DS rear bumper question

pottsy

pottsy

Citroen Loony & BMC Nutter.
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I've recently become aware that the rear bumper section of Moby Dick is actually rubber mounted. I found this by wondering (a) what the horrible bang I heard occasionally was and (b) pulling the bumper off after finding it would wobble up and down by an alarming amount.

My question for the brains trust is: Why?

I know that to a purist the answer would simply be "Because that's the way Mr Citroen made it so there!" but I've not always subscribed to that rather dogmatic view. I like to know reasons and rationales for things that, on the face of it, are not self evident.

I found that my wobble was because a part of the inner mount on the body work had fatigued and presented a somewhat larger hole than that originally designed, permitting bumper wobbling.

My solution, for the nonce at least, has been to plate the broken bit, add a large washer at the outer ends and bolt the whole lot rigidly to the bodywork. A liberal application of Penetrol to everywhere it would reach should at least stave off degradation for a while.

The original rubber sleeves (part number 615-7 from the parts book) along with the rubber washers (615-75) are still extant, but severely degraded. I've left them out for now as it seems to me that the whole boxed assembly in which these parts fit supporting the bumper in cushioned comfort is a rust trap just looking for moisture.

I'm prepared to be swayed by a reasonable explanation as to why the bumper needs such cosseting, but in the meantime it is non-rattly and firmly fixed.

Looking forward to any ideas we may have.

Cheers, Pottsy
 
Yep a rust trap just waiting to bite. It was DS design philosophy of easily replaceable ( read throw away ) panelwork. ....even the original advertising made the point. While you are there check out the horizontal panel join across the back of the boot space( below the boot lock and behind the tail light structure ). These leak too and rather than draining to the outside it allows water to stay inside the boot space and rust the felt covered floor. It would be wise to poke around the boot crimped lid lip seals too, especially near the elephant ears. The DS design ( unlike modern or even Traction practice ) was to use small pressed metal bits welded or in some locations braised to make the caisson. These things were never rust treated internally I suspect, just given a quick spray of gloss black, even the B and C pillars. Hollow and untreated.
 
I like the rubber mounts, as they can absorb small bumps without damaging the bumper or car.
Yes they can trap water, but if the rubbers are intact (fill the holes) water can't get in.
The whole area can be protected from moisture using your favourite spray or brush on sealant.
I like CRC Soft Seal.
Just spray on, it sets to a firm goop, never to a film..... which can harbor rust.

In out of sight structural bits I never use a hard film type of paint, even if it says it's the best rust preventer in the world. Rust will creep under a film pushing it off as it goes.

Waxy or semi fluid like lanolin will stick, and cannot be lifted.
It's great to spray up inside the side boxes and front footwell voids.
 
I like Lanotec for those situations. It goes have a sheepish wiff ( no jokes about Kiwis here !!! ) ... or comments about rusty sheep, but it seems to stick on and stay for a long time and being a spray is so easy to retreat. Also being non petroleum base it will not perish rubber.
A firm goop .. just the sort of comment you want after an X ray. It almost betters the "echogenic sludge" I got after a scan.
Would Nigella use the term " a firm goop " I suspect she would !
 
That lanotec is good stuff, I sprayed it around inside the door seams and all over the place. it smells alright. Better than fish oil!

Ray the bumper should have two brackets either end side with a rubber stop that protects the rear panels from being gouged from the bumper when removing too. In case yours are missing, which seems to be pretty common after many moons.
 
forumnoreason said:
That lanotec is good stuff, I sprayed it around inside the door seams and all over the place. it smells alright. Better than fish oil!

Ray the bumper should have two brackets either end side with a rubber stop that protects the rear panels from being gouged from the bumper when removing too. In case yours are missing, which seems to be pretty common after many moons.
Click to expand...
Yeah, I've used about three cans full of Lanotec on the 2CV when building him, and in the DS when opportunity arises. The bump rubbers to whic you refer are there and in good nick. Strangely they aren't shown in the 648 parts book.

Have to laugh, though. The small black buffers on the main bar are called "Gummipuffers" in the German!

So no-one has any idea why the thing is rubber mounted then?

Cheers, Pottsy.
 

Attachments

  • 648 D Parts pages 552 and 553.pdf
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I wonder if it was to allow the bumper to have some give in the event of a rear end collision. That said, the front bumper is hard mounted to the chassis with zero give so who knows what they were thinking
 
H-Hmmmm

The original and best DS design DID mount the front bumper on similar rubbers!
20210117_131927.jpg
 
pottsy said:
Yeah, I've used about three cans full of Lanotec on the 2CV when building him, and in the DS when opportunity arises. The bump rubbers to whic you refer are there and in good nick. Strangely they aren't shown in the 648 parts book.

Have to laugh, though. The small black buffers on the main bar are called "Gummipuffers" in the German!

So no-one has any idea why the thing is rubber mounted then?

Cheers, Pottsy.
Click to expand...
No idea! But see #3 above.... first two lines.....
 
Could it be to absorb vibration, so that the mounts don't fatigue (long term) and crack?
 
Buttercup said:
H-Hmmmm

The original and best DS design DID mount the front bumper on similar rubbers!View attachment 129472
Click to expand...
Thank you for that pic. I did not realise the original DS was so. The original ( and best ??? ) DS19 also had different engine mounts that were adjustable for height and IIRC requiring specialised pipe type not quite ring spanners with very long handles to allow access from below.
 
Yes, everything is adjustable, everything is serviceable.
After 1957 it was a slippery downhill slope for the DS.
Aluminium boot lid
Trompettes de Jericho
Rear side reflectors
Rubber mounted bumpers
Real solid metal door handles and winders
A manual wiper actuator, in case the wiper motor failed... (well.. yes it did sometimes)

Many many more refinements lost to economy over the next 18 years.
 
No..... I'm sorry, they might vibrate a little!
If a mosquito gets stuck on the windscreen, and not quite dead yet...... continues to buzz.
 
Buttercup said:
Yes, everything is adjustable, everything is serviceable.
After 1957 it was a slippery downhill slope for the DS.
Aluminium boot lid
Trompettes de Jericho
Rear side reflectors
Rubber mounted bumpers
Real solid metal door handles and winders
A manual wiper actuator, in case the wiper motor failed... (well.. yes it did sometimes)

Many many more refinements lost to economy over the next 18 years.
Click to expand...
I have to agree with you. The best DS we owned was a 68 DS21 Pallas ( palladium grey, carburettor, manual box, black leather, orange brake lights). The 69 DS 20 that replaced it was not as well finished being just a "normal DS" but it lacked paint quality and seemingly any bodywork rust preparation. My 74 DS 23 Injection Pallas Borg Warner was frankly a disaster .. broke my heart and the bank balance. It had preprogrammed self destruct plans ..everything from piston sleeve seals to camshaft pulley failure....cooked engine mounts on the exhaust side and sphere to match. .... far too much extra heat generating "stuff" jammed into the same space as the humble 1911 cc engine.
 
OK, so the consensus seems to be just to absorb gentle bumps. Seems a lot of extra engineering just to do that, but I guess that's the Citroen Way. Being an Aficianado I guess I wouldn't have it any other way.

That being said, the original rubbers were far from stopping ingress into the box section, so I shall explore the possibilities of replacing, or at least re-creating, them. I'll also look into Soft Seal, thanks for the tip BB.

I think it's informative for everyone to have these types of discussion. Every time I work on (play with?) Moby Dick I learn something new. Front bumpers are definitely solid mounted, but since the D-Special is the poverty pack edition I suppose they had to draw the line somewhere. At least he has the proper fungoid brake system and a lot of other good things.

Cheers, and thanks Chaps.
 
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