Renewing Camshaft Belt. Problem.

[Ian21401]

1992, 940, B200F.
I’ve renewed the cambelt on this car twice before without any problems but it has all gone wrong this time.
Everything lined up on TDC on compression stroke. ( two front cam shaft cams uppermost ) tensioner slackened and pinned back, old belt removed and Volvo replacement belt fitted with the white marks on it correctly orientated on the cam sprocket and the auxiliary shaft and camshaft sprocket. Release tensioner.
Replace lower timing cover and replace crankshaft pulley.
Begin turning engine over by hand using rachet drive on the crankshaft pulley bolt.
Notice cam belt is gradually moving forward off the tensioner and the cam shaft sprocket.
Pin back tensioner and push belt back on to where it should be then release tensioner again.
Turn over by hand again but belt moving off pulley and sprocket again so pin back tensioner and push belt back on again.
Decide to remove crankshaft pulley and lower timing cover then replace crankshaft pulley and release tensioner again.
Turn over by hand again but cannot see anything wrong.
Continue to turn engine by hand to see if belt eventually runs as it should but it didn’t and the belt slipped off the tensioner so now the timing marks are all wrong.
This has never happened before, why should it do this this time?
Regarding the timing marks. As there is no belt in place, if I position the camshaft sprocket correctly with the two front cams upwards, and position the auxiliary shaft correctly then position the crankshaft correctly, will it be ok to refit the belt?
I think that it will but I may be wrong.
Even if it is ok, why is the belt running off?
Helpful advice will be greatly appreciated.

Edit: Just a thought. Given that I can reorientate the timing marks, I think that I may refit the old belt and see what happens.

[Laird Scooby]

Before you reorientate the timing marks Ian, make sure the crank pulley is about 90deg BTDC so that as you rotate the cam there is no chance of the valves making unintentional contact with the pistons. I believe the jury is still out on whether the B200 is interference or not, safer to move the pistons down the bore before you start turning the cam. As the distributor is driven off the back of the cam, there's no real need to align the aux shaft to be honest other than making it all look nice.

When you were turning it over by hand, had you released and locked the tensioner? If it was unlocked it's possible that it was allowing the belt to creep forwards off the pulleys.

[baggy798]

The belt nearly walked off my gears when the tensioner nut was not tight.

[360beast]

Yes I've done this before on my own 940 last time I did the cambelt, I had a brain fart and forgot to torque up the tensioner nut so when I was spinning the engine over by hand it was walking forwards, I quickly realised what I'd done and all was well again.

[RollingThunder]

Thanks for posting this, it is a timely warning for me as I'll be doing this job on my 940 soon.

I found this video on youtube which may help - it shows where all the alignment marks are which should help you to realign everything https://www.youtube.com/watch?v=7eIFWUbSZTw

Good luck!

BTW my understanding is that the only redblock engine that is an interference type is the 2.3 16 valve?

[Ian21401]

Thank you everyone for the prompt replies.
Thanks Dave for the info. re positioning the crankshaft before rotating the camshaft. I hadn’t thought of that.
Whilst thinking of this overnight I suspect that although I had released the tensioner I cannot recall whether I had tightened the nut. I’m thinking that I had not tightened it and three of you have suggested/described similar scenarios. So that is the first check later this morning.
It was that scenario again, time marching on, tired and hungry, thought important part of task almost completed then something not right.

[360beast]

Originally Posted by Ian21401

Thank you everyone for the prompt replies.
Thanks Dave for the info. re positioning the crankshaft before rotating the camshaft. I hadn’t thought of that.
Whilst thinking of this overnight I suspect that although I had released the tensioner I cannot recall whether I had tightened the nut. I’m thinking that I had not tightened it and three of you have suggested/described similar scenarios. So that is the first check later this morning.
It was that scenario again, time marching on, tired and hungry, thought important part of task almost completed then something not right.

It just goes to show the importance of spinning the engine over by hand multiple times so you can spot any small issues before they become a serious one.

Hopefully it is just the fact the tensioner was loose Ian, let us know how you get on

[Ian21401]

It was caused by not tightening the tensioner nut. When it was loose it permitted the roller to droop slightly which encouraged the belt to wander off.
I followed Dave’s advice re repositioning the camshaft and crankshaft, pinned back the tensioner and fitted the belt then unpinned the tensioner and tightened the nut. I refitted the crankshaft pulley without fitting the lower timing cover then turned it over by hand. All seemed good so removed pulley and refitted the lower cover. I lost count of the number of times that I turned it over by hand and all seemed well so I finally tightened the crank shaft pulley bolt. Mine is 24mms. Torque wrench to 60Nm is the easy bit. The 60 degree angle was achieved using my 1.5 metre breaker bar extended with another 0.5.metre of scaffolding tube, same as I used to free it at the beginning, with the rear wheels chocked and the gearbox in 5th.
Given what had gone before it was with some trepidation that I fired the engine up before refitting the upper timing case cover and fitting the other auxiliary belts but all seems well.
Thanks again for your input guys.

[griston64]

Originally Posted by RollingThunder

Thanks for posting this, it is a timely warning for me as I'll be doing this job on my 940 soon.

I found this video on youtube which may help - it shows where all the alignment marks are which should help you to realign everything https://www.youtube.com/watch?v=7eIFWUbSZTw

Good luck!

BTW my understanding is that the only redblock engine that is an interference type is the 2.3 16 valve?

From Volvo Owners club FAQ

B230 Series Engines:

Do I Have an Interference Engine? [Editor] An "interference" engine is one in which the tops of the pistons and the valves may collide if the timing belt breaks or is misaligned. If you have an interference engine, you MUST change your timing belt on schedule or else you risk very expensive damage. You must also pay closer attention to the condition of the tensioners, pulley bolts, and front seals: anything that can cause the belt to fail prematurely must be repaired quickly. Not all Volvo engines are non-interference. [Colin Shepherd/Peter Milnes]

"Interference" Engines:

B200 series (including E, F, G, FT, GT)
B230E (high-compression B230 sold outside of North America)
B204 series (including E, F, FT, GT)
B234 series (including F, G)
All B5XXX five-cylinder inline engines and 6XXX six-cylinder engines
The B230 series is non-interference with the exception of the B230E.

[Forrest]

I have had the same problem of turning the engine over by hand without fully tightening the tensioner bolt and then wondering what on earth was happening. My most puzzling one was where I found it impossible to align the timing cover, belt and pulley marks without it looking as thought the timing was a tooth out. However, the engine ran perfectly normally. I subsequently discovered this was due to the plastic positioning peg having snapped off the rear timing cover so it was able to move relative to the block. Never a dull moment with these cars!