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RWD - Defective fan belt?

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Defective fan belt? 900 1994

1994 940.

So four months ago I put on a new accessory belt (water pump, power steering). Yesterday, it became distorted, failed and caused overheating. It looks like the cords on one side snapped part.

It was correctly tensioned, the accessories all turned well, and seemed to be aligned. It was Genuine Volvo. I have to conclude it was defective. I am scratching my head.

Anybody else have anything like this happen?

Thanks,

Alex





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Defective fan belt? 900 1994

Could be defective, yes. Where is this car from?

The 94 should have had a two-piece (rubber fuses them together) harmonic balancer, but people have been known to replace them with the older one-piece parts.

The water pump is not likely to be misaligned, but the power steering pump itself or the bracket can fail and cause misalignment. Either the aluminum (stupid design) holes can be "wallered out" into ovals, or the shaft seal for the pump can go bad. Often a bad bracket leads to a damaged pump seal. Either one will cause belts to wear unevenly, although this is the first I've seen a belt totally failing. I think the seals are usually damaged by overtensioning the belt.

Good luck!





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Defective fan belt? 900 1994

Dear U.S. Diver,

Hope you're well. The mountings for the water and power-steering pumps do not rely on rubber bushings, as do the alternator and air-conditioning compressor.

The water pump is bolted to the engine block. The power steering pump is direct-bolted to a mount, that is bolted to the engine block. The drive belt can be mis-aligned, if the power-steering pump mounting bracket (#1346267 - no longer available from Volvo) is loose or worn.

A steel ruler can show power steering pump misalignment. Put the ruler across the face of the crank pulley. See if the ruler's edge is precisely parallel with the power steering pump's pulley face.

You may be able to use duct tape (or a magnet) to hold the ruler to the crank pulley's face. Then, measure the distance between the ruler and the inboard edge of the power steering pump pulley (the edge closest to the engine) and the outboard edge of the power steeing pump pulley (the edge closest to the wheel well). The two measurements should be equal. If so, the power steering pump is properly aligned.

If the two measurements are the same, the crank pulley may have failed. Use white paint to draw a line from the crank pulley bolt's head, out to the crank pulley's outer-most edge. The painted line should span the rubber insert, that ties together the crank pulley's core (secured by the bolt) and the outer section, which has the grooves into which fit the accessory drive belts.

Turn on the engine and let it run for a few minutes. If the painted line separates into two sections - say one at three o'clock and one at 11 o' clock, the crank pulley needs to be replaced: the rubber insert has failed. This cannot be repaired.

It is perhaps possible that the water pump pulley - held to the water pump's flange by four, 10mm bolts - was badly mounted, so that the water pump pulley's face is not parallel with the water pump's flange. That can be fixed by removing the four bolts, re-seating the pulley against the flange, and tightening the four bolts in two or three steps, rather than tightening one all the way, tightening the next all the way, etc. Step-tightening reduces the risk of misaligning the pulley vis-a-vis the flange.

Hope this helps.

Yours faithfully,

Spook





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Defective fan belt? 900 1994

Okay, reunited with my car after some travel.

I painted the crank pulley, then ran the engine a few minutes.

Results: the marks all line up.

My records 21 year old maintenance records do not indicate that this part has been replaced. I examined it with a flash light and I could detect no cracking, etc. in fact I dont see any rubber portion at all.

In a way I am disappointed, as I thought this was the most likely culprit for the new fan belt failing.

Can I conclude that the fan belt was defective? I have long trip coming up, and I need to rely on this car.

Anything else I should check out? Again, alignment and tension both seem good.

Thanks.





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Defective fan belt? 900 1994

"Can I conclude that the fan belt was defective? I have long trip coming up, and I need to rely on this car."

--> Well it looks like that - faulty belt. I'm sorry I don't have any additional tips to offer as I'm also in similar situation i.e. belt suddenly snapped. Belt change is no big deal only that I'm perplexed as a well looked after 940 usually has respectable parts longevity. Just be prepared. Bring along tools and spares. Go on and have a nice trip : - )

Amarin.





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Defective fan belt? 900 1994

Dear U.S. Diver,

Hope you're well. If the crank pulley paint marks stay aligned after 20-30 minutes, then the crank pulley is in good order.

Have you checked alignment of power steering and water pump pulleys? If those pulleys' faces are parallel with the front of the engine, the only conclusion left is that the Volvo-supplied fan belt must be defective.

Hope this helps.

Yours faithfully,

Spook





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Defective fan belt? 900 1994

Thanks, Spook for the thoughtful response. Of your hypotheticals, I find the failed crank pulley to be the most likely. I will test this out and report back.

Thanks,

Alex





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Defective fan belt? 900 1994

Just a slight clarification - the studs that hold the fan to the water pump flange are 6mm with a wrench size of 10mm for the nuts. - Dave





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Defective fan belt? 900 1994

I think Its just a normal practice among us. We always refer to the size of the hex head whether its bolt or nuts. It follows that these sizes help us to choose suitable wrench or socket to be used. Whereas when ordering a replacement - let say to replace a rounded head fastener - the bolts and and nuts sizes are specified according to its thread width. For example, I've ordered copper-flashed replacement exhaust nuts for the car with thread size 8mm 1.25mm pitch at eBay. The exhaust studs are 8mm width. However the order arrived with 12mm hex head, not 13mm as per original Volvo.

Amarin.





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Defective fan belt? 900 1994

Dear Amarin,

Hope you're well. Volvo VADIS uses a mix of US and UK English. I understand both.

Volvo VADIS uses "flange screw" to define a fastener, that to me is a "bolt": whether the head is hexagonal or square, a wrench (UK "spanner"; or socket) is needed to install or to remove it. A "screw" has a circular head with a recess:a screw-driver is used to emplace or to remove it.

As the task at hand involved removing and re-installing bolts, I thought it more helpful to specify the wrench (or socket) needed. Had the bolts been stripped, then the bolt's diamenter, length, and thread pitch would have been relevant.

Hope this helps.

Yours faithfully,

Spook





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Defective fan belt? 900 1994

Dear Volvo from Heck,

Hope you're well. On '93 and later 940s (non-turbo engine) an electric cooling fan was standard: no fan is mounted to the water pump.

On cars with an electric cooling fan, diagrams in Volvo VADIS - a superseded dealer parts/service database - show the water pump pulley is secured to the water pump flange by four flange screws (6 x 16mm; Part #946544). If memory serves, these screws' heads are 10mm hex format.

Hope this helps.

Yours faithfully,

Spook





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Defective fan belt? 900 1994

This happened twice but only involed my alternator belt. Installed for one year then it became frayed and snapped. Belt did vibrate at idle but run steady at higher rpms. Noticed this months before it snapped. I suspect worn mounting bushings but haven't got time to replace them yet.

Amarin.





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Defective fan belt? 900 1994

maybe just misaligned





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