'92 Volvo 740 turbo wagon...Does ANYONE know why this damper is running out-of-round? This happened 2 weeks ago, & lost the alternator fan belt due to this pulley running out-of-round. Replaced this damper 3 times, first with some Chinese junk, then a Dorman damper, finally with a Volvo damper. ALL are running out-of-round. A dial indicator placed on the crankshaft end shows NO out-of -round condition. ALL dampers were torqued to 60 lb/ft . Any suggestions welcome.

 

Clearly the crankshaft dampers are bad. Why, I have no idea other than poor quality. I think that the engine was last used in the North American market in 1995 so you're sourcing parts for a 23+ year old car.

I doubt that Volvo still has any OEM ones. I just had a call today from our local dealer who referred me a customer who has a 1993 Volvo 850 who can't find the correct inner tie rod. Volvo no longer has the part reference in their database.

If you are satisfied that the crankshaft is straight and the damper is sitting square on the crankshaft belt gear, then try another one and see what happens. The damper will not be absolutely perfect like a brake rotor from a trueness standpoint, but it should not shake the belt off either.

 

Simple logic would certainly agree with your diagnosis, however, this problem, having bugged me since 1 July & not having been resolved as yet, I spoke to a shop foreman (Volvo dealer) in Colorado who graciously gave me his time & told me the problem was due to the washers located both in front of as well as the rear of the crankshaft gear. With the damper off, I pulled the lower timing assembly cover off & found a huge amount of black residue covering the timing assembly including the tensioner, etc. I do NOT know why this has occurred & frankly am fed up with this problem. None of it has any mechanical logic to it I changed this belt a year ago & all the markings on the belt are gone. I assume the black debris is belt related, but I don't know why. As for the washers, they are installed correctly. The outer washer is concave, with a nub embossed on the nether side. It fits into the crank keyway and the washer is installed concave side OUT. So it appears there is no problem with the washers, but what is the reason for the debris????

 

I found a diagram of the lower crank belt gear and timing components.

At 5:40 in the video, notice that he installs the rear "washer". Notice that it cups away from the belt. Then, at 6:32 in the video, he installs the front washer. If you look overhead at the washers, the view would generally look like this: )=(. Notice that the beveled edge of the washer faces away from the belt.


Are you sure that you don't have one of the washers against the belt, either like this: (=( or )=) or (=)? The only way that I can envision black debris is from the belt itself.

 

Hiflier, my 240 ( the same basic redblock motor as in your 740) requires the single 24mm bolt holding the balancer on to be torqued to 60 lbs/ft of torque FOLLOWED BY AN ADDITIONAL 66 DEGREES OF ANGULAR ROTATION. This is admittedly difficult to do, except with the crankholder tool ( unless your car is a manual trans) If the bolt loosens under use (make sure the back of the pulley fits over the little nubin on the crankshaft gear) as others have mentioned. One more thing..... if you post your issue in the Volvo 240/740/940 section of this forum, you will get quicker and more knowledgeable response.

 

Dear Sambar..................Please ignore my stupidity, but I find your comment most interesting but unfathomable...Would you please explain what "additional 66 degrees of angular rotation " means, and what this activity relates to? Does this action assure that the damper goes onto the crankshaft end squarely?.........If it relates to torquing the 24mm pulley bolt, allow me to say this: From reading the several posts concerning replacement of this damper, it would seem that those folks seem to be able to merely push the damper onto the crankshaft end and then torque the bolt. I however, cannot do this. The fit of the damper to the crankshaft end is so tight that I must wiggle the damper just to get it onto the shaft. I CANNOT push the damper up to the large washer covering the timing gear, so if I begin to tighten the 24mm bolt, I never know if the pulley is being pushed concentrically onto the crankshaft end. Is this then a possible reason why these 3 dampers I have attempted to install all run out of round when engine is started??? As I said, I am at a complete loss as to a fix for this problem.

 

I think that the idea in Sambar's post was that perhaps the center bolt was coming loose and causing the harmonic damper to wobble.

If you install the center bolt with an impact gun that is good enough. However, I still think that we need to figure out where that black residue comes from.

 

Hiflier, I was chagrined to note that part of my response was overtyped by me with my crappy old computer. Yes, as tony suggests, I'm wondering if your balancer was not tightened enough and became loose, wobbling on the shaft until the belts broke. The repeated replacement could also have worked itself loose and done more wear damage to the crank, causing any wobble present to have gotten worse. Could the black residue be particles of the lower timing cover that gradually wore away? I would think if that was the case, you would have heard an awful squeal. Re: the tightening torque- I just referenced my Bentley manual and it describes the tightening sequence as : First tighten to 40ft/lbs of torque, then an additional 60 degrees. Imagine your loooong breaker bar ending up at the 12 o'clock position at the 40ft/lb point. Then continue to tighten the wrench until it is around the 4:30 position. That is really tight; I always need help from one of my 20 something sons to do this. You will also need some way to keep the motor from turning. If manual, put it in gear with the parking brake on. If auto, use the crankholder tool or the "rope trick" BTW, the crank bolt is what is known as a Torque To Yield bolt and should be replaced with a new one each time, per Volvo. Hardly anyone does this anymore; but beware a previously fully tightened bolt could could break off , leaving you with a lot of additional work.

 

Oh, and yes the impact wrench is also a reasonable proposition; kind of hard to judge the tightness , though

 

As a neophyte to this forum, I wish to thank all of you knowlegable folks who gave their insightful input toward what was becoming for me an insufferable problem. As an aircraft mechanic, I have no tolerance for redundant mechanical work which addressed the same problem. In my work, you have one chance to get it right, you may imagine the result of an incorrect fix on aircraft. With that said, I understand the 60 degree thing mentioned, but if I may, here's what I found re: "The damper problem". First, I now believe there was nothing wrong with those three dampers. What I did incorrectly was to think the crank bolt would, once tightened, would set the damper squarely & fully onto the crankshaft. WRONG! What I finally did was, once I was able to wriggle the damper onto the shaft, I used a heavy rubber mallet & tapped the damper along its entire circumference until the damper would go no further. Then, using a supposed 130 lb/ft torque wrench (will NOT develop 130 lb/ft of torque) i torqued the bolt until the socket stopped. THEN, with nothing attached to the pulley, I started the engine and by God, the pulley was running true. Then, using one of you folks suggestion, I stuck rope in #1 cyl on TDC of the comp stroke and using a 1/2" Snap-On torque wrench set to 166 lb/ft, tightened the bolt. I installed a new tensioner. Next, with the torque set, I removed the rope from the cyl, set the timing marks on cam, idler & crank & installed the new timing belt. Oddly, I had to move the crank only a few degrees to mate all the marks. Installed new belts & did an engine runup. All went well. After wife drove the car for three days, I pulled the timing cover plug, released tension on the tensioner bolt, then retightened. As of now, all is OK. I used a borescope to check inside of the timing case. There is NO residue present. Frankly, and as of this moment, I have NO idea as to why that residue was present, or what malfunction caused it. I can only assume it may have been caused by the old tensioner which somehow caused the belt to rub on something. There's no wear evidence on the timing covers. Thanks again to you all. Ric Lang

 

Was so elated by conquering this problem, I got the sequence of repair that I described on the last post incorrect, as I know, all of you would have leaped onto. I did all I said, but of course, I had the belt on BEFORE I finally was wise enough to hammer the pulley on with the mallet...........Oh well.