Hood pad alternative - PeachParts Mercedes-Benz Forum

#1 03-29-2002, 08:27 AM

I am in the process of replacing my hood pad. I found a material at my local HVAC supplier. Duct board, stiff fiberglass 1" thick with a foiled side. It slips into the lips on either side of my hood for a tight fit. About $20 for a 4x8 sheet. You can cut it with a utility knife.

#2 03-29-2002, 08:48 AM

Let Us know how it works. I was thinking on doing the same thing as my pad is missing on my 280. I am curious to see how it will affect the noise level inside and outside the car.
Regards,
Bryan

#3 03-29-2002, 10:46 AM

Yes, I would like to hear what differance it makes, and some photos if it were not too much trouble.

Thanks,

Craig Amos
1987 D Turbo
277,000 mi

tcane · #4 03-29-2002, 11:33 AM

I just received a product called quilted fiberglass that I am going to make a hood pad out of and a barrier around the engine to lower noise into the driver's compartment. Quilted fiberglass is made to be a sound absorber and is made with a nylon skin with accoustic fiberglass attached. Quilted fibergalss is rated for its noise reduction capability and temperature rated with the same classification of several well-known hood pads made by high-end car stereo installers for noise reduction.

I will be doing the first part of the install this weekend - the hood pad - using 3M adhesive and then universal hood pad attachment washers that are 2" in diamemter (I want this to be a permanent fix and not have to worry about the hood pad again - and get away from the foam pad). Then I am going to make the engine sound barrier - you've probably read about this product on this forum or seen on eBay the diesel sound shield. I am using the same or similar material this product is made from, but mine will be longer and enclose more of the engine compartment so it should be better at noise reduction.

I was going to post this info after I did the job, but since Steve019 posted his repair I thought I would share what I am going to do. It sounds like what Steve is doing will work fine, although I am curious about how well the stiff duct board bends to conform to the contours of the hood (the outline of the hood should not be a problem).

My $0.02 Worth!
Tom

#5 03-30-2002, 01:57 AM

Installed material this evening and went out to eat. Made a noticable difference in noise level inside. My daughter even commented on it. tcane had a good point about contouring to the hood, I will back cut it tomorrow to allow better clearance for the throttle linkage. But I am satisfied for my $20 investment. I plan to use it for the under-dash covers as well, I have over half the sheet left over. The acustic quilted stuff sounds like an excellent material but funds are tight for me right now. I would like to hear the results and possibly upgrade when I find steady employment again.

tcane · #6 03-30-2002, 08:45 PM

Steve:

I'm sure the engine noise was less, the panel you bought should have pretty good sound absorbing abilty. And $20 is cheap compared to a regular hood pad costing about $25-$45, plus you have some of the panel left to do other areas.

The quilted fiberglass I bought cost $39 for a piece measuring 48" x 5' with two sides bound with a binding tape that is stitched on. I bought the binding tape to put on the sides because they are not sealed. I could probably not use the binding tape on the hood pad, but I wanted to seal the sides of the hood pad, and I need the tape for the engine compartment shield that I'm making. The tape cost $20 for a 4" x 100' roll, so I'll have lots left over. Spent 3-4 hours removing the old pad and soaking the remainder with mineral spirits to loosen/ease the scraping off of the left over foam pad and old 3M weatherstrip used to attach the old pad. The jerks that installed the pad used 3M from a tube and spread it around, but not very well because the area above the injection pump was not glued and fell off - bad area because the IP makes a bit of noise - otherwise the rest of the pad was in fair condition and would have worked longer if the 3M had been spread better.

Driving without the pad did result in more noise from the engine, but not as bad as I thought - the engine I just rebuilt is pretty quiet, especially for a diesel.

Tomorrow I begin to fit the quilted fiberglass to the hood and stitch the tape to it. It looks like I can use 2" hood pad mounting washers across the front and back of the hood, then washers on two support bars running from front to back of the hood, the middle part of the hood will have to be glued because there's no place to mount the washers - so I'll glue the entire pad and use the washers as extra insurance to keep the pad mounted.

Than I'll begin making the shield that goes around the engine. I'll let everyone know how it turns out.

Tom

jbaj007 · #7 03-31-2002, 03:06 AM

tcane,
Did you get your sound barrier from McMaster-Carr? I made the firewall "sound shield" with deeper and wider coverage than the ones you see advertised with the same material you describe. One thing i did was temporarily "seam" my cuts with duct tape as I found that I wanted to change the shape here and there from my original due to linkage and exhaust issues. I made it fairly long and have to get under the car to really pull it down into some of the tighter spots. The under hood temperatures have proven to be no problem with the quited vinyl covered fiberglass or with the tape. I gave the steering connections a little wider berth. I thought it made a difference in noise, but my friend (an MB tech.) laughs. I think he feels REAL diesel drivers don't need it. Of course he's the one who refuses to help me with pressing the lower ball joints if I put the sound encapsulation panels back on the underside.

Bruce

Gary F. · #8 03-31-2002, 09:27 PM

Steve,

Did you install fiberglass side down or foil side? Does it matter.?
Just curious. Suggestion to others. Do not use duct tape for seams. It will fall apart from the heat. Use foil tape instead.

tcane · #9 03-31-2002, 10:09 PM

Bruce:

Yep, bought the quilted fiberglass from McMaster-Carr. I had to search pretty hard to find them, and it was worth it. I'm using the single sided for the hood pad and the double sided for the sound shield (I did not like the idea of a scrim backing on the single sided because of exposure and then removing it for repairs/maintenance - I don't want fiberglass floating around). Glad to hear you're satisfied with the results and thanks for the tips. I plan on making a pattern from thin cardboard for the sound shield and then transferring to the quilted fibergalss. Then I was also going to use duct tape temporarily to reinforce the cut outs to figure what else I needed to do to make it fit well. I plan on cutting the sound shield in the middle to get two two foot wide pieces that will be four feet long, then connect at the middle to make an eight foot long section to wrap around the engine compartment up to close to the headlights (I'll adjust the length as I see how the pattern works. About what are your dimensions for your sound shield?

For the hood pad I'm using a new foam hood pad for the pattern and since this installation has no problem with lines, linkages, etc. I figure it will fit really well the first time. Also, starting with the hood pad is the easiest and I thought the best place to start.

Tell your M-B tech that all you're doing is improving on what M-B began as to sound deadening diesel engine noise. The old 240 in the W115 had next to none except for carpet in the driver's compartment, then the early non-turbo W123 had a bit more in the driver's compartment (thick, rubber backed carpet), then the later turbo W123 had that metal panel at the firewall with padding on it and extra padding on the firewall, and then the W124 diesels had even more sound deadening material.

Gary:

I would use metal AC duct tape if this was going to be permanent - the regular duct tape is temporary to see how things fit. Also, the metal tape is not as flexible as the binding tape that I am going to stitch on.

I would hope that the foil side is facing the heat source.

Tom

#10 03-31-2002, 10:24 PM

I installed foil side to engine. I did not need to use any tape as it is held in place by the lips on th under side of the hood.

jbaj007 · #11 03-31-2002, 11:18 PM

Tom,

Yours will be much longer than mine. Mine goes from even with the air cleaner on the passenger side to even with the rear of the A/C compressor on the driver's side. I also use McMaster-Carr's mass loaded vinyl material (Comes in different thicknesses) as door vapor barrier (thin stuff) and as trunk and deck sound deadener (a la' Dynamat). It really took some contortions from underneath to get my quilt down deep in the bay and I think I could have done better there. Do you have your original sound encapsulation panels? Since my friend won't look for any for me, it's off to the dismantler's to try to find some clean used ones and I'll layer those with some of the fiberglass quilt probably. I like the diesel a lot, but the family wouldn't mind a little more noise reduction.

Bruce

tcane · #12 04-02-2002, 12:01 AM

Bruce:

Sounds like you've spent a lot of time trying to reduce noise. Do you have a killer stereo system or just want a very quiet ride? Quiet ride = less wear and tear on the driver = more alert and able to drive longer distances without tiring, or reduce the noise coming from the guy next to you with 6 12" subwoofers and a couple of thousand watts of power blasting away .

By the way what model/year is your M-B?

What do you mean by "sound encapsulation" panels? Are these the liners in the sides of the trunk, if so, mine are in good condition. I've thought about doing some more things to reduce noise, but my car is pretty quiet especially with the rebuilt engine. I saw the mass loaded sound vinyl also and may use some of it later. Lately, I was more concerned with rebuilding the engine and while R&R'ing the engine had more of the hood pad dropping off everywhere. So, once the engine was in and running the next thing I wanted to do was R&R the old pad and make the sound shield.

Other things kept me busy this weekend and I got no where on the hood pad. During the week I'll get it done and mounted. Steve's install was easy just having to cut the HVAC duct panel to size and pushing it into the grooves on the edge of the hood. Like usual, I find a way to do something that is more effort that may be better in the long run.

Steve:

What year and model is your M-B? You don't have any info about it on this post. How long have you owned it and how do you like it?

Tom

#13 04-02-2002, 01:25 AM

Tom,

Mine is a 76 300D, the last year for the 115. Love the car the more I work on it. The hood pad almost cut the cab noise in half according to the stereo volume number I use now. Highly scientific method ! I got the cart for $100 bucks last year for a project car but find mtself using it for my daily driver, beats 10mpg in my truck and looks good too. tie rods are next!

jbaj007 · #14 04-02-2002, 01:58 AM

Mine's a 1984 300SD. Bought it new in 1984. Sold it in 1988. Bought it back in 2001.(Yes, there is a long story there).

The sound encapsulation panels are the composite panels under the engine and the front of the trans. Some think that they are for airflow (both aerodynamically and cooling), some say for protection from H2O; but MB calls them sound encapsulation panels (makes sense to me). Most of the time the techs don't care for them because they're in the way of undercar service and mine got tossed years ago. Hence my friend's disdain. I like it quiet in the car because I don't mind driving and I prefer it peaceful in the vehicle.

My sound system is a poor man's system considering my high frequency hearing is typical middle aged. New Blaupunkt head unit with new 4x6 Blaupunkt speakers and a Jamo 12" amped in the trunk and ported with flex tubing thru the rear parcel shelf med. kit box. That produced lots of bass rattles and I spent some time with foam tape and "earthquake bric-a-brac putty" isolating various squeeks and noises. Next on my list of noise abatement is to silicone spray some door panel and upholstery squeeks. I'm no audiophile but I enjoy music and not noise.

The real reason for quieting the car down is for the peaceful feeling.

jcd · #15 04-02-2002, 07:27 AM

There are some creative approaches to address this issue. Not to be contrary, I love the sound of the engine. I admit to being more of a conservative talk show and sports listening fan, than music, so to me sound is not a big problem.

I just love the sound of the engine, so I;ll never compete with you all in the market for sound deadening materials.

JCD

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