IDIOTIC MISTAKE - Sheared Top of Hex Nut for Timing Tensioner Piston

[91FourDr5spd318i]

Well guys, I completely blew it. I've never messed up anything auto/engine related this badly.

I went out a bought a torque wrench, quadruple checked my settings, yet somehow broke the head of the tensioner piston's bolt clean off.

This leaves the tensioner piston in the engine, decompressed, but leaking oil as there's not a full seal around it.


Am I completely screwed here?

Thanks in advance.

[varg]

Probably. You're unlikely to be able to get it out with the timing cover on the engine. Looks like it's time to pull it off and since that's a pain, you may as well replace everything you can afford to replace behind it.

[91FourDr5spd318i]

Probably. You're unlikely to be able to get it out with the timing cover on the engine. Looks like it's time to pull it off and since that's a pain, you may as well replace everything you can afford to replace behind it.

Yeah, that's what I figured. Need the guides/gaskets replaced anyway, the tensioner piston itself did nothing to fix the horrible noise. Probably would just end up getting the whole timing kit some stores offer.

The threading from the top nut that broke is still in the tensioner hole. Would an extractor ruin the threads of the engine block (if I haven't already done that...)


What else do you think needs to go?



PS: The link in your signature needs modification; I had to remove all but the "www.r3vlimited.com/board/showthread.php?p=4162247" section to get it to load. Great build, by the way. I remember watching it from the beginning, long before I ever thought I'd be an E30 owner. Hope to have the same type of setup someday...

[DesktopDave]

I'd be tempted to get a pick in there and slowly rotate the stub of that hex-head plug out. I know the tensioner piston sticks out a bit, but if you pushed the piston in slightly with a drift or screwdriver you might just get lucky. I wouldn't use a hammer to drive the drift in there - you could crack the timing rail. Just use it to apply a little pressure to the hydro piston and unload the collar of that broken plug.

Otherwise...yep...it'll have to come apart. You might need a new case if a tap can't restore the threads.

You might have a bad bearing in the cam idler gear. Common problem with the older M42. Replacing it with the late-model M42 chain case eliminates the problem.

[91FourDr5spd318i]

I'd be tempted to get a pick in there and slowly rotate the stub of that hex-head plug out. I know the tensioner piston sticks out a bit, but if you pushed the piston in slightly with a drift or screwdriver you might just get lucky. I wouldn't use a hammer to drive the drift in there - you could crack the timing rail. Just use it to apply a little pressure to the hydro piston and unload the collar of that broken plug.

Otherwise...yep...it'll have to come apart. You might need a new case if a tap can't restore the threads.

You might have a bad bearing in the cam idler gear. Common problem with the older M42. Replacing it with the late-model M42 chain case eliminates the problem.

Thanks so much for your reply! What exactly do you mean by "drift" and "pick"? Is the pick just a type of extractor? I'm really hoping it won't have to be tapped, as hopefully the case's threads are still good... But I doubt it. I've tried pushing the tensioner in, but it won't budge. Maybe I'm too weak in this cold/can't get a good angle (the engine's in the car). I'll add some photos of the situation as it stands.


I'm assuming that later year M42s are nearly the same? Would they still be a bolt in replacement? Only asking because this engine's mileage is unknown, has god knows what else that's going to fail on it next, don't have the time to rebuild it myself, and may potentially have the opportunity to get a rebuilt M42 from Bavarian Engine Exchange http://www.bavengine.com/engine.html

There are drastic torque rating changes between the 90-91 and the 92-93, 94-95 M42s on the linked page. What's the difference? I haven't heard or read anything about that before, and am having trouble finding anything.

[bmwman91]

If you do decide to tear down the timing case / chain assembly, look for a 1994+ M42 timing case. It eliminates the awful deflector sprocket, which is a huge reliability problem, and uses another plastic guide instead. It is more or less a direct bolt-on, just make sure you get the proper gaskets in the cases where they differ. You should be able to get a used late-model timing case + covers on the forums for under $100. It is possible to swap timing cases without removing the head, but it is a real pain and I only recommend it if you are somewhat experienced in working on engines and comfortable with digging in to them.

Late-model timing parts:
http://www.realoem.com/bmw/enUS/showparts?id=BE53-USA-10-1994-E36-BMW-318is&diagId=11_1370

Related gaskets for late-model timing case:
http://www.realoem.com/bmw/enUS/showparts?id=BE53-USA-10-1994-E36-BMW-318is&diagId=11_2683
http://www.realoem.com/bmw/enUS/showparts?id=BE53-USA-10-1994-E36-BMW-318is&diagId=11_6003


Also think about replacing parts 5-8 if you pick up a used late-model case.
http://www.realoem.com/bmw/enUS/showparts?id=BE53-USA-10-1994-E36-BMW-318is&diagId=11_6009



The M44 timing case is also an option, with the advantage of a bigger oil pump. However, it is not a direct bolt-on and you would need to buy a custom bracket to hold the crank position sensor since the M44 case does not have anything to hold it.

Personally, I would consider doing what Dave mentioned and try to get the threaded collar out. Push the piston in a bit to make room, and then see if you can get a pick in there to try to push/rotate the threaded part out. Without the head on the cap, I don't think that the threads should be too hard to rotate out.

[91FourDr5spd318i]

If you do decide to tear down the timing case / chain assembly, look for a 1994+ M42 timing case. It eliminates the awful deflector sprocket, which is a huge reliability problem, and uses another plastic guide instead. It is more or less a direct bolt-on, just make sure you get the proper gaskets in the cases where they differ. You should be able to get a used late-model timing case + covers on the forums for under $100. It is possible to swap timing cases without removing the head, but it is a real pain and I only recommend it if you are somewhat experienced in working on engines and comfortable with digging in to them.

Late-model timing parts:
http://www.realoem.com/bmw/enUS/showparts?id=BE53-USA-10-1994-E36-BMW-318is&diagId=11_1370

Related gaskets for late-model timing case:
http://www.realoem.com/bmw/enUS/showparts?id=BE53-USA-10-1994-E36-BMW-318is&diagId=11_2683
http://www.realoem.com/bmw/enUS/showparts?id=BE53-USA-10-1994-E36-BMW-318is&diagId=11_6003


Also think about replacing parts 5-8 if you pick up a used late-model case.
http://www.realoem.com/bmw/enUS/showparts?id=BE53-USA-10-1994-E36-BMW-318is&diagId=11_6009



The M44 timing case is also an option, with the advantage of a bigger oil pump. However, it is not a direct bolt-on and you would need to buy a custom bracket to hold the crank position sensor since the M44 case does not have anything to hold it.

Personally, I would consider doing what Dave mentioned and try to get the threaded collar out. Push the piston in a bit to make room, and then see if you can get a pick in there to try to push/rotate the threaded part out. Without the head on the cap, I don't think that the threads should be too hard to rotate out.

Thank you for the information, this seems like the way to go now. I'm still unsure as to what you folks are meaning by "pick." I looked up variations of "[noun/adjective] pick" and "mechanic pick" seems to show what's been mentioned. Is this correct?


Also, it seems unreasonably difficult to compress the piston again. I installed it whilst decompressed to avoid the "rev to 3K and pray" and a potential chain jumping due to broken guides. Would this have anything to do with the difficulty? Engine's in the car, leaving little room. My plethora (or lack thereof) of tools is somewhat limited, any ideas as to what to use to get this thing compressed?


Sorry for all the continuous questions, just figured I'd get all the info I can.  Thanks again for the help, all of you.

[bmwman91]

A "pick" in this case would be something like these:


The idea is to use the pointy end to stick into the remaining part of the cap and push on it tangentially to rotate it out.

Did you turn the engine on at all? If so, the piston is full of oil which makes it very hard to compress since the oil has to be squeezed out of a tiny hole in the opposite end (where it squirts onto the tension rail). The piston might also be partially jammed in the remaining part of the cap. Anyway, firm pressure for a couple of minutes should compress the piston. That area is sort of a pain to get at to apply force, so it's easier said than done.

[DesktopDave]

Thanks so much for your reply! What exactly do you mean by "drift" and "pick"? Is the pick just a type of extractor? I'm really hoping it won't have to be tapped, as hopefully the case's threads are still good... But I doubt it. I've tried pushing the tensioner in, but it won't budge. Maybe I'm too weak in this cold/can't get a good angle (the engine's in the car). I'll add some photos of the situation as it stands.

A drift is like a screwdriver, but with a blunt end. A nail-set is a drift, if you're more into carpentry. It's used for tapping or driving seals, plugs and suchlike.

BMWMan91 is completely right about the chain tensioner. It's just a spring-loaded tube that fills with oil via a very small hole. A one-way valve prevents the oil from flowing back out. As oil cannot compress, the tube is locked and prevented from retracting. With a good bit of pressure you can slowly force the oil back out of the fill hole. It takes a lot of time and a surprising amount of force. BMW requires that you retract a used tensioner before re-use, they suggest a c-clamp or bench vise.

There isn't a lot of space under there, unfortunately. I had thoughts about a similar sized hole saw (take the sheared head to match up the diameter), you could possibly get enough grip to twist it out. I also thought you could pick up a cheap set of chisels at Harbor Fright and use a correctly-sized one to tap into the sheared bolt shaft. If you could work a few notches into the bolt shank without messing up the timing case threads, you'd be in business.

I'm assuming that later year M42s are nearly the same? Would they still be a bolt in replacement? Only asking because this engine's mileage is unknown, has god knows what else that's going to fail on it next, don't have the time to rebuild it myself, and may potentially have the opportunity to get a rebuilt M42 from Bavarian Engine Exchange http://www.bavengine.com/engine.html

There are drastic torque rating changes between the 90-91 and the 92-93, 94-95 M42s on the linked page. What's the difference? I haven't heard or read anything about that before, and am having trouble finding anything.

The M42 went through one major redesign and a few minor changes. They are more or less bolt-in replacements. The blocks and heads are all the same, but the intake and accessories were updated several times. The E36 version also has a different oil pan, dipstick, etc. The later E36 model has an updated "DISA" intake manifold, knock sensors, and updated cam chain case, chain tensioner and a different accessory drive system. The later M44 is a closely related engine, as is the Euro-only M47 diesel.

[91FourDr5spd318i]

Those sound like good plans, definitely will look into doing them, but I'm not sure I have the expertise (I definitely don't have all the tools!) needed to do a full timing rebuild.


Dave, if I were to go ahead and get a late/last year M42 replacement engine (just because the ones on that site have an option to be rebuilt with better cams), would my engine accessories not be compatible with them? And could I use the oil pan that comes with the new engine, or would I have to keep mine? I know that's a dumb question, but I've seen something about that mentioned on here, and searching for late year M42 conversions/replacements hasn't yielded the answers I need.

[DesktopDave]

Those sound like good plans, definitely will look into doing them, but I'm not sure I have the expertise (I definitely don't have all the tools!) needed to do a full timing rebuild.


Dave, if I were to go ahead and get a late/last year M42 replacement engine (just because the ones on that site have an option to be rebuilt with better cams), would my engine accessories not be compatible with them? And could I use the oil pan that comes with the new engine, or would I have to keep mine? I know that's a dumb question, but I've seen something about that mentioned on here, and searching for late year M42 conversions/replacements hasn't yielded the answers I need.

You'll need to swap a lot to make the later motor fit. It's all bolt-on from what I've heard (I haven't done it myself). What I can tell you first-hand...I'd absolutely try my darndest to get that tensioner bolt out before contemplating a swap. Just the front crank bolt by itself is a complete PITA. It's torqued to something like 350ft-lb and it laughs off anything but the largest pneumatic impact guns or breaker bars.

Anyhow...strip the E36 block and swap the E30 oil pan, dipstick, motor mounting arms, intake manifold, wiring harness and accessories. Then install! Should take a good long weekend if you have an engine hoist & load leveler.