer. What was involved in the original rebuild?

Rings, bearings, valves on one bank, chains, etc., nothing major. You can look it up at the show&tell section, there`s a lengthy thread about it, if interested.

What did you set the ring end gaps at on the new rings?

I am sorry to hear that this happened to you.

Sorry to hear that especially after all the work of the rebuild.

I had a friend with a very similar failure - looked like a slipped sleeve (#6) on a '99 with under 100k miles on it. Pic is from the guy that bought it afterward when he had the engine torn down:
http://986forum.com/forums/uploads02...1660587669.jpg

I had sold him the car about a year earlier thinking that the engine was in great shape and that by the age and mileage it was past the chance of having the 'early Boxster' failure modes.

I didn`t touch them. The two rings on top were ~ 0.4 and 0.8, similar to that of the originals, when I placed old and new on top of each other in the bore there was no difference. The side rails for the oil rings had smaller gaps than the original, but those looked worn and I didn`t adjust those either. But don`t you think if there had been a problem with the gapping then the engine wouldn`t have lasted this long but would have fallen apart earlier?

Another thing: the exhaust header was full of coolant, yesterday it was still dripping at the gaskets, indicating a lot of coolant got into the cylinder. Maybe the cylinder head cracked, the piston sucked coolant in causing hydrolock and the pressure cracked the cylinder wall? Just wondering if that`s possible :confused:

Wow, that`s crazy. Looks like the piston got seized and pulled the sleeve. I`ve never seen such a failure. These engines are truly amazing with all these unique failure modes :)

0.4 - 0.8 what? MM, inches?

No, improperly gapped rings can fail at different times and in different ways, depending upon which way they were off. Engine failures are a cascading event, the only way to try and figure it out is to pull it apart and look at each failed part. And yes, and casting failure can lead to hydro locking and blown out cylinder walls

MM.

These were the gap values that I measured in the original engine, the new ring gaps were very close:

http://986forum.com/forums/uploads02/ring1660596783.jpg

Yes, I`m curious to see what went wrong.

OK, lets start with the top ring. Based upon accepted standards for ring end gaps, based upon bore diameters: Most piston ring manufacturers recommend a minimum end gap of .004 inches times the bore diameter for the top piston compression ring. So for a 4 inch bore, the standard end gap would be .016 inches. As you have an 85.5 mm, or 3.366 inches. Using the suggested rule of thumb, which would work out at 0.004 X 3.366 = 0.013 inches, or 0.33 mm. So that ring gap is way too wide.

Mahle, the makers of these pistons have published ring end gap guidelines for the 2.5 and 2.7L M96 engines:

Mahle
Top ring-0,15...0,35mm....006"-.014"

2nd ring-0,60-0,80mm....024"-.032"

oil control-0,50-0,75mm...020"-.030"

Again, your gaps appear excessive. Overly large ring end gaps can cause a myriad of issues, from compression loss to oil consumption, and most importantly, excessive piston rock in the bore, which can result in ring land (the piston metal that separates the rings from each other) failures.

When a piece of ring land material breaks loose, it can get wedged between the piston and cylinder wall, stressing both. I would not be surprised to find that if you pulled the pistons out, you would find multiple ring land failures. I also noticed from your assembly photos that there were significant gaps between the rings and the cylinder walls, indicating oval cylinder liners, which would also exacerbate that piston rocking problem even more.
http://986forum.com/forums/uploads02...1548034577.jpg

Lawyers often like to say that, "the devil is in the details". That is also very true for engine assembly.

This is what ring land failure looks like:
https://slautoworks.com/wp-content/u...and-Subaru.jpg

Thanks for looking into this! We should have had this conversation 2 years ago.. As I can recall I could not find specifications for the ring end gaps so I just went with the new rings assuming they should be ok. Based on the values you posted from Mahle the old worn rings were within or just out of spec, the new ones had similar or slightly smaller end gaps. The picture shows an old side rail from the oil ring, it came out stuck and probably deformed from the ring groove where it was stuck in gunk. With the new side rail there was no gap between the rail and the cylinder wall. Also, the car was running strong, no smoke, no excessive oil consumption. I didn`t find metallic particles inside the oil filter at the last oil change.

I`ll see what`s inside, it will be a great learning experience.

Hello Homeoboxter, bust just ran into this engine (not affiliated), but it seems that could be a great deal for the price, if it works out you could have with a nice powerplant for your Boxter :-)

https://rennlist.com/forums/market/1313957

Thanks! Wow, indeed sounds like a great deal. However, I would have to replace or reprogram the DME for this and modify a number of things, and probably it wouldn`t pass the smog test easily. Not sure if it`s worth the hassle... It would be great though :cool:

2,500 mile 2006 Cayman S engine with low leak down test numbers.

Why would one do a leak down test on a 2500 mile engine? It`s basically brand new. And why would one swap an engine after 2500 miles? Just wondering..

That engine was one of my options when deciding what to do with my bore scored CSS. He's dropped the price substantially since I was looking 1.5 yrs ago.

Sorry to hear about this. What year was it and what displacement? I have a bunch of parts from a 99 2.5L that I don’t have a use for(probably just jinxed myself) if you decide to rebuild.

Thanks, it`s the same, 99, 2.5L. I`m looking for a complete engine that I could just swap out, but actually I might rebuild it if i find a usable short block. Can you PM me with a list of what you have?

Sorry about what happened, Homeoboxster. A catastrophic engine failure is probably on the mind of everyone on here. I've actually been looking around for a shop that would convert mine to electric if that were to happen. Do you know of any, and is that something you've considered? I know it's sacrilege for truists on here, but I think it would be interesting.

It's been done:
https://www.youtube.com/watch?v=4_SOP86n-PM

Yes, I've seen that. But it's well above my skill level so I'm hoping to find a shop that would do it.

I found a place but they want upwards of $60K, IIRC. I thought around $20K would be reasonable, but I don't know.

I would, however, be comfortable with a bolt-on DIY kit specifically designed for the Boxster, if I could find that.

Yes, I thought about that and it would be a perfect solution because I use the car for short rides. It would be an exciting project! It`s a lot of work though and it`s out of the budget too. It seems that the easiest and cheapest solution now is just to swap the engine out with the same 2.5 engine or rebuild it again if I find a low mile donor engine with good cases.

I would just swap with another one. Why buy a block, then tear down the old, build the replacement....doubles the time. Get one from a doner, replace the plugs, wp, change the oil and be done with it. Get it done in time for fall which I think is one of the best times of the year to be driving these.

Thank you for the link, it was pretty interesting to watch :-)

Agree ion that.

But do i really want a Boxster that sounds like a tram? I don't know. :D

Yeah, for ~ the same $ you can get a nice 3.4-3.8 motor in the back and get around the same performance you could from the electric.

One thing about the electric conversion is that there a bunch of places to put batteries on a 986 so range would only be a limitation of $ for batteries.

I'd look at car-part.com for a complete engine and probably get one with a 90 day or 6 mo warranty. Here's a few in Northern California:

http://986forum.com/forums/uploads02...1661774341.jpg

Swap the best bolt-on stuff from your rebuilt/bad engine.

Thanks, I didn`t know this site!
I`m thinking of getting this:
https://orangecounty.craigslist.org/pts/d/aliso-viejo-1999-porsche-boxster-engine/7516701025.html
Price is largely negotiable.

I also thought about this, for a rebuild:
https://sfbay.craigslist.org/sby/pts/7527129249.html
I assume this wouldn`t work with the 2.5 heads, clutch and transmission though, so I dropped the idea.

Nice build thread - sorry to hear about the recent development.

I've not done any rebuilds but am considering one on my 03 986 S.

Can you give a little more detail about using the extra oil pump housing and pre-filling the oil on the build stand please? Did you fill completely (from the top I assume)? You used the dip stick to measure as you got close to the right amount? You used the drill to load up the block while you were filling? You just swapped out the cover with the drive and the hole-less cover when you were done (messy?)?

Yes, to each of your questions :) This whole procedure is not really necessary, I just did it because I had an extra pump and I wanted to make sure that the variocam system is filled up because I was testing those, see the video somewheer in the thread. I saw some builders using an external pump (any kind) to fill the engine with oil via an opening of the oil circulation system, probably the heat exchanger or the oil filter inlet could be used for this. Some builders just pre-lube everything with the assembly lube and that also works, I personally don`t like that though.

More details on blown engine
 

Hey All,

Last year I ended up selling the Blue boxster as a roller to a friend nearby who needed a donor car for his race car. After he took off everything he needed he gave the engine back to me so I had a chance to take a better look inside. I took a couple pictures before I scrapped most of the engine, here they are, just fyi.

Head off:

http://986forum.com/forums/uploads02...1685424211.jpg

This is where the thick white smoke was coming from:

http://986forum.com/forums/uploads02...1685424316.jpg

The other 5 cylinders looked totally fine.

http://986forum.com/forums/uploads02...1685424483.jpg

The top of piston #1 broke off:

http://986forum.com/forums/uploads02...1685424551.jpg
http://986forum.com/forums/uploads02...1685424619.jpg

I don`t know how could I miss this completely during the rebuild, but one bank had been resleeved.

http://986forum.com/forums/uploads02...1685424742.jpg

Here`s what the other bank looks like from the bottom:

http://986forum.com/forums/uploads02...1685424995.jpg

I`ve read somewhere that some early bore scored blocks were sent back to Porsche in warranty and got resleeved. Later these engines had a tendency to fail. Perhaps mine was one of them?

When this engine blew up, it was a hot day and I was stuck in traffic, and the coolant temperature was higher than ever before. I had been going to clean the radiators and check the fans because I suspected they are not blowing at the highest speed. I never got around doing it. Nevertheless, now that I think about it, probably the engine got overheated. Another suspect is the aftermarket rings which perhaps didn`t like the Lokasil bore too much. Anyway, my theory now is that somehow the piston got seized for a moment and pulled the sleeve down, then in the next cycle the rings got stuck in the shoulder of the sleeve and that broke off the top of the piston. Also possible that that the rings broke first, hard to tell at this point. Just thought I share.

Classic example of trying to put a square peg in a round hole.

You put so much work into that engine, too bad it ended like that.

Lesson learnt, I guess, hopefully the next one turns out better :) I`ll stay away from these resleeved engines.

It`s interesting to see that the sleeve slipped the same way as in mine. Perhaps this was a factory resleeved engine as well?