Timing on 740 Volvo

We’re told to line up the crankshaft pulley mark with No. 0 on the plate above it. All very well, but the plate is a fair distance from the pulley and not vertically in line with the centre of the crankshaft and it’s almost impossible to tell top dead centre (TDC) with any accuracy by using the plate as a reference. TDC is where the engine is supposed to be orientated to synchronise with the camshaft cog marks. So the only way to get the necessary accuracy is to remove the spark plug from cylinder No. 1, roughly get the piston to the top, then put a screwdriver in so it touches the cylinder. You can put a springy plastic tube or something across the screwdriver so the handle is pulled up. So when you rotate the crankshaft very slightly back and forth – this can be done with both hands: one on the alternator pulley and one on the power steering pulley – you can get TDC pretty exact when the handle of the screwdriver reaches its lowest point as the piston rises to TDC. The spark plug hole acts as a fulcrum.

The camshaft cog synchronises every second turn. Now theoretically there should be a white mark on the camshaft cog and another white spot on the plastic housing with which it should line up. Fortunately in my case there were in fact these marks, which probably saved me heaps of trouble. I don’t know what you can do if they’re gone – maybe someone has some ideas on that. I’m sure it’s probably happened. The white mark on the camshaft cog is only painted on after all, not a definite groove cut into the steel like in the camshaft pulley.

I actually just replaced the front camshaft seal, and in trying to undo the camshaft cog bolt I must have skipped a couple of teeth on the belt. I thought I razzed the bolt drive ratchet, but when the motor wouldn’t run properly I realised the belt might be wrong. She idled OK but when you accelerated she died. It was out two teeth anticlockwise, according to the above orientation test. So I slackened the camshaft belt tension bolt and loosened the belt, locked the crankshaft with a socket with the handle resting against the fanbelt pulley, and with a 17 mm socket drive advanced the cog two teeth. You can actually do this just by undoing the top plastic camshaft housing cover and bending it back a bit. It’s a bit of a cow to put it back to match with the bottom half if it’s removed completely. Can be done though.

By the way to undo the top camshaft cog 17 mm bolt – it’s generally pretty tight. I did it with a super large shifter that fitted around one of the cams to hold the camshaft in place. Even then I needed to extend the handle with a piece of tubular steel about two feet long. The same went for the bolt: I used a socket with a fixed drive arm that I extended about two feet with a pipe. And even then it took a bit of power! I can recommend it as a fitness appliance.

All because of the blocked flame guard that blows out the seals. I just put in a vent hose that runs into a drip container, because according to one respondent you have to be a prehensile monkey to get to it and change it. See Flame Trap FAQs

Incidentally if you have a front camshaft seal blown the symptom is oil everywhere and then some. It pumps out the whole sump in about five miles, depending on the traffic. By the time the oil warning light comes on it’s turned the car into an oil refinery. And it’s hard to see where the leak is because the fan blows the oil everywhere. Look for a drip when the engine is running just below the left front top of the motor. That’s your camshaft seal. You can actually see the seal having come out in the gap between the top housing and the front plastic camshaft drive casing. What you can do immediately with total success is to push the seal back in with a bent nose pliers or screwdriver or something, and then temporarily keep it there with one or two plastic straps inserted around the camshaft in the gap as a distance piece. In my case it stopped the leak completely, except of course for the oil that was already there dripping off the engine and transmission all over the place and generally making a pigs breakfast of any surface the car might be standing on. Environmentally friendly? Ah, not exactly.