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Discussion Starter · #1 ·
Good morning all,
I have a '98 S70 that recently has started making an odd sound when started after sitting for a few hours. As soon as I put pressure the gas pedal, there's a high pitch whine that spins up, sounds like it could be either a pump or a blower, and runs all-out for about 45 seconds to a minute. After that time, it goes away, and the engine sounds normal... and if I start it within an hour or two of shutting it off, it doesn't make the sound. The noise does not respond to changes in RPM.

Does anyone have an idea about what might be causing it?

Thanks for any help!
 

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Hi there. Could be several things, as you say.

Have all drive belts been replaced at recommended intervals, including the cambelt & its tensioner?

If so, I would try a small amount of WD40 or other quality spray light lube oil on the grooved drivebelt(s) (NOT on the toothed cambelt). It is best to do this with the engine running, carefully avoiding getting yourself trapped in moving parts (and the cooling fan) and too much overspray. Take it easy, only a little is needed so use the little pipe that usually comes with the can & attaches to the spray nozzle. Get some on both sides of the belt.

If this stops the noise then the belt will probably need replacing soon. Otherwise, suspect things like water pump, a/c pump, power steering pump or alternator - you may be able to hear these if a helper starts the engine while you listen with the hood up. If the noise is there but you cannot pin it down then you may be able to put a looooong screwdriver's blade against each of these components in turn & then put your ear to the handle to see whether the noise is transmitted up to the handle.

If none of the above, when was the last oil change, was the engine flushed, is the engine oil breather pipe clear & what grade & type of engine oil are you using? Just wondering whether the top of the engine might be being starved of oil for a while after start up for some reason.

Interested to hear whether you manage to solve it kageryu. Best of luck!
 

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Discussion Starter · #3 ·
- Last oil change was done by a trustworthy Volvo dealer about 1500 miles ago. Don't know the specifics, but I'm pretty sure they'll have done everything to spec.
- 120,000 mile svc done just before I bought the car last January, at 119,000. Selling dealer claims timing belt was done at 70k, servicing dealer I go to says while there is no sticker verifiying that but they don't see anything to indicate it wasn't.
- A friend suggested a long cardboard tube as a listening device, I'll try the really long screwdriver idea as well.

The noise doesn't sound like the squealing I've heard slipping belts make on other cars as they drove past.. it's more of a whirring whine than a... for lack of better terms, friction-induced whine.

I'm taking the car to aforementioned service shop this afternoon, to leave there overnight and have them test it in the morning. Here's hoping they read the service notes about not moving it until they have the tech standing there listening!

I will post anything they discover, and provide updates on the (hopefully short) ongoing saga.

Thank you for the suggestions!
 

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Hmmm. I have heard a loose balancer shaft drive belt on a Porsche make a whirring noise. That's a toothed belt like a cambelt, so if you cannot be certain when/whether the cambelt was changed & whether the tensioner has been changed, then maybe you should consider changing both these items now, sounds like they'll be due soon anyway. If changed, make sure they put a sticker on!!!

You haven't said whether your car is n.a. or turbo. Turbos can make a whirring noise but if the noise wasn't there before & it is now, pray it isn't the turbo (if fitted). I've also known failing alternators to start to "whir" then quieten down when they warm up - they get worse & worse & eventually the bearings fail.

Thanks for promise of update.
 

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Discussion Starter · #5 ·
It's the "light pressure turbo" model that was at the middle of the normal aspiration - light - high pressure turbo range that year. I have heard my turbo spin up and down when the boost kicks in... I'm praying that the fact that the noise does not change with RPM rules out turbo problems, because I know they get expensive. *crossing fingers*

I've found a few other posts that hint at an air pump problem.. hopefully I'll know more tomorrow. It's so hard to troubleshoot because the noise doesn't occur even if the car is left for 4-5 hours.. it really does seem to have to be overnight.
 

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Most likely the Air pump then the Air pump only comes on when the car sits for a really long period of time.
 

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It could be the air pump or possible the piston cooling valve. This was added to the 5 cylinder engines as an additional valve to supply oil at certain times. I may be incorrect as that this valve may only have been used on 01 and up. Usually if the air pump is at fault the CEL will be illuminated. At my dealership we refer to the air pumps as bilge pumps because they will suck alot of water from the exhaust system when the valve fails.
 

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QUOTE(volvotek @ Sep 24 2005, 03:10 PM)It could be the air pump or possible the piston cooling valve. This was added to the 5 cylinder engines as an additional valve to supply oil at certain times. I may be incorrect as that this valve may only have been used on 01 and up. Usually if the air pump is at fault the CEL will be illuminated. At my dealership we refer to the air pumps as bilge pumps because they will suck alot of water from the exhaust system when the valve fails.
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But sometimes it will take a while to set the CEL.
 

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It turned out to indeed be the air pump -- the nickname of "bilge pump" seems to be very accurate, as that's exactly what I was told happened. Valve failed, got water into the pump, ruined the bearings on the pump.

I'm sure those who replied with tips on this thread know this already but for anyone with a similar problem who finds it in the future, I got a good explanation of what the pump does - as part of the emissions control system, the pump gets kicked in to supply extra fresh air to the exhaust to burn off uncombusted material before it exits the car. It's nice to know what the part I just got replaced does!

Thanks to all for the help


Addition:
I feel a lot better about the repair bill now. One of my friends who has a 97 850 heard about my adventure, so he called his mechanic of choice to see if he should get his check valve changed out pre-emptively. Apparently, if the failed pump gets to the point that it seizes, that causes some electronic relay to fry too!

It sounds like this mechanic described the valve as one of those "sometimes never fails" parts that doesn't get included in a regular maintenance routine, but is (obviously) prone to fail by about 120k.

I guess it just goes to show, "funny noises never get better, they just get more expensive!"
 

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QUOTE(kageryu @ Sep 27 2005, 01:46 AM)
I guess it just goes to show, "funny noises never get better, they just get more expensive!"
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