Booming noise at 40 - 70 mph

[Ozzie61]

I have a Saab 95 2.2 TD Linnear. About a week ago I noticed a booming sound that starts at about 30 - 40mph and disappears at around 70mph. It is a fairly constant sound from the central front (ie: it doesn't get louder or change pitch the faster I go). It does seem louder when I take my foot of the accelerator. The engine seems rougher and performance has dropped off I think.

There are no warning lights coming on.

I have taken a look under the bonnet - can't find any noticeable problems except an oil leak around the clutch connection. The air inlet hoses seem intact and connected.

Any thoughts or ideas on where to start looking please?

[planosaab]

Hard to say without hearing it. Is it possible a splash shield or wheelwell is loose and at high speed it is slapping wildly under the car or into your tires?
Hoping the engine isn't making boom noises. I had a shield bolt in front of my wheel on the passenger side go and it would pop loudly like a cvshaft when i would let off the gas. That is why i ask.

the popping was constant and would change in speed depending on my speed.
I would inspect the center splash shield as well including the deflectors. look for anything that is loose and that can catch air and flap.

[mgmt585]

i had the same problem. turned out my brakes were warped and needed new discs. was weird because the booming/shuddering in my car didn't get faster with speed either. also explains/explained to me why i was losing performance. drive like 10 mph with windows down and see if you can hear quite a subtle rubbing sound