Our Lag 1's are getting older and this is the SECOND time I have had to deal with a stuck bonnet so I thought I would add to some of the excellent feedback already on the site.
My lag 1 is UK model, steering wheel on right and location references are as sitting in the driver seat.
First, here is a very useful post with photos I dug up from the archive:
I have never been so lucky to bounce the bonnet and get that to work. However I have learned that you never pull excessively hard on the bonnet release handle. Breaking the cable or parts is a much bigger repair job. The only way to sort out stiff and stiffening latch pivots is to remove the 2 bolts holding each latch, clean, degrease, lubricate and replace. Spraying WD40 on them is not a long term fix.
Several years ago the bonnet release went all floppy as if the cable had broken. I put the car on ramps and removed the engine tray. From underneath using a small light, I could see the bonnet mechanisms high up and to the left and right. The right drivers seat side is less cluttered to start with. You see the shiney cable wire first and the part you push from right to left (made of black plastic) with a very LONG screwdriver is at the extreme right of the wire.
That releases the right side latch. If you are lucky (and there are reasons why) it will be the right side latch that has seized up and the left side may release by pulling the release lever.
The bonnet wire is connected to the left side latch first and gets a lot more pull. They then use a connection wire linking the left side across to the right latch. The right side latch furthest from the pull point is more likely to seize or stiffen first. Most important is the wire length and distance between the two pull points on each latch. Surprisingly, Renault did not fix the latches with oval holes to take up any wear or slack. Therefore you must make sure that when the bonnet release is pulled slowly, BOTH attachment points move together and release at the same time. Do this check before you slam the bonnet down!! If you turn their plastic cable holder upside down, you can get a couple of mm shorter on the distance.
If you do need to manually release the left side latch, the procedure is the same locating the attachment point for TWO thin wires (not the outer jacket) and pushing it to the left.
The design of the latches is rubbish. The pull points for the cable wire are through plastic mouldings which can break. This feels like a broken cable at the release lever end. The worst plastic piece is the first one on the left side, because it takes the force of the cable pulling on both latches. The best fix for this is to take a short piece of square aluminium stock bar (can't remember the size, but about 10mm square) and re-make both plastic parts from solid aluminium. It is a fairly simple job of filing to get the same external profile, then drilling holes to take the cable wire nipples, mounting tab and hacksaw slots for the wires. The tab that locates each pull block is then drilled 1.5mm at the end to take a wire to stop the blocks jumping off the tabs. Never again will you have these parts break but the cable may with excessive pull.
Now I have revisited a jammed bonnet for the second time. There were no broken parts but the right side release mechanism was jammed hard at the point where the cable operates on a steel pivot pin. The design of these things is so bad! because the bonnet has no decent weathstrip seal, water easily gets on to the bonnet latches and these pivots (there are 2) seize up. Despite all the warnings about lubrication, these parts and poor weather protection are just made to seize up.
Both latches need to be unbolted, dunked in kerosene, thoroughly cleaned and the pivot parts worked hard until running free. After drying I lubricated mine with liquid ptfe, but I still expect seizure every seven years! Before putting them back, paint the black plastic/aluminium 'toggles' holding each cable wire white - it will help you find them from underneath next time!
The long screwdriver is essential but may not be in your toolkit. The end of the latch which needs moving may be seized quite hard and most long screwdrivers will bend. I cut a 24 inch lenth of 1/2 inch steel bar then ground the tip one side 45 degrees with the angle grinder. The bar is long enough to rest on the side chassis box frame as a pivot point. The flexy led light (Ikea) was excellent, as I could poke it right up to the top of the rad.
As any remaining Lag 1's get older, this will become a more common problem (maybe Lag 2's?), so I hope my added notes to this thread help as there is not much else on the web but moans and groans.