Why did timing belt fail?

George Bear · Oct 8th, 2006, 02:04

HI, The timing belt on my 440GL (B20F engine) failed. The belt teeth were stripped by the crankshaft sprocket.
Three valves were damaged, I fixed the lot and I've finally got the thing back together again, but I haven't put the new belt on yet.
I want to know why the belt failed, before I start the motor again.
The camshaft was ok, and not seized.
The belt had done 100,000km and overdue for service, but I would have thought there was some safety margin here.
I suspect the auxillary shaft, but I'm not sure. It turns OK, but when I pull down hard on the auxillary shaft sprocket, it gets a bit tight when I try to turn it. What is the best way to check this out without taking the whole thing out?
Any ideas anyone?
George Bear

bob13 · Oct 8th, 2006, 10:36

The belt may have had its time, why to light bulbs blow. The tightness may have made it fail a little early but the belt has to put up with alot. Cam shafts are hard enough to turn anyway.

CTCNetwork · Oct 8th, 2006, 10:41

Hi,

I may have been that one of the drives on the belt became stiff, which has since been partially resolved with the work you have recently completed.

In a case where you have stripped teeth on the belt, I would make sure that all drives from the belt have been worked on, reconditioned etc, to make sure they are Ok.
Even slight stiffness will affect the movement and could result in another belt failure...

Des. . .

James_N · Oct 8th, 2006, 13:08

Sounds like it went just through wear and tear. 100,000km is probably right on the interval for changing it, so i guess you were a little unlucky, but id always change it early rather than later for the sake of a £5 belt

Oct 8th, 2006, 02:04	#1
George Bear New Member Last Online: May 2nd, 2009 06:34 Join Date: Oct 2006 Location: Sydney	Why did timing belt fail? HI, The timing belt on my 440GL (B20F engine) failed. The belt teeth were stripped by the crankshaft sprocket. Three valves were damaged, I fixed the lot and I've finally got the thing back together again, but I haven't put the new belt on yet. I want to know why the belt failed, before I start the motor again. The camshaft was ok, and not seized. The belt had done 100,000km and overdue for service, but I would have thought there was some safety margin here. I suspect the auxillary shaft, but I'm not sure. It turns OK, but when I pull down hard on the auxillary shaft sprocket, it gets a bit tight when I try to turn it. What is the best way to check this out without taking the whole thing out? Any ideas anyone? George Bear

Oct 8th, 2006, 10:41	#3
CTCNetwork Forum Support Team Join Date: Dec 2004 Location: Liège, Belgium View Photos By: CTCNetwork	Hi, I may have been that one of the drives on the belt became stiff, which has since been partially resolved with the work you have recently completed. In a case where you have stripped teeth on the belt, I would make sure that all drives from the belt have been worked on, reconditioned etc, to make sure they are Ok. Even slight stiffness will affect the movement and could result in another belt failure... Des. . . __________________ Density:- Not just a measurement ~ It's a whole way of Life.! ! ! I drive a Volvo, Please Don't Get In My Way! OldVolvos4Ever He shows up. People die. He vanishes. People should not be afraid of their governments. "He'll deliver more justice in a weekend than 10 years of your Governments should be afraid of their people... "V" courts & tribunals. Just stay out of his way." "I plan to."

Oct 8th, 2006, 13:08	#4
James_N VOC Member Last Online: Jan 4th, 2024 11:32 Join Date: Jan 2006 Location: Stafford View Photos By: James_N	Sounds like it went just through wear and tear. 100,000km is probably right on the interval for changing it, so i guess you were a little unlucky, but id always change it early rather than later for the sake of a £5 belt __________________ 1997 Volvo 940 LPT Celebration. 187,700 miles, manual.

Oct 8th, 2006, 10:36	#2
bob13 Senior Member Last Online: Jul 20th, 2014 21:11 Join Date: May 2006 Location: Bridgend View Photos By: bob13	The belt may have had its time, why to light bulbs blow. The tightness may have made it fail a little early but the belt has to put up with alot. Cam shafts are hard enough to turn anyway.

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