Bolt

[The Dan]

Hello all, this is something many of you may or may not know about so I thought I would put it up and see what people think.

Recently an engine was built by me and the bolt for the idler pulley on the timing belt snapped. This happened about 2000km in (I think). All my engines get new bolts there so it came as quite a surprise. The owner and I decided to investigate. I have never had a new bolt break in this way.

He flies aircraft and has contacts for testing bolts etc so we bought 10 8.8 high tensile M10 x 70 bolts and sent them to his guy for MPI (Magnetic Particle Inspection) testing.

7 out of the 10 failed the MPI due to surface irregularities that are at high risk of a crack starting in that area.

So we had three we could use on his engine. I decided to send the other 7 off to be treated to see if we can improve the statistics and then have them re-tested.

I'll let you all know the result once I have them

[NYTSKY]

Same thing happened to my engine, 500kms in.

New piston, valves, head and a new idler bolt later. Was rebuilt and has been going strong.

If you eventually get a new stronger replacement, i would be buying one off you in a second if i or anyone i knew was building an RB.

As the result of a snapped $15 bolt creates a whole word of heartache

And Daniel im sure you have done a few timing belts, but i think the tension has a part to play with these bolt failures also.

[Psymon]

Out of interest, was any other damage caused when this bolt snapped? Was it a bolt supplied by Nissan or otherwise?

[The Dan]

Out of interest, was any other damage caused when this bolt snapped? Was it a bolt supplied by Nissan or otherwise?

yeah every valve touched. Decoro valves too.

I know what you mean NYTSKY but I can assure you overtension is not a problem.

I would have done 20 belts this year alone. Always set them a certain way and double check deflection after 4 rotations.

It was a genuine Nissan bolt and washer. The other 10 purchased are aftermarket bolts

I'm going to try cryogenic treating them first, then back in for MPI

[Dorifta]

never heard of it, are those bolts being torqued up or by hand, Ive done many on rb engines and never felt the need to replace the bolt, i tension by hand with loctite using original bolt, Is sounding like the brand new replacement bolt isn't up to the original spec.

[ahh 33 s2]

i hate reading this kind of stuff.. always seems to be something else that can go wrong.. i have got new stud and bolt for my build. it would be just my luck for something like this to happen.

[Wacky Dee]

the new bolt that snapped was a genuine nissan bolt made for the idler pulley specifically ??

[The Dan]

never heard of it, are those bolts being torqued up or by hand, Ive done many on rb engines and never felt the need to replace the bolt, i tension by hand with loctite using original bolt, Is sounding like the brand new replacement bolt isn't up to the original spec.

Go and get an old idler bolt xrayed. You'll never put one back in, I gaurantee it!

the new bolt that snapped was a genuine nissan bolt made for the idler pulley specifically ??

yes it was.

[Swiper the Fox]

Go and get an old idler bolt xrayed. You'll never put one back in, I gaurantee it!

yes it was.

yes the new bolts are actually a Navara part number which is a little bit of a concern.

Edited October 1, 2009 by DiRTgarage

[Wacky Dee]

Um couldn't you simply sue Nissan for the damages if you can prove, with xrays and whatnot, that it was their genuine bolt that snapped due to shoddy QC ?

[The Dan]

Um couldn't you simply sue Nissan for the damages if you can prove, with xrays and whatnot, that it was their genuine bolt that snapped due to shoddy QC ?

Already considered that but it's not really in my best interest (or budget) to chase a large car dealership for around $2000

[Wacky Dee]

small claims tribunal costs nothing .. I'm sure they'd pay up to avoid bad publicity if you had expert opinions (and xrays) that it was their bolt that failed under normal conditions.

[The Dan]

small claims tribunal costs nothing .. I'm sure they'd pay up to avoid bad publicity if you had expert opinions (and xrays) that it was their bolt that failed under normal conditions.

1. It's probably like 3 - 4 days of my time which works out to be about $3k

2. It's not working under normal conditions considering its a RB26/30

3. They could just say I have to prove it wasn't my fault, which there is no way that I can other than going off the other gazillionty timing belts I have done without problems.

[grigor]

Haven't got an Rb in bits to see but will an Unbrako socket head capscrew fit instead of that hex head HT bolt.

Unbrako's are grade 12.9

That's 1080MPa compared to a grade 8.8 HT bolt of 640MPa.

[Dorifta]

if it aint broke dont fix it, seems to be the qoute for this and many other issues

[Jmaac]

+1 Get a higher grade. The extra safety factor in property class 12.9 or 10.9 bolts will help or you can try removing the surface irregularities by polishing

Property class 12.9 is 1200MPa UTS and 0.9x(1200)=1080MPa yield

Property class 10.9 is 1000MPa UTS and 0.9x(1000)=900MPa yield

as compared to

Property class 8.8 is 800MPa UTS and 0.8x(800)=640MPa yield

[Psymon]

Anyone had this problem with the tensioner pulley stud? I just snapped mine!

Luckily no engine damage though!

[The Dan]

Anyone had this problem with the tensioner pulley stud? I just snapped mine!

Luckily no engine damage though!

Yeah I had a guy come in with a noise once. Turns out the tensioner stud broke and the belt was pushing the bearing into the side of the lower cover. Lucky save that one was.

[Wacky Dee]

I wonder if this is in any way related to power levels ? ie. has anyone had either the factory tensioner or idler pulley bolts snap out of the blue on a mildly modified car ie 200-270kw?

[Psymon]

Yeah I had a guy come in with a noise once. Turns out the tensioner stud broke and the belt was pushing the bearing into the side of the lower cover. Lucky save that one was.

Yeah... pretty much the same problem here. The car started making a horrible noise. Pulled off the timing covers to find heaps of slack on the tensioner side of the belt. So lucky not to skip any teeth!

I wonder if this is in any way related to power levels ? ie. has anyone had either the factory tensioner or idler pulley bolts snap out of the blue on a mildly modified car ie 200-270kw?

Mine would fall in this category.