PaulW

Was taking measurements with just the LH TB cover off.....unlocked the cams later.

ttuling

to other segments of the belt beside the one which has the damper, due to the camshafts having favorite resting spots. If I'm interpreting the pictures in the Bentley correctly, the damper length goes down if the belt gets tighter between the crank and driver's side cam pulleys, correct? So if the cam pulleys aren't loose and the driver's side camshaft would rather rest somewhere before where it stopped, it can slowly back up, pushing in the damper and delivering the extra belt length to maybe the segment between the two cam pulleys. Remember the discussions about intercam belt slack on a stopped 5V motor?

So I don't think the fact that the damper length goes down as the car cools means anything unless you have the cam pulleys loose.

What I don't understand is how you got 5.970" on Wednesday (warm) when you'd adjusted to 5.280" on Sunday (warm). I can't see where the extra slack would come from, unless if on Sunday one or both of the cam pulleys had stuck and was letting slack hide out elsewhere in the system during the tensioning. Or maybe your tensioning roller's insert is more than literally eccentric.

PaulW

45 minutes after shutdown I took my first measurement, then about 1.5 hours later, it relaxed to the as-left measurement from two days before. As the block cools (it was really hot when I first measured it), it relaxes.

And once again, this morning it didn't make any noise until the car was at normal operating temperature for about 10 minutes because I wasn't on the highway.

Then the block starts to really heat up and it tensions the heck out of that belt.

When I took my old belt off, it was significantly looser than it is now, and MUCH looser than it was when it was way too tight. ScotD's was, and so is Airbill's. Maybe that's the way they should be when they are cold, i.e. they seem like they are loose, but really they aren't. Once the engine heats up, they are perfect and don't make any noise.

pw

ttuling

Because I'd bet your cool-down "tightening" of the belt between the driver's camshaft and the crank was due to the driver's camshaft turning backwards after the engine was off.

PaulW

First of all, when the engine is warm, you can't tighten it to the levels they say to do warm. With full tension on the ecentric pulley, it won't get to the final dimension.

Second, my belt is still too tight. When cold, it's just fine, but with the block warm or hot, it's too tight.

I wish I could have somebody like you see what it is doing.....you would be flustered too.

Thanks for your input. I suppose I could be wrong, but I don't have data to support that.

pw

ttuling

I'm sure I don't know what's going on here, how you can have 5.970" 45 minutes after shut off but too-tight noises when really hot.

I may yet be convinced that the belt gets tighter as the engine cools (opposite what Bentley says) but only if the damper length measurements couldn't have been influenced by torques exerted by the crank- or camshafts. If the damper gets shorter as the engine cools with the crank at TDC, the camshafts locked and their pulleys loosened, then I'll get on board the "Bentley has it backward" train.

PaulW

and he said after I explained most everything....."your belt is too tight".

No doubt about it. I think I'm just going to stop talking about it.

If you drove my car, saw that you can't tighten it to the Bently spec when hot because it won't go that tight (which is drum tight) and now that I remember all the other belts and how loose they were when the engine was cold (which now I see as normal)....you'd understand.

It's loose when the engine is cold, and this allows it to get to tension when the engine warms up.

Just because tightening the belt with the tensioner causes the damper length to get smaller doesn't mean that when the engine heats up it has to do that.

The block really changes dimensions due to the coefficient of expansion and the belt tightens up even though the damper gets longer.

I'm telling you, that's how it is. I've convinced myself of what I need to do.....and my belt is WAAAY to tight, even set like it is now.

You would agree on that if you drove my car.

Oh well, I guess I will do it one more time, this time with the engine at ambient temperature before setting it.

Then I won't care anymore because it won't make anymore noise. I hope others don't make the same mistake that I did, but most likely they will.

pw