Up to temp, sputters, then dies

[ankana]

[Precise1]

LOL, nice improvised 90 degree milling set up !! I have to ask though, why didn't you just use a woodruff cutter ? You get an A for the set up though.

 

B

[ankana]

I have to ask though, why didn't you just use a woodruff cutter ?

Didn't happen to have one laying around.

[Animal]

This problem is not that uncommon, but I don't believe the woodruff key is the cause. I'm sure I will be corrected if I am mistaken, but these keys are meant to align, not drive the parts. So, even if the keys somehow went bad after they were installed, the pulleys shouldn't have slipped.

 

With the miles on the vehicles I've read having this problem I'd guess the T-belts been replace at least once, if not 3 times. I'm theorizing that when the pulleys were reinstalled, the bolt was not properly torqued - without looking in the FSM, I recall it's around 2.5 x stupid.

 

I doubt anyone would admit to this, so I don't expect anyone to own up, just something to think about next time.

[ankana]

Allrighty then... I suppose that this could be a rebuild caused failure. Since I do most of my own maintainence, I think I may thake this personally...God knows that Nissan doesn't have any engineering problems--(cough)exhaust studs!!--

Edited August 24, 2006 by ankana

[Precise1]

Didn't happen to have one laying around.

 

LOL, next time ask... They aren't very expensive either.

 

Exhaust stud issues are minor in my book, I like the solid motor. Working on the outside is ok, working on the inside irritates me...

 

B

[Animal]

Allrighty then... I suppose that this could be a rebuild caused failure. Since I do most of my own maintainence, I think I may thake this personally...God knows that Nissan doesn't have any engineering problems--(cough)exhaust studs!!--

Nothing personal intended, though I do my own work and will admit I've screwed up before. So, if it isn't lack of torque on the bolt, it is something else, maybe an engineering flaw (perhaps the pulley and harmonic balancer are only good for one use), but I don't beleive the keys are the cause.

[ankana]

I don't know if the problem was related to a loose bolt or not. It would certainly accelerate the problem if that bolt were not torqued properly. The fact that this is not an isolated problem would indicate that either there are alot of crappy mechanics out there, or there was an error in engineering this part.

 

Merely for the sake of debate, I will give you my take on this thing.

 

-stepping up on soap box-

 

Ladies and gentlemen,

This is a rotating assembly with a slide fit.- averaging around 3000 rpm for 220,000 miles @ an average of 50 mph= approximatly 792,000,000 revolutions so far- I don't care how much you tighten that bolt, anything short of welding the thing in place is going to see a tiny bit of movement every revolution. Because the surface area on the components are so much greater, and the key is made of softer material. Even the slightest movement causes the woodruff key to wear on the power side. Here is where I think there is an engineering problem. Even with a new key there nearly .07in difference between the height of the key and the size of the slot. Because of the shape of a woodruff key, when it wears on one side, it rises in the slot and suddenly there is more room to move. Eventually the key rises and wears so badly that damage occurrs to the crankshaft and you get to where I was with a factory tech telling you to replace your motor. I think this whole situation could have been prevented if Nissan had used a keyway which has a much greater surface area that distributes the load more evenly. It is a bit more expensive to produce a crank that way and I would bet that was the drivig factor in this instance. One drawback I can see is that cutting a keyway removes alot of material and thus weakens the end of the crank. That problem could be rectified by making the diameter of the crank greater where you would position said key. I don't know why engine manufacturers may have gone to a woodruff key, but most engines I have dealt with have had a keyway/key setup and I have never seen one of them fail. I just hope that my efforts to salvage this engine are not in vain.

 

Presice1

Sure, now you tell me! I suppose I could have repositioned my timing gear and HB, but that would have been too easy. What fun is that? Besides I have all these toys laying around. Gotta have a use for them, or they're just junk.

 

Oh by the way, I love my Pathfinder, and it has given me many care-free miles, but I consider the exhaust manifold stud problem a disgrace to Nissan that they should have acnowledged and fixed as a design flaw. Instead they caused all of us to pay good money to fix their design flaw. - recall -

 

I could be wrong, usually am.

[Animal]

Well, there was a recall on the exhast studs, but you had to have the problem and get it to the dealer with under 100K miles - rules most of us out. It would be nice to have a lifetime warranty, but you really don't expect that, right? Yes, that was a design flaw and Nissan, arguably did more than they had to.

 

A few points on the key topic, in light of dicscussion (not even debate) are:

1. judging from the damage, the keys aren't that soft and actually wouldn't have caused as much damage had they been softer.

2. I still do not believe the keys are intended to take any torque, but we'd need to speak to a Nissan engineer to find out what they had in mind, why a woodruff, etc.

3. For all the revolutions the pully to crank force is only substantial when the rpms are changing (very minor to drive the belts at steady rpms).

4. I couldn't find the torque spec in the FSM, but Haynes says it's a bit under 100 ft/lbs. With that much force, assuming the pulleys and the crank are still matched and no rust or dirt to keep the parts from seating, it should be nearly as good as a weld. Think of the old MGBs with spinner hubs; same basic principle, but with considerable more driving torque considereing the application and, for the most part, no slipage.

5. I truely wish you the best on your project, since all of the above, right or wrong, means squat to you now.

 

BTW - I still have to do my exhaust studs. I've put it off in order to help others with more major work, but I'll get to it soon enough.

[ankana]

Agreed... the actual revolutions involved probably are not as much as a factor as change in rpm- say during a gear change.

Agreed...the woodruff key is not "soft" but mine had literally turned to dust.

-Enough to allow the timing gear to rotate 15 degrees on the crankshaft.

Do not agree... No matter how tight you make that bolt there will allways be movement although it may be minute.

Do not agree... The woodruff key is obviously for torque. Otherwise mine would not have rotated on the shaft as the bolt holding it all together still had tension on it when it was dis-assembled.

I'm not sure why you are taking this side on this "discussion" especially in defending thermal expansion inconsistancy involved in breaking manifold studs. A first year engineering student could have predicted that, and it was certainly Nissans responsibility to fix it. This is not a wear and tear thing, it happened to ALL of these engines.

I'm not going to respond any longer. You are clearly more educated than me in this area and I know when I am outwitted.

 

By the way.

I drove my Pathfinder this evening

Nice to be back on the road!

-bounce-

Edited August 25, 2006 by ankana

[Animal]

Glad to hear you got it done and are back in business. I didn't mean to sound like I was taking sides though I'm not sure which issue you were referring to. If it was the studs, while I agree it was a flaw, Nissan did make an effort to correct the problem well beyond the warranty period, more than most manufatures have done for anything not safety related - that was my only point. On the key issue, some have had problems, some have not and I was attempting to find out why. No offense meant on either subject and I don't play matching wits.

 

I do find it a bit disturbing that it is hard to have discussions unless everyone agrees - perhaps this is a sign of the times, just look at politics.