1845 owners, check your VV pump bolts

marrt · Oct 28, 2007

Twice in the last few months, I've had the VV pump bolts fail. The second time, I replaced the grade 5 bolts with grade 8...and they failed in less than 50 hours (too brittle I suppose). The only warning sign was additional vibration. Everything continued to work fine. There's a lot of weight hanging off these two bolts, subjected to a lot of vibration from the engine.

The pictures below came from Sedgewood's site. Sedgewood, these pictures are much better than the one's I took. I hope you don't mind that I posted them here (if so, send me a PM and I'll remove them).

Bob999 · Oct 28, 2007

Have you talked to Terry about this? I am wondering if there might be some problem on your machine that is breaking the bolts.

So far as I know I have not had any problem--I am traveling now so can't check my machine--and no other person has posted a similar problem. It is also puzzling why you could operate for an extended time without a problem and then begin breaking bolts unless something has changed.

marrt · Oct 28, 2007

The first time, I only had one bolt break at about 500 hours. These were grade 5 bolts and probably originals. I'd noticed unusual vibrations at certain RPMs but wondered if it was my imagination. When I would throttle up, the vibration would go away. One day, I was idling the machine and had the hood up. I could see the rear of the pump assembly clearly vibrating. When I looked at the right bolt, it was missing. I found the bolt in the bottom of the tub. I retrieved another bolt but could get the new bolt to start. While taking a break, I happened to clean up the old bolt and examine it closer. I could see from the end of the bolt that it had broken. I inserted a very small bolt in the hole and concluded, correctly, that the end of the bolt was still in the hole. To retrieve it, I had to disconnect the pumps (by removing to other bolt), unbolt the engine from the tub, and push both apart. I placed a 6x6 from the ROPS to the hood and used straps to winch up the pump assembly and engine so I could move them. I could then get some pliers on the back of the bolt and screw it out the back easily. I was working by myself and this took a long time to figure out and execute. Today's job only took two hours because I knew what to do and had a helper. I actually pulled to pump mounting plate out and examined it. To my eye, it looked fine. However, the pump mounting plate is only 1/2" steel. Having this entire pump assembly hanging off of two bolts threading through mild steel seems...not optimal. But its not the steel that's failing, it's the bolts. I replaced the grade 5 bolts bolts with grade 8. I then read somewhere that grade 8 bolts, while much stronger overall, do not like vibration. One bolt was completely broken today the other bolt also broke easily when I applied a little torque to tighen it again. In any case, I will definitely call Terry tomorrow. I suspect there has been a design change and the new models aren't built this way. Hopefully, there's an upgrade I can purchase. If not, I already have an idea how to fix it. But let's see what Terry says first.

toy · Oct 28, 2007

marrt said:
Twice in the last few months, I've had the VV pump bolts fail. The second time, I replaced the grade 5 bolts with grade 8...and they failed in less than 50 hours (too brittle I suppose). The only warning sign was additional vibration. Everything continued to work fine. There's a lot of weight hanging off these two bolts, subjected to a lot of vibration from the engine.

The pictures below came from Sedgewood's site. Sedgewood, these pictures are much better than the one's I took. I hope you don't mind that I posted them here (if so, send me a PM and I'll remove them).

Do you think that it might have been caused by the vibration causing the bolts to loosen up and when the torque of the motor hit the resistance of the pumps it caused pump to jerk which caused the bolt to break?

Marks481 · Oct 29, 2007

toy said:
Do you think that it might have been caused by the vibration causing the bolts to loosen...

Sounds like a very likely scenario, especially since he said that he could easily back the broken off portion of the bolt out of the holes with pliars. Sounds like a prime candidate for some locktight application to ensure the bolts don't vibrate loose and subsequently break (have to look and see what it looks like on my 422...)

SnowRidge · Oct 29, 2007

Locktite and a torque wrench. Too bad PT doesn't provide tables with fastener torque values for their machines. The pump manufacturer may provide one, though.

J_J · Oct 29, 2007

Marrt, I would put grade 8 bolts through a drilled out hole and install nylon lock nuts.

marrt · Oct 29, 2007

I have plenty of locktite but was afraid to apply any due to my concern about getting the end out if the bolt breaks again. Since I know I can pull the mounting plate without too much trouble, I'll put a little 2760 on it this time. If it fails again, I'm going to take the mounting plate to a machine shop and get them to add some 9/16 fine threads at a different location on the plate. This will allow me to use a little larger bolt. I spoke to Terry and there hasn't been a design change. He says this is not a common problem at all. So that relieves some of my concern. Terry agrees that a grade 5 bolt is a better way to go in this high vibration environment. However, the more I read online, the more I'm convinced that it's a myth that grade 8 bolts are more brittle.

As someone suggested, it's quite possible these bolts had loosened a bit, contributing to the problem. I'll check them very frequently for a while.

Regarding torque specifications, check this site: SAE standards for bolts

toy · Oct 30, 2007

marrt said:
I have plenty of locktite but was afraid to apply any due to my concern about getting the end out if the bolt breaks again. Since I know I can pull the mounting plate without too much trouble, I'll put a little 2760 on it this time. If it fails again, I'm going to take the mounting plate to a machine shop and get them to add some 9/16 fine threads at a different location on the plate. This will allow me to use a little larger bolt. I spoke to Terry and there hasn't been a design change. He says this is not a common problem at all. So that relieves some of my concern. Terry agrees that a grade 5 bolt is a better way to go in this high vibration environment. However, the more I read online, the more I'm convinced that it's a myth that grade 8 bolts are more brittle.

As someone suggested, it's quite possible these bolts had loosened a bit, contributing to the problem. I'll check them very frequently for a while.

Regarding torque specifications, check this site: SAE standards for bolts

Did the bolts have lock washers under the head of the bolts, if not that might be all you need to get them to tighten up and hold.

SnowRidge · Oct 30, 2007

On my PT-425, the tram pump requires careful alignment. Is it possible that the pump is misaligned on your 1845? A misaligned pump might contribute to bolt loosening.