Hi I have a old Renault 5... Love it!but when I go over uneven road or small bumps there's a knocking noise like something's loose under the passenger floor mat.. If you sit in the passanger side you can actually feel the knocking under your feet...yet I've looked underneath the exaust is not loose and I cant see anything else...

Hi Geoff. For first just go on the front Stabilizer links which are giving this knock, Also check the stabilizer bushing in the center bar of it.

look for loose mud flaps. check under the front of the vehicle as there is a plastic panel from under the radiator back to the front cross member. This is light weight plastic and held in position by small plastic plugs/clips Hitting something on the road (small bird-- clump of rag or parking over a tire stop in the parking centre )will break it and it hangs down and flaps as you drive.

There is something else loose check sway bar joints front and back, Muffler/exhaust brackets,and gas tank brackets..

loose exhaust system check for dangling pipes/muffler.

I have the same problem i think.
The noise is something to do with the air con inlet gate???
Q. is there a fuse to isolate this as the position of the problemis above the glove box and can only be accessed with the dash board out and that would be very expensive.

I had the same problem. It was the front sway bar bushings. I took it to the dealer when it was still under warrantee. The replaced everything from struts to the steering linkage. And it still made the annoying knocking noise. I was changing the oil one day and while I was under the car I started looking where the noise was coming from. I grabbed the sway bar and pulled on it. It was loose. I bought bushings for about $12 and that fixed it.
Hope this helps

See if you can bounce car and replicate the noise. If you can, you should be able to find it, and put your hand on it. Stabilizer bushing are a place to look, both at the lower a arm and on the frame. If you narrow it down to the strut, it will need to be replaced. The front trans mount also goes bad, try putting it in drive with your foot on the brake and give it some gas and see if the engine moves an excessive amount.

Check your exhaust and rear suspension for something loose or broken. Problem could be the exhaust, a hanger or cracked pipe. In the suspension it could be shocks, worn bushings, track arms etc. When a problem like this happens you have to get under the car and grab and try to move things checking for loosness. In general try to see what is loose enough that a bump causes it to rattle or bang. Other than inspecting the rear area there is no short cut that can be taken to solve the problem. You don't want to just start replacing parts hoping to fix the problem, that can be expxnsive and unnecessary. Good Luck!!!

It could possibly be a shock or strut bracket.

renault grand espace , i have a knocking noise when i go over any bumps at all from the drivers side of the vehicle