MB Motorsports Engine Rebuild - A Warning

I�m writing this post to share my experience with a rebuilt engine from MB Motorsports. Some of this information has been posted in THIS THREAD , as my situation progressed and I sought advice, but I wanted to post the complete story here, along with the name of the company so that others can be informed. Around the Spring of 2022 I decided the engine in my 1999 C2 was quite tired. The engine hadn�t failed completely, but it had a few oil/ coolant leaks, smoked and rattled a bit on startup and popped the occasional CEL for lean running/ misfires. Since I planned on keeping the car into the foreseeable future, I wanted to put a completely fresh engine in. I called around to a few places, and most were quoting around $16-$20k and up to a year+ waiting period. I found MB Motorsports and they quoted $12k (+$4k core charge) and around a 9 month waiting period. I figured the reason they were a bit cheaper is that they actually do the rebuild overseas in Poland, where labor is a bit less costly. They do have a shop in Florida as well, so they are a US- based company. I also did some cursory searching around the internet/ forums and found at least a couple of posts from people saying they had good experiences with MB Motorsports rebuilt engines in the past. They offer a pretty standard rebuild procedure: steel sleeves are installed, the original pistons are reused, but with new rings, original rods are reused with new bearings, etc. They install an upgraded IMS roller bearing, lower temp thermostat, etc. Nothing fancy. I opted to pay a core charge and have them build the engine from one of their units, so that I could keep the engine in my car until the new engine was received. In December of 2022, I received the fresh rebuilt engine and set upon swapping it into my car. The first problem I encountered was that it was missing the water pump and thermostat/ housing, which according to my invoice, should have been included. I reached out and they quickly had the missing parts delivered to me. I was a little concerned that this oversight may have been indicative of them rushing the job on the engine, but ultimately figured it was no big deal. Mistakes happen. I carried on and got the engine in the car. Along the way, I installed many new parts including: clutch, flywheel, AOS, spark plugs, fuel filter, vacuum reservoir and lines, MAF, coolant hoses, pulleys etc. I even bought and used the special "Air Lift� vacuum coolant fill tool and borrowed my neighbor�s air compressor to make sure the coolant system was properly vacuum filled with no possibility of significant air bubbles. It took a week or two to get everything back together and I was so excited to get the engine started and begin driving. After a bit of priming of the fuel and oil systems, the engine started. It smoked and ran a bit rough for a few minutes, but ultimately settled into a nice idle and all seemed well. I ran the engine for a while to get it up to temp, occasionally giving it some revs by hand operating the throttle body. I watched the coolant temp and oil pressure gauges like a hawk, making sure everything stayed within range. Again, everything was good. I kept the bleeder valve on the coolant reservoir in the open position so that any air in the coolant system could escape. I turned the engine off, let it completely cool, and started it again. Again, I gave it some mild occasional revs to get it up to temp, watched the gauges, and when I was satisfied that the engine was running well and not going to overheat, I put the rest of the car together and got it on the ground. According to the documents from MB Motorsports, the only break-in requirement was to not exceed 4,000RPM within the first 1,500 miles. After which time, the oil should be changed. I abided by this rule and started driving the car around town to get the engine broken in. It seemed to run wonderfully. Again, my eye was constantly on the oil pressure and coolant temp gauges. Everything looked good. Never a sign of anything anything abnormal. A few days later, I was driving the car back from a car meet on a cool January San Diego evening and noticed a distinct lack of power. I was heading uphill, going about 60 MPH around 3,500 RPM at maybe half throttle. I thought maybe I was getting a misfire. The car slowed down to maybe 40 MPH and around 2,500 RPM. I downshifted and gave a bit more throttle. Now the car was dying completely. The engine stalled. I hit the hazards and coasted for a bit while I restarted the engine and attempted to give it more power to get to the top of the hill. Now I noticed a terrible sound (like a bucket of bolts rattling around) and a massive plume of smoke behind me. My heart dropped to the pit of my stomach. I pulled to the side, shut it down, and got AAA to flat-bed me home. I was devastated. I called MB Motorsports to advise of the failure. They requested that I look in the intake manifold to see if there was oil there. I pulled the throttle body to take a look and sure enough, there was a massive pool of oil in the manifold. This would explain the smoke� They asked if I had installed a new air-oil-separator (AOS) along with the new engine. I informed them that I had indeed installed a new AOS. They explained that sometimes even brand new AOS units were prone to failure and advised that I put another new AOS on and try to run the engine again. We were hoping this would be a simple fix, but I was dubious. It seemed the engine was catastrophically damaged. Regardless, I cleaned the oil out of the manifold as best I could, installed a new AOS, new spark plugs, and tried to run the engine. It ran, but continued to smoke profusely and the rattling, �bucket of bolts� sound persisted. It was definitely damaged. At this point, I decided to do a compression test. This is what really confirmed it�. cylinders 4 and 6 had 15 to 25 psi, compared to the rest in the 165 to 180 range. I also bore-scoped the cylinders and found what I would describe as catastrophic scoring on those cylinders. Cylinder 1 also had significant scoring but still seemed to hold compression. At this point, I advised MB Motorsports of my findings and they agreed to have the engine shipped back to their shop (In Poland!) for examination. After all, the engine came with a one year warranty and this failure happened within the first couple of weeks. However, I could already tell they were preparing to pass the buck on this one. I made sure not to accuse them of incompetence or insult the quality of their work, but things happen. I�ve worked in automotive performance shops my whole adult life and I understand that sometimes mistakes just happen, or a part is faulty, sometimes it�s just bad luck. I also understand that sometimes the problem lies with the installer or the end user (in this case, me). MB said that they would have the engine builder take a look to try to determine the cause of the failure, but that they have been building these engines for years and they were all but ruling out the possibility of a problem from their end. Sure enough, they came back and told me that the cause of the catastrophic damage was a rapid overheating of the engine. They basically said that I must not have filled the coolant system correctly and that a massive air bubble caused the failure. They also noted that I had installed an under drive crank pulley (they knew I planned to do this, as I swapped it from my old engine, which had no cooling issues) and that this somewhat limited the efficiency of my water pump. Essentially, there was nothing I could do. They gave me my $4,000 core deposit back, but basically said I was out of luck and would have to pay them full price to completely rebuild the engine again. I was gutted. In the mean time, I ended up moving to Europe with my wife. I rented my house and sold all my cars, including my beloved 996 with the old tired engine which needed to be gone through and re-installed. The whole thing left a very bad taste in my mouth. I�m not saying it�s 100% impossible, but I find it hard to believe that the engine overheated so badly and so rapidly due to my negligence. I used the Air Lift vacuum fill system to fill the coolant and followed all the bleeding/ burping procedures while always watching the temp gauge. The gauge never indicated an overheating condition during idle or during driving. I would think that if the engine overheated to the point of catastrophic damage, it would indicate on the dash gauge. The engine also failed after running fine for about 100 miles. If the engine was going to overheat so dramatically due to an air pocket, I would think it would do so much sooner into the course of normal operation. Forum members whose opinions I respect have suggested that the failure could be due to a number of other issues relating to the way that MB Motorsports rebuilds these engines using steel sleeves and re-using pistons. Potential causes of failure involve incorrect ring gaps, incorrectly paired used pistons to new cylinders, and issues around unpredictable thermal expansion qualities of the materials are all above my pay grade, technically. The lesson learned here is: don�t cheap out on your rebuild. Go with a respected builder like LN Engineering/ Flat Six Engineering who will correctly re-hone and coat your cylinders, rather than slapping in some steel liners. So that�s basically where we left it, I�m out $12,000 for an engine which I got to use for around 100 miles before it blew up. Since they have refused to offer any additional refund or reparations, I�m posting this here so that others can be informed and make a their engine rebuild decision accordingly. TL;DR: Freshly rebuilt engine from MB Motorsports blew up after 100 miles of use. Engine builder denies any culpability, doesn�t honor 1 year warranty, says I must have overheated it. I have my doubts. Expensive lesson learned.

Some photos of the carnage: Metal shavings in the oil/ filter: Cylinder 1 Damage: Cylinder 4 Damage: Cylinder 6 Damage:

Engine disassembled at the builder after being sent back. Shows complete destruction of cylinders 4 and 6 pistons/ rings:

Thank you for sharing this experience even though it was not a pleasant one. Hopefully reading this may save someone else from a terrible shop like this that apparently doesn't even know what they did wrong -- unbelievable. I am sorry this happened to you. I hope you are enjoying living in Europe having moved on from this fiasco.

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Is MB owned by that Martin guy that used to come on here and pick fights with FSI all the time? He got banned years ago.

Quotes source post: 19111943

I believe he is that guy.

Yes it is the same guy

Sorry this happened to you... Makes no sense to me for an obvious mistake by builder. Engine builder will lose a lot more in bad publicity than a new set of pistons($1k) and some honing/clean up costs. Even if builder doesn't believe it was his fault, right thing for him to do financially for his business is to make it right... To me, this looks like insufficient piston to wall clearance for a slow expanding steel cylinder and rapid expanding used oem aluminum silicone alloy piston. I'm sure if this is the way they do m96 rebuilds they've come up with wall to piston clearance that works well for them. my guess is, unfortunately a mistake was made in the final honing/fit of cyl to piston wall clearance and the usual clearance they've used was not done/measured correctly.... In most post failure analysis the causes are hard to positively determine. In your case, with that picture of piston, not so hard to determine imo.... To bad you didn't take it apart and measure the piston to wall. My guess, those pistons 'squeaked' once it really fully warmed up under load... And its a possibility, depending on the thickness of the sleeves, and the bore size they gave you,,, you could of had the block/sleeves honed (on a professional machine like a Sunnen Hone) to clean them up and set the proper clearance for steel sleeves, and fit .50mm over sized pistons & rings. Clean up the engine good, reassemble and be ready to go again. all at a relatively low cost... Thats the nice thing about steel sleeves. My guess is thats just what they did, then resold the engine. jmo

Very sad & infuriating, thank you for the service of writing this up. While a lawsuit would have been nice in this situation, it's already coming up as the #4 result on Google for "MB Motorsports Porsche," so they will pay the price for their decision to not make you whole.

Our old friend Martin! Always had a feeling he was a flim flam man�

And this is why I opted to send my block to LNE for their liners, and their new pistons, and their rings.

Lmao. OP blows it himself and claims bad rebuild. If it was a bad rebuild it would�ve blown well before it did. You said it was around 1,500 miles until it blew??? Or you overheated it like they said, or you didn�t install your AOS correctly. Hydrolock from bad AOS is curable btw - sounds like you kept driving it and that�s what caused 4 and 6 to fail. edit - I think my favorite part of the post is the �carnage� oil filter 😂 editx2- goodluck with whatever you do next op.

Quotes source posts: 19113998, 19111745

Reading... Can be tough.

Do you know how to read? He clearly says the engine made it only 100 miles. We already went over this in another thread, the build was trash.....that they were using steel liners to begin with is very telling of the type of work this shop does.

Oof whoops! Yeah missed that one.

If I ever need a rebuild I am going with MB though

You can lead a horse to water..................

Quotes source post: 19114043

I highly approve of your decision.

Quotes source posts: 19114043, 19114049

Oof! Exactly.

Usually engine builders will put special tabs on an engine that will fall off if the engine reaches a certain temperature. If the engine overheated, that's one of the items they would have pointed out. They messed up and didn't admit it.

Quotes source post: 19119077

Yep, any engine builder who does any kind of volume at all will put "heat tabs" on the block and/or heads as a "cover their ***" method to ensure against overheating. If the heat tabs have melted they do not warranty... This should have been at the center of the discussion post mortem , unless I missed it somewhere ..

Correct. Yes this was fully covered in the original thread about this and was central to the discussion as you say. 100% crap builder�.

Quotes source post: 19114043

Please post pics of your last 150MPH run to the liquor store, thanks.

Quotes source post: 19121306

I think the last trip I hit ~140 but don't remember it ...the empty svedka shooters are still under my passenger seat. it's prob best I stick to drinking dt40

I have owned a rebuilt engine from MB Motorsports for five years now, during which I have driven it for 45,000 kilometers. I typically participate in 2-3 track days each year and use the car for various drives. My location is Ontario. As an Airbus mechanic with an M2 license, I understand that any mistake can be quite costly. Many individuals attempt to diagnose issues with their vehicles in hopes of resolving them without professional assistance. It is essential to thoroughly disassemble and take your time when working on these engines. My close friend who referred me to MB Motorsports has now reached nearly 100,000 kilometers on his 997.1 c2s. In the five years of ownership, the only problem I encountered was an instance of overheating. I turned off the engine, replaced the thermostat, and bled the coolant simply by pouring it in while leaving the valve open for about 1 week 30-40 min of driving each time which resolved trapped air issue completely. You can find me on Instagram: Lbvirus_

Sounds like these guys must have a few spots available in their queue.

Sucks man. Heart dropped reading all that.