Exhaust question

[Andrew S]

I have been trying for many years to get rid of a vibration and have found the fault

My problem is it keeps coming back. The problem is, where the rear exhaust pipe goes through the drivers side rear cross member,it keeps getting too close to the member and transmitting road noise through the car. I have just covered a 550 mile run and it is coming back after I adjusted the hanger and it was certainly tight on the cross membertop part of the hanger, but not the bottom.

I am certain thatit is the shape of the pipe that goes through the member and across the diff. I know that the pipe is on possibly too far onto the box pipe and maybe the shape of the bend is too close to the member. Maybe if it is pulled off a little more, the bend of the pipe would miss the member. I have tried pulling hard on the pipe downwards to pull it away from the member and then tighten the hanger and this works for many miles but its not long before I can feel the pipe at say 60mph resonating. The pipe seems to touch more or get very close to the member under acceleration.

So, I havebeen looking at my options:-

Do I buy another pipe sectionin stainless

Do I buy a mild steel pipe section so that it can be bent if needed

Or, is there any other reason why it could be fighting the hanger which is all new and from LD Part so I know its correct?

Any suggestion much appreciated as when tightening the hanger, I had to put a block of wood between the diff and the pipe to get enough down pressure to keep the pipe away whilst I tightened it all up. That's how much pressure was required other than ripping the tail pipe hangers off the boot floor

Any help or advice much appreciated.

Thanks

Andrew

[catlotion]

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funny - I just had the same thing mentioned yesterday when I had my MOT done - I mentioned that there was a vibration/resonance between about 55 and 70 and suspected the prop-shaft. We had a look on the ramp and the guy noticed the same thing about the exhaust - pipe is almost sitting on the bottom of the cross-member hole.

Can you tell me the symptoms you experience exactly please?

cheers,

Toby

[Tdm]

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Hi Andrew

Not sure exactly where you say the pipe is catching, but perhaps you could try this.
Loosen all the exhaust clamps that hold the exhaust together and take the rubbers off where they attach to the bodywork. Then use one or two jacks to hold the exhaust up in exactly the right place (centre of the cross member holes). While the pieces are not clamped tightly together manipulate the pipes (left/right/up/down) to the correct position & then tighten everything up again, and if necessary bend the bodywork brackets that the exhaust rubbers attach to, to make them hold the exhaust exactly where you want it. Remove the jacks holding the exhaust and check that they stay exactly in place. You may need to borrow a bottle jack to use under the exhaust piece that connects the two exhausts together if you have already used your only jack to lift the car.
Ideally you need the car up on a ramp, or have use of a pit.

[peter f]

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Hi Andrew,

Just thinking outside the box - are the engine mounts OK?. Dont't know if it would have the effect you mention if they wre perished/soft/oil affected, but might explain the movement on acceleration. Obviously an easy one to check, and eliminate.

FWIW

cheers,

Peter f

[Tdm]

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peter f wrote:

Just thinking outside the box"

Peter f

I tend to shoot off on a tangeant and "off topic" when I think outside the box.

[Andrew S]

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Thanks for all the responses.

Toby, I used to get vibration under acceleration at 25mph and despite going through this speed and it disappearing, it is now evident as it has disappeared that there was transmission of vibration at all speeds.I know how to cure it and it works, its just that the exhaust wants to go back to its original position after time.

Peter, my engine mounts are all new and although I may not have any forward and aft movement, Iam sure that I read on this forum that the hanger bolt on the exhaust should allowfor any movement.

Terry,as you look from the rear of the car, the exhaust is very close to the upper left hand side of the cross member and if I put a block of wood between the diff and the pipe and loosen it all off and then retighten, it cures the problem, but obviously, it works it way back to how it was. Maybe the pipe is the wrong shape. I note your suggestion about removing all and bending the hanger brackets to suit and then reassemble.

The system came from Rimmers many years ago and was called Continental. Lovely sound. I am toyingwith the suggestion of getting a mild steel section that goes through the cross memberto the tail pipes so that I could bend it to shape.Saying that, if it is the shape of the pipe, then may be Icould bend it underheat, but it is very close to the proximity of the petrol tank vent pipe :shock:

Thanks again for everyone's suggestions

Andrew

[StagnJag]

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I don't know if this tip is of any use, but when I put my exhaust back together, I used the subframe hanger to position the exhaust, and a separate clamp to clamp the joint at that location. It made it much easier to get everything lined up properly.

Rgds

Dave

[Andrew S]

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Thanks Dave, thats interesting and may give that a try

Cheers

Andrew