V70 Engine noise not smooth

alx · Post by **alx** » 02 Oct 2002, 11:42

I just bought a '99 V70 (base engine, no turbo, 5-spd manual)
and am noticing especially in 1st and 2nd gear that the engine noise is
not smooth, but rather makes a rough/dissonant bass sound as I accelerate. If you're musically educated, it's like the beating sound produced when 2 notes played together have almost but not the same frequency... like you're on a ferry with 2 engines or something.
Is it because it's a 5 cylinder engine, or might there be a problem?
It seems to work great, it's just that the engine noise is very different
than that of the 4-cylinder cars I've had in the past

Alex

Post by **matthew1** » 02 Oct 2002, 12:08

It's probably the engine mount(s). There are three below the engine, and one above. You can easily check the one above... it's anchored to the firewall via a metal arm. It's a rubber bushing, and it will crack and fail with age. New ones are available for ~$20 at many places. Search this forum for a link -- I just posted it.

BTW, five cylinders will produce a smoother idle than 4, just like 6 tops 5. Five goes nicely into 360 as a divisor, otherwise 5 would be an impossible number of cylinders. Notice there's no 7-cylinder engines

alx · Post by **alx** » 02 Oct 2002, 18:39

On a related note, whenever I change direction, meaning put 1st, go forward a bit, put reverse, go backward a bit and so on, I hear a cracking noise as the car starts moving.
Could it be that the engine or differential moves till the mountpoint reaches each side limit because of the torque forces? You think it's the same problem that causes the engine noise?
Note that I don't hear the engine noise during idle, but rather as I accelarate, mainly between 1,500-2,500 rpm

Alex

Post by **matthew1** » 02 Oct 2002, 19:09

alx wrote: Could it be that the engine or differential moves till the mountpoint reaches each side limit because of the torque forces? You think it's the same problem that causes the engine noise?

Yes, and yes.

alx · Post by **alx** » 06 Oct 2002, 23:03

I drove a similar car (99 v70 only it was automatic) and the engine makes the same noise as mine. ie, not smooth, felt especially between 1500-2500 rpm. (I'm sure it's not the engine mount for this particular noise, since it's very different than the crack I hear when I go forward/reverse.
I suspect this non-smooth noise is entirely normal.
A 4-stroke engine needs to turn 360*2 = 720 degrees for all 4-stroke operations. On the Volvo, does a cylinder fire every 720/5 = 144 degrees?
If not, then that would explain the noise not being smooth.
Is there a chart/animation anywhere showing the operation of Volvo's 5 cylinder engines?

Alex

Post by **matthew1** » 07 Oct 2002, 11:07

I'd be inclined to delve into the math in detail... but my 850 is fine. Our engines are nearly identical, by the way. No undue vibrations at any rpm, no weird sounds (well, one when it's cold, but I think that's the timing belt rubbing against its guard or the air pump).

Volvo spent years developing this engine with the aid of Porsche engineers -- they did a good job by all accounts.

So, did you check the mount?

Guest · Post by **Guest** » 08 Oct 2002, 15:59

Yes, the dealer replaced my upper engine mount (under warranty) because it was cracked.
However that didn't fix the weird engine nose. Actually I read in several reviews on the Net that the engine makes odd noises. The most fun was when a guy thinking he rode in a 6 cylinder car said to the driver:"
- I think the engine is "missing"
(ie a sparkplug is dead)
the driver replied:
- Yes, it's missing a bloody cylinder

As I said, I drove a different V70 and it had the exact same engine sound, a wavy/vibrating "vumvumvunmvum" sound instead of a smooth "vvvvvvvvvvvv" hum.
Perhaps you're used to how Volvos soundm that's why you're not noticing this

Cheers,
Alex

Post by **matthew1** » 09 Oct 2002, 10:58

If it's pulsing in thrust and sound (describing sounds with words -- my least favorite thing!), that happens to me, and I don't consider it a 'rough' sound, rather a mechanical one.

It's certainly not part of the design, and more likely you/I need
new spark plugs or
rotor/cap or
spark plug wires or
cleaning of the injectors.

Hope this helps,
Matthew

alx · Post by **alx** » 09 Oct 2002, 13:43

Yup, it's rapidly pulsing in accordance to the rpm.
I'm pretty sure brand-new volvo's sound the same. A well designed engine can still sound odd you know, unless it's designed by musicians

By the way, does the 850 have a cap/rotor and not an electronic ignition?
I'm pretty sure my V70 does not have a cap/rotor

Alex

240beater · Post by **240beater** » 09 Oct 2002, 19:20

My dad just turned 78,000 miles in his 99 s70 that got rough around 50k miles the warranty was up so he didn't bother to have it looked at. We just turned it back in on the lease and over all it was nice the exhaust also started to go at 78k