Any idea what this noise is caused by? (Video link in msg)

[AllHailKingVolvo]

I noticed this noise today when running the car after tinkering...the noise is coming from the back of the engine and is louder under the car than via the engine bay. I suspect the cheap pattern clutch is rattling, it makes a racket unless the pedal is depressed in general, but this noise happens whether the pedal is down or not.

It only happens when sharply and suddenly hitting the throttle from idle, and is briefly audible when starting the car too. It doesn't sound like rod knock as it doesn't rise and fall with the revs, just a grumble when stabbing the throttle. It doesn't seem to happen when in gear and clutch fully engaged, although the sound is briefly audible when letting the clutch out and pulling away in first.

I don't suspect a big end issue as oil pressure seems good and, other than when starting from cold, the oil light goes out before the car fires up.

It did occur to me that it might be a sticky injector or maybe a plug not firing properly, possibly a timing issue too.

Any ideas would be most welcome. The car drives very well otherwise and is smooth and quiet when on the move. 75,000 miles and masses of history, it's a well cared for car and hasn't been abused.

https://youtu.be/qA4HZ72hszs

[Pete940]

It might be the mic making it sound external, but it sounds like objects colliding. Checked clearance around the exhaust?

[AllHailKingVolvo]

Originally Posted by Pete940

It might be the mic making it sound external, but it sounds like objects colliding. Checked clearance around the exhaust?

That's an interesting and very valid thought, I will check clearance and the bellhousing bracket for the downpipe-I hadn't thought of that. I fitted a full cat-back exhaust (genuine Volvo) last week so it could be settling in. The noise is coming from the rear of the engine/bellhousing area to my ears. I'm hearing noise from the clutch when it's engaged in neutral as I mentioned, so it could be clutch or DMF rattling. I wondered if it might be the input shaft bearing/pilot bearing of the gearbox, but of course the M90 doesn't have one!

It only seems to happen when the car is warm-I just popped out to start it cold out of curiosity (it's minus 5 here and it has been sitting for five hours) and it started beautifully and wasn't exhibiting the knock at all.

[Laird Scooby]

Originally Posted by AllHailKingVolvo

That's an interesting and very valid thought, I will check clearance and the bellhousing bracket for the downpipe-I hadn't thought of that. I fitted a full cat-back exhaust (genuine Volvo) last week so it could be settling in. The noise is coming from the rear of the engine/bellhousing area to my ears. I'm hearing noise from the clutch when it's engaged in neutral as I mentioned, so it could be clutch or DMF rattling. I wondered if it might be the input shaft bearing/pilot bearing of the gearbox, but of course the M90 doesn't have one!

It only seems to happen when the car is warm-I just popped out to start it cold out of curiosity (it's minus 5 here and it has been sitting for five hours) and it started beautifully and wasn't exhibiting the knock at all.

Sounds like pre-igntion Phil. More commonly known as pinking, as long as it only does it hot when snap-opening the throttle from idle, i wouldn't worry about it. Part of the price to be paid for having the MAF so far away from the throttle body, i can even get my n/asp B280E to do the same and that has a shorter (but still long) distance between the MAF and throttle body.



You can just see the MAF halfway up on the right so you can get an idea how long the MAF to throttle body hose is, from the throttle body where #4 inlet valve is on yours to about halfway between the suspension turret and N/S headlamp - yours is considerably longer though! It will take the MAF slightly longer to respond to throttle opening on yours than it does on mine.

[TonyS9]

I would be worried something important is loose, like the crank pulley or crank timing gear. If the big bolt isn't tightned properly or the rubber separates it might cause such a clunk... until it shears off.

The clutch should be clamped up tight at this point, might be worth removing the front guard and checking if the flywheel moves (without spingyness), maybe checking GB mounts too.

[AllHailKingVolvo]

Thanks all, I will give the car a going over today and check for any loose bits and bobs. It seems a lot less pronounced this morning (just finished the school run!) and I have to work hard to get it to do it at all. Perhaps the fact that I was very low on fuel and finishing up a tankful of injector cleaner was a factor...just put 1/4 of a tank of BP Ultimate in it and it's smooth as can be.

I'm not concerned that it's a fundamental mechanical issue such as big end failure etc as the car is is very smooth with no unusual engine vibrations or weird resonances when driving. I've owned a couple of cars previously with tired big ends and always found them very agricultural and rough.

In fact, I took my parents out to lunch yesterday and my dad (former development engineer for Standard Triumph who later became one of the team who worked for the Tecalemit/Bosch collaboration to develop fuel injection for road use in the early '60s, ex works SAAB racing driver and garage owner for 25yrs until he retired...he knows his onions!) remarked that it was the smoothest Redblock engines car he had ever been in, and said it reminded him of the late 760s that he worked on in the late '80s with the B230ET engines with Motronic FI.

[Laird Scooby]

Originally Posted by AllHailKingVolvo

it reminded him of the late 760s that he worked on in the late '80s with the B230ET engines with Motronic FI.

That's exactly what you've got Phil but about 50bhp short on what the 760 Turbo made because of the fact it's an LPT version and 135bhp instead of the "full-fat" 185bhp version of the 760 Turbo.

Rumour has it you can literally bolt on the actuator from an HPT in place of your original and gain 30bhp, it's another Volvo part so a "hidden" mod that would be difficult for anyone to know the difference without physically testing that specific component.

Not that i'm suggesting you do that of course!

[AllHailKingVolvo]

Originally Posted by Laird Scooby

That's exactly what you've got Phil but about 50bhp short on what the 760 Turbo made because of the fact it's an LPT version and 135bhp instead of the "full-fat" 185bhp version of the 760 Turbo.

Rumour has it you can literally bolt on the actuator from an HPT in place of your original and gain 30bhp, it's another Volvo part so a "hidden" mod that would be difficult for anyone to know the difference without physically testing that specific component.

Not that i'm suggesting you do that of course!

Okay NOW we're talking!! I'll see if I can find an HPT actuator, it sounds like a lot of fun...the car is quick as it is, but more horses are always nice!

Incidentally, with the clunking noise, I think it's related to the previous noise I posted a couple of weeks ago-I remember you mentioned layshaft noise in the box, and the car doesn't do the clunking thing (the one mentioned in this post) with the clutch down and the box in gear. Definitely time for a gearbox oil change methinks, then see where we are.

It doesn't affect the drive so is just a niggle at this stage, but I like to sort niggles before they become major issues

[Laird Scooby]

Originally Posted by AllHailKingVolvo

Okay NOW we're talking!! I'll see if I can find an HPT actuator, it sounds like a lot of fun...the car is quick as it is, but more horses are always nice!

Incidentally, with the clunking noise, I think it's related to the previous noise I posted a couple of weeks ago-I remember you mentioned layshaft noise in the box, and the car doesn't do the clunking thing (the one mentioned in this post) with the clutch down and the box in gear. Definitely time for a gearbox oil change methinks, then see where we are.

It doesn't affect the drive so is just a niggle at this stage, but I like to sort niggles before they become major issues

I'm sure you can find an HPT actuator on fleabay Phil and equally sure some of the turbo owners will give more advice than i can on it.

If you can get your glamorous (or maybe not so glamorous!) assistant to sit in the drivers seat with the clutch down and blip the throttle aggressively from idle and you still get that rattle for a similar time (possibly shorter as it won't have the added, albeit small, load of theg gearbox) but it follows the same pattern of not being there at higher revs then i'd say i was probably right with what i suggested. If not and i'm wrong then perhaps worth looking at another way but it isolates the gearbox from the equation.

Always good to investigate minor niggles before they turn into something nasty! I once had a nasty knocking and vibration coming from the front end of my Rover, when i investigated all the wheel nuts were loose on both front wheels!

I had previously checked them with a torque wench two days before so knew they were tight - or so i thought!

If the nuts had come loose at 2 miles+ per minute, it doesn't bear thinking about!
Even at 1 mile a minute it would have been nasty!

[MiniNinjaRob]

If you want to replicate a HPT (like mine - smug face ahoy!) then a HPT actuator is the best and most controlled way to go.
The slightly more common way is a manual boost controller with a calibrated boost gauge to help you dial in the MBC to the correct boost pressure. This means mounting a boost gauge in the car though which is a bit more involved but not hard.
All models will boost to 190-200bhp (very ish) very easily which is beyond a HPT level but you must not go beyond the safe level of 12psi. HPT pressure is around 7.5-8psi, LPT I think around 3psi.
Post 1990 740 and 940’s moved to Bosch LH2.2 management (later 2.4 which is even better) which constantly learn and can adapt to higher boost levels.

Above 12psi you’ll get pinking and to get more power you’ll need to change the ECU chips (cheap and easy), get a bigger exhaust, AF meter.

An engine like mine has the thicker con rods and piston cooling oil spray bar and can handle 350bhp with bigger turbo, injectors etc. Beyond that I would need forged pistons and ideally a 531 head and a monster turbo. Search YouTube for b230 turbo engines with 600bhp+!!

They really are wonderful engines.