Slack cam belt/ noisy top end

SilverSwede · Oct 23rd, 2022, 19:13

Hi guys,

Just bought a '98 v70 tdi non-runner and got it running after replacing fuel pump belt/ tensioners etc. Unusually, it sounds like a noisy cement mixer but starts fine and runs on all pots. The rest of the car is is in great shape and has obviously had some careful owners.
I noticed a lot of slack in the cam belt when I got it running...switched it off immediately! Is the clacking noise likely to be valves hitting the pistons and if so is it too late to be worth replacing cam belt and tensioners now! (I had intended to replace belt/tensioners as a matter of course).

Martin Cox · Oct 23rd, 2022, 21:52

A few things come to mind.

Firstly, you may get a better response by posting in the 850, S70 & V70 96-99 section of the forum rather than here which is for much later cars.

Secondly, I'd suggest finding out why the cambelt seems to be slack. The belt may have been mistensioned or the tensioner or water pump may be worn or the belt may have stretched.

The tightening of the crankshaft pulley bolt is critical on these engines: 160 Nm and angle tighten by a further 180 degrees. Any less and it will come loose with catastrophic results.

Thirdly, these are not the quietest of engines and the vacuum pump is a notorious source of a metallic sounding clatter.

Assuming the cambelt is in good order, the usual way of checking is to start the engine and press the brake pedal a few times. If the clatter disappears or changes significantly, it's the vacuum pump.

Hope this is of some help

Martin

1998 V70 Tdi Auto

SilverSwede · Oct 24th, 2022, 02:54

Many thanks Martin, this is very useful info.

Oct 23rd, 2022, 19:13	#1
SilverSwede Junior Member Last Online: Today 09:28 Join Date: Aug 2016 Location: Plymouth	Slack cam belt/ noisy top end Hi guys, Just bought a '98 v70 tdi non-runner and got it running after replacing fuel pump belt/ tensioners etc. Unusually, it sounds like a noisy cement mixer but starts fine and runs on all pots. The rest of the car is is in great shape and has obviously had some careful owners. I noticed a lot of slack in the cam belt when I got it running...switched it off immediately! Is the clacking noise likely to be valves hitting the pistons and if so is it too late to be worth replacing cam belt and tensioners now! (I had intended to replace belt/tensioners as a matter of course).

Oct 23rd, 2022, 21:52	#2
Martin Cox VOC Member Last Online: Today 10:23 Join Date: Dec 2001 Location: Hull	A few things come to mind. Firstly, you may get a better response by posting in the 850, S70 & V70 96-99 section of the forum rather than here which is for much later cars. Secondly, I'd suggest finding out why the cambelt seems to be slack. The belt may have been mistensioned or the tensioner or water pump may be worn or the belt may have stretched. The tightening of the crankshaft pulley bolt is critical on these engines: 160 Nm and angle tighten by a further 180 degrees. Any less and it will come loose with catastrophic results. Thirdly, these are not the quietest of engines and the vacuum pump is a notorious source of a metallic sounding clatter. Assuming the cambelt is in good order, the usual way of checking is to start the engine and press the brake pedal a few times. If the clatter disappears or changes significantly, it's the vacuum pump. Hope this is of some help Martin 1998 V70 Tdi Auto

Oct 24th, 2022, 02:54	#3
SilverSwede Junior Member Last Online: Today 09:28 Join Date: Aug 2016 Location: Plymouth	Many thanks Martin, this is very useful info.

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