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240 rattles

I know diagnosing rattles over Usenet is asking the impossible, but I'll give it a shot anyway.

The car is a 1991 UK spec 240 SE. B200F engine. 157000 miles (give or take).

There is a _horrible_ rattle between 2000 and 2500 rpm from the underside exterior of the car. I cannot find the source of it. Thought at first it was the exhaust but a good bashing didn't leave me suspicious. Everything visible is tight on the underside. It does only seem to happen when the vehicle is moving.

Before I start the wild goose chase, has anybody had a similar problem that they've fixed? It may just help me locate this thing which is letting the car down - at all other speeds it's a silent as the grave.

Many thanks, David

Reply to
David Balfour
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I have one of those myself- the rattling is at just over 2000 RPM.

Take a rubber or rawhide mallet and get under the car. If yours is the same as my 1990 you will find a curved, dual header pipe (tweo parallel pipes as one) leading from the cast exhaust manifold towards the catalytic convertor (if so equipped). Give the double pipe a rap or two and you will probably hear the rattle.

CAUSE: this is a double walled pipe with an insulating layer between. The insulation breaks down and allows the inner pipe (or the insulation) to rattle together.

CURE: get some self-tapping sheet metal screws and install a few through the outer pipe so they push against the inner pipe to stop them from moving and thus rattling.

__ __ Randy & \ \/ /alerie's \__/olvos '90 245 Estate - '93 965 Estate "Shelby" & "Kate"

Reply to
Randy G.

Randy, many thanks for that - I'll take a look tomorrow. It does sound likely, as the rattle is absent when the car is cold. I don't really understand the magic behind these Volvo cats, but it could be this double pipe you speak of that's causing the problem.

David

Reply to
David Balfour

The rattle has nothing to do with the cat itself but the pie that is a ways in front of it.

The other likely places are:

1) The heat riser pipe (aluminum duct work leading from the heat shield to the air cleaner box. These will vibrate and rattle against body work which wears the pipe as well as the paintwork. 2) The heat shield around the cast iron header 3) The heat shield that is above the catalytic convertor (less likely). In some cars the shield is bolted to the exhaust, in others to the body.They sometimes can come loose and drop onto the exhaust which can make a real racket. usually not so RPM dependent.

__ __ Randy & \ \/ /alerie's \__/olvos '90 245 Estate - '93 965 Estate "Shelby" & "Kate"

Reply to
Randy G.

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