[RESOLVED] Bad Timing Belt Tensioner

[DSMboostin15]

So I've finally had time to take apart the new car and check for a rattling noise coming from the timing belt side. The guy I bought it from said the original owner told him that the rattle could possibly be the timing belt tensioner. Upon closer inspection, the tensioner looks to be shot. As you can see from the pic, the hydraulic tensioner arm is completely inside the tensioner housing and the idler lever it presses against is touching the tensioner housing. Since it looks shot, I'm just wondering how the engine managed to hold time? I just want to get a second opinion on this. I'm going to replace it anyway, but it's good to know what to look for in the future.

 

[gurmanator]

the tension arm bolt is still tight.lucky the bolt didnt come lose and throw the belt.

 

[steve]

So the auto-tensioner is bottomed out. That's either because it failed and now the belt is loose or it was over tightened with the tensioner pulley and the belt is really tight.

 

[DSMboostin15]

That's the weird thing. The belt feels like it has the abouth right amount of tension - maybe a little on the loose side. But the belt is not completely tight to where there is no deflection. How much belt deflection should the timing belt have between the cam gears? I'd use my FWD as a base point, but that's down at school with a broken transmission, so I can't easily measure it.

 

[steve]

Normally when it's running and right after you shut it down there is very little deflection between the cam sprockets. The belt will be tight like a string on an bow but you can cause deflection if you push hard enough. Once the car sits for a while the belt tension can relax a bit and coupled with the spring pressure from the cams give some slack between the sprockets.

 

[DSMboostin15]

I haven't measured the deflection, but it appears to be ~0.125 in between the sprockets. I haven't ran the engine since I moved it around the garage, before that I hadn't driven the car for a month. I'm still going to replace the tensioner for the time being, just to be safe. As for the rest of the timing parts, I'll wait until I have more money, time, and warmer weather. Thanks for the advice Steve.

 

[DSMboostin15]

Well the tensioner is completely shot. I was finally able to take it off and check it, sure enough, I was able to compress it in my hand with my thumb. Good thing I order a new one from Parts Dinosaur yesterday.

 

[Colt4G63 also]

After you have it installed you can check your tension using the following method:

Turn the crankshaft clockwise at least two full revolutions with a 1/2" ratchet.
Check the clearance between the tensioner arm and the body of the tensioner plunger body. It should be around 3.8mm to 4.5mm. I use a 4.5mm allen wrench, to measure it.

if it's too small or too large of a gap, you have to turn the tensioner pulley cog counterclockwise to tighten, or clockwise to loosen, and retest it.

 

[DSMboostin15]

Thanks for the tip. I'll have to keep an eye out for that.

 

[Colt4G63 also]

Here's some more accurate instructions. My previous post has been edited for accuracy.

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[tkelly27]

I'd go ahead and put a new belt on as well. All the tensioner/bearing things and everything else too. You're going to have to jump through all the hoops anyway, and you'll know it's good for a long time afterward if you change it all. If any of those fail, your belt will fail.

 

[DSMboostin15]

I know I should change the belt now, but I'm on a truncated time table, so it will have to wait for a few months. Besides, when I bought the car from the original owner, he gave me a gigantic book of reciepts and he has the one for the last timing belt change - about 30k miles ago. It's getting close, but like I've said, I'm on a truncated time table. I've done the timing belt on my other DSMs, so I know what's all involved. I was planning on changing the HG, valve guides, ARP's, and other misc. things as well.

 

[tkelly27]

It's one of those things that if it goes, you'll kick yourself for not changing it while you already have it all apart.

 

[DSMboostin15]

I know, but I don't have the cash for the ARP's, HG, etc. so there is no point in doing it now and doing it again later.

 

[91dsmgsx]

i have the same problem except i was the one that ruined the hydralic tensioner by compressing it to fast like with a huge pliers to quickly and didnt find out i ruined it until a few months later when i descovered how loose the timing belt was

 

[RyAn007]

Yea I see what you mean, just save for those parts and you could swap them out easily in a couple hours, and just make sure you do a timing belt when doing the others, and dont wait too long.

 

[DSMboostin15]

Well to wrap things up: I ended up replacing the tensioner - was completely shot, tensioner pulley, and timing belt. I forgot how much a PITA it can be to line up the timing marks and account for the rotation of the tensioner applying tension. Now things are all lined up correctly and running well. The great thing is that I hooked up the timing light to adjust the ignition timing and found that it was still dead on at 5* BTDC. I recommend Bruce at Parts Dinosaur if you need engine parts. They are very reasonably priced, quality parts, and a pleasure to deal with.