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sa1 06-14-2015 01:46 PM

Help please! Like buses problems also seem to come along in 3's...
Hi guys,

I think something has gone terribly wrong with the volvo, any help would be much appreciated, here's the back story.

I have a 86 740 wagen and I seem to be getting quite a few issues! Originally I had a smoking issue so took it to the local garage for some diagnosis and apparently the sprocket on the back of the camshaft was loose! So after that was tightened, smoking was a lot better but injectors 2 and 6 could do with a refurb, so I took it away to fix at my leisure...

After driving it back home (around 3 miles) I tried to put it into park (its an auto) and a very loud screeching noise occurred, so I tried to put it into neutral, the same noise happened so I put it back into drive and switched it off with the key.

I then tried to turn her back on, the engine cranks over but I can see the timing belt and ignition pump sprocket are not turning at the same speed - the ip belt is turning maybe 1 revolution to every four of the cambelt and it even rocks back and forward! I took the cam cover off and the cam is not turning at the same speed as the cranking engine but the cam sprocket connected to the cambelt is, so my questions are:-

1. Could it be the cam sprocket bolt is not tight enough so the camshaft is not turning?

2. What damage could have occurred as now the timing is all out of whack (the car has not ran, just cranked over)

3. What could have cause the transmission to make that noise and could it be related to the timing / cam issue

4. How is it possible for the engine to run pretty sweet and then after I stopped it with the key the timing issue arises?

4. Any quick checks I can do before I tow it back to the garage?

Any help would be much appreciated


v8volvo 06-15-2015 04:04 PM

Welcome to the forum! Sorry to hear about these issues.

What you're describing is a bit unclear, hopefully you'll dig a bit deeper and discover it's a fairly easy fix... but from the sound of it, it's certainly possible that you're facing some serious problems.

You said a mechanic tightened a loose rear cam bolt and that cured some smoking. Did they also reset the timing, do you know? Or just tighten the bolt? Typically if that bolt comes loose, the IP will come out of time completely and the engine will quit running until timing is properly reset. Even if that didn't happen, simply tightening the loose bolt would not have fixed the smoke, they still would need to do other work to get it right first. It would help us to know what exactly they did, and also to know how they tightened the bolt. If they let the front timing belt absorb the torque as they tightened that rear bolt, then it could have damaged the belt, or caused the front pulley to slip, etc...

Can you give more detail about what you're noticing in how the front and rear cam sprockets move? A speed difference is hard for me to imagine, since anything that would cause the two sprockets to lose sync (i.e. slippage of a sprocket or broken cam) will just cause the rear to stop completely. Keep in mind the front sprocket is bigger than the rear one, so appearances as to their speed can be deceiving. You're sure the front is definitely turning more revolutions than the rear? (Also, you're sure you're looking at the cam sprocket in the front and not the P/S or alt pulley, right?)

Can you mark both sprockets and, using a socket on the front of the crankshaft, manually turn the engine over exactly two full revolutions (mark the crank balancer too if necessary), and tell us what happens? If everything is right, for two spins of the crank, both cam pulleys should do one full revolution. If you see anything different than that, that will be a clue.

You said you saw the rear cam pulley walking in and out, which made me think broken cam for a moment, but then I remembered the thrust flange is on the rear cam journal so that's pretty impossible unless things are really badly busted up. You took the valve cover off, right? Is the cam all in one piece? Anything abnormal happening in there? If you grab the cam (not on a lobe) with a pair of locking pliers, can you rotate it independently of the front sprocket?

Are you also saying the cam looks like it doesn't spin as fast as the front cam pulley and the timing belt? Are either of the two cam sprocket bolts obviously loose now?

To answer one of your questions -- we hope we'll find out that this is not the case -- but if things indeed have come out of time, then regardless of what the reason is, you are looking at a major repair. However, it also sounds like you're saying the engine never quit except for when you shut it off with the key, and you're saying it has been cranking OK, so it's hard to guess what's really going on. When you crank the motor, does it sound abnormal, in terms of cranking speed, rhythm, etc?

Any chance of adding some photos of the valve train, video of it turning over on the key, etc?

Any further detail about the transmission noise? Hard to guess how that plays in, unless something went wrong with it that is causing a lot of drag on the crank and slowing down the starter so much that it can't spin fast enough to catch. Any other trans problems before this happened?

How many miles on the car, the timing belts, etc?

Your location might be helpful to know as well. Hope we're able to help you get it figured out! :cool:

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