Bolt question
04-26-2020, 01:13 AM
#1
Bolt question
Bolt
what is purpose of this bolt? It's directly below oil line for turbo on balance shaft cover? It doesn't thread in. In process of doing clutch/oil pan gasket/turbo rebuild/short shift kit/control arm rebuild/Nissan alternator/rod bearings. Either bolt snapped when I was undoing something, or it's been that way. Should I kill myself now?
04-26-2020, 01:47 AM
#2
Three Wheelin'
That's one of the balance shaft bearing cap bolts----the 1987 and newer 944 blocks had updated balance shaft covers with integrated bearing caps. So, that bolt is important, since it affects proper clearance at that balance shaft bearing, which helps to maintain oil pressure not only at the balance shaft but to the turbocharger itself.
Unfortunately, you will likely need to pull the balance shaft cover and repair the threads and/or extract the broken piece of the bolt.
Unfortunately, you will likely need to pull the balance shaft cover and repair the threads and/or extract the broken piece of the bolt.
04-26-2020, 01:51 AM
#3
That's one of the balance shaft bearing cap bolts----the 1987 and newer 944 blocks had updated balance shaft covers with integrated bearing caps. So, that bolt is important, since it affects proper clearance at that balance shaft bearing, which helps to maintain oil pressure not only at the balance shaft but to the turbocharger itself.
Unfortunately, you will likely need to pull the balance shaft cover and repair the threads and/or extract the broken piece of the bolt.
Unfortunately, you will likely need to pull the balance shaft cover and repair the threads and/or extract the broken piece of the bolt.
04-26-2020, 02:27 AM
#4
Three Wheelin'
Ok. Does anything else bolt onto that bolt? Heat shields/ brackets etc? I've been running like that for years unless it's something I just undid, which I don't think so. Oil pressure has always been good. And next question, with junk removed, any way to pull balance shaft cover without undoing front of engine again. Did front reseal last year.
If the bolt is broken, then you should pull the cover and extract the broken part. You will need to remove the balance shaft belt and the upper balance shaft spocket and front cap again (and get new seals for those), but that is not too bad of a job. You won't have to touch the timing belt.
This would not likely affect your overall oil pressure, but could possibly cause a pressure drop specifically at that bearing and at the turbo or at least cause wear at that balance shaft bearing. Imagine a main crankshaft bearing cap that is only fastened by one of the two nuts. Sure, it might have been like that for a while and you've had "no issues," but it would be foolish to leave it as is when you have all of this stuff apart.
04-26-2020, 02:48 AM
#5
Is the bolt broken, or is it cross-threaded? If it's just the threads, you might be able to repair them and use a new bolt if you are lucky, but you need to be careful to not get any metal shavings anywhere they shouldn't be. But, if you can't get the bolt to torque to spec, then you'll have to pull the cover and install a Time-Sert.
If the bolt is broken, then you should pull the cover and extract the broken part. You will need to remove the balance shaft belt and the upper balance shaft spocket and front cap again (and get new seals for those), but that is not too bad of a job. You won't have to touch the timing belt.
This would not likely affect your overall oil pressure, but could possibly cause a pressure drop specifically at that bearing and at the turbo or at least cause wear at that balance shaft bearing. Imagine a main crankshaft bearing cap that is only fastened by one of the two nuts. Sure, it might have been like that for a while and you've had "no issues," but it would be foolish to leave it as is when you have all of this stuff apart.
If the bolt is broken, then you should pull the cover and extract the broken part. You will need to remove the balance shaft belt and the upper balance shaft spocket and front cap again (and get new seals for those), but that is not too bad of a job. You won't have to touch the timing belt.
This would not likely affect your overall oil pressure, but could possibly cause a pressure drop specifically at that bearing and at the turbo or at least cause wear at that balance shaft bearing. Imagine a main crankshaft bearing cap that is only fastened by one of the two nuts. Sure, it might have been like that for a while and you've had "no issues," but it would be foolish to leave it as is when you have all of this stuff apart.
04-26-2020, 05:29 PM
#6
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Keep in mind that the balance shaft spins at 2x the crank speed - so at 13,000 rpm its kind of important!!
I doubt its broken, cant imagine how that woudl happen, did you try to crew it back in?
I doubt its broken, cant imagine how that woudl happen, did you try to crew it back in?
04-26-2020, 05:55 PM
#7
Ill have the turbo off today so I will be able to then pull the bolt out and fiddle with it.
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04-26-2020, 08:25 PM
#9
Rennlist Member
Well that's unfortunate. I think it's a hardened bolt too, making the extraction all the more fun. 
Whatever you do, don't use a screw-in EZ-OUT... Is there any part of the threads sticking out still? If so, that may be a great place to try welding a nut on and spinning it out.
Whatever you do, don't use a screw-in EZ-OUT... Is there any part of the threads sticking out still? If so, that may be a great place to try welding a nut on and spinning it out.
04-26-2020, 08:37 PM
#10
Well that's unfortunate. I think it's a hardened bolt too, making the extraction all the more fun. Whatever you do, don't use a screw-in EZ-OUT... Is there any part of the threads sticking out still? If so, that may be a great place to try welding a nut on and spinning it out.
Whatever you do, don't use a screw-in EZ-OUT... Is there any part of the threads sticking out still? If so, that may be a great place to try welding a nut on and spinning it out.
04-26-2020, 09:11 PM
#11
Three Wheelin'
I have no idea if there are any threads sticking out. will have to pull balance cover to do that, which means pulling balance belt, and I don't know how i will get back plastic cover off without pulling timing belt also. would also have to hire a guy with a welder to do that as well if it comes to that.
Sadly, that bolt is snapped right at where the threaded portion begins, so I doubt there will be enough sticking out to be able to get a nut welded on. Which means you'll probably have to drill out the broken section, which is tedious but is doable if you get your center punch dead in the center of the broken bolt and go slowly and in several stages. Just be sure to mask off the remainder of the balance shaft opening to ensure no metal shavings get in there. I have occasionally had success using left-handed drill bits for drilling out broken bolts. The idea is that once enough of the bolt is drilled out, the anti-clockwise rotating drill bit will at some point "grab" the hollowed-out bolt section and back it out without having to drill out all the way to the threads. This sometimes works, but oftentimes doesn't.
I agree with Tom about extractors, do not use them unless you are to the point where you have a weakened shell of a bolt, if at all. Those suckers are even harder to drill out than the original bolt!
04-26-2020, 09:31 PM
#12
Oh yeah, sorry, forgot that you do have to pull off the rear timing belt cover to get the front cap off the balance shaft . . . but at that point, removing timing belt isn't all that bad if you've just done the job and already know what to do.
Sadly, that bolt is snapped right at where the threaded portion begins, so I doubt there will be enough sticking out to be able to get a nut welded on. Which means you'll probably have to drill out the broken section, which is tedious but is doable if you get your center punch dead in the center of the broken bolt and go slowly and in several stages. Just be sure to mask off the remainder of the balance shaft opening to ensure no metal shavings get in there. I have occasionally had success using left-handed drill bits for drilling out broken bolts. The idea is that once enough of the bolt is drilled out, the anti-clockwise rotating drill bit will at some point "grab" the hollowed-out bolt section and back it out without having to drill out all the way to the threads. This sometimes works, but oftentimes doesn't.
I agree with Tom about extractors, do not use them unless you are to the point where you have a weakened shell of a bolt, if at all. Those suckers are even harder to drill out than the original bolt!
Sadly, that bolt is snapped right at where the threaded portion begins, so I doubt there will be enough sticking out to be able to get a nut welded on. Which means you'll probably have to drill out the broken section, which is tedious but is doable if you get your center punch dead in the center of the broken bolt and go slowly and in several stages. Just be sure to mask off the remainder of the balance shaft opening to ensure no metal shavings get in there. I have occasionally had success using left-handed drill bits for drilling out broken bolts. The idea is that once enough of the bolt is drilled out, the anti-clockwise rotating drill bit will at some point "grab" the hollowed-out bolt section and back it out without having to drill out all the way to the threads. This sometimes works, but oftentimes doesn't.
I agree with Tom about extractors, do not use them unless you are to the point where you have a weakened shell of a bolt, if at all. Those suckers are even harder to drill out than the original bolt!
04-26-2020, 09:36 PM
#13
Rennlist Member
There is also EDM extraction, but you'd likely need to get your car to a shop that can do that...
I've been using my 3D printer lately to make drill jigs for situations like this where the drill bit needs to be placed exactly right. The idea is to make a piece, maybe an inch+ thick, that bolts on to the balance shaft area using 4 or 5 of the existing bolt holes. Where the broken bolt is, you just have a small hole exactly in the center of the broken bolt. That hole is the size of whatever drill bit you are using (start smell, with reverse bit), so that you can drill it dead center without it dancing around on you or going in on an angle. You could make one free hand out of wood or metal with a lot of care, but the 3D printer can put the hole exactly where you want it every time. If you have a little time, I could probably even make one for you...
Here's a picture of a similar jig:
https://www.garagejournal.com/forum/...&highlight=jig
That one was to make a mounting bracket/flange, so the plate was drilled on a drill press. For drilling free-hand, you'd want it much thicker so the bit is sure to be plumb...
I've been using my 3D printer lately to make drill jigs for situations like this where the drill bit needs to be placed exactly right. The idea is to make a piece, maybe an inch+ thick, that bolts on to the balance shaft area using 4 or 5 of the existing bolt holes. Where the broken bolt is, you just have a small hole exactly in the center of the broken bolt. That hole is the size of whatever drill bit you are using (start smell, with reverse bit), so that you can drill it dead center without it dancing around on you or going in on an angle. You could make one free hand out of wood or metal with a lot of care, but the 3D printer can put the hole exactly where you want it every time. If you have a little time, I could probably even make one for you...
Here's a picture of a similar jig:
https://www.garagejournal.com/forum/...&highlight=jig
That one was to make a mounting bracket/flange, so the plate was drilled on a drill press. For drilling free-hand, you'd want it much thicker so the bit is sure to be plumb...
04-26-2020, 10:07 PM
#14
There is also EDM extraction, but you'd likely need to get your car to a shop that can do that...
I've been using my 3D printer lately to make drill jigs for situations like this where the drill bit needs to be placed exactly right. The idea is to make a piece, maybe an inch+ thick, that bolts on to the balance shaft area using 4 or 5 of the existing bolt holes. Where the broken bolt is, you just have a small hole exactly in the center of the broken bolt. That hole is the size of whatever drill bit you are using (start smell, with reverse bit), so that you can drill it dead center without it dancing around on you or going in on an angle. You could make one free hand out of wood or metal with a lot of care, but the 3D printer can put the hole exactly where you want it every time. If you have a little time, I could probably even make one for you...
Here's a picture of a similar jig:
https://www.garagejournal.com/forum/...&highlight=jig
That one was to make a mounting bracket/flange, so the plate was drilled on a drill press. For drilling free-hand, you'd want it much thicker so the bit is sure to be plumb...
I've been using my 3D printer lately to make drill jigs for situations like this where the drill bit needs to be placed exactly right. The idea is to make a piece, maybe an inch+ thick, that bolts on to the balance shaft area using 4 or 5 of the existing bolt holes. Where the broken bolt is, you just have a small hole exactly in the center of the broken bolt. That hole is the size of whatever drill bit you are using (start smell, with reverse bit), so that you can drill it dead center without it dancing around on you or going in on an angle. You could make one free hand out of wood or metal with a lot of care, but the 3D printer can put the hole exactly where you want it every time. If you have a little time, I could probably even make one for you...
Here's a picture of a similar jig:
https://www.garagejournal.com/forum/...&highlight=jig
That one was to make a mounting bracket/flange, so the plate was drilled on a drill press. For drilling free-hand, you'd want it much thicker so the bit is sure to be plumb...
04-26-2020, 11:05 PM
#15
Three Wheelin'
There is also EDM extraction, but you'd likely need to get your car to a shop that can do that...
I've been using my 3D printer lately to make drill jigs for situations like this where the drill bit needs to be placed exactly right. The idea is to make a piece, maybe an inch+ thick, that bolts on to the balance shaft area using 4 or 5 of the existing bolt holes. Where the broken bolt is, you just have a small hole exactly in the center of the broken bolt. That hole is the size of whatever drill bit you are using (start smell, with reverse bit), so that you can drill it dead center without it dancing around on you or going in on an angle. You could make one free hand out of wood or metal with a lot of care, but the 3D printer can put the hole exactly where you want it every time. If you have a little time, I could probably even make one for you...
Here's a picture of a similar jig:
https://www.garagejournal.com/forum/...&highlight=jig
That one was to make a mounting bracket/flange, so the plate was drilled on a drill press. For drilling free-hand, you'd want it much thicker so the bit is sure to be plumb...
I've been using my 3D printer lately to make drill jigs for situations like this where the drill bit needs to be placed exactly right. The idea is to make a piece, maybe an inch+ thick, that bolts on to the balance shaft area using 4 or 5 of the existing bolt holes. Where the broken bolt is, you just have a small hole exactly in the center of the broken bolt. That hole is the size of whatever drill bit you are using (start smell, with reverse bit), so that you can drill it dead center without it dancing around on you or going in on an angle. You could make one free hand out of wood or metal with a lot of care, but the 3D printer can put the hole exactly where you want it every time. If you have a little time, I could probably even make one for you...
Here's a picture of a similar jig:
https://www.garagejournal.com/forum/...&highlight=jig
That one was to make a mounting bracket/flange, so the plate was drilled on a drill press. For drilling free-hand, you'd want it much thicker so the bit is sure to be plumb...
I can't see the pics of your 3D-printed jigs on that forum, but put me down for some when you are done, I will gladly purchase something like that!