W126 Sedan Bonnet Insulation

A few months ago I replaced the under bonnet insulation pad on my 560SEC.   This job also needed doing on the 300SE.   I purchased both pads at the same time, and finally got a chance to do the second one today.   Note, if you’re looking for more information on forums, American sites will refer to this as a hood pad.    There are youtube videos by Kent Bergsma and Pierre Hedary on Hood Pad replacement.

For the 560SEC, I had a genuine Mercedes part.    The coupe is different to the sedan.   For the 300SE, I have one made by Febi.   Unlike the genuine pad I put on the 560SEC, the Febi pad is smooth.   The fit was very good – it did not need any trimming.

The procedure is the same as before – first step is to scrape off the remains of the old one.    There was a lot more debris on the 300SE.   You could also see where somebody had tried to use some sealant on the edges to try and glue it back up in vain.

As with the 560SEC, I used an old bed sheet (the same one) to catch the debris.   I also used a plastic tool to scrape the old one so as not to gouge hole in the paint.    It is not essential to get every last trace of the old pad off.   if it is not coming off with a plastic scraper, the glue will stick to it just fine.

The bedsheet also makes collecting the debris into a rubbish bin rather easy.   A queen size sheet means the whole engine bay is covered.  Three months later, the 560 pad is still holding well.  Based on that, I used the same Seallys Kwik Grip Vertical Gel.   This product is rated to 130C.   If the temperature near the insulation gets above that, the engine is well and truly cooked and the insulation is the least of my concern.   It spreads on easily with a 7mm nitrite glove and being the gel doesn’t drip down when being applied.

The gel product does look a lot like I have applied butter to a rather large piece of toast.   As with the 560, I used 1.5 800g cans   The leftover half can from May was a little runnier than the new can, so I used it on the pad rather than the bonnet.

While applying the pad, I found it easier to put the bonnet in the normal position.   When fully vertical, I could not reach the top very well.  Once finished, I put the bonnet vertical as I figured it would dry better that way.   I will be using the E350 for the next couple of days to allow it properly dry.    This job should protect the paint and reduce the noise on the 300SE.   As with the 560, I was able to do this on my own with relative ease.