My timing belt failed recently which resulted in quite a bit of damage to the engine ($3600 worth). I come to find out that when I had the timing belt replaced less that one year and about 10K miles ago, the mechanic did not replace the tensioners at the same time. The mechanic looked at the parts and agrees that a failed tensioner caused the problem, however, he said that it was not customary to replace the tensioners unless that were making noise. They did ask me if I wanted to replace the water pump which I agreed to and would have agreed to replace the tensioners as well if I knew it was optional and not customarily done. However, I was never presented with that option.

I am considering further action but wanted to get some feedback before I go further. I talked to one dealer already that basically said its silly not to replace the tensioners when replacing the timing belt and that they normally would not replace a timing belt w/o also replacing the tensioners.

 

I just did the timing belt on my 03 monty. I did not replace the tensioner but did replace the water pump. My understanding that it can be replaced but not necessary. Its kind of like the h2o pump - you can do it and its cheap while you are in there but not a requirement. I chose not to replace pulleys since the truck only has 60k miles. If the truck had 100k miles, I probably would have changed it.

BTW, I found out that if you remove the fan pulley and serpentine belt the GEN III trucks have an access hole to allow you to feel if the belt is properly tensioned.

Im not sure how much liability the mechanic has by not replacing or suggesting a replacment. Good luck and sorry that this happened (My worst nightmare....)

TJ

 

Thanks for the reply. Most everything I've seen or heard so far suggests that the tensioners should be replaced. One reply on another site said the mechanic should look for signs of wear on the tensionsers but I would think internal wear could easily be overlooked. I had 90K miles on mine so I was pushing it a little bit anyway before I had the belt replaced which is even more reason to replace the tensioners.

 

Not sure how one would look for wear on the pulley???? The service manual has a test that you can do to test the spring force of the plunger that keeps so many pounds-force on the pulley and belt. I did not do it, cause I would have to jig the pulley and use a torque wrench to test spring force. I was concerned about doing more damage fixturing the pulley assembly in my vice rather than leaving it in place. I dont believe the Mitsu officially recommends replacement of the pulleys even under severe service - someone else chime in - but it does devote a few pages to test the integrity of the pulley spring plunger.

I would be worried more about the pulley plunger failing rather than a bearing catastrophically failing. What speciifcally failed? If the plunger failed, belt would slacken and OHC cams would have jumped, damaged valves would result and 3600 leaces your pocket..

Are you sure that the pulley was not assembled (by your mechanic 10k miles ago) incorrectly? Say your mechanic was a moron, maybe the belt did not have proper tension to begin with.

If I were you, I would get my hands on the pulley (take pictures if it was not removed already. You can test plunger spring force right now out of the vehicle. Check for wear on the aluminum housing were the tensioner pulley bolts onto the motor - maybe it was loose which is big liability to the mechanic......

 

I'm not very "handy" when it comes to automechanics, however, I did have valve and cylinder damage as you suspected so maybe it was the plunger that failed. I still have all the parts. The belt is intact but it basically burnt up or melted as if something locked up. There was kind of a "pop" sound as I was going down the road at about 80mph and I immediately pulled over and was dead in the water. There were no fluids leaking and no visible damage under the hood but all that stuff is basically hidden anyway. When I showed the mechanic the box of parts (he wanted to see the belt) he saw the tensioner and said "there's your problem" and I asked him if he had replaced the tensioner with the belt and he said no. My theory all along (well more the opinion of the other mechanic that fixed it) was that the tensioner failed which caused a change reaction or at least caused the timing belt to fail.

Who knows but I'm considering some type of action against the mechanic. I'm not a litigious person either but this just seems negligent to not at least ask me if I wanted the tensioners replaced (not to mention the cost to repair the damage). What was even worse is that I was was 200 miles away from home when it happened. They DID ask me if I wanted to replace the water pump which I agreed was a good idea.

 

Dont mean to belabor the point - but how did the mechanic know the pulley was bad? Is the pulley bearing seized? Can it be rotated? Sounds like that was the problem since the belt was melted.

 

I'm not really sure how he knew but he seemed pretty sure of it after he saw the belt. All the old parts are just loose in a box. I talked to another dealer mechanic and he said they don't replace the tensioners unless they are noisy or they see something so I've gotten conflicting feedback and it might be more of a judgement call. I like a mechanic to have better judgement obviously.

I won't be going back there again for repairs or maintenance........thats for sure.

Might have to chalk it up to a life lesson.

 

I may be wrong, but I think it is a judgement call. Usually mecahnics are more than willing to throw parts at your car because they make more money. Seems like mechanics usually err on replacing good parts rather than not replacing bad or potentially bad parts. Then they are accused of artifically racking up the bill and gouging the customer.

Thats some bad luck and sorry it happened. These kind of stories make me nervous and will cause me to do the timing belt tension check every so often. Since the pulley is deep inside, they dont get exposed to moisture (unless your water pump is bad) or the elements so the pulley bearing is protected pretty well. Your serpentine belt pulley bearings theoretically will dry out long before the timing belt will.

Glad that you are fixed and back on the road!!!

 

Timing belt tensioners and idler pulleys are generally recommended as cheap insurance in preventing catastrophic failure. Generally, the only added expense is due to the added parts, NOT due to the added labor. With that being said, it is NOT ABSOLUTELY neccesary to replace them unless having obvious signs of wear or damage. As a mechanic, i'll always recommend them with interference engines such as yours wether they show wear or not. In almost every case- the pulleys or tensioners did NOT show any signs of wear during the 1st timing belt replacement interval.

Joel, CA

 

Joel:
Are you saying that the pulleys never showed wear at the 60k interval but at higher miles they did? Was it the bearing or the spring plunger that was worn?

TJ