Ever since I bought this brick ( 100k mi) I'm puzzled about the noise coming from the engine. First I found that it was the

exhaust system which had several major leaks. Replaced it with Starla kit that turned out to be the Walker. Things got

quieter a bit but not much. When cruising at 60 mph the car is nice and quiet. As soon as I go over 2800 rpm or 70 mph it

is significantly louder. The noise is very audible when sitting in the driver seat. Passenger location is much more quieter. It

looks like it is not dependent on speed but more of the rpm the engine's running at. Boost condition has no mayor effect

on it.

Is this condition normal for the bricks or do I have a problem? I don't want to end up a pass in this car........

Please help!Any sugestions will be appreciated...

Could it just be exhaust system resonance? When I first got my 740 (at 77,000 miles), I found that the car was distinctly louder when cruising over 2900-3000 rpm. The exhaust system has been replaced twice since that time (seven years and about 220,000 miles ago), and the resonance doesn't seem to be as pronounced now - or maybe I've simply become accustomed to it. I can't say that I'm driving the car any slower now.

I recently bought some 5/8 inch foil backed insulation from an upholstery shop and a can of 3M heavy duty spray adhesive to soundproof the firewall. Cut small pieces to fit and glue foil side out. It is noticeably quieter. A good deal for about 25 bucks.

That's great info!

The four cylinder volvo's have so much exhaust resonance, you'd think volvo coluld have come up with this solution at the factory. Looks like I have my weekend project :)

It looks like I'm not alone on this issue.

Do you have factory or aftermarket exhaust?

Mine is sized for the turbo engine aprox 2.25 in. I can realy hear it under full bust condition.....

Rob

Look for loose heat shields underneath, broken brackets around the manifold or possibly a crack in the exhaust manifold.

It just so happens that I too have some similar issues with my 740 N/A with B230F. I just had the harmonic balancer replaced (it was separated). That was good. Also, the crank sprocket gear? (you know the one I'm talking about? Behind the harmonic balancer?) Anyway, the key was sheared off. Wasn't sure what caused that. After all that was replaced, checked the timing and it was apparently 15 degrees too far advanced!!! At idle, made a huge difference after adjusted. What changes did I notice? Well...the brick idles a hell of alot better now (ie: not as noisy). However, the engine noise/vibration that was noticeable at 2500 rpms has now moved up the rpm curve to about 2900rpms. It seems very noticeable at that point and higher. It is the same thing that the others are experiencing but I also FEEL it as well. Could this be from exhaust cracks around the header area? If so, wouldn't I get backfires or hear it when not at such a high rpm? The current exhaust from the catalytic on back, is 1.5 years old. I've spent a bit 'o change on this issue and it is still there! I guess the good news is now I have to drive the car to 72mph to make it happen. I guess I could keep it below that speed, but what fun is that? Would bad manifold to block gaskets do this? Again, I keep thinking if it were the exhaust, wouldn't I get some indication (like popping when decelerating)?

I need your mighty wisdom Steve,

Thanks,

Could that be that the noise is coming from the right side of the engine, where the suction manifold is? But the noise is more mechanical in my opinion. It might be connected with piston slap....Or maybe bad motor mount ( not flexible enough) Do you have volvo or aftermarket mounts ( they can be bouth hydraulic)?

Robert

My brick is an 86 740 and these were OEM solid motor mounts that were put on about 2 years ago along with the tranny mount (by th dealer). These mounts should not be the problem as when the car is under 2900 there is no noise/vibration. I will rule out the knock sensor or see if that is the problem. Maybe it isn't adjusting the timing as the throttle is depressed--causing excess engine vibration. The only other thing that it could be is the flywheel (maybe out of balance)???

Also, when depressing the accelerator pedal (to what I think is the floor) and it doesn't accelerate as quickly as I think it should, all of a sudden, there is more pedal to depress. Almost like it gives way. Is there something that stops the throttle pedal until extra pressure is put on it to depress further? When I get this excess pedal travel, it seems as if the engine rpms jump from 2900 to 3500 instantaneously and the excess vibration/ noise is very noticeable. The car then accelerates appropriately. Is there a throttle pedal stop? This is just a very wierd condition that I don't think I've heard of happening before.

Thanks,