Just got a 2009 MDX with 108k miles on it which recently had a timing belt break, wondering if the engine is really in good condition still like the dealership service department assures me. What happened was PO got the 105k service but declined to get the timing belt tensioner changed. 2000 miles later the bolt from said 9 year old tensioner shreds and breaks the timing belt. This is when PO trades in the car and walks away... New belt and tensioner put on. I ask about bent valves, engine damage, told nope, all is good, it didn't go out of time and is running normally.

My concern is that I heard if a belt breaks like this it causes engine damage that the dealership service department might not have found, or else purposely didn't go looking for. I am not really familiar with all the ins and outs of how the engine works, just read that belts breaking like this are bad and looking for more advice. Thanks for your help.

 

I should add the the car seems to run great. I don't hear anything odd, it idles well, almost can't even tell it's on at a stoplight. I drove it around a bit, got up to 80 MPH and seems smooth (other car is a Ford Escape so seems a lot smoother than that at least). I guess I don't know what to look for, but would valve damage be obvious? There's no puttering or sputtering or backfiring or anything like that.

 

Here's the thing, while I have heard a few anecdotal reports of timing belts breaking while the engine was in operation and *NOT* damaging at least some of the valves, I have never seen it first hand and I rather doubt any such reports of no damage. Said another way, if your belt broke while the engine was turning, I believe you have valve damage.

With the above said, any damage at this point may well be minor enough to not notice it while driving, however, if the valve face to valve seat seal is even a tiny bit compromised, the valve in question will burn to the point where the engine will run worse and worse and worse. Were I in your shoes, I'd have a "cylinder leak-down test" performed on your engine; I strongly suspect some bad valves will be discovered.

 

I agree. the damage might be so slight that you might never feel it. however, over time....it will get worse and eventually throw misfire codes

 

so you buy a vehicle knowing the timing belt broke and you may have engine problems?

 

I appreciate the advice and may be taking it in for the leak-down test, but I called my mechanic (good rep shop that took care of my CL from 64k to 230k) and explained the situation, and he told me that if the valve was damaged it would probably not be running, or else running very badly. Like it would be very obvious that there was some damage to the valve. He said if it were him he wouldn't even worry about it.

I'm wondering it the belt actually broke while the car was running - it says on the service records that "customer states the check charging sys light came on and makes loud noise, timing belt was just done and found that the timing belt was shredded from a bolt that was installed from the idler pulley" but the person I spoke with at the dealership service dept. said it was broken. Maybe he was just mistaken...

 

Nope bought before getting the detailed service records, my fault, salesman probably didn't know either but I still think it was shady for them to not reveal this info, all he did was verify the 105k service was done.

 

They knew the condition of the vehicle when they took it in or rather had it towed in for trade. That's shady and although they gave you the service history they were hoping you wouldn't ask because surely they weren't gonna offer up the information and lose the opportunity to move the unit off the lot. I would write a letter to the owner because that is a matter of safety aka life and death with a busted engine. (potentially)

Hope you have no problems my friend

 

I'd return the car ..

 

I would not worry, because mechanics know the difference between "shredded" and "broken". Your documentation says "shredded".

There is a difference between a "shredded belt" and a "broken belt".
The previous owner may have even driven the MDX to the shop, on his shredded belt.

A broken belt is completely different, because of Acura's interference engines, where one part has to get out of the way of another part. The belt coordinates the movement of the parts.

You can not slightly screw up an interference motor.
Example: You do the TB job, but you didn't do it right.
Let's say you left the Woodruff Key off (of the crank pulley), then you tried to move your crank with a wrench, to make sure the timing marks were aligned correctly. You feel it's a little hard to spin, so you try a little harder. You just bent a valve.

 

Have the dealership pull a copy of the repair order and show you what it says. If they give you a hard time about having the prior owner's info on it or whatever, tell them to hide/remove/black all that out. You just want to see the repair order with the matching VIN on it. $0.02

 

Doubtful the belt "broke" and as the prev user mentioned it was likely a case of the belt being "damaged" by the bolt, not broken (caught in time).
Or, a "drive" belt break mistakenly listed as a timing belt break (?)

Either way you would definitely know if that timing belt broke while driving (you'd never buy it).
Not sure why/how some here are stating otherwise (correct, you don't "sort of" break an interference engine like these).

Relax and make sure the TG belt was done along with all pulleys and tensioner.

 

Good information here. The point is, the Dealer has no legal obligation, to disclose this type of major issue, to you. Does the Dealer have a moral obligation? I think yes. Would you have purchased this vehicle, had you known about the timing belt breaking/shreading? Probably not. What can you do about it now? Perhaps, negotiate with the Dealer, for an extended, after-market power train warranty, in the interest of quality customer service. Such a warranty, would, at the very least, provide you with piece of mind going forward.

 

SHREDDED is not the same as BROKE. Your mechanic is right.

 

On a different car, I had the timing chain break, bending some valves... Believe me,if you have bent valves, you'll know....

 

In some cases yes, in other cases where the valve is just slightly bent, it can take time for the escaping combustion gases to erode the valve face enough to notice.

 

If it's slightly bent, the valve won't seat properly, which means you won't have proper compression, so that cylinder will misfire, particularly at higher rpms. You'll notice that.

 

buddy mis-shifted in his 2005 6MT TL. caught the clutch in time, or so he thought.
a year or so later...multiple misfires...from his mis-shift.
so, no. you wont feel it right away if it's slightly bent until it gets REALLY really bad

 

No you won't. A compression test will show the cylinder down on compression, however, when the engine is running the lack of a positive seal will not initially be felt.

 

You can't really compare bending a valve from valve float during a misshift to breaking a timing belt tho. Much more potential for damage with a busted belt, especially when you try to restart. I also happened to replace the valves myself, and they weren't bent too bad. They just didn't seat properly. But like I said, this was on a differt car. The valves on a Chevy small block are much bigger than the valves on a TL, so valves not setting properly would also be much more pronounced, so there's that too I suppose.

 

Dpends on why you are down on compression. But a valve that won't seat correctly will typicslly cause a backfire during the powerstroke which is readily noticable, especially if it's an intake valve, which in my case, I bent two of them.

 

Update: I have since asked another trusted shop owner about this situation and he told me "more often than" he's seen Hondas and Toyotas come out with no problems at all after a broken belt. He also told me it would be a waste of money to run a compression test. My other mechanic also told me that if there was some sort of very minor issue that wasn't currently causing me any problems, they'd have to take it apart to inspect the valves to look for any damage. In short, both of my shops are telling me I'd know if I had a bent valve, don't bother getting the test, just drive and enjoy the car.

I still am not sure if the belt was just shredded, like the paperwork says, or broken, like the dealership service rep told me. I think he was just wrong, which would not surprise me knowing this dealership and the whole buying experience I had with them... At this point I've stopped caring and worrying about this, I own the car and will just have to deal with any issues that come up. I've put 1000 miles on it now and it's been smooth as silk. My only regret is not buying it sooner, I love driving it so much. Previously my main car was an older Ford Escape and now driving that feel very very sad. I didn't realize what a bad driving experience I was getting, I think it's the handling on this MDX, it is so nice, and the power, well, a lot of things, I got the all black interior I really loved in my old '03 CL.



.

 

Correction; a backfire during the powerstroke will only happen if intake valves don't have a positive seal.