PDA

View Full Version : Inspecting crank damper...



Kit Sullivan
05-07-2007, 12:26 PM
I know these cars have a reputation for the bad dampers installed from the factory.
Mine is still the original one, but seems fine for now.
Is there a way to check to see if it is in good shape?

On a stock engine that is not driven hard, is the stock piece adequate?

How much for a replacement and are they hard to install?

(Boy, I ask a lot of questions!)

LJGriggs
05-07-2007, 12:41 PM
Do a visual inspection with the engine running to see if the balancer is wobbling. You will probably detect some "normal" engine vibration, but balancer wobble is more pronounced. With the engine off, check to see if the bolt is still in the center of the balancer and check the torque on the bolt. On a couple of occasions when my stock balancers broke, there was an unusual rumble from the engine. It was similar to having a hole in the muffler. I'm not sure why this happened, but the balancer broke soon afterwards. You may also notice a decline in engine performance, jumping tach, or an unusual miss in the engine. This is typical when the bolt breaks and the balancer starts walking forward off the crank. The drive belt may also be misaligned on the tensioner pulley. If the balancer has never been removed from the crank, it may last for as long as you have the car. I never had any trouble until the original was removed and reinstalled (a big no-no I've come to learn). Even a new stocker will break if the center bolt isn't torqued properly (around 115 ft/lbs, if I remember correctly). If you are in doubt, get a BHJ (well worth the price if you have ever had to remove a broken bolt and the remnants of the balancer from the crank).

Mike8675309
05-07-2007, 08:29 PM
You should take the crank pulley off and get under there and visually inspect it. Specifically you want to inspect the rubber that is a layer between the outer ring and inner hub. You don't want to see any pieces missing and you don't want it to appear that the outer ring is not firmly attached.

It seems the thing that causes these to fail the most is oil or coolant leaks soaking the balancer. This breaks down the elastomer faster than just plain age causing it to soften and eventually come apart. When this happens the balancer is no longer effectively dealing with harmonics which rapidly degrades the remainder of the balancer. Luck seems to determine of the balancer will break off the end of the crank, or just move forward enough to damage the crank sensor.

They will fail over time, but knock on wood, I have a stock balancer on my 1990 SC that's been 800 miles, run down the strip 10 times and then driven back with nary a hickup. That's on a car that already had 135000 miles on the stock balancer.

thus I believe the exposure to oil and coolant is probably a significant contributor to failure of these things.

That said, I'd never be willing to put a stock unit back on a car once it's been removed.

amcdv
05-08-2007, 07:33 PM
Does anyone have pictures of a stock balancer and an aftermarket one. I had to replace the crank sensor on my 91 and I took a good look at the balancer while the pulleys were off. It lookas as if the center section is aluminum and the outer ring is cast iron....is that right for a stock unit ?? amcdv

Mike8675309
05-08-2007, 10:33 PM
Yes, that is stock.