Torsion damper crankshaft broke...

Gerard van Santen

Gerard van Santen

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Torsion damper (balancer) crankshaft broke...

This is unbelievable. A view days ago I started this thread about loosing power http://www.nsxprime.com/forums/showthread.php?s=&threadid=33096

I now know what caused the loss of power. Inside the crankshaft pulley there is a torsion damper mounted (I didn't know of before). This rubber damper was broken and parts of it came between the timing belt and the timing belt drive pulley. Because of this the timing belt slipped about 6 teeth over the drive pulley. Slipping over the pulley means, that everything went off time.

First I will set everything in time and check the compression and try to start the engine. I hope this will do it. If I am unlucky I have a few bent valves or worse broken pistons. Or if I am lucky nothing is broken. And I only have to replace the crankshaft pulley.

I will keep you all informed about the results.

My questions are: Is there someone who has had the same experience? And is it possible that the cause is partly because of the double disc Exedy racing clutch I have installed a few months ago?

Thanks,
Gerard
 
Last edited:
6 teeth might be enough to bend some valves. I’d be surprised if there was any piston damage. Good luck and let us know how your compression test comes out!

DanO
 
I skipped 5 teeth on the crank on my H22a once...nailed 4 valves...I'm surprised you didn't bend any valves. Do a compression test to be sure.

As for the pulley, the H-series motors also have a rubber dampener to reduce the effect of the crank vibration on the main bearings.

usually though a dampener is needed for a larger displacement/stroke inline4 or 6 motor. V-6's naturally counter many of the crank vibrations, much like a boxer motor attempts to counter the majority of them.

If there is a solid billet aluminum lightweight aftermarket pulley available I don't see much risk in eliminating the rubber dampener.

You'll pick up a bunch of low end pep from the less drag.


Even if you bent some valves I doubt you did any siginifcant damage to the piston. Best of luck.
 
j14nsx said:
Is this the same as the harmonic balancer? This is the thing that the pulley for the BaschBoost removes?
Click to expand...

Yes it's sometime referred to a harmonic balancer or harmonic damper
 
I think that I would be inclined to go with a new HB unit as the rubber in these things ages and causes the failure. I have had these fail in a Fiat X1/9 with catastophic results...all valves bent except 2, a Mk1 MR2, and an Eagle Talon (the parts guy tells me that they replace one or two of those per week at that particular smallish dealer!)
 
Another photo including a part of the lower timing belt cover (ring). Parts of the cover came between the push pulley and the belt.
 

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That sucks. Sorry to hear of your problems. I don't think it has anything to do with your clutch though, with the possible exception that it was somehow damaged when the work was being done, which seems unlikely.

I will advise against the use of a solid aluminum crank pulley though. I have seen too many main bearing failures that happen within the 10K miles following an aluminum pulley installation. The damper is there to suppress vibrations in the crankshaft, and by eliminating it you then force the bearings to deal with those vibrations.

If you want to eliminate the OE part, I would recommend contacting Fluidamper for a custom replacement.
 
Old pics- $5.00
Good info- $10.00
Lessons Learned- Priceless

Interesting (to me) related anecdote- A while ago an NSX owner called my shop to say he had a noise he was worried about in his engine. I suggested he drive by the shop, but he said he was way too busy.
He called a week or two later to say it was getting worse. I suggested he still needed to come by the shop, or perhaps get it towed in. I offered to send a flatbead for it, but he said he had planned to go to the track that weekend. I suggested he enjoy driving the '53 D Type, or one of the two Lotus 27's he often took to the track. No deal. :confused:

Monday morning he calls to say a flatbead was on the way over with his car.
(interesting note about Karma- a minute or so before the engine 'unseated' on the track, he had a big row with some NSX club members because he did not have 'time' to move his thtree car trailer which was really hogging up the paddock and making everybodies moves difficult) Car arrives, I crank it over and immediately recognize the sound of an NSX motor without compression.

The noise he had been hearing was the broken damper inner portion broken loose. The noise getting worse was that same piece rubbing thru the timing cover. A small crescent shape piece of timing cover was neatly cut away, and even more neatly deposited between the t-belt cog and the t-belt. I never bothered to count the slipped teeth as the gears were all 30 to 70 degrees out of time on quick inspection.

17 bent valves and $7200. (with a new CTPGII) later, no noise, all good.

Moral of the story-
Hear a noise, get it inspected. Hear a noise getting worse, get it inspected faster. :rolleyes:

Gerards is the only other one I have heard of, and both are track cars, FWIW.


MB
 
NSX-Racer said:
That was a year ago, I'm sure Gerard has nearly forgotten the hazzle and drives a clean and well running NSX. :wink:
Click to expand...
As you probably know, I changed my engine (to much damage) with Guus his engine (almost 350,000 km). It is running fine and It is like I am driving with his soul.
Disaster
 
What about the Grump M type of pulley system it does not use the balancer at all it is replaced by a pulley.Is this a better setup since it will never break?
 
I was hoping for a happy ending to that story....replaced engine? too much damage?? I am getting ready to tackle this same problem. Two days ago, getting onto the interstate in my 93 BBSC, shifting into 3rd gear, instantly lost power, and had to baby it home, barley made it, and I probably smoked my clutch getting it there. Anyway, the exhaust got quite a bit louder, and it was hard getting my rpm's up in gear, but seemed to be easier in neutral. After a day, I tried to restart it, and could barely get it to run at all. I then removed the cats, and exhaust, and it helped...i could run up the rpm's a little, but still not anywhere close to fixed. I also disconnected the Paxton from the TB, and no change. I then called it quits, and got onto Prime for some input. Hope someone has some words of encouragement.
 
nsxhk said:
so.... should we replace this crankshaft pulley on the early nsx?

Henry.
Click to expand...

I don't remember that my 91 had this type of pulley on it. I always inspect parts when I take off, but sure don't remember seeing any rubber on the back side of the pulley. It has been a year though. I'm sure that someone out there knows. This may only be a problem for the 3.2 engines. Says something for the old original design, hard to beat.
 

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