Damn - lost compression in a cylinder :-(

[Doingitsideways]

I'd still say a tensioner/idler pulley or water pump.
May be worth checking cam belt tension to make sure it's not over tight.

If it was anything to do with the drive belt/tensioner/PAS pump/alternator, the noise would most likely change in pitch with the A/C compressor kicking in and out, which it doesn't seem to do.

I've heard my S70 make the same noise before, only from a cold start.
Never quite got round to figuring it out!

[TenaciousC]

Yes confirmed. Noise still present with auxiliary belt removed.

Is it possible it is something inside the head like a camshaft bearing not getting proper lubrication? I was very careful with quantities of liquid gasket and would be very surprised if anything got blocked.

C

[Tim Williams]

With it doing the same noise with the aux belt off just try running it with the cam belt cover off and the the top cam belt cover that's under the fuel pipes. If it still makes the same noise it's most likely the water pump seal.

It may be incorrect antifreeze you're using but the White Blocks that use either type of antifreeze use the same pump.

It would be wise to fit a hose clip on the thermostat top hose and if possible not the type with the band cut all the way through as those do damage hoses.

[TenaciousC]

How could the cam belt tension be over-tight? I wasn't aware that the tension was adjustable. Doesn't the hydraulic tensioner just a apply a set force?

Cheers

C

I'd still say a tensioner/idler pulley or water pump.
May be worth checking cam belt tension to make sure it's not over tight.

If it was anything to do with the drive belt/tensioner/PAS pump/alternator, the noise would most likely change in pitch with the A/C compressor kicking in and out, which it doesn't seem to do.

I've heard my S70 make the same noise before, only from a cold start.
Never quite got round to figuring it out!

[Dangerous Dave]

Have you checked the PCV vacuum pipe that goes to the end of the inlet manifold (behind the steering pump)?

On mine the elbow which connects the plastic pipe to the manifold had perished and was collapsing under vacuum causing pretty much the same sound you're getting.

Worth a try

[TenaciousC]

I will double check.....It was OK when I put it on... also wouldn’t it make a noise all the time, rather than when hot?

C

Have you checked the PCV vacuum pipe that goes to the end of the inlet manifold (behind the steering pump)?

On mine the elbow which connects the plastic pipe to the manifold had perished and was collapsing under vacuum causing pretty much the same sound you're getting.

Worth a try

[Dangerous Dave]

It sounds like it's only under certain vacuum level (hence the on/off whilstling). Could be when the engine is cold the idle valve is open more to maintain the revs so the vacuum level will be different. Could be the elbow has a little hole in it so it only collapses under a certain vacuum.

Of course I could be talking complete rubbish LOL but still worth a try as it's only a pipe, plus check all your other vacuum pipes.

[TenaciousC]

Had a crack with my new "Mechanic's Stethoscope" (h/t Orca2) and it revealed something rather interesting. The noise is really loud when I put it on the thermostat housing. Could it be the thermostat is making some kind of sound as it opens and water passes into the radiator??

C

[TenaciousC]

I've changed the thermostat. Noise still there.

Had a bit more of listen with the stethoscope. It's loudest still on top of the thermostat housing, but I suspect that's because of its shape it amplifies the sound. It's also audible around the top of the cylinder head on the thermostat corner. I couldn't hear it around the water pump of any of the cam belt pulleys.

Could it be a lubrication problem inside the head around a cam shaft bearing nearest the thermostat perhaps??? NB. It only makes the noise when hot and at idle speed.

Any one got any suggestions as to what to do next?

C

Video link again: https://goo.gl/photos/KRjFU9mPY1aKWAFQA

[960kg]

When idling squirt some WD40 with the red plastic pipe on at different pulleys and also the A/C clutch! to see what happens to the noise?

[wellsy]

my car is making pretty much the same noise , it has dne it before and went over a period of time never figgured it out , im having running issues at the moment and think ive traced lean running on cylinder1-2 to the sealsand washers in the injectors being broken and worn ,thans Dangerous dave , i am changing my inlet manifold gasket and checking over pcv system so will have a good check arounf all the pipes .
hooe you get it sorted soon :-)

[Boomy]

Not saying for definite, but you could try changing the oil filter (genuine would be best) if not done recently. Had similar noise from a recent V70 which stopped after doing this.

[TenaciousC]

The noise appears to have gone. I wanted to be sure, before posting back here, but I haven't heard it since Sunday.

What did I do on Sunday? Put a can of engine flush in and went for a few power runs down the motorway. When I got back, I didn't hear the noise. Changed the oil and filter. Went for another drive still no noise and none since.

So I guess this was an oil starvation issue. Perhaps filter was blocked and pressure was low enough at idle that oil want getting to the cam bearing.

Anyway Cigar to Boomy.

Thanks for all your help.

C

Not saying for definite, but you could try changing the oil filter (genuine would be best) if not done recently. Had similar noise from a recent V70 which stopped after doing this.

[Tim Williams]

You should never run a car hard with oil flush in as it thins the oil significantly. I'd strongly advise a thicker oil than recommended if you have had problems as low oil pressure is a killer for these engines.

[LeeT5]

The noise appears to have gone. I wanted to be sure, before posting back here, but I haven't heard it since Sunday.

What did I do on Sunday? Put a can of engine flush in and went for a few power runs down the motorway. When I got back, I didn't hear the noise. Changed the oil and filter. Went for another drive still no noise and none since.

So I guess this was an oil starvation issue. Perhaps filter was blocked and pressure was low enough at idle that oil want getting to the cam bearing.

Anyway Cigar to Boomy.

Thanks for all your help.

C

You did what??

You should never run a car hard with oil flush in as it thins the oil significantly. I'd strongly advise a thicker oil than recommended if you have had problems as low oil pressure is a killer for these engines.

What Mr Williams said! Wise words!

TenaciousC..did you not read the instructions on the tin? From memory, I'm sure it says something like ...warm up engine to temperature and pour in contents. Then fast idle at approx 2000rpm for 10-15 minutes. Switch off and drain sump.

I don't recall anywhere it saying thrash your car up the motorway a few times!

You Sir are a very lucky boy indeed as you could have so easily destroyed your shell bearings or seized the engine.

NOTES FOR NEWBIES: Do not do what he did with engine flush in your engine.

[TenaciousC]

Heh, I know, but it felt the right thing to do at the time... and seemed to help. I'm assuming that it's very difficult to know if the oil pressure is low, other than seeing the red oil light (which has never been on in this car except when an oil cooler hose popped off last summer!). I suppose fitting a gauge would be most indicative.

C

You should never run a car hard with oil flush in as it thins the oil significantly. I'd strongly advise a thicker oil than recommended if you have had problems as low oil pressure is a killer for these engines.

[TenaciousC]

Meh. No I did read the instructions and went into that with my eyes open. It seems none the worse for its ordeal... better as already explained. Obviously one wouldn't normally do this.

C

You did what??



What Mr Williams said! Wise words!

TenaciousC..did you not read the instructions on the tin? From memory, I'm sure it says something like ...warm up engine to temperature and pour in contents. Then fast idle at approx 2000rpm for 10-15 minutes. Switch off and drain sump.

I don't recall anywhere it saying thrash your car up the motorway a few times!

You Sir are a very lucky boy indeed as you could have so easily destroyed your shell bearings or seized the engine.

NOTES FOR NEWBIES: Do not do what he did with engine flush in your engine.

[Tim Williams]

Meh. No I did read the instructions and went into that with my eyes open. It seems none the worse for its ordeal... better as already explained. Obviously one wouldn't normally do this.

C

Just to clarify if anybody else is thinking it's ok and hasn't done any harm it almost certainly will of caused massive wear to the big end bearings. Driven hard with flushing oil in will give oil pressure of about 2.5 Bar depending on engine condition. 3.2 Bar is the absolute minimum to avoid bearing wear and that with oil intended to lubricate and not clean. The idiot light comes on under 0.5 Bar.

[leet5r]

Just to clarify if anybody else is thinking it's ok and hasn't done any harm it almost certainly will of caused massive wear to the big end bearings. Driven hard with flushing oil in will give oil pressure of about 2.5 Bar depending on engine condition. 3.2 Bar is the absolute minimum to avoid bearing wear and that with oil intended to lubricate and not clean. The idiot light comes on under 0.5 Bar.

good info that tim

[Boomy]

The noise appears to have gone. I wanted to be sure, before posting back here, but I haven't heard it since Sunday.

What did I do on Sunday? Put a can of engine flush in and went for a few power runs down the motorway. When I got back, I didn't hear the noise. Changed the oil and filter. Went for another drive still no noise and none since.

So I guess this was an oil starvation issue. Perhaps filter was blocked and pressure was low enough at idle that oil want getting to the cam bearing.

Anyway Cigar to Boomy.

Thanks for all your help.

C

Great to hear it seems to be sorted. It appears to be more common with cheaper filters, but I assume age can play a part. Had it happen on two of mine now as it happens. Both times a new filter cured it. I would imagine a few people have replaced far more expensive parts or have paid out money to garages etc to find a cure all for the sake of an oil filter!