MatraSport Forum

The engine cover on the Murena is held in place by a pair of brackets with a screw that goes into a nut in the deck. The nut is rectangular and "floats" in the deck, held in place in a cradle in the sheet metal.

The problem on my Murena is that the cradle has rusted and no longer keeps the nut from falling out of the cradle. If I were to remove the screw completely, the nut will fall into the chassis. I can see no way to get in there to hold on to the nut or to re fasten it, short of cutting a hole in the deck.

I was wondering if anyone has refurbished this little part and has some suggestions. Obviously I could just weld a new nut in place, but I am hoping there is a way to get in there and I just haven't found it yet. :)

I have exactly the same problem.  Some years ago I saw a system that could fix a captive nut to sheet metal using something similar to a pop riveter.  Is my memory playing tricks on me or do others know anything of this?  If this is still around, I wonder if this would be the solution to our problem?

regards
Ron

The previous owner of my car seems to have had the same problem.  His solution was to secure a threaded rod to the channel round the engine hatch on each side, drill a hole in the cover in the corresponding place, then use a wingnut to hold the hatch down.  Not very original looking, but it does the job.  I think the product Ron had in mind was something like this http://www.harrisonsilverdale.com/products/BUSHES.html

So do I.
I'm interested in a good solution.

Kind regards,
Jan

I think this is what I remember seeing

http://www.frost.co.uk/item_Detail.asp?productID=8490

I wonder if it would work in our case?

regards
Ron

Another thought that has just crossed my mind is to cut a square hole in the deck and use a cage nut.

I'm a bit confused now - first of all I had to lookup what a cage nut is - and google showed me this:

(http://www.matrasport.dk/Icons/cage-nut.jpg)

My car has always (since I bought it in 1995) had such cage nuts for this purpose - and it looks to be of the same age as the car, but I can't be sure.  The left one is however rather weakened by age, so it easily pops out - mainly if someone unfamiliar with the car tightens the lid. Personally I just always only tighten it "just enough" which doesn't cause the nut to pop free.

As I read Jon's post, his system is the same ?  - but  suffolkpete, your car appear to not have a square hole for this ??


/Lennart

As I said in my earlier post, my car was modified by the previous owner.  It's not high on my list of non-original things to correct.  If there is a square hole, I haven't found it , although it could be covered by trim.  It looks as if I've re-invented the original setup :)  I wonder how they were inserted during manufacture.  All the cage nuts I've come across are inserted from the rear.

That is why I was thinking of the threaded pop rivet type solution and because I didn't particularly want to be welding around that region (not with my lack of skill anyway)!

regards
Ron

Hi Ron.

Excellent idea.  :) I don't know why I didn't think of it already, because I already have the pop rivet nut tool. I guess I will just move the hole a few cm and cover up the old hole.

Suffolkpete's cage nut would be an excellent solution too, if there was a way to get it mounted from below. :(

I just hope I can get the square nut out so it doesn't rattle around. As I wrote I can find no way to access the space, except by cutting a hole in the deck.

Actually both mine have always been mounted from above - they only need to provide very little tension - the engine-cover stays there by gravity anyway, and the rubber trim around the hole stops it rattling.

How does it look on other cars ? - maybe this is another thing where later models have the shortcut-solution like the non-hidden screws fitting the rubbertrim at the rear ? :)

/Lennart

I had a look at a captive nut setup yesterday in an electronic equipment rack, the most common commercial use.  They are definitely inserted from the rear as the nut body will not pass through the square hole.  I think that if you made the hole big enough to insert it from the front, it would be very loose.

Hi Lennart.
Do you have a photo showing how it is mounted on you car?

not at hand (I'm in Denmark this weekend - car is in the UK)

However, the nut itself is simply sitting above the hole, with the captive spring holding it in place.
This obviously means they will come off of you tighten the lid more than the springs can withstand, but frankly I have never had a problem with that - as the lid stays there almost by itself to begin with.

Is there a way to access the underside eg via the shockabsorber mounting hole ? (would require removal of the absorber etc, so it would require determination, and/or great enthusiasm :-) )

/Lennart

Well, Lennart. It required a great deal of determination to get the old nuts out of the cavity, once I took the screws all the way out. Needless to say, the nut fell down and was out of reach on one side, but could be seen on the other.

After quite a bit of "fishing" and trying to pry the nut out, I finally had to get a file and enlarge the opening enough to get the nut out. It wasn't until I could get my Beltzer mechanics magnet tool in there, that I succeeded in extracting the nuts. See the various photos. As can be seen on the last photo, the nuts are indeed cage nuts, like the ones that Lennart describe. However, they are modified so that there only is half a "hook" on one side of the nut, as can be seen. On both mine, and yours too I suspect, the hook on one side has broken off, thus leaving nothing to prevent the nut from falling in. The nut itself is has been shaved in a 45  degree angle on the sides. I suspect that it is to allow the nut to be inserted from the top. With hooks only on half the edge and the nut shaved in an angle, I suspect that it may be possible to slide it in sideways and then twist it into place. As can be seen on the last photo, the nuts are different size, making me think that one side has been replaced. On that side the hole is also larger.

Well, I think that what I will do is to tack a piece of metal over the holes, drill a 10 mm hole, and put a 6 mm pop rivet nut into the hole. If it fails again, I can drill it out and pop in a new one. More after Jan comes back from vacation and I have access to his CO2 welder again. ;D

Oh, by the way. There IS a hole into the space where the cage nuts are mounted. However, it is only about40 mm in diameter and located forward of the shock absorbers and accesible from the engine compartment. So it would require a very specialized and flexible tool to get a new nut in that way. >:(

You can buy the correct caged nuts for these clamps and they are easy to fit.  I always keep some stock.  Usually one of the 'ears' breaks off, mostly from over-tightening the wing bolts.  To fit the new ones you simply insert them from one end of the hole and slide them towards the other end until the nut will drop in (as it has the underside chamfered to allow it) then slide the hole back towards the centre putting both edges of the nut under the chassis hole to brace against it as you tighten the wing nut.

Renault part number: 77 01 397 154 I think but it is a while since I bought some so please check.  They come in a pack of 20  These also fit in the front chassis to hold the front bumper and driving lamp brackets and since the lamps earth via this bracket is it good to have these bolted securely.

Roy